Quest 11(1)

Science for South Africa

Shaping light: using light waves

ISSN 1729-830X

Volume 11 | Number 1 | 2015

Molecular movies: unravelling ultrafast processes Saving nerve cells and saving memories Lasers: producing coherent light

Light and our understanding of the universe Light in art: the light fantastic

Acad e my O f Sci e n ce O f South Afri ca

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ontents Volume 11 | Number 1 | 2015

Cover Stories 6 Modulating light

Dirk Spangenberg and Melanie McLaren explain the applications of shaping light in space and time

10 Laser light

Andrew Forbes explains the science of lasers

14 Making movies of atoms:

how to unravel ultrafast processes

Gurthwin Bosman shows us how to make molecular movies

17 Saving nerve cells – saving memories

Ben Loos shows how microscopes can be used to find ways to treat neurological diseases

18 Light in a dark universe:

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Celebrating the International Year of Light

Understanding light is vital to understanding our universe, as Michelle Cluver explains

24 The light fantastic

Marcus Neustetter has produced wonderful works of art using light

Features 3 Light: beyong the bulb

Quest and the International Year of Light take a look at the history of light

6 17 18

12 Exploiting quantum entanglement with photons

Melanie McLaren and Andrew Forbes show the relationship between light and quantum physics

32 Groundwater-dependent alien invasive species

Scientists from the CSIR work out exactly how much groundwater is being used by alien invasive plants

36 Climate change and natural systems

Candice Lyons looks at how climate change may affect our natural systems

40 Growing veggies for a green economy

Constansia Musvoto looks at small-scale vegetable production in South Africa

42 Living with wildlife

Lize J van der Merwe shows that we can live side by side with nature – if we are careful

Regulars 46 News

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10

More shark attacks do not mean more sharks New shrimp species discovered in Cape Peninsula waters

48 Books 50 Subscription 52 Back page science • Mathematics puzzle

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Science for South AfricA

Shaping light: using light waves

iSSn 1729-830X

Volume 11 | Number 1 | 2015

Molecular movies: unravelling ultrafast processes Saving nerve cells and saving memories Lasers: producing coherent light

Light and our understanding of the universe Light in art: the light fantastic

AcAd e my o f Sci e n ce o f South Afri cA

Images: Marcus Neustetter, CSIR, NASA

Editor Dr Bridget Farham Editorial Board Roseanne Diab (EO: ASSAf) (Chair) John Butler-Adam (South African Journal of Science) Anusuya Chinsamy-Turan (University of Cape Town) Neil Eddy (Wynberg Boys High School) George Ellis (University of Cape Town) Kevin Govender (SAAO) Himla Soodyall (University of the Witwatersrand) Penny Vinjevold (Western Cape Education Department) Correspondence and enquiries The Editor PO Box 663, Noordhoek 7979 Tel.: (021) 789 2331 Fax: 0866 718022 e-mail: ugqirha@iafrica.com Advertising enquiries Barbara Spence Avenue Advertising PO Box 71308 Bryanston 2021 Tel.: (011) 463 7940 Fax: (011) 463 7939 Cell: 082 881 3454 e-mail: barbara@avenue.co.za Subscription enquiries and back issues Tsepo Majake Tel.: (012) 349 6624 e-mail: tsepo@assaf.org.za Copyright © 2015 Academy of Science of South Africa

Published by the Academy of Science of South Africa (ASSAf) PO Box 72135, Lynnwood Ridge 0040, South Africa

Permissions Fax: 0866 718022 e-mail: ugqirha@iafrica.com Subscription rates (4 issues and postage) (For other countries, see subscription form) Individuals/Institutions – R100.00 Students/schoolgoers – R50.00 Design and layout

The science of light

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015 was proclaimed as the International Year of Light and Light-based Technologies by the United Nations General Assembly in 2013. The aim of the year is to promote awareness of how light-based technologies promote sustainable development and provide solutions to global challenges in energy, education, agriculture and health.

We – and the world around us – would not exist in our current forms if we did not receive light from our Sun. The science of light cuts across most disciplines of science – microscopy and lasers in medicine, communication via the Internet are just two examples. The Sun is a sustainable source of energy and light-based technologies are allowing us to harness this energy – solar panels that power batteries and turn this light into heat and electricity are a good example.

Light is made up of particles called photons and photonics is the science and technology of generating, controlling and detecting photons. Photonics underpins technologies of daily life, from smartphones to laptops to the Internet to medical instruments to lighting technology. The 21st century will depend on the science of photonics, as the 20th depended on electronics. And just as electronics drove business opportunities in the last century, so photonics will open up major business opportunities and drive societal growth during this one.

Communication is more part of our daily lives now than in any previous time – social media, low-cost telephone calls, Skype – none of which would be possible without light-based technologies.

This issue of Quest covers many of the main topics in the fascinating science of light. Enjoy the read.

Bridget Farham Editor – QUEST: Science for South Africa

Creating Ripples Graphic Design Illustrations James Whitelaw Printing Fishwicks

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All material is strictly copyright and all rights are reserved. Reproduction without permission is forbidden.

Every care is taken in compiling the contents of this publication, but we assume no responsibility for effects arising therefrom. The views expressed in this magazine are not necessarily those of the publisher.

A city illuminated at night. Image: Tokino, via Wikimedia Commons

A cloud in the sunlight. Image: Ibrahim Iujaz, via Wikimedia Commons

Light: Beyond the bulb Quest gives a brief overview of the history of our understanding of light.

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he glow of a candle, the rise of the Sun, and the illumination of a lamp are things that can bring comfort and warmth to our lives. Humans are, after all, drawn to light. But there is much more to light than meets the eye. Light takes on many forms that are largely invisible and undetectable without modern technology. Light allows us to communicate, entertain, explore, and understand the world we inhabit and the Universe we live in.

A brief history of light From early attempts to understand the motion of stars and planets to the appreciation of the importance of light in photosynthesis, efforts to understand the nature and the characteristics of light have revolutionised nearly every field of science.

An important stage of the evolution of the universe occurred around 300 000 years after the Big Bang, when the temperature was cool enough (around 4 000°C) for neutral atoms to form. Before that time, there were too many charged particles to allow light to travel more than a very short distance. After atoms were formed, light could travel immense distances. In fact, we can receive ‘light’ (in the form of microwaves) today that has been travelling for over 13 billion years.

Perhaps of more importance to us was the formation of the Sun and the solar system – including our planet – about 4.5 billion years ago. Earth has been bathed with light from the Sun ever since; it is our most important source of energy. Sunlight warms us, causes weather patterns, allows plants to manufacture oxygen and our food from carbon dioxide and water, and it allows us to find our way around in the daytime!

The use of sunlight in photosynthesis, to make oxygen and carbohydrates from carbon dioxide and water, is

This galaxy, nicknamed the ‘Whirlpool’, is a spiral galaxy, like our Milky Way, located about 30 million light years from Earth. This composite image combines data collected at X-ray wavelengths by Chandra (purple), ultraviolet by the Galaxy Evolution Explorer (GALEX, blue); visible light by Hubble (green), and infrared by Spitzer (red).

Image: X-ray: NASA/CXC/SAO; UV: NASA/JPL-Caltech; Optical: NASA/STScI; IR: NASA/JPL-Caltech

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Image: X-ray: NASA/CXC/UMass/D. Wang et al.; Optical: NASA/ESA/STScI/D.Wang et al.; IR: NASA/JPL-Caltech/SSC/S.Stolovy

Our Milky Way In celebration of the International Year of Astronomy 2009, NASA’s Great Observatories – the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory – have collaborated to produce an unprecedented image of the central region of our Milky Way galaxy.

In this spectacular image, observations using infrared light and X-ray light see through the obscuring dust and reveal the intense activity near the galactic core. Note that the centre of the galaxy is located within the bright white region to the right of and just below the middle of the image. The entire image width covers about one-half a degree, about the same angular width as the full moon.

Each telescope’s contribution is presented in a different colour: - Yellow represents the near-infrared observations of Hubble. They

a process first established over two billion years ago by cyanobacteria. They made the large quantities of oxygen in the atmosphere which allowed oxygen-breathing life to evolve. Today plants use chlorophyll to achieve the same

Carbon filament lamp, grey coloured bulb results from sublimated carbon, which has been deposited at the inner glass surface. Image: Wikimedia Commons

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outline the energetic regions where stars are being born as well as reveal hundreds of thousands of stars.

- Red represents the infrared observations of Spitzer. The radiation and winds from stars create glowing dust clouds that exhibit complex structures from compact, spherical globules to long, stringy filaments.

- Blue and violet represent the X-ray observations of Chandra. X-rays are emitted by gas heated to millions of degrees by stellar explosions and by outflows from the supermassive black hole in the galaxy’s centre. The bright blue blob on the left side of the full-field image is emission from a double star system containing either a neutron star or a black hole. When these views are brought together, this composite image provides one of the most detailed views ever of our galaxy’s mysterious core.

result, keeping the atmosphere breathable, and providing food energy for us and all other advanced life forms.

Of course, mankind has found other sources of light over the course of history. Fire is obviously the earliest of these: from the camp fires of our cave-dwelling ancestors to the spirit lamps still used where there is no electricity. But electricity is the source of artificial light today, starting with the invention of the incandescent light by Joseph Swan and Thomas Edison and progressing via fluorescent lighting to modern light-emitting diode (LED) lights.

Mankind has also learned to control light. The use of mirrors and lenses to divert light, or to magnify images, dates from pre-history. Microscopes and telescopes, using multiple mirrors and/or lenses are two closely related inventions from just a few hundred years ago. They allow us to study objects smaller than our naked eyes can see, and objects at large distances, whether ships at sea, or astronomical bodies at enormous distances.

We can also send light from one place to another using optical fibres or ‘light guides’. These allow us to use light to transmit large amounts of information, and to explore regions where we cannot go, such as in medical probes or endoscopes.

Material for this article was sourced from: http://www.light2015.org/Home/ScienceStories/A-BriefHistory-of-Light.html Q

❚❚❚❙❙❙❘❘❘ Fact file Did you know the speed of light is always constant?

The speed of light is always constant. This is the foundation of the Special Theory of Relativity for uniform motion. Based on this principle, the speed of light came to be used as the ultimate standard for length and time. http://www.canon.com/technology/s_labo/light/001/10. html#c001s010h003

Is there anything faster than the speed of light?

The letter ‘c’ represents the speed of light in formula: c = 2.99792458 x 108 m/sec.

The speed of light will always be the same, no matter who measures it or how fast the measurer is moving. It is the fastest thing in the universe. Einstein is credited for this discovery. http://www.canon.com/technology/s_labo/light/001/10. html#c001s010h003

How long does it take a sunbeam to reach Earth?

Light travels at nearly 300 000 km/sec. Since the Earth and Moon are 380 000 km apart, light from the Moon takes about 1.3 seconds to reach us. And since the sun is 150 million km from the earth, the light we see right now left the sun about 8 minutes ago.

A light year (the distance light travels in a year) is 9.5 trillion km. http://www.canon.com/technology/s_labo/light/001/10. html#c001s010h003

Did you know the basic unit of length (one meter) is based on the speed of light?

We all know the basic unit of length is one meter. But did you know that today one meter is defined as the distance light travels in 1/299.792458 million seconds. This definition allows us to use light to accurately measure the distance to the moon with extremely high accuracy (error of 30 cm or less). http://www.canon. com/technology/s_labo/light/001/10.html#c001s010h003

Did you know light particles are weightless?

Light is both a wave and a particle, but how much do the particles (called photons) weigh? The answer is: nothing. Photons are particles with zero mass, no electrical charge and a spin (rotation) value of one. That is why they can travel so far, because they weigh nothing. http://www.canon.com/technology/s_labo/light/001/10. html#c001s010h003

I am a ghost, I may be weightless but I still have energy – Who am I? In 1900, Planck (a German physicist who lived from 1858 to 1947) announced that oscillating electrons radiate electromagnetic waves with intermittent energy. Before that, it was thought that electromagnetic energy fluctuated continuously and could be endlessly split into smaller and smaller parts. According to Planck, energy is emitted in proportion to oscillation frequency.

This proportionality constant is called ‘Planck’s constant’ (h = 6.6260755 x 10-34), and oscillation frequency times Planck’s constant is known as an ‘energy quantum’. If we try viewing this as light particles, we can consider electromagnetic waves of a certain oscillation frequency to be a group of photons with energy equal to oscillation frequency times Planck’s constant. Photons are zeromass particles, but because they have energy, they also possess momentum. http://www.canon.com/technology/s_labo/light/001/10. html#c001s010h003

Did you know energy from the Sun can be converted into electricity?

Governments and scientists worldwide are working to develop affordable and clean solar energy technologies. Solar energy will provide a practically inexhaustible resource that will enhance sustainability, reduce pollution and lower the cost of mitigating climate change. http://www.light2015.org/Home/WhyLightMatters/Energy.html

Did you know lasers are a form of artificial light?

The laser beam was discovered in 1960. The term laser is an acronym for ‘light amplification by stimulated emission of radiation’. Lasers are a form of artificial light with uniform direction,

Marcus Neustetter created these images in Williston, Fraserburg and Sutherland for the start of the International Year of Light, 2015.

phase and wavelength, and they are produced by precisely controlling the excited and ground states of electrons. Unlike other forms of light that do not have uniform wavelength and phase, lasers can create intense light spots from faint light sources and are thus one of the most important forms of artificial light. http://www.canon.com/technology/s_labo/light/002/05.html

Who invented the laser beam?

Theodore Maiman developed the first working laser at Hughes Research Lab in 1960, and his paper describing the operation of the first laser was published in Nature three months later. Since then, more than 55 000 patents involving the laser have been granted in the United States. http://www.laserfest.org/lasers/history/early.cfm

What is photonics?

Photonics is the science and technology of generating, controlling and detecting photons, which are particles of light. Photonics underpins technologies of daily life from smartphones to laptops to the Internet to medical instruments to lighting technology. http://www.light2015.org/Home/WhyLightMatters/What-isPhotonics.html

Photonics is everywhere Even if we cannot see the entire electromagnetic spectrum, visible and invisible light waves are a part of our everyday life. Photonics is everywhere: in consumer electronics (barcode scanners, DVD players, remote TV control), telecommunications (Internet), health (eye surgery, medical instruments), manufacturing industry (laser cutting and machining), defence and security (infrared camera, remote sensing), entertainment (holography, laser shows). http://www.light2015.org/Home/WhyLightMatters/What-isPhotonics.html

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Modulating light Dirk Spangenberg and Melanie McLaren explain how the spatial and temporal modulation of light is used in many applications.

