Weird and Wonderful

Illuminating the Northern Lights

The northern lights, or ‘aurora borealis’, are without a doubt one of the most beautiful sights in nature and have inspired many stories to explain their cause, from the twinkling of the Valkyrie’s shields to the spirits of the dead playing football with a walrus skull. However, my personal favourite is that which is told by physics.

Kristian Birkeland was the first to suggest a scientific theory for the Northern lights in the early 1900s but even now the details are not fully understood. The phenomenon involves a complex interplay of solar physics, electrodynamics, and atomic physics. Here I will focus on the most visually spectacular part; how do the Northern Lights get their colours?

The Northern Lights are caused by the interaction of the solar wind with the Earth’s magnetic field. The solar wind consists of a plasma of particles including protons and electrons which are directed towards the Earth’s poles by its magnetic field. When these particles reach the upper regions of the atmosphere, they collide with atmospheric atoms and molecules and gain energy, which excites them.

After a particle has been excited, it moves back to a lower energy state by emitting a photon, the colour of which is determined by the energy difference between its excited and final states. These energy differences are unique to each element meaning each one will emit a unique spectrum of colours. Most of the colours we see in the Northern Lights are caused by just two elements: oxygen and nitrogen. Oxygen is responsible for the green and yellow hues whereas nitrogen causes the reds, purples, and sometimes blue. LH

enAntiomers Are molecular mirror images of each other. This means they have the same chemical composition, however their bond positions are reflected in such a way that the two molecules can no longer be superimposed. This can confer different biological properties to each molecule.

These chemical differences can be experienced in the kitchen. One of the major essential oils in citrus fruit is limonene, which comes in two different enantiomers. The R form of limonene is responsible for the smell of oranges and the S form for lemons. One small change in positions of the atoms causes a drastic change in how we perceive the chemical. It is worth giving them a sniff!

A more extreme example of the effect of enantiomers is thalidomide, a drug which was historically used to treat morning sickness. One thalidomide enantiomer causes birth defects and high infant mortality rates, whilst the