L

ight is made up of electromagnetic waves which exhibit all the wave properties you would expect to see when there are waves on water. Just as a wave always travels perpendicular to the wavefront on the spatial plane of water, so too light always travels perpendicular to the wavefront of light. Modification of the shape of the wavefront results in modification of the propagation direction of light as does modification of the amplitude of the respective sections of the wavefront. The systematic modification of light is referred to as the modulation of light, thus modulating light in space is referred to as spatial light modulation.

The point about the spatial modulation of light is that by modulating the light waves, information can be encoded into a beam of light, such as a laser, in exactly the same way that a transparency ‘encodes’ information for an overhead projector. Spatial light modulators can be used as part of holographic displays, in optical computing and in holographic optical tweezers.

Optical tweezers are scientific instruments that use a highly focused laser beam to provide an attractive or repulsive force (a very, very, very small force) to physically hold and move microscopic objects in a way that is similar to the way that ordinary tweezers hold objects. They have been used to study a variety of biological systems.

In the illustration a single short pulse results (bottom) from the summation of a set of colours (top). Image: Stellenbosch University

In the illustration a double pulse results (bottom) by summation of a set of colours (top) after modification of the amplitudes and their relative position.

Image: Stellenbosch University

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Just as light can be modulated in the spatial co-ordinates, so too light can be modulated in time, i.e. along the propagation direction. If you think of a laser pointer, the spatial co-ordinates is the spot on the wall whereas the temporal co-ordinate is along the beam. Modulation of light along the time axis is referred to as temporal pulse shaping.

With temporal pulse shaping the time and amplitude scales reachable allows us to experimentally measure the fundamental physics of molecules on ultrafast time scales. A wide range of physical phenomena can be examined in this way, from photosynthesis to optical pulse activated superconduction phases in crystals.

The nature of light We know that light is made up of electromagnetic waves.

These waves oscillate at a particluar frequency. The colour of light is determined by the wavelength of the light wave.

Blue light, for example, has a wavelength in the range of 400 nm to 480 nm and red light has a wavelength in the range of 600 nm to 750 nm. Each colour propagates at the same velocity, namely the speed of light 2.998 ✕ 108 m/s. The wavelength is defined as the distance a colour propagates in a single oscillation.

Shaping laser pulses The difference in wavelength for the oscillating colours results in them adding up in phase for some parts and out of phase for other parts of the wave in what we call constructive and destructive interference. This property is exploited in order to do temporal pulse shaping. If, for example, we are able to take several colours of light and bend them into a box where we can modify their amplitude and relative position with respect to each other, we can make a beam of light that consists of pulses. If we arrange these colours differently we could even generate a double pulse beam. The relationship between the colours you need for these beams, along with their relative position (called their phase) is given by the Fourier transform and can easily be calculated. The Fourier transform is a mathematical method to determine the required wavelengths, each with specific amplitude and phase, which would add up to give the required waveform shape. In the example, the modification to the spectrum required to convert the single pulse into a double pulse is achieved by modulation with an oscillating amplitude function. An example of such a box would be a setup that contains a spatial light modulator (SLM) to be able to adjust the phases of the different waves to obtain arbitrary shaped time pulses which you may require.

Combination of different colours of light and systematic modification of their amplitudes and relative positions in the blue box results in laser pulses due to the way they interfere and add up.

Another example where the modification to the individual colours is shaped (modulated) according to an oscillating function resulting in double pulses when the colours add up afterwards.

Image: Stellenbosch University

Image: Stellenbosch University

It is the scale of these pulses that is incredible. Achievable pulse lengths are in the order of the wavelengths, that is from 1.5 to 50 µm for highly sophisticated broadband laser sources to simple laser oscillators. In terms of time, this translates to 5-100 femto-seconds (1 ✕ 10-15 seconds) time duration, that is, ultrashort pulses. These very short pulses can be generated to contain a finite amount of energy, 10 nanojoules to millijoules, which translate to enormous instantaneous intensities. Translated to instantaneous power the value becomes very large, easily in the order of terrawatts. As a comparison, the average power consumption of the Earth in 2008 was 16.42 terrawatt. One terrawatt is 1 ✕ 1012 watt. With these high instantaneous intensities and ultrashort duration molecular dynamics in the order of femtoseconds can be resolved in a nondestructive manner.

Not only can laser pulses be shaped in time, the laser beam can also be shaped in space, that is, the intensity pattern can be manipulated.

Shaping laser beams If you look at light from a laser pointer shining on a wall, it appears to have a circular shape. When seen on a camera, this laser beam would be brighter at the centre and then becomes less bright at the edges. This type of beam is called a Gaussian beam and is a common laser output that is used in standard laser cutting and welding as well as in CD players. However, some applications require beams with different properties and shapes.

In optical tweezing, Gaussian beams have been used to demonstrate three-dimensional manipulation of microscopic particles, such as blood cells, by simply focusing the beam very tightly. In microfluidics, this technique is extremely useful as precise control over fluids in a small area is required.

Figure 1: Intensity distributions for (a) a vortex beam, (b) a Bessel beam, (c) two vortex beams added together and (d) two Bessel beams added together.

Image: Stellenbosch University

Microfluidics is a branch of science that cuts across many disciplines such as engineering, physics, chemistry, biochemistry, nanotechnoloty and biotechnology.

It has practical applications in the design of systems in which small volumes of fluids will be handled – it deals with the behaviour, precise control and manipulation of very, very small fluids.

However, by simply changing the shape of the beam and as such, the properties of the beam, from circular to a ‘donut’ shape, the microscopic particles can be made to rotate. These beams are often referred to as vortex beams (Fig. 1(a)) and have been applied to microscopic gears.

Microscopic gears are exactly what they sound like – tiny, tiny gears. Insects have them, for example on their legs, to allow them to jump enormous distances. Directing the angular momentum that is carried by vortex beams onto microscopic gears that have been made for specific uses, allows the gears to rotate at a specified speed.

These rotating gears are often used as a way to control the mixing of specific solutions.

So by changing the type of beam, we can explore novel applications. Within optical tweezing, for example, it was found that red and white blood cells could be separated from one another using a beam with a bright central spot 11| 1 2015

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Box 1: What is phase?

Often when we describe the propagation of light, we refer to it as acting like a wave, or more particularly, like a sinusoidal wave, where its position is a function of time: 2λx + Ø h(x) = A.sin λ

(1) where A is the amplitude, λ is the wavelength and Ø is the phase of the wave. Consider two identical waves of the form in equation (1). If these waves are not aligned with each other, for instance, the peak of one aligned with the peak of the other, then there is a phase shift, or phase difference, between them (see Figure 2). This phase shift can be measured in radians, degrees, or fractions of a wavelength.

For example, a wave that is shifted by 360˚ (same as 2π radians) is shifted by one wavelength, which means the waves are still aligned.

However, a 180˚ phase shift (same as π radians) is a shift of half a wavelength, so the peak of one wave lines up with the trough of the other. This phase shift can also be applied to a single wave when compared with a reference point. Phase elements such as holograms shift the phase of the original light waves by specific amounts.

(

)

Figure 2: The peaks of the two waves are not aligned and are therefore ‘out-of-phase’ with each other. Image: Stellenbosch University

surrounded by many concentric light rings, called a Bessel beam – see Figure 1(b). These beams have two interesting properties. Firstly, they are non-diffracting over a distance, which means that their size does not change or spread out over a distance. Secondly, they have the ability to ‘self-heal’ after encountering an obstruction. Most beams become completely distorted if an object is placed in their path, but Bessel beams will recover their shape after a distance over the obstruction. This reconstructive property has been used in tweezing to vertically stack multiple particles and in quantum entanglement as a way to preserve information for quantum communication (see a later article in this issue of Quest for more information about quantum entanglement).

Methods to shape beams There are a number of methods that can be used to shape a laser beam. The most convenient is a spatial light modulator

Figure 3: (a-c) Intensity distributions of a Gaussian, vortex and Bessel beam, respectively, with (d-f) their corresponding phase distributions. Image: Stellenbosch University

Figure 4: A spatial light modulator consists of a phase hologram that varies the phase of the incident beam in such a way as to produce a new type of beam.

Image: Stellenbosch University

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(SLM). An SLM consists of a liquid crystal display (LCD) made up of a number of pixels, each of which is addressed by two electrodes in a way that means that the molecules making up the pixels are aligned parallel to the electrodes. By applying an electric field to the electrodes, the molecules tilt in the direction of the field. This tilt changes the refractive index seen by the light and in turn changes the phase of the incident light beam.

Each part of the beam experiences a different phase change, so that if we took a picture of the phase of the entire beam, it would not be uniform. This phase distribution can be seen in Figure 3 for three different types of beam. The phase of the beam can be varied between 0 and 2π, which is represented as a colour change from blue to red in Figure 3.

An SLM connects to a computer so that the computergenerated holograms are then displayed on the LCD screen.

This allows the displayed hologram to be changed quickly and easily without re-alignment. This process also works in reverse – a complex beam shape can be converted back into a Gaussian beam (see Figure 4). This process of converting the complex beam shape back into a Gaussian beam is called modal decomposition, which can be used to work out the spatial properties of an unknown beam.

These applications using the spatial modulation of light are adding new dimensions to many branches of science, from biology to quantum mechanics. q Dr Dirk Spangenberg completed his PhD in laser physics at Stellenbosch University in January 2015. His proof of principle work which extends ptychography to the time domain made extensive use of temporal pulse shaping.

Ptychography is a spatial lens-less imaging technique, originating from around 1970, which allows for the recovery of phase information of an object illuminated by coherent electromagnetic radiation which is too fast to be measured directly. The phase is reconstructed from diffraction images recorded of the object illuminated at different positions.

Extending this spatial technique to the time domain allows one to reconstruct signals with higher temporal resolution than classic pump probe methods would allow and the technique can be applied to a wide range of temporal applications. Later this year he will continue with his research in this field at the University of Bern, Switzerland.

Dr Melanie McLaren is currently a post-doctoral researcher in the Physics Department at the University of the Witwatersrand.

Her research looks at methods used to shape light beams and scientific fields where these beams can be applied.

The electromagnetic spectrum. Image: Wikimedia Commons

Laser light All about lasers. By Andrew Forbes.

2015 is the International Year of Light. How did it come to be? Well in 2010 we celebrated the 50th anniversary of the laser. As the story goes, John Dudley made the comment that it was a pity we (the laser community) missed the opportunity to have an International Year of the Laser event.

When the audience asked why not then initiate one for light, the ball was set in motion. On 19 January 2015, at the UNESCO headquarters in Paris, the International Year of Light was officially launched.

When most people think about light they imagine what we can see – the visible spectrum, The largest laser on Earth: the National Ignition Facility (USA). 192 laser beams but in fact light in its strictest sense means are combined on a small target to create star-like temperatures on Earth. any wave or particle (photon) within the Image: Lawrence Livermore National Laboratory electromagnetic spectrum, of which the visible Making lasers part is very small.

Lasers produce light that is coherent (see ‘Shaping Light’ The light we see in our everyday lives is mostly what Quest 2010 6(3), pp. 10-13 and ‘Shape-shifting beams’ is called incoherent. This means that the light waves that arrive from any source travel in many directions, in what Popular Mechanics 2010 April, pp. 50-53 for more appears to be a random fashion. Random in the sense that information on how lasers work). In fact, this is one of the there is no phase relationship between the various emitted defining properties of lasers. In a standard laser design a waves. An example would be torch light. Because the light medium is placed between two mirrors, forming a ‘box’ is not coherent, and the phase between different parts of that confines the light. The medium is then excited out the light is always changing, you cannot interfere the waves. of equilibirum and starts to emit photons. Because the To see this, take two torches and overlap the disks of light medium is excited, these photons interact with the medium on a wall. Where the disks overlap, the light is brighter to release more photons through a process known as than where they don’t. This is how incoherent light adds: stimulated emission. The photons bounce back and forward add light to light and you get something that is brighter. between the mirrors, all the time passing through the Coherent light is different: it is possible to add light to light active medium where they excite still more photons, until and the result can be darkness, or what we call destructive many photons are circulating in what is similar to a chain interference. reaction. We deliberately make one of the mirrors partially 10

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transmitting so that some of the light leaks out – this is our laser light. The first laser demonstrated using this principle was made by Theodore Maiman (see http://laserfest.org/ lasers/history/early.cfm), who used ruby as his active medium, which he excited by using a very bright pulse of white light.

Since then lasers have been made in all shapes and sizes, from very large to very small, from very powerful to almost single photons.

Today researchers continue to explore how to make lasers and how to apply them. Their usefulness has touched our everyday lives: lasers are used in DVD players and remote controls, cell phones and, of course, are the backbone of our modern communication systems. Imagine how slow your internet downloads would be if we were still using electrons down copper wires for communication, as was the case in the last century, rather than light down fibre-optics, as we do today. The 20th century was the electronic century, where the electron and electronics revolutionised our lives.

Today we enter the century of the photon: the 21st century will see photonics replace electronics in many applications.

The story of light, which has been around since the beginning of time, is in some sense only just beginning.

Who makes lasers in South Africa?

You may have heard recently of a laser that was in the news …. the digital laser? (South Africa launches new digital laser: https://www.youtube.com/watch?v=eu8U_n3k2Mg) The digital laser replaces one of the mirrors in the ‘box’ with a liquid crystal display (LCD), just like your LCD television at home. Well, not quite – it is much smaller, about the size of your thumb print. Just as your LCD television can change pictures it displays, so does the LCD screen inside the digital laser. The result is that when the picture changes on the screen, the beam of light that comes out of the laser also changes. I call this ‘on-demand laser beams’ because the properties of the laser are changed with just a picture. This is perhaps one of the more famous examples of lasers in South Africa. But in fact laser development in South Africa has a long history (C Bollig et. al., 2007 Photonics in South Africa Nature Photonics 1:673-675).

In the early days laser research was undertaken at both the CSIR and the University of Natal (now the University of KwaZulu-Natal). Later, the largest laser programme in the country was undoubtably the Atomic Energy Corporation’s endeavour into laser-based enrichment of uranium. This programme spanned many years and saw the development of core skills in laser technology in South Africa. When the programme ended, the seeds were sown for new centres of laser-based research: the CSIR National Laser Centre and the University of Stellenbosch. But laser development is not only academic. South Africa has two strong centres of commercial laser development too, where solid-state lasers at Airbus (Irene) and gas lasers at Par Systems (Pretoria) are

A myriad of laser beam shapes created in the digital laser. Image: Andrew Forbes

A young researcher working in a typical laser laboratory. Image: Andrew Forbes

made for export. We have a long way to go to realise a larger fraction of the worldwide laser market (estimated at over $9.3 billion in 2014), and to do so requires bright young minds with a passion for light. q Prof. Andrew Forbes has been Chief Researcher at the CSIR National Laser Centre, where he led the team that developed the digital laser. He has recently started a new laboratory for Structured Light at the University of the Witwatersrand.

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Exploiting quantum entanglement with photons Melanie McLaren and Andrew Forbes explain how light and quantum physics are inextricably linked and how this linkage is applied in everyday life.

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he theory of quantum mechanics was first introduced over 100 years ago when Max Planck, often referred to as the ‘Father of quantum theory’, planted the seed of quantum mechanics in a number of scientific minds. The origin of the science of quantum mechanics lies in Planck’s theory of black body radiation – called Planck’s Law. One particular mind was that of Albert Einstein, who built upon Planck’s work to explain the photoelectric effect, for which he won the Nobel Prize in Physics in 1921. After this the theory of quantum mechanics was the accepted way to describe physical processes at the atomic level. Einstein, however, was not comfortable with various conclusions made by quantum theory and together with Boris Podolsky and Nathan Rosen, published work that concluded that quantum mechanics was, at the time, an incomplete theory.

Without knowing it, Einstein, Podolsky and Rosen had

Box 1: Planck’s Law All physical bodies spontaneously and continuously emit electromagnetic radiation. Under conditions of thermodynamic equilibrium the emitted radiation of nearly described by Planck’s Law. For our purposes, it is described by Planck’s Law. The higher the temperature of a body the more radiation it emits at every wavelength. Planck radiation has a maximum intensity at a specific wavelength that depends on the temperature. For example, at room temperature (about 300 degrees K) a body emits thermal radiation that is mostly infrared and invisible. At higher temperatures the amount of infrared radiation increases and can be felt as heat and the body starts to glow red. At even higher temperatures a body becomes a dazzling bright yellow or blue-white and emits significant amounts of short wavelength radiation, including ultraviolet and even X-rays. The surface of the Sun, for example, has a temperature of about 6 000 degrees K and emits large amounts of both infrared and ultraviolet radiation – its emission is peaked in the visible spectrum.

Source: Wikipedia

Planck’s Law (coloured curves) accurately described black body radiation and resolved the ultraviolet catastrophe (black curve). The ultraviolet catastrophe was a prediction of late 19th century/early 20th century classical physics that an ideal body at thermal equilibrium will emit radiation with infinite power. Image: Wikimedia Commons

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described quantum entanglement (see Box 2) or as Einstein famously described it, ‘spooky action at a distance’.

Nowadays we can test for the presence of entanglement using a theory derived by John Bell in the 1960s and despite its rocky start, quantum entanglement has become the focus within a variety of scientific fields.

Communication Continuous developments in technology have led us into a world where online communication is a necessity, whether you simply communicate with friends via email or transfer funds via online banking. The demand for more secure lines of communication has therefore increased, particularly in cryptography, where sensitive information is encoded and can only be deciphered using a common key. If an eavesdropper/ hacker has access to the key, then any and all private messages between senders can be read. However, if the key is sent using quantum entangled photons then it becomes impossible for an eavesdropper to obtain the secret key. Once a measurement/ observation is made on one particle in an entangled system, it affects the other (see Box 2) and as such, the sender would know that the key had been intercepted and that a new key was required. The encoded messages could still be sent in the traditional way as they could not be deciphered without the key. Realising secure communication outside the controlled lab environment is a high priority in many countries. In April last year, it was announced that both China and the USA are in the process of installing 2 000 km and 650 km quantum communication networks between landmarks, respectively.

Microscopes Biological samples are commonly imaged using a method of differential interference contrast microscopy, a technique that looks at the interference pattern of two light beams reflected off a sample. This technique allows scientists to accurately measure in three dimensions. However, there is a limit to this accuracy, known as the standard quantum limit. Last year, Japanese groups demonstrated that by making use of the unique properties of entangled photons, this limit could be surpassed. They were able to measure a height difference of just 17 nanometres, which is 1.35 times more accurate than before.

Entanglement-enhanced microscopes can produce much sharper images but at a wavelength that is safe for living cells.

Teleportation If you thought the transporter from Star Trek was completely fictional, never to be experienced in real life, then you’re absolutely correct. Teleportation of humans may never arise.

However, a group in Austria have demonstrated quantum teleportation of photons over 143 km of free-space. Using a pair of entangled photons and an additional single photon, they showed that information from the single photon could be transferred to one of the entangled photons, that is, the

(a)

(b)

information was ‘teleported’. It may not be as glamorous as TV has made us believe, but this is an important step in quantum computations and communication.

Quantum entanglement in South Africa Within South Africa, quantum entanglement has developed quickly since the first experimental demonstration of entanglement was performed in 2011. This initial demonstration encoded only two bits of information per photon, making use of only two dimensions. However, the value in quantum communication lies in the ability to encode and transmit large bits of information per photon securely.

Our group at the National Laser Centre (NLC) at the CSIR, together with a Canadian group, was able to able to not only demonstrate high-dimensional entanglement, but also quantify the level of entanglement, which is crucial in developing a sustainable communication link. In 2013 we demonstrated high-dimensional quantum key distribution in the laboratory.

Another important thing to consider when applying entanglement to the real world, is the effect of turbulence, in particular atmospheric turbulence, on the level of entanglement.

For example, the brightness of the light from a torch is significantly reduced when shone through mist or a sand storm.

Likewise, when entangled photons pass through clouds or even air turbulence, the strength of the entanglement between these photons, decreases. This effect was investigated in the NLC laboratory where the amount of turbulence or distortion could be controlled and the effects quantified. It is now a priority to determine a manner in which these negative impacts can be lessened. One possible solution is to alter the type of measurement and thereby alter the properties of the photons. In 2014 we showed that by changing the properties of the photons, from a vortex beam to a Bessel beam, the entanglement could ‘self-heal’ after being affected by an obstruction.

If you still feel uncomfortable or confused about entanglement and the world of quantum mechanics, remember what Richard Feynman once said, ‘If you think you understand quantum mechanics, you don’t understand quantum mechanics’. q Dr Melanie McLaren completed her PhD in Physics in 2014 and is now a Research Fellow in the School of Physics at the University of the Witwatersrand.

Prof. Andrew Forbes has been Chief Researcher at the CSIR National Laser Centre where he led the team that developed the digital laser. He has recently started a new laboratory for Structured Light at the University of the Witwatersrand.

By changing the type of measurement, the property of the photon changes. (a) For example, the photon can be changed from vortex or ‘donut’ type mode to a Bessel mode, which has many concentric rings around the centre. Bessel modes are able to ‘self-heal’ after being distorted by an obstruction, and this is also true for entanglement. (b) The level of entanglement is calculated at different distances after the obstruction and it is clear that the entanglement slowly increases from a low value of 0.44 to a very high level of entanglement of almost 1.0, which is the highest level of entanglement.

Box 2: What is entanglement?

Consider two dice, die A and die B, placed in two separate rooms. These are ordinary dice, but they are entangled with each other. The dice are rolled by two separate people in separate rooms at the same time, and each time they write down the number that lands facing upward. They repeat this 20 times, compare their answers and find that for each of the 20 rolls, they have identical numbers (i.e. roll one they both observed a six, roll two they both observed a three and so on). How is this possible? Did they cheat? Are the dice loaded in some way? The trick is entanglement.

Entangled particles intrinsically share the same information/properties until one of the properties is recorded/measured. This means that particles cannot be described independently, but rather as a two-particle system. So if we flip two entangled coins, coin A and coin B, then before we look at coin A to see which side is facing upward, the two-coin system is written as a sum of probabilities: f sysytem = P [(Heads)A(Tails)B] + P[(Tails)A(Heads)B], where: P [(Heads)A(Tails)B] is the probability of finding coin A with ‘heads’ facing upward and coin B with ‘tails’ facing upward.

After a measurement is made, the particles do not affect one another, so if coin A is turned over to show ‘tails’ then coin B will not experience a change. This is a phenomenon that is observed only at the quantum level, for example with single light particles called photons, and you cannot see it in large objects such as dice or coins.

Entangled particles share information until a measurement/observation is made on one of them. If ‘heads’ is observed on one coin, then we immediately know that the other coin will show ‘tails’ and visa versa.

Box 3: How to generate entangled photons Step 1: Use a laser beam together with a crystal with specific properties to generate two entangled photons from a single pump photon.

Typically, a UV laser at a wavelength of 355 nm is used to pump a non-linear crystal, such as a barium borate crystal. In a process called spontaneous parametric down-conversion, a single pump photon is converted into two entangled photons with a wavelength double that of the pump, that is at 710 nm.

Step 2: Choose a property of photons to measure, e.g. polarisation or energy, and use appropriate equipment to measure that property. For example, use a polariser to measure polarisation.

Step 3: Use two single-photon detectors (avalanche photo-diodes) to record the arrival of each measured photon. Attach these detectors to a counter that will record when two photons arrive at the separate detectors at the same time. Sometimes only one photon arrives at a detector, but in entanglement we are interested in the pair of photons.

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Making movies of atoms: how to unravel ultrafast processes Imagine for a moment being able to view in real time how various photo-induced reactions take place. Sounds interesting?

What if these reactions occur on a timescale that is so short that they appear to happen instantaneously? How would you be able to know exactly what occurred? By Gurthwin Bosman.

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he answer to these questions is to use a ‘camera’ capable of resolving really fast phenomena. The camera used for this type of work is no ordinary imaging device and as such will be discussed a bit later. For now, let’s focus rather on how the scientists in the field of laser physics are tackling the problem of capturing and understanding ultrafast processes.

At the Stellenbosch University Laser Research Institute in the laboratory of Prof. Heinrich Schwoerer physicists investigate exactly these photo-induced reactions of atoms and molecules in matter with microscopic resolution in time and space. Simply put: making movies of atoms moving in matter.

In these ‘molecular movies’ they try to observe, understand and modify microscopic dynamics such as configuration changes, charge and energy transfer reactions in organic and organo-metallic molecules, and photo-induced macroscopic Photo-induced reactions: Any reaction initiated by light.

Femtosecond lasers: A laser which emits short duration light pulses of order 100 femtoseconds.

Diffraction: Is the general characteristic of wave phenomena which occur when a wave encounters a given physical obstacle.

A schematic of the optical setup used for taking molecular movies.

Image: Stellenbosch University

Molecular movie setup in action. Image: Stellenbosch University

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phase transitions in inorganic and organic crystals.

The ongoing research projects in Prof. Schwoerer’s lab include the investigation of substances that are capable of changing their colour when light shines on them, investigating how charges propagate in solar cells and using femtosecond lasers to generate electron bunches for diffraction measurements.

So far we have only stated the importance of making ‘molecular movies’ in these projects. Therefore we will dig a little deeper, starting off with the making of the molecular movie followed by a brief summary of two of the projects mentioned above.

Making a molecular movie Making a molecular movie requires various scientific instruments, the most important of which is a femtosecond laser. This is because if a short light pulse from the laser starts a reaction, another light pulse can be used to monitor the influence of the first pulse at any time later. A neat thing here is that the arrival time of the monitoring pulse at the sample is fully adjustable. In fact the arrival time can be set to values as short as or even shorter than the duration of the light pulse.

To understand this, recognise first that the speed of light is a constant and as a result the time it takes for light to travel over a specific distance is known if the distance is known.

Therefore if one is required to change the arrival time of a light pulse, it is as simple as changing the distance the light has to travel in a controlled way. Being able to control the arrival time of the monitoring pulse is actually the main reason why making a molecular movie is possible.

This is because through monitoring at different arrival times a snapshot at each time-point is created. Taking all of this into account, the molecular movie is subsequently generated from a collection of the monitoring snapshots at discrete time intervals. This is similar to how a conventional video camera operates. The only difference here is that each snapshot is not a photograph but rather a measure of the amount of light that passes through the sample (change in optical transmission).

Investigating colour changing substances The metal-complex dithizonatophenylmercury is a specific type of crystal which, when dissolved in the appropriate solvent and illuminated with blue-green light (450 - 500 nm wavelength), undergoes a stark colour change from orange to blue.

The scientific term for this colour-changing phenomenon is photochromism and the process is understood as a structural change that occurs within the molecule due to the light. To understand this process we must understand that light is a form of electromagnetic radiation, which intrinsically contains

Molecular movie of dithizonatophenylmercury dissolved in methanol. The graph shows how the transmission (ΔmOD) of light through the sample changes with respect to time (t) and wavelength (λ). Image: Stellenbosch University

Charge propagation in a dye sensitised solar cell. Dye sensitised solar cells consist of a light absorbing material (dye) which is photo-excited by sunlight and donates charge to a nanoporous semiconductor that serves as the charge acceptor.

Charge separation occurs at the dye/semiconductor interface thereby producing oxidised dye molecules, which are reduced by an electrolyte. Image: University of Stellenbosch

Dye-sensitised solar cell made by adsorption of the dye to the porous semiconductor surface.

Image: Stellenbosch University

energy. The energy, when deposited into the molecule, in this case causes a rotation to occur within the molecule. This newly rotated molecule therefore looks different to the original one and consequently also has a different colour.

Making a molecular movie of this orange to blue reaction allows scientists to determine the time it takes for the colour change to occur. This reaction takes place in roughly one picosecond, which is one millionth of one millionth of a second. In other words, seriously fast!

The propagation of charges in a solar cell Using the electromagnetic radiation from the Sun to generate electricity is a concept that is well understood. In short, light from the Sun, when viewed on the quantum scale, consists of elementary particles known as photons. These photons interact with the solar cell and generate free charges (electrons) which, when connected in a closed electrical circuit, can do work.

Currently there are various types of solar cells on the market, either based on high-purity silicon semiconductors or on blends of organic and inorganic materials. While the silicon solar cells are still more efficient, the novel cells based on organic matter offer the potential to be much cheaper and provide the option to be incorporated into flexible materials such a plastic films or even fabrics. Nevertheless, the efficiency is still a very important parameter to consider as it ultimately affects the plausibility of large-scale reproduction. In this regard, tracking how the charges propagate in a solar cell through a molecular movie is crucial, as it allows for viewing the various paths an electron can take in the solar cell. Knowing the paths and their probabilities gives one insight into the ultimate performance of a cell, as not all paths are beneficial for generating electricity.

The projects discussed above form a subset of the research currently being conducted in the laboratory of Prof. Schwoerer, where the aim ultimately is to broaden our understanding of light-matter interactions. q Dr Gurthwin W Bosman is a laser physicist and researcher at the Laser Research Institute, Department of Physics, Stellenbosch University (SU). He works with Prof. Heinrich Schwoerer, who holds the South African Research Chair (SARChi) in Photonics at SU.

Image of a femtosecond pulse train. Image: Stellenbosch University

Image of the solar cell within the molecular movie setup. Image: Stellenbosch University

The author at work in the laboratory. Image: Stellenbosch University

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❚❚❚❙❙❙❘❘❘ Medicine

Saving nerve cells – saving memories Using microscopes to find ways to treat Alzheimer’s. By Ben Loos

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hat is a person without memories? We spend our lives creating beautiful memories for our spouse, children, parents, friends, colleagues and ourselves. However, when the nerve cells are diseased and die, memories disappear. Neurodegenerative diseases are incredibly complex, which makes finding a treatment a major challenge.

Identifying the problem Many neurodegenerative diseases, such as Alzheimer’s disease (AD), are characterised by what is called proteostasis. This means that the breakdown of proteins in nerve cells slows down and leads to the build-up of toxic protein clumps or aggregates.

My group is interested in how exactly this dysfunction starts. The main problem with Alzheimer’s is that most nerve cells have already died by the time the person shows symptoms. A disease-altering treatment has not yet been found. So we want to identify the problem long before it leads to the death of neurons.

To do this, we search for the earliest signs for neuronal stress by looking into the nerve cells, while exposing them to an environment that mimics that in AD. Finding these early molecular clues is difficult, because the cell can compensate for most problems. And a plastic dish with nerve cells is different from a whole brain.

A nerve cell from a brain that is suffering from Alzheimer’s disease is extremely stressed. Effectively the cell lives for many years in agony, under the worst conditions, before it finally dies, often by committing cellular suicide, which is called apoptosis.

Amyloid, tubulin and autophagosomes The first pathological process is an accumulation of a protein called amyloid, which forms toxic ‘hot spots’. Then the transport system within the cell fails and a protein called tubulin collapses, because it is no longer sufficiently stabilised by another protein, called Tau. When tubulin collapses, the cell has lost its ‘road network’. Tau is, together with amyloid,

another major protein that forms clumps.

Toxicity arises inside and outside the cell.

There is another major issue with tubulin: two important systems depend on it for transport. Firstly, the mitochondria, which are the powerhouses of the cell, making energy (ATP). Nerve cells need lots of ATP. If the mitochondria cannot be transported to the corners of the cell, there will be a lack of energy in these areas.

The cell can still operate, but not as well as it has to if a certain workload is to be maintained. The corners of the cell contain the synaptic connections, a place where ATP is in high demand.

Secondly, the organelles that transport protein for degradation, the autophagosomes, do not reach their target and accumulate. The nerve cell becomes filled with what we call autophagic vacuoles and multi-lammellar bodies. For the cell this is like a traffic jam where everything is ‘bumper to bumper’ – nothing moves.

We are interested in how we can better measure this dysfunction of autophagosome-facilitated protein breakdown. We wish to measure it as accurately as possible, and then re-activate it in a controlled manner, thereby preserving nerve cell function. In physiology we use (physiology = the science of function of living organisms, their tissues or cells) many techniques that give us a complete picture of cellular function and dysfunction.

Microscopes to the rescue My fantastic group of students uses specialised microscopy techniques.

Each student addresses one problem area, one molecular puzzle piece of the disease condition. Here, we can keep cells alive, and observe, for example, the autophagosomes and the mitochondria as they move, and the tubulin network and the proteins that accumulate. To achieve that, we ‘paint’ them with a fluorochrome or connect them with a fluorescent protein. This glows when excited with a specific laser light and reveals the protein, almost the same principle that fireflies use to glow in the dark. Since some structures are very small, we often employ what is

Autophagosome (green) fusing with a lysosome (red). Image: Courtesy of Dr Ben Loos

Mitochondria. Image: Courtesy of Dr Ben Loos

Autophagosomes normal (left) and superresolved (right). Image: Courtesy of Dr Ben Loos

Stellenbosch University has the only facility in South Africa that can help researchers to observe what is happening inside the cell at such high resolution. These are some of the images, produced by using specialised microscopy techniques, which help researchers to understand the nerve cell better. By understanding better the molecular mechanisms and early events that become faulty and lead to neuronal cell death, researchers hope to provide information that can be taken further for the development of new treatment avenues for Alzheimer’s disease.

Lab address: http://www0.sun.ac.za/ physiologicalsci/eng/research.php?id=29

called super-resolution microscopy. q Dr Ben Loos is a senior lecturer in Physiological Sciences, Stellenbosch University, heading the DSG-Neuro Group.

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LIGHT IN A DARK UNIVERSE:

Celebrating the International Year of Light Michelle Cluver takes a look at the role of light in understanding our universe.

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n 2015 we celebrate the International Year of Light (and light-based technologies), acknowledging the fact that human existence is strongly dependent on light, providing food and safety from the earliest times. We are also acknowledging its role at the forefront of modern technology and innovation, as we strive to capture, understand and harness light energy. It is light that carries information from the depths of our visible universe

to where we can collect and analyse it. The Hubble Space Telescope (HST for short) is a ‘time machine’, showing us distant objects as they looked in the past when the universe was far younger.

What we see The first light-sensitive astronomical detector was also the very first astronomical detector – the human eye. The part of the electromagnetic spectrum visible to the human eye starts at a wavelength of around 400 nanometers (nm; billionths of a meter) to approximately 700 nm. The eye sees different wavelengths of light as different colours, i.e. the shortest wavelength light (400 nm) is violet and the longest wavelength (700 nm) is red light. A rainbow is visible light

The farthest and one of the very earliest galaxies ever seen in the universe appears as a faint red blob in this ultra-deep-field exposure taken with NASA’s Hubble Space Telescope. This is the deepest infrared image taken of the universe. Image: NASA, ESA, G Illingworth (University of California, Santa Cruz), R Bouwens (University of California, Santa Cruz and Leiden University), and the HUDF09 Team

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The eye as a photoreceptor cell. Image: imgkid.com

The Milky Way arch emerging from the Cerro Paranal, Chile, on the left, and sinking into the Antofagasta’s night lights. The bright object in the centre, above the Milky Way is Jupiter, somehow elongated due to the panoramic projection. The Magellanic Clouds are visible on the left side, and a plane has left a visible trace on the right, along the Vista enclosure. Image: www.eso.org

that is separated into the individual wavelength bands: violet, indigo, blue, green, yellow, orange, red. Our visual sensitivity is probably the result of the available energy output from the Sun combined with the energy bands of organic molecules.

The retina of the human eye has two types of photoreceptor cells stimulated by visible light: rods and cones. Rods are sensitive at very low light levels, but have no sensitivity to wavelength (colour), whereas cones are either ‘red’, ‘green’ or ‘blue’ based on the light they are sensitive to. This means that in the dark, you will predominately rely on your retina’s rods, but see in black and white. Since rods are concentrated at the edge of the retina and used mainly for peripheral vision, at night your peripheral vision is actually better for seeing faint

The Sun The Sun is our closest star, at a distance of 8 light minutes from us. That means that light from the Sun takes 8 minutes to travel to Earth. The surface temperature of the Sun is approximately 6 000°C and its emission peaks in the yellow-green part of the visible spectrum. But the Sun gives off plenty of energy at ultraviolet and infrared wavelengths, and although the atmosphere protects us to some extent, extra protection is needed. For example, by applying sunblock, you protect your skin from harmful UVA and UVB rays coming from the Sun.

A full-disk multiwavelength extreme ultraviolet image of the sun taken by SDO on 30 March 2010.

False colours trace different gas temperatures.

Reds are relatively cool (about 60 000 Kelvin, or 107 540°F); blues and greens are hotter (greater than 1 million Kelvin, or 1 799 540°F).

Visible wavelengths. Image: www.cyberphysics.co.uk

Image: NASA/Goddard/SDO AIA Team

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The Hale telescope. Image: http://www.astro.caltech.edu

The Australian Aboriginal constellation of the ‘Emu in the Sky’, which stretches from the Coalsack at its head, to Scorpius to the left.

Image: www.abc.net.au via Wikimedia Commons

objects, which is particularly useful if you’re looking at the starry night sky. Just remember that it takes approximately 30 minutes to become fully dark-adapted.

The night sky When you gaze at the night sky, it is filled with patterns of stars and it isn’t difficult to imagine them as figures when you connect the dots. These big pictures in the sky formed part of the folklore of generations of cultures from across 20

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the globe. The Khoisan of the Kalahari believe that the night sky was once completely dark; to light the way, a girl threw ash from a fire into the sky and created the Milky Way. Many African groups refer to the Milky Way as ‘the backbone of the night’ which kept the darkness from falling on their heads.

In Eastern Asia, the Milky Way was a ‘Silvery River’, while for the Chumash Native Americans, inhabiting Southern California, it was a pathway for departed souls. And to many Aboriginal Australian groups it was the ‘Great Emu’ in the sky.

Indigenous peoples were all astronomers – the movements of the Sun, phases of the Moon and visibility of star patterns were usually part of a sophisticated calendar, allowing them to plan and prepare for key times of the year such as the coming of winter, sowing and harvesting. The celestial sources of light were a crucial part of their existence, but there was no way to know what secrets these patterns harboured.

Our view of the universe is vastly different today. When Galileo aimed his primitive telescope at Jupiter, one light source became four and then five. He had discovered that Jupiter had four moons – we know today that Jupiter has many more. Like microscopes, telescopes allow us to see more detail, which can make things look very different. We are limited by the amount of information our eyes are sensitive to. A whole new world of discovery awaits us if we can better ‘see’ what we are looking at. Humankind has been striving to look deeper and deeper into space ever since, exploring the unknown with our telescopes as ‘time machines’.

NGC 4261, Left: A ground-based composite optical (white) and radio (yellow/ orange) image. Right: HST image of the galaxy centre showing the disk of dust.

Interestingly, the suspected SBH is some 20 light years from the geometrical centre of the galaxy. The reason for this misalignment is unknown.

Image: astronomy.swin.edu.au

Our eyes act like light buckets because they catch light (which our brain then converts to a picture). To see more, we need bigger buckets (like telescopes) and we use detectors, called CCDs or charge-coupled devices, to take the pictures in exactly the same way your digital camera works. Astronomers often refer to telescopes by the size of their mirrors, and that’s because the mirror is the light bucket, which determines how much detail, and how far, we can see.

For instance, between 1948 and 1993, the 200-inch Hale telescope just outside San Diego, was the largest effective telescope in the world. Its mirror is 200 inches in diameter (or 5.1 m) and it is affectionately known as ‘The Big Eye’.

Construction of the telescope began in 1935 and building it required developing new methods and innovative technology, much like we will need to build the Square Kilometre Array in the Karoo, which will be the largest radio telescope in the Solar System.

But even with the largest optical telescopes on Earth, we can’t compete with the detail we obtain with space-based telescopes, like Hubble. HST only has a 2.4 m mirror ‘light bucket’, so how is it able to take such fantastic pictures?

Because HST is in orbit high above Earth and it doesn’t have to deal with the ‘wobble’ as light travels through the Earth’s atmosphere. The hot and cold parts of the atmosphere bend the light as it travels through and causes the ‘twinkle’ of stars as we see them from Earth. In space there is no twinkling and that means the light is very stable as it hits the detector, which results in crystal-clear pictures with exquisite detail.

When astronomers analyse the light we get from telescopes we either take images of a chunk of (red or blue or green, etc.) light coming from the object (photometry), or we split the incoming light into a spectrum (rainbow of wavelengths) and see the relative energy at each wavelength (spectroscopy).

In the late 1970s, two astronomers were taking images (photometry) of galaxy clusters and noticed giant luminous arcs in their pictures. What they were seeing were lensed galaxies – galaxies behind the clusters whose light was

The farthest cosmic lens yet found, a massive elliptical galaxy, is shown in the inset image at left. The galaxy existed 9.6 billion years ago and belongs to the galaxy cluster, IRC 0218. Image: NASA and ESA

‘Invisible’ radiation Visible light is just one part of the electromagnetic spectrum that astrophysicists use to study the universe. Although other wavelengths are ‘invisible’ to us, with specialised detectors we can capture this information and it often tells us a lot more about what is going on. When you feel the warmth of the Sun, it is just the infrared radiation you experience as heat. Infrared cameras are sensitive to this ‘heat’ light (particularly useful in the dark). Imagine you are running a fever – a digital photograph of you wouldn’t show anything, but an infrared camera would show your elevated body temperature and you would appear to glow.

Radio waves are also part of the electromagnetic spectrum – we definitely can’t see them, but the receivers in our radios can convert those waves of energy information into sound.

These elephants were out in the sun on a warm day (the air temperature was about 24°C) and photographed using infrared cameras. Elephants are warmblooded and put out their own heat.

Also, the elephants' skin was warmed by sunlight. The warmest areas are the parts of the elephants' bodies which were in direct sunlight. Notice how cool the tip of the elephant’s trunk is after being in the water.

Image: coolcosmos.ipac.caltech.edu

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In this beautiful image by SAAO Astronomer Stephen Potter we see the Milky Way setting behind the 20-, 30-, 40-inch MONET and SALT telescopes. Jupiter is the bright star at the top and Venus is setting into the MONET dome. The bright glow on the horizon is from distant city lights. Image: Stephen Potter, SAAO

being bent (and magnified) by the gravitational pull of the clusters in the foreground. As light travels through space, it follows the shortest distance. Mass actually ‘dents’ space-time, in other words, the light that travels close to a cluster will bend due to the gravitational influence of the structure. So lensing gives us a glimpse of distant objects we wouldn’t normally detect, allowing us to peer even deeper into space. At the moment, the furthest galaxy imaged in this way existed 9.6 billion years ago. When we look out into space, we are actually looking back in time because the light information takes time to reach us. The most distant galaxies we see are therefore ‘imaged’ when the universe was far younger.

Astronomers rely on light, coming from different parts of the electromagnetic spectrum, to study the universe.

Sometimes things are not visible, but we know they must be there because we see their effect on other objects. For instance, we know when it is windy, even though we never see the wind itself!

Detecting the universe Scientists observe the universe with different detectors, each sensitive to specialised information. But there is some information we still can’t ‘see’. Just as scientists were once trying to study ‘invisible radiation’, like the infrared, we are faced with ‘invisible matter’ – also known as dark matter.

Dark matter makes up more than one-quarter of the universe; it has mass like ‘normal’ matter, what physicists call baryonic matter, but is invisible to us. But it betrays its presence by exerting a gravitational influence on the things we can see. For instance, when we study lensed galaxies, we know how much mass the cluster (acting like a lens) must have. But when we add up all the visible matter, we fall short – clusters must contain large amounts of dark matter. The motions of stars in disk galaxies suggest a similar picture.

We are still in the dark … but when we finally understand what is behind this elusive mass in the universe, it will 22

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revolutionise our understanding of fundamental physics and the nature of the universe – just as infrared detectors and radio telescopes have.

In order to expand our understanding, we need more information and we need to put it all together within a cohesive scientific framework. This translates into big telescopes, producing big data for the biggest computers to sort and simplify. Astronomers will be at the forefront of this technology, because we tend to ask big questions.

But dealing with big data generated, for example, by the MeerKAT radio telescope, will provide know-how and tools that can be used to take the data we humans collect and generate every day to streamline everyday challenges – from predicting the weather to easing traffic congestion to fighting pollution. And we will use light to move this information around – fibre-optic communication will be key to innovating the future.

So much has changed since humans first became fascinated by the patterns of stars in the night sky. For one thing, light pollution makes it far more difficult to stargaze, a problem affecting many observatories and telescopes all over the world. The momentum of progress should never come at the cost of being respectful of our planet – instead we should look for smarter solutions. Why not switch off the lights, go outside and reconnect with the night sky? The light that has travelled so far to reach you will undoubtedly make you consider your place in the big picture, much as our forefathers did thousands of years ago. q Dr Michelle Cluver is an NRF Research Career Advancement Fellow at the University of the Western Cape and Associate Astrophysicist at the Iziko Planetarium in Cape Town. She is an active member of the GAMA (Galaxy and Mass Assembly) collaboration, researching the WISE mid-infrared properties of galaxies, particularly those in groups. Her first postdoctoral position was at the California Institute of Technology using Spitzer Space Telescope data to study the evolution of galaxies in compact groups. She completed a PhD at the University of Cape Town in 2008 on the physics and fuelling of star formation in an unusual, gas-rich disk galaxy in the local universe.

The light fantastic For the past 15 years, Marcus Neustetter’s interest in the crossover of art, science and technology has led him to creating light interventions and experiments as a way of expressing his ideas or attempting to simulate natural phenomena and imaginary expeditions.

The rocket factory. Image: Marcus Neustetter

The rocket factory A building, thought to have once been a place where rocket parts were manufactured, carries its legacy in the artistic interventions by Marcus Neustetter. The artworks have been produced in conjunction with the transformation of the building. Large paint and light facade transformation, an illuminated rocket sculpture on the roof and an integrated 24

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design language throughout the building, marries artistic expression, reference to the mysteries and myths surrounding this building and contemporary living. Temporary and permanent light interventions, performances, artworks, design and functional living are fused into a visionary new development – The Rocket Factory.

Space journey. Image: Marcus Neustetter

Space journey Exploring spaces of mystery, a series of light experiments are used to create magical expeditions that reference imaginary outer space discoveries. Using mainly materials found in and around the sites and assembled with simple light sources such as torches, lazers and projections, these become tools for exploration and setting the scene for short documentary films and photographs.

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The global water crisis. Image: Marcus Neustetter

The global water crisis Commenting on the global water crisis, Marcus Neustetter creates drawings under UV light as public performances on functioning and abandoned water fountains and features.

Once the UV light performance is complete, the remaining artwork is invisible unless seen under UV light.

The vertical gaze Fascinated by what the artist calls the Vertical Gaze, up at the astronomical mysteries and down into the archeological unknowns, Marcus Neustetter has been exploring caves at the cradle of humankind. Photographing the light through cave openings and projecting them back onto the landscape has led to a series of light drawings making reference to the caves below the surface and to the night sky, both hosts to evidence of the past.

The vertical gaze. Image: Marcus Neustetter

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The big bang. Image: Marcus Neustetter

The big bang Sutherland in the Karoo is host to the South African Astronomical Observatory and the Southern African Large Telescope. Inspired by the scientific pursuit and the challenges of the engagement with the local disempowered communities, Marcus Neustetter, with his partner Bronwyn

Lace, has been developing community programmes in Sutherland. Attempting to visualise the scientific studies has been part of this. Here a group of Sutherland youth are using rope lights to create long time exposure photographs of the big bang.

Sunrise on a volcano Celebrating the light of the sun, Marcus Neustetter planned an expedition onto the volcano Mount Teide in the Canary Islands, for a sunrise summit.

The sunlight of that morning became the artists’ tool to reveal the volcano.

Sunrise on a volcano. Image: Marcus Neustetter

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Vredefort. Image: Marcus Neustetter

Vredefort Using gauze fabric and lazer pointers in the Vredefort meteorite impact crater, Marcus Neustetters reflected on the cataclysmic event that changed the Earth’s surface.

His pursuit has been to try to understand the relatively temporary presence of human existence on the planet.

The expanding universe This image, presenting the ever-expanding universe was created with the youth of the Space School South Africa using lazer pointers and fabric in an experiential workshop trying to make sense of natural phenomena.

The expanding universe. Image: Marcus Neustetter

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Light and sound. Image: Marcus Neustetter

In a series of city light and sound interventions with performers and glow-sticks, Marcus Neustetter questions the temporary nature of cultural action in transforming

cities and neghbourhoods. Through current rejuvenation and commercialism of many city spaces, local cultural identities are shifting.

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Calling lights. Image: Marcus Neustetter

Calling lights Because Marcus Neustetter failed to see the Northern Lights on several occasions, he has attempted to call the Northern Lights into being by finding the highest point possible and to call them through his own light drawings in the sky.

Chasing light Chasing Light is based on Marcus Neustetter’s excursion to Norway where he attempted to see the Northern Lights. Due to bad weather Neustetter was unable to fulfill his goal, leaving Norway with an experience lost.

However, Neustetter was able to gather some relevant documentation from his search in the form of sound recordings of aurora borealis activity. On his return to his studio, the artist attempts to re-visit his journey using the sounds to vibrate a tray of water and bouncing a lazer off it onto a white wall. The result is his visual representation of the Nothern Lights in the form of video and stills.

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Chasing light. Image: Marcus Neustetter

Telling stories. Image: Marcus Neustetter

Telling stories Gathering stories from local fishermen in Plettenberg Bay, Marcus Neustetter’s large-scale building projection on the Beacon Isle hotel makes reference to land use before

development of the town and pays tribute to the ocean and personal relationships to the ocean the fishermen call ‘Susie’.

Contemplation The artist’s time for contemplation of his impact on the planet through light drawings with LED lights, glow sticks and torches.

Contemplation. Image: Marcus Neustetter

For the International Year of Light, Marcus Neustetter is creating several light interventions throughout South Africa, exhibiting producing light related artworks in the Michael C Carlos Museum, Emory University, Atlanta as part of African Cosmos: Stellar Arts exhibition that is travelling from the Smithsonian Museum of Africa Art and producing an International Year of Light stamp sheet for the South African Post Office. q Johannesburg based artist, cultural activist and producer, Marcus Neustetter, reflects critically and playfully on his context through his art and collaborative projects. His strategy has been to pro-actively create, play and experiment to build opportunities and experiences that investigate, reflect and

provoke. Mostly process driven, his production of art at the intersection of art, science and technology has led him to use a multi-disciplinary approach from conventional drawings to permanent and temporary site-specific installations, mobile and virtual interventions and socially engaged projects internationally (www.marcusneustetter.com).

Marcus Neustetter has a BA in Fine Arts from the University of the Witwatersrand, and an MA. During this time he launched sanman (Southern African New Media Art Network). In the past 14 years he has been consistently producing and exhibiting art and, in partnership with Stephen Hobbs, has been active in The Trinity Session and in their collaborative capacity as Hobbs/Neustetter (www.thetrinitysession.com).

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Prosopis and the indigenous V. karroo forming closed canopies in the invaded area. Darker canopies depict V. karroo while lighter canopies are the Prosopis canopies. Image: CSIR

Groundwater-dependent alien invasive species A first of its kind study, quantifying groundwater use by alien invasive plant species, with preliminary results disproving previous literature, is being conducted by a group of hydro-scientists from the Council for Scientific and Industrial Research.

‘T

his is the first detailed study of its kind in South Africa quantifying the hydrological impacts of Prosopis invasions taking into account the effects of co-occurring indigenous vegetation that would normally replace Prosopis once it has been cleared,’ explained Dr Sebinasi Dzikiti, a CSIR expert in eco-

David Le Maitre (team member) and Peter Louw (farm owner) inspecting a dry borehole in the Prosopis invaded area. Image: CSIR

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hydrology. He further explained that, contrary to previous research, one cannot simply ignore the fact that indigenous vegetation uses groundwater. However, ‘how do the water uses or the impacts compare?’.

Rationale for the study The threat of groundwater-dependent alien invasive plants individually consuming up to 50 L of water per day, presents multiple challenges for an already water-scarce South Africa.

Approximately 10 million hectares have been invaded by alien plants in South Africa. This study looks at the impact the alien invasive species, Prosopis, has on groundwater supply to communities dependent upon groundwater for their livelihoods.

Prosopis is a dominant groundwater-dependent alien invasive species found in the arid and semi-arid parts of South Africa. Despite its dominance in the country, there is a lack of detailed studies articulating the impact of the species on groundwater. In addition, there are no tools quantifying the impact of alien invasive species on groundwater supply to communities. This study seeks to fill this gap by delivering on two key objectives.

Firstly, to quantify the interactions between deep-rooted alien plants and groundwater in the water-stressed parts of the country, and secondly to develop a robust remote sensing-based methodology for quantifying water use by groundwater-dependent alien invasive plants close to

❚❚❚❙❙❙❘❘❘ Alien invasive plants

Above: View of the entire study area with Prosopis trees appearing as light and V. karroo as dark coloured plants. Size of invaded area of the farm is about 400 ha. Image: CSIR

groundwater-dependent communities as case studies. It is important to note that the methodology has the potential to be applied to other deep-rooted alien plants in similar habitats.

Dr Dzikiti, who is also the project leader for this study, explained that apart from invasive alien plants, deep-rooted indigenous plants also use large amounts of groundwater.

Therefore, there is a need to determine the baseline of water use by indigenous vegetation that would, potentially, replace the invasive alien plants if we are to accurately quantify the impacts of the invasions on the water resources.

Vachallia karroo (V. karroo) was found to be the dominant indigenous species at Brandkop Farm, the study site close to the groundwater-dependent town of Nieuwoudtville in the Northern Cape.

While clearing continues to be the most common management practice when it comes to the control of alien invasive species, this study found that the amount of water transpired by individual Prosopis trees was either equal to or lower than that by the indigenous, co-occurring V. karroo of the same canopy size.

‘This intensive monitoring campaign is the first of its kind in South Africa which has involved detailed assessments of the interactions of both invasive alien and indigenous trees with groundwater in the drier parts of the country,’ said Dr Dzikiti.

Groundwater and alien invasive species in South Africa Approximately 13% of the water consumed by South Africans is sourced from groundwater, translating to

An eddy covariance flux tower for measuring evapotranspiration over the entire invaded area. Image: CSIR

approximately 65% of the country’s population being dependent upon this resource. Prosopis, which is dependent on groundwater, are unfortunately found in areas where communities depend, to a large extent, on groundwater for their livelihoods. Some of these areas include the towns of 11| 1 2015

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Project team members installing an automatic weather station at the farmer’s yard. Image: CSIR

Beaufort West, Graaff Reinet and Mussina.

The Northern Cape, South Africa’s most arid province, is under great threat from the spread of Prosopis. In 1990, only 400 000 hectares had been invaded by the species, and by 2007, this figure had mushroomed to approximately 1.5 million hectares. Estimates suggest that up to five million hectares could be invaded by this species countrywide. Therefore, comprehensive baseline studies are required to develop policies to minimise the long-term impacts of the species.

Thus, in order to assess and effectively quantify groundwater use by individual Prosopis species, the study also included the co-occurring and indigenous V. karroo, formerly known as Acacia karroo.

Dr S. Dzikiti installing soil water content sensors in the root zone of Prosopis.

Image: CSIR

Sap flow sensors for monitoring tap and lateral root water uptake patterns. Image: CSIR

A typical Prosopis tree with multiple branches close to the ground. Image: CSIR

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Monitoring water use: Prosopis vs. Vechallia karroo To quantify the extent of dependence of alien invasive plants on groundwater, detailed transpiration, soil water content, evapotranspiration (ET), weather, groundwater level and site data were collected from Prosopis and indigenous trees at the study site during the first one-and-half years of the three-year project. Prosopis are currently being cleared to allow for the monitoring of V. karroo.

Four boreholes were drilled at various locations within the invaded site close to the plant water-use monitoring equipment. The boreholes facilitate groundwater level monitoring, and they provide a mechanism to identify the relationship between plant water uptake and groundwater.

Information on the size of the wounding width and sapwood depth of the trees is required in order to calculate the actual volumes of water transpired by the trees using the heat pulse velocity sap flow technique. Evidence collected so far suggests that the maximum water taken up by a large V. karroo is up to 58 litres per day, compared with between 40 and 50 litres a day taken up by a Prosopis tree of a similar canopy size.

However, in a one-hectare area of the invaded site, the density of Prosopis was six times higher than that

Prosopis Description: A warm, desert phreatophyte that often develops multiple stems that branch off close to the ground. The species is well known for its very deep tap roots allowing it to survive under arid conditions by relying on groundwater.

Conservation status: The International Union for the Conservation of Nature has declared Prosopis to be one of the world’s worst invasive species. It is estimated to invade approximately five million hectares, with the largest density being in the Northern Cape.

Due to the fact that the higher stand level water use by Prosopis invasions is more a consequence of higher plant densities than high individual tree water uses, Dr Dzikiti recommends that organisations such as Working for Water and local municipalities target sparse stands of Prosopis and then work towards dense stands. Dense invasions of Prosopis are found predominantly along river courses and on flood plains. The next phase of this Water Research Councilfunded study will involve data collection after Prosopis has been removed, in order to establish the impact of the removal of Prosopis on the groundwater. q Student (Zanele Ntshidi from the University of Western Cape) downloading data from the transpiration monitoring equipment at the V. karroo site. Image: CSIR

of the indigenous V. karroo. Consequently, the former contributed up to 82% to the total stand level water losses.

While Prosopis root water uptake measurements showed evidence of hydraulic redistribution, this was not the case with the V. karroo growing adjacent to the Prosopis.

Hydraulic redistribution is the process whereby abstracted groundwater is deposited in shallow soil layers by the lateral roots of the trees. This effectively led to a relatively wetter soil profile below the alien invasive species than the co-occurring V. karroo.

‘This was an interesting observation,’ explained Dr Dzikiti. ‘Groundwater taken up by the Prosopis tap root was not immediately transpired. Rather a substantial amount of the water was redistributed and deposited in the shallow layers of the soil profile, presumably for later use when water availability became limited’. This, combined with the fact that the wet soil conditions sped up nutrient cycling, in turn, significantly enhances the chances of survival of young Prosopis seedlings in dry regions such as the Northern Cape.

The amount of water transpired by individual trees is strongly dependent on canopy size. However, in similar size trees, V. karroo had higher transpiration rates than Prosopis.

This is due to the larger sapwood to heartwood ratio in V. karroo than in Prosopis. ‘This study disproves the literature that often generalises that individual invasive alien plants use more water than indigenous vegetation,’ said Dr Dzikiti.

While it is true that some invasive alien plants may use more water than indigenous vegetation, this is not always the case, especially for drought-adapted species like Prosopis.

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Arctic ice caps are melting fast. Image: imgkid.com

Climate change & natural systems Candice Lyons takes a look at the potential effects of climate change on a range of natural systems.

O

ne of the most talked of topics today is climate change, and whether or not we are seeing the effects of anthropogenic (human-induced) climate change in our natural systems and dayto-day lives. Many people view climate change or global warming (two different issues) as the same phenomenon.

Definitions The term ‘global warming’ refers to the long-term average rise in temperatures, while ‘climate change’ refers to the changes in the Earth’s climate shown by melting ice caps, warming oceans and rising sea levels, and changes in natural phenomena such as droughts, floods and very heavy rainfall. However, some of the lesser known and understood consequences of climate change may happen at a smaller biological scale, not evident worldwide, but nevertheless having profound impacts on the Earth as we know it.

Heavy rain and high tide causing flooding in Darwin, Northern Territory, Australia. Image: Wikimedia Commons

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Extinctions, migrations and other natural events In the last twenty years, several species are thought to have gone extinct as a result of combined climate change and

❚❚❚❙❙❙❘❘❘ Climate change

Male golden toad – none have been seen since 1989 and this male was the last record of the species. It last bred successfully in normal numbers in 1987, when, as a result of erratic weather the pools dried up before the tadpoles had matured. Out of a potential 30 000 toads, only 29 survived. Image: Wikimedia Commons

habitat impacts. For example, the extinction of the golden toad Bufo periglenes has been attributed (in combination with disease spread) to rapidly increasing temperatures and the drought associated with climate change.

Although tempered by the annual discoveries of new species across the globe, the rate of extinction in natural systems has seen a several-fold increase in the past decade.

Species migrating to more suitable climatic areas as a result of unsuitable environmental conditions, coupled with habitat degradation, and increased conflict with human settlements, is likely to exacerbate the threat of extinctions within natural systems. Although migrations and species distribution shifts may not seem like cause for concern, several biological processes can be negatively affected by such occurrences. Distribution shifts in hundreds of species are already apparent – moving away from the equator, towards the poles. These shifts may lead to conflict with humans, or increased competition from similarly adapted species already present in the region. Shifts in the timing of important biological processes (e.g. flowering events) have also been observed for several species, with the potential consequence of mismatch in plant-pollinator interactions, and hence, potential reductions in biodiversity, and potential increases, in the long term, of extinction events. Determining which traits make a species more vulnerable to extinction risk than another species, is potentially problematic and a very contested issue. Many believe that species that currently either hold a ‘vulnerable’ or ‘critically endangered’ status based on the IUCN Red List status, are potentially more vulnerable to extinctions from combined climate change

and habitat loss influences. Furthermore, species that are specialists and display relatively narrow niches are likely to be at greater risk of extinction in the face of changing climates.

It is predicted that by 2050 almost 25% of the current species on the planet will have become extinct.

And humans?

You may think that these extinctions will not affect you.

However, more imminent threats to the human population can result from changing environmental conditions associated with climate change. Changes in the distributions of disease vectors, for example, could result from climate change. With warming temperatures and changes in rainfall patterns, shifts in some populations of disease vectors have already been seen. Although these are not always readily ascribed to climate alone, these shifting populations have the potential to increase disease burdens in many regions (although there is evidence that these same vectors will reduce in number in yet other regions of their current distribution range).

For southern Africa, shifting rainfall patterns have been linked as a potential culprit in expanding the future range of Anopheles mosquitoes responsible for malaria transmission. Expansions of the suitable habitat type for these malaria mosquitoes have also been observed at higher altitude regions in Africa, Asia and Latin America. In Europe and parts of North America, diseases such as tick-borne encephalitis, West Nile virus, cholera and Lyme disease have all shown increases in numbers of cases and increases in suitable habitat type, attributed to warming weather.

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The sixth extinction We are living in the geological epoch called the Holocene – since about 10 000 years ago. Many people talk about the Holocene extinction – or the sixth extinction – which is the extinction event that has occured during our present epoch, due mainly to human activity. There have been large numbers of extinctions, spanning numerous families of plants and animals – mammals, birds, amphibians, reptiles and arthropods. Most of these are undocumented – 875 occured between 1500 and 2009 (International Union for Conservation of Nature and Natural Resources). Based on various theories many believe that the present rate of extinction may be up to 140 000 species per year.

The Holocene extinction includes the disappearance of large mammals, known as megafauna, that started between 9 000 and 13 000 years ago, the end of the last Ice Age. It may be that this was caused by the extinction of mammoths in the northern hemisphere, who maintained the ecology of the grasslands on which they lived, which became birch forests without them. The new forests and resulting fires may have started climate change. Mammoth extinction may well have occurred, at least partly, through hunting by early modern humans.

It is only during the recent parts of the Holocene extinction that plant species have suffered large losses. Overall, the Holocene extinction can be characterised by human impact on the environment.

The dodo, a flightless bird of Mauritius, became extinct during the mid-late seventeenth century after humans destroyed the forests where the birds made their homes and introduced mammals that ate their eggs. Image: Wikimedia Commons

The caribbean monk seal was officially declared extinct in 2008.

Image: Wikimedia Commons

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A changing world Whatever your opinion on the causes of climate change might be, there is no denying the evidence for a changing world. Last year was recorded as the hottest year experienced in recent history (since 1880) and it is predicted to get worse. Increased temperatures, however, are not our only concern. Changes in rainfall patterns and temperature variability across and within seasons are also predicted and observed consequences of climate change.

But why should we care? If you don’t live in a region affected by disease, drought or famine, you may not think that the consequences of climate change affect you directly.

The variability in rainfall events, magnitude and seasonality, as well as the variable temperatures and daily temperature fluctuations, will undoubtedly influence urban water supply and agricultural practices.

Even though some uncertainty exists regarding the exact nature and manifestation of climate change, and whether or not some species distributions will shift as a result of rising temperatures and changing rainfall patterns, there is still enough evidence that the world is changing. What we do know is that the human population is increasing at an unprecedented rate, and without interventions to secure our food and water supplies, there is no way of knowing for how long the planet can sustain our ever-increasing population.

What we decide to do about it in the foreseeable future will undoubtedly shape the planet for future generations.

We may be able to slow the impacts of climate change if industry and the public alike make a conscious effort to shift to sources of renewable energy such as solar power or wind turbines. More sustainable agricultural practises – crop rotation and planting carbon sink species in areas no longer used for agricultural purposes – could lead to additional reductions in our carbon footprint, effectively reducing the negative impacts felt by global warming and climate change – at least in the foreseeable future. Q Candice Lyons completed her BSc, Hons and MSc at UCT and her PhD at Stellenbosch University in 2013. She worked as a postdoctoral research fellow at the Wits Research Institute for Malaria from 2013-2014 and has since been employed by the Agricultural Research Council in Stellenbosch, working on biological control of invasive weeds. Her PhD focused on the ecophysiology of two prominent malaria vectors within southern Africa, and the potential of these vectors to be influenced by climate change.

WHEN YOU SEE THE LIGHT

The world of science opens up to you

Think about light for a second. Without it, the Universe would simply not exist.

Meanwhile, back here on Earth, we have discovered that light has many uses from microscopes to telescopes, the Internet to the infinite. The science and technology of light is, quite literally, illuminating.

The South African Agency for Science & Technology Advancement (SAASTA) is committed to engaging South Africans in understanding the benefits of science. Its programmes and initiatives not only shed light on how science can help build society, but also steer learners towards careers in science, technology, engineering and maths. w w w.saasta.ac.z a

By supplying vegetables to national supermarket chains, fresh produce markets and vendors within their communities, small-scale farmers contribute to food supply, job creation, national and local economic development and are well placed to contribute to a green economy. Image: CSIR

Growing veggies

Constansia Musvoto asks ‘could small-scale vegetable production contribute to a green economy in South Africa?’

for a green economy

S

outh African agriculture is dominated by the largescale commercial sector. However, the government of South Africa recognises the potential role of smallscale farming in the economy of the country and in job creation. In the context of Outcome 7 of the Presidential Outcomes Approach, which states that ‘vibrant, equitable and sustainable rural communities and food security for all’ will be achieved, the Minister of Agriculture has explicitly stated the need to encourage small-scale farmers to produce and drive economies in their respective communities. Smallscale farming is also aligned with government priorities to address poverty and unemployment and to achieve sustainable development driven by a green economy.

Food security and a green economy South Africa has adopted the principle of a green economy, and is in the process of moving to a low-carbon, resourceefficient economy. The green economy – a response to the challenges of sustainable development – integrates social, economic and environmental objectives. This approach also tries to improve human well-being and social equity while protecting the environment. A green economy is explicit about addressing social factors such as job creation, poverty reduction, livelihoods and equity. The move to a green economy in South Africa will require certain enabling conditions for such an economy to establish and grow. The United Nations Environment Programme (UNEP) states that creating the right conditions for green economic activity requires a combination of appropriate policies, capacity, information, dissemination of good policy practice, social assistance, skills, general education and awareness. If met, these conditions would help ensure that green economy initiatives are well designed, implemented, enforced and understood; and would not cause unintended impacts or be hampered by practical or political challenges.

Agriculture is key One of the essential elements of human well-being is food security, and this places agriculture at the core of a green economy. There is international consensus on the key role that agriculture, and in particular small-scale farming, has

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to play in a green economy, and this has been articulated by the United Nations Food and Agriculture Organization (FAO) and the African Union (AU). In South Africa, agriculture has been identified as one of the sectors that will drive the green economy. The green economy strategies of Limpopo, KwaZulu-Natal, Western Cape and Gauteng provinces and the city of Tshwane all list agriculture/food production as one of the drivers of a green economy. South Africa’s focus on the green economy is particularly directed at creating jobs and addressing poverty.

Agriculture is well placed to contribute to a green economy as many agricultural activities potentially offer solutions to the social, economic and environmental challenges that South Africa and the rest of the world face. However, the kind of agriculture that is relevant to a green economy is different from regular industrial agriculture, which is dependent on practices and inputs (such as chemical fertilisers and pesticides) that require large quantities of fossil fuels and so contribute to climate change. For agriculture to contribute to the green economy, it has to be able to produce food and other commodities, meet social objectives such as equity, poverty reduction, job creation and livelihoods while protecting the environment. Although agriculture is a well-established sector, the green economy concept is relatively new, and the information base required for the implementation of a green economy in general and an agricultural green economy in particular has not yet been assembled. The Natural Resources and the Environment (NRE) unit of the Council for Scientific and Industrial Research (CSIR) is, in collaboration with various stakeholders, conducting research to build the information base required to facilitate South Africa’s transition to a green economy. One of the focus areas of the CSIR research programme is the role of agriculture in South Africa’s green economy.

Small-scale vegetable production Vegetable production, a subsector of agriculture, could contribute to a green economy. Experiences from countries such as Cuba and Moldova show that small-scale organic vegetable production can drive green economic growth. In South Africa, small-scale vegetable production could help meet some of the

❚❚❚❙❙❙❘❘❘ Science & society

country’s key green economy objectives such as job creation.

South Africa’s National Planning Commission has emphasised the importance of small-scale labour-intensive agriculture in job creation and highlights that the vegetable industry could be one of the largest contributors to job creation and the improvement of livelihoods in South Africa.

Rural communities in different parts of South Africa practise small-scale farming, and some produce a variety of vegetables for sale. While not conceived for the green economy, these small-scale initiatives may provide opportunities for participation in the green economy. As part of its green economy research programme, CSIR, in collaboration with the Limpopo Department of Agriculture (LDA), is analysing small-scale vegetable farming to identify potential facilitating and constraining factors for contribution to a green economy.

Such an analysis would be useful for identifying interventions that are required to create an enabling environment for a green economy. The analysis is being conducted in Tzaneen, Limpopo province. The information generated in Tzaneen would be relevant to other parts of the country as conditions are generally similar.

Farmers in Tzaneen grow a variety of vegetables on areas ranging between one and 20 hectares. Some farmers use organic production methods, while others use industrial farming methods. The farms which use organic methods use compost and organic fertilisers and do not use chemical fertilisers and pesticides, thus reducing the risks of fertiliser and pesticide pollution and poisoning. On the other hand, the farms which follow industrial farming methods are characterised by frequent applications of an assortment of chemicals, mainly pesticides.

The use of pesticides can potentially have negative impacts on the environment and on people. Organic farming generally uses resources more efficiently and has fewer negative implications for the environment than industrial farming.

Tzaneen farmers use water-saving drip irrigation, which also reduces leaching of plant nutrients from soil. Leached plant nutrients can pollute both surface and ground water. The water economy of drip irrigation systems also means that less water has to be pumped, and this saves energy. Drip irrigation equipment is expensive, and although most of the farmers would like to increase production, they generally cannot afford extra irrigation equipment. A common factor across all the farms in the analysis was inefficient irrigation management, as evidenced by routine irrigation which was not based on soil water measurements or known crop water requirements.

This method of managing irrigation increases the likelihood of applying too much or too little water relative to crop requirements, and thus using water sub-optimally.

Each farm employs between five and 20 people at any time, and thus contributes to employment creation and poverty reduction. The creation of jobs on farms is aligned with the objectives of South Africa’s green economy. The farms also contribute to food security and to the local and national economy as they supply produce to national markets through production contracts with some of the major national retailers and sales to national fresh produce markets. At the local level, produce is sold to informal bulk traders. The informal traders in turn supply local vendors, and this contributes to the local informal economy and provides livelihoods for some people.

The concept and framework for producing vegetables for the

market exists among small-scale farmers in Tzaneen and would provide a base for a green economy.

Currently, both organic and industrial small-scale vegetable production in Tzaneen is aligned to the objectives of a green economy – providing employment, contributing to food security, using water-efficient irrigation methods and producing for sale. These factors would need to be reinforced and/or built upon in the development of a green economy. Constraining factors include inefficient irrigation management, restricted access to drip irrigation equipment and risks to the environment posed by industrial farming methods. These factors would need to be addressed. Overall, farms that use organic methods are more aligned to the green economy as they pose fewer risks to the environment than those which follow industrial practices.

However, industrial farms also have green economy potential and benefits. The transition to a green economy should be a process where alternatives to practices which are not compatible with green economy principles are identified and introduced into farming practices over time. The situation of small-scale vegetable producers in Tzaneen highlights the fact that some of the practices of these farmers are compatible with a green economy and with interventions that improve alignment with green economy principles, small-scale agriculture is a sector that could contribute to South Africa’s green economy and open up options for people who currently have very few opportunities for participating in the economy. Q Connie Musvoto has a PhD in agricultural ecology and is a senior researcher in the Natural Resources and the Environment Unit of the Council for Scientific and Industrial Research (CSIR). Her research interests include environmental change and agriculture, the green economy and its role in enhancing rural livelihood and economic opportunities, systems approaches for managing agricultural landscapes and environmental impacts of agriculture.

She is currently leading a research programme on the role of the agriculture sector in a green economy.

Useful websites Gabara, N. 2012. Small-scale farmers encouraged to drive economy. South African government news agency. http:// www.sanews.gov.za/business/small-scale-farmers-encouraged-drive-economy. [accessed 20 December 2014].

UNEP, 2011. Enabling conditions: supporting the transition to a global green economy http://www.unep.org/greeneconomy/Portals/88/documents/ger/GER_14_EnablingConditions.pdf [accessed 14 February 2015].

UNEP, 2014. Green economy success stories. Organic agriculture in Cuba. http://www.unep.org/greeneconomy/ SuccessStories/OrganicAgricultureinCuba/tabid/29890/Default.aspx [accessed 05 January 2015] UNEP, 2015. Organic agriculture in Moldova. http://www.greenup-unep.org/story/~organic-agriculture. htm?lng=en#.vkusxiuuceg [accessed 06 January 2016].

NPC (National Planning Commission), 2011. National Development Plan: Vision for 2030. http://us-cdn. creamermedia.co.za/assets/articles/attachments/36224_npc_national_development_plan_vision_2030_-lores.pdf (accessed 05 January 2015)

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Living with wildlife Lize J van der Merwe discusses how wildlife shapes our lives, and how we shape theirs.

T

he ever-increasing size of the human population means the expansion of urban and agricultural areas, causing human activities to encroach on wildlife in remaining natural areas. Some animals are sensitive to these human-induced (or anthropogenic) changes, which makes them retreat into remote areas far from human settlements (e.g. the Cape leopard). Other animals, however, are highly adaptable and actually benefit from anthropogenic changes (e.g. barn owls).

The public’s willingness to share the landscape with wild animals depends on (1) financial cost/benefit; (2) safety concerns (e.g. allergies to bees, risk of being bitten by snakes, and risk of disease transfer by ticks); (3) ecosystem services (e.g. pollination by butterflies and soil enrichment by earthworms); (4) ecosystem products (e.g. honey produced by bees) and (5) superstition (e.g. owls as bad omens).

Barn owls control rodents, such as mice and rats, in farm buildings.

Here, a barn owl laid her eggs on the ledge of a chimney. A wooden plank was placed over the hole to prevent the chicks from falling down the chimney. This home owner bought an owl box after discovering these chicks to accommodate them and encourage them to settle on his property. Image: Lize van der Merwe

The upper parts of Simonsberg, in the Cape Winelands, act as a wildlife refugium, as it is still pristine fynbos. The vineyards in the lower-lying valleys and foothills are managed more intensively. Image: Lize van der Merwe

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‘Problem’ animals Generally, people are not prepared to share space with animals that damage human properties. Conflicts between humans and such animals may result in lethal interventions.

But before killing or removing problem animals consider the following: n Certain animals will always be a problem to humans (e.g. rats and cockroaches). This group of animals typically have a large number of offspring, and reach sexual maturity very young. Rapid reproduction causes the population to grow at an exponential rate. An increase in population size and density translates into a measurable (not imagined) risk of financial loss, disease transmission, suffering, and potential death. The only management objective is to humanely control the number of animals.

There is a small risk of ‘managing’ these animals into extinction, but this is unlikely given the problem animals’ ecology. n Some animals are only a problem at certain times. For example, in the Western Cape, porcupines have learnt to chew through water pipes during severe droughts, but stop this behaviour once natural water sources are replenished. Similarly, in the southern Drakensberg region, KwaZulu-Natal, large herds of eland graze in kikuyu pastures on commercial dairy farms during winter, when the nutritional value (i.e. palatability) of natural grassland in the mountainous nature reserves is extremely low. One herd of eland eat as much as a herd of cattle of the same size. However, the problem will probably go away when the first summer storms arrive, and natural grasslands produce new growth. Management of periodic problem animals involves mainly treating

❚❚❚❙❙❙❘❘❘ Ecology & conservation

symptoms, i.e. chase eland off kikuyu pastures, and patch water pipes damaged by porcupine. More aggressive interventions depend on (1) financial resources to absorb the damage caused by the problem animal, and (2) how sure you are that the problem will eventually solve itself if you just leave it alone. Intervention may also be necessary to prevent people from taking things into their own hands, which could damage conservation efforts. n Context-specific problem animals only cause economic loss within a specific land use type (e.g. urban, fruit orchards and livestock farms). In agricultural landscapes, for example, caracals are notorious predators of lambs on sheep farms, and cause significant economic losses to farmers. Unfortunately, controlling their numbers requires killing animals. However, in the Boland region, farmers depend on fruit production and are not affected by caracal. This means that the Boland region can be a refuge for caracal conservation. The opposite is also true.

Many problem animals specific to fruit orchards and vineyards (e.g. frugivorous birds, such as weavers) are not a problem to sheep farmers. So, sheep farms can be a refuge for these orchard-specific problem animals. This means that a landscape made up of many different landuse types contributes to the conservation of biodiversity in the whole region.

The role of landscape composition In a commercial agricultural landscape, it is very difficult to strike a balance between biodiversity value and economic viability. While the existence of ‘places of safety’ (or refugia) that allow wildlife to live in agricultural landscapes is a good thing from a biodiversity perspective, refugia can become a problem for farmers, particularly with conflict at transition zones, i.e. where two land use types meet. Quite often, the spatial extent and arrangement of different land use types (i.e. landscape composition) will have a large influence on the potential for human-wildlife conflict situations.

In landscapes that are topographically diverse with many mountains, rivers and valleys, such as in the Western Cape, we find intensive and extensive farming practices in different parts of the landscape. The spatial distribution of these farming practices is governed by productivity (e.g. soil type and water availability) and accessibility in terms of road and irrigation networks. Because valley basins are more fertile and easily accessible, they lend themselves to intensive farming practices (e.g. fruit orchards). Meanwhile, mountainous areas are more suitable for extensive land uses, such as livestock and game farming, or for conservation.

The spatial separation of intensive and extensive farming practices has implications for the conservation of biodiversity in agricultural landscapes. In particular, we find that higherlying, extensively-farmed areas act as wildlife refugia. However, whether these refugia are desirable from a farmer’s perspective is debatable. For example, along the Kogmanskloofriver between Ashton and Montagu, conflict arises between farmers and baboons that move out of the Langeberg mountain range into the lower-lying fruit orchards along the river, where they break off peach tree branches in their attempts to pick as many of these fruit as possible before they are chased away. A similar problem existed in Kenya, where wild elephants raided the local communities’ crops. Fortunately, the problem of crop raids by

Porcupines are shy, nocturnal animals that will eat fallen fruit in orchards and pumpkins from vegetable gardens. Two electrical wires (top wire ~ 40 cm high) around your vegetable garden will keep porcupines at bay.

Image: Lize van der Merwe

African wild cats adapt quickly to human care. Sometimes, they hybridise with domestic cats, which erodes the genetic diversity of the wild species. Therefore adoption of African wild cats is not encouraged. Image: Lize van der Merwe

This nest was built by honey bees in an empty farm building in South Africa a few decades ago. This photo was taken in 2005, but the nest is still intact. Bees produce honey, which is a highly sought-after commodity. However, because many people are allergic to bee stings, bees are not always welcomed into residential areas. Image: Lize van der Merwe

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Some swallow species build their nests in buildings or underneath roofs. The nest in this picture was built during a drought when mud was scarce. Mud was gathered from different patches in the garden when these patches were irrigated. Therefore, the differently coloured bands also represent the diversity of soil types in the immediate vicinity of this nest. Image: Lize van der Merwe

The elephant and bee project Dr Lucy King from Oxford University and Save the Elephants recently proposed a viable, effective, ethical and award-winning solution to this problem (St. Andrews Prize for the Enviornment, 2013). Finding effective ways to protect rural farms from damaging crop-raids is a major goal for elephant researchers and wildlife managers across Africa. It has been shown that African elephants will actively avoid the threat of African honey bees. So, to deter the elephants researchers fixed bee hives to fences surrounding croplands. Elephants do not care much about fences, but they are afraid of angry bees. If nothing else, bees get angry when their hive are subjected to an elephant-induced earthquake! (www.elephantsandbees.com)

The scratch marks indicate a leopard marking its territory to the south of the Langeberg Mountains. The neighbouring farmer keeps his cattle with young calves away from this area to prevent financial losses. Image: Lize van der Merwe

elephants were solved by fixing bee hives to fences surrounding croplands (more information in the Box). A similar brilliant solution to the baboon problem in South Africa is still lurking in the shadows, waiting to be discovered.

However, not all animals living in these wildlife refugia are damaging. Many beneficial insects, such as ladybirds that feed off damage-causing aphids, also inhabit them, although the intensively managed orchards are not ideal habitats. This means that the ladybirds operate mainly along the edges of orchards. An orchard with an irregular shape and curved boundaries has a longer ‘edge’ than a similarly sized semicircular orchard. Therefore, the irregularly shaped orchard will benefit more from the ladybirds. On the other hand, the irregularly-shaped orchards will also suffer more from visits by damage-causing animals. Designing landscapes that balance damage by ‘bad’ animals with services by ‘good’ ones is a practical problem that needs practical solutions, and is one of the challenges that we, as researchers, face.

However, while we continue in our search for practical solutions, we will treasure the value of different land use types in the country … and acknowledge the role that each one plays in conserving South Africa’s biodiversity. q Lize J van der Merwe is part of the Mondi Ecological Network Programme at Stellenbosch University. This research team tackles real-life conservation problems in commercial landscapes and focuses strongly on the role of landscape composition on biodiversity.

Dr Lucy King with one of the protective bee hive fences. Image: Lucy King

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Suggested reading Gebeyehu S, Samways MJ, 2006a. Topographic heterogeneity plays a crucial role for grasshopper diversity in a southern African megabiodiversity hotspot. Biodivers Conserv 15:231–244. doi:10.1007/s10531-004-7065-7 Gebeyehu S, Samways MJ, 2006b. Conservation refugium value of a large mesa for grasshoppers in South Africa. Biodivers Conserv 15:717–734. doi:10.1007/s10531-004-1062-8

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News

More shark attacks do not mean more sharks

Shelly Beach in Ballina – scene of a recent shark attack. Image: Bridget Farham

The recent death of a surfer on Shelly Beach, Ballina in northern New South Wales, Australia, is the latest in a series of fatal shark attacks off the coast of Australia.

However, according to scientists, this is not evidence of rising shark numbers.

Tadashi Nakahara died after both his legs were severed at Shelly Beach in northern New South Wales. The incident occurred just a week after beaches further south were closed for a record nine days following shark sightings.

This is the third fatal attack in New South Wales in the past 12 months, and the sixth in Australia, compared with just four in 2012 and 2013. But ‘there is no data to suggest that there has been an increase in shark numbers’, says Christopher Neff from the University of Sydney. The rise in attacks could be random, or it could be driven by other factors that bring sharks closer to the coast, such as small changes in thermal currents or bait fish movements.

There may also be more people in the ocean, he says.

The attack at Shelly beach is thought to have been carried out by a great white shark. According to Neff, it is ridiculous to search for the shark responsible, since a great white can travel between 70 and 125 km a day. He says that if the beach is closed, the shark will naturally move on.

New shrimp species discovered in Cape Peninsula waters

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A tiny new shrimp, called the ‘stargazer mysid’ by divers because of its eyes’ apparent permanent upward gaze, has been found in the extensively sampled waters of False Bay, Cape Peninsula, South Africa.

The new shrimp species is described in a joint paper by Emeritus Professor Charles Griffiths from the University of Cape Town (UCT) and international shrimp expert Professor Karl Wittmann, which was recently published in the journal, Crustaceana.

The shrimp is the ninth Mysidopsis species found in southern Africa and is officially named Mysidopsis zsilaveczi after the diver, UCT alumnus Guido Zsilavecz, who made the discovery.

‘Though previously unknown to marine biologists, the pretty shrimp is a common sight among divers,’ says Zsilavecz, an avid underwater photographer who brought the shrimp to UCT marine biologist Emeritus Professor Griffiths to identify.

Emeritus Professor Griffiths was unable to identify the species and sent the samples to Professor Wittmann at the University of Vienna in Austria, who confirmed that it was indeed a new species.

Emeritus Professor Griffiths was surprised by the shrimp’s bawdy colouring and ‘fake eyes’. ‘They act like the eye

spots on moths’ wings,’ he explains.

The divers who first saw the small crustacean, a mere 10 to 15 mm long, calls the shrimp ‘stargazer mysid’ because its eyes seem to gaze permanently upwards. The apparently large, upward-staring eyes are just a trick of nature, as the eyes of shrimps don’t have a pupil or iris.

Instead, they are compound eyes like those of insects and consist of many simple elements that each look in a different direction. The vivid ringed patterns are thought to be there to make the eyes appear to belong to a much bigger creature, and hence to scare off predators.

Professor Wittmann only had males among the first few samples sent to him and asked that Emeritus Professor Griffiths and Zsilavecz send him female samples of the stargazer mysid. They collected eight more specimens from the same reef, which they thought looked different to the males. But when Professor Wittmann opened each of the first two vials the shrimps were not females; they were in fact two more completely new shrimp species – and there may be more in the unopened vials.

‘These can form the topic of another paper next year, but we wanted to get the description of this first species published in the interim,’ says Emeritus Professor Griffiths. ‘It’s amazing that we’re still finding so many new species in heavily dived waters such as False Bay, right on our doorstep.’

Finding the stargazer mysid is the latest ‘catch’ in an ongoing partnership between citizen scientists and UCT. ‘We’re a bridge between the public and science,’ says Zsilavecz.

Zsilavecz recently also found a new species of nudibranch (a soft-bodied sea slug) at Long Beach in Cape Town, which is a flashy, fleshy little creature with large green lobes and ‘wings’ that resemble the Sydney Opera House. ‘Some 30 new marine species are found in South African waters annually,’ adds Emeritus Professor Griffiths.

The stargazer mysid. Image: Guido Zsilavecz

Issued by: UCT Communication and Marketing Department

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Books

Identifying trees

201 4 SAK LYS VAN

Suider-Afrikaanse Inheemse Bome

NIGI NG DEN DRO LOG IESE VERE VAN SUID -AFR IKA

Pocket List of Southern African Indigenous Trees/Saklys van Suider-Afrikaanse Inheemse Bome Dendrologiese Vereniging van Suid-Afrika. By H von Dürckheim, B van Wyk, E van den Berg, M Coates Plagrave and M Jordaan for the Dendrological Society of South Africa.

(Rustenburg. Briza Academic Publications. 2014)

This is an academic publication, produced by an academic society and as such is invaluable to those who IETY pursue botany seriously and have the DEN DRO LOG ICAL SOC OF SOU TH AFRI CA ability to read keys to identification.

POC KET LIST OF This fifth edition of the Pocket List Southern African has remained concise, allowing it to Indigenous Trees be carried in the field. Its main aim is to be an aid to memory for the scientific and common names of trees native to the Flora of Southern Africa region. The areas covered are South Africa, Botswana, Namibia, Lesotho and Swaziland.

The book is in Afrikaans and English and the trees are listed in alphabetical order in the book, starting with the Latin name of the genus, followed by the full species name, a distribution map, the tree’s common name in English and Afrikaans, a line drawing of leaves and/or fruits and the countries in the region in which the tree is found. This is followed by a listing of the common names in English and Afrikaans, alongside the Latin name. There is also a list of the common names in the Bantu languages of the areas covered, the changed scientific names where new information has led to changes in classification and the Flora of Southern Africa tree numbers.

This is an indispensable book for anyone who is interested in the diverse tree flora of the region.

Gardening for beauty and charm Orchids in South Africa – a Gardener’s Guide.

By Hendrik Venter. (Pretoria.

Briza Publications. 2014) This book is aimed at people who want to grow orchids, either in their garden or greenhouse, but it is an excellent guide to the group generally. The first chapter covers the history of orchids, the largest group of flowering plant species in the world, 48

11|1 2015

with approximately 30 000 species found in the wild, with more discovered regularly. There are also tens of thousands of man-made hybrids, many of which are registered on a global central database maintained by the Royal Horticultural Society at Kew in England.

Orchids are found everywhere in the world, from sea level to the snowline, but mainly in warmer areas, which should not be a problem for those wanting to grow them locally. Orchids are slow growing – taking 4 - 7 years from seed to flowering, sometimes up to 15 years or longer.

The basic botanical information on orchids is covered well, including the structure of the flower and the different types of orchid flowers and their parts. There is also a section on the growth types, essentially variations of two types – monopodial and sympodial growth. There is a comprehensive glossary of terms placed before the main section on growing the species, which is useful for the rest of the book, which is devoted to how to grow these plants and a comprehensive review of orchids by genus, recommended orchids and indigenous orchids.

There are more than 460 indigenous orchid species, making these good plants for those who wish to stick to indigenous gardening.

Written by Hendrik Venter, who has been growing orchids for 40 years, this is a wonderful introduction both to the species and their cultivation – a must for any serious gardener.

All about aloes Guide to the Aloes of South Africa.

By Ben-Erik van Wyk and Gideon F Smith.

(Pretoria. Briza Publications. 2014) Aloes are such distinctive plants and so common in our landscape that this book immediately appeals to anyone who enjoys the natural world around us.

This book is a lovely, easyto-use guide to all the 155 species of aloe found in South Africa. There are short descriptions and clear photographs of each species in their habitat, with individual photographs of particular distinguishing features. The book is aimed at as wide an audience as possible, including field botanists and naturalists, students and gardeners.

The 12 groups into which the aloes are placed in the book are based mainly on size, growth habitat and branching pattern. This means that closely related

❚❚❚❙❙❙❘❘❘ Books

species that differ in their growth habit may have landed up in different parts of the book, but the aim is for easier identification.

The book is beautifully illustrated with colour photographs of aloe species. The group description for each type of aloe also includes a colour illustration to accompany a clear description of the type of aloe, for example, the creeping aloes. There is an illustrated glossary, explaining the terms used in the book and a clear description of the species relationships and generic concepts around the group. The groups are also described clearly with colour coding for the different habits, for example, tree aloes, rambling aloes and so on. There are also sections on medicinal use, cosmetic and tonic use and conservation.

This book should make it very easy for aloe enthusiasts to identify these fascinating plants.

African animal tales How Crab lost his Head and other animal tales from Africa.

By Nick Greaves, illustrated by David du Plessis.

(Cape Town.

Struik Nature.

2014) The oral traditions of Africa have left a ‘rich legacy’ of stories and many of them are about animals. These legends – why dog and man are friends, when hare tricked leopard, how the vultures lost their sister – have value on many different levels. They are a source of enjoyment and they provide a glimpse into our past.

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Ha-ha hadeda Hagedash the Hadeda. By Charles de Villiers, illustrated

by Claire Norden.

(Cape Town.Struik Nature. 2014) This charming book is a story, told in rhyming verse, about a hadeda that loves to sing – and consequently disturbs the peaceful early morning with her raucous ‘song’. The hadeda ibis is a strange looking bird, of great character, that we all see daily in our gardens and around the countryside, and this book will immediately appeal to children.

The story is about Hagedash and her mate Hagar and their growing family. It draws on the real traits and habits of hadedas and so acts as a source of information as well as entertainment. There is also a full page of stickers for children to take out.

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This in turn gives us insight into our own development and our understanding of the environment and the other animals and plants around us.

The stories in this book are drawn from Xhosa, Tswana, Ovambo – all the various indigenous groups in Africa and are correspondingly diverse. Each species that is the subject of a story is also described and illustrated, with information about its distribution, numbers and conservation status.

Colour illustrations fill the book and make reading it even more enjoyable – a treat for young and old.

11|1 2015

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Back page science

UCLA study finds that regulating body temperature may be a key factor for zebras’ stripes ​ ne of nature’s fascinating questions is O how zebras got their stripes. Now a team of life scientists led by UCLA’s Brenda Larison has found at least part of the answer. The amount and intensity of striping can be best predicted by the temperature of the environment in which zebras live.

Zebras in warmer climates have bolder stripes that cover the entire body. On others — particularly those in regions with colder winters such as South Africa and Namibia — the stripes are fewer and are lighter and narrower. In some cases, the legs or other body parts have virtually no striping.

Analysing zebras at 16 locations in Africa and considering more than two dozen environmental factors, the researchers found that temperature was the strongest predictor of zebras’ striping.

The finding provides the first evidence that controlling body temperature, or thermoregulation, is the main reason for the stripes and the patterns they form.

What’s more, they also found that a zebra’s stripes are unique, like fingerprints, so you can distinguish one zebra from another. Source: UCLA

A mother zebra with a foal in Tanzania’s Tarangire National Park. Image: Brenda Larison

Heat waves becoming more prominent in urban areas, research reveals Prolonged periods of extreme heat increased significantly between 1973 and 2012 in almost half of the urban areas analysed by the researchers.

The frequency of heat waves has increased dramatically over the past 40 years, and the trend appears to be growing faster in urban areas than in lesspopulated areas around the world, a new

study suggests.

‘Our findings suggest that urban areas are experiencing a kind of double whammy — a combination of general climatic warming combined with the heat island effect, wherein human activities and the built environment trap heat, preventing cities from cooling down as fast as rural areas,’ said Dennis Lettenmaier, a co-author of the study and a UCLA geography professor. ‘Everything’s warming up, but the effect is amplified in urban areas.’

Lettenmaier and his co-authors studied 217 urban areas across the globe and found that prolonged periods of extreme heat increased significantly in 48% of them between 1973 and 2012.

The results show that about 2% of those urban areas experienced a significant decline in heat waves. And the change was more dramatic at night: almost two-thirds of the urban areas showed significant increases in the frequency of extremely hot nights.

‘In urban areas, buildings are disrupting the air flow, which affects not only the immediate area of buildings, but apparently the larger regional wind fields,’ Lettenmaier said. ‘The reduction in wind may well be exacerbating the heat island effect.’ Source: UCLA

The polar ring of Arp 230. Image: ESA/Hubble and NASA

Hubble’s view of the polar ring of Arp 230 Arp 230 is a galaxy of an uncommon or peculiar shape, and is therefore part of the Atlas of Peculiar Galaxies produced by Halton Arp. Its irregular shape is thought to be the result of a violent collision with another galaxy some time in the past. The collision could also be held responsible for the formation of the galaxy’s polar ring.

The outer ring surrounding the galaxy consists of gas and stars and rotates over the poles of the galaxy. It is thought that

the orbit of the smaller of the two galaxies that created Arp 230 was perpendicular to the disk of the second, larger galaxy when they collided. In the process of merging, the smaller galaxy would have been ripped apart and may have formed the polar ring structure astronomers can observe today.

Arp 230 is quite small for a lenticular galaxy, so the two original galaxies forming it must both have been smaller than the Milky Way. A lenticular galaxy is a galaxy with a prominent central bulge and a disk, but no clear spiral arms. They are classified as intermediate between an elliptical galaxy and a spiral galaxy.

Credit: European Space Agency / Source: NASA

Fewer surgeries with degradable implants Until now, in cases of bone fracture, doctors have used implants made of steel and titanium, which have to be removed after healing. To spare patients burdensome interventions, researchers are working on a bone substitute that completely degrades in the body. Towards this end, material combinations of metal and ceramic are being used.

No other joint in the human body is as mobile as the shoulder. However, it is also very sensitive and prone to injury, with athletes being particularly affected.

The most common complaints include tendon rupture, which has to be treated surgically. The surgeon fastens the cracks using suture anchors. Such implants used to be made of titanium or non-degradable polymers – with the disadvantages that either they remain in the body after healing has occurred or doctors have to remove them in a second procedure. To avoid this, researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM) in Bremen have developed load-bearing, biodegradable implants that are completely degraded in the body.

In the project ‘DegraLast’, IFAM has worked jointly with the Fraunhofer Institutes for Laser Technology, for Biomedical Engineering and for Interfacial Engineering and Biotechnology in establishing a materials and technology platform to produce degradable bone implants for use in trauma surgery and orthopaedics. These materials are to be gradually absorbed by the body while, at the same time, new bone tissue is formed.

Source: Fraunhofer-Gesellschaft

MIND-BOGGLING MATHS PUZZLE FOR Quest READERS Q uest Maths Puzzle no. 32

What is the only number in which you can add up all it's digits, and then multiply that number by 3 and get your original number?

Answer to Maths Puzzle no. 31: The answer is 11, since the sum of the three numbers in the 2 diagonals is the same (they have the same middle number so 9 + 13= 5 + ? and clearly ? is 17). The bottom row has a sum of 33, therefore the middle number must be 11.

The winner for Maths Puzzle no 31 was Hettie Glass from Cape Town. Well done!

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Win a prize!

Send us your answer (fax, e-mail or snail-mail) together with your name and contact details by 15:00 on Friday, 8 May 2015. The first correct entry that we open will be the lucky winner. We’ll send you a cool Truly Scientific calculator! Mark your answer ‘Quest Maths Puzzle no. 32’ and send it to: Quest Maths Puzzle, Living Maths, P.O. Box 195, Bergvliet, 7864, Cape Town, South Africa. Fax: 0866 710 953.

E-mail: livmath@iafrica.com.

For more on Living Maths, phone (083) 308 3883 and visit www.livingmaths.com.

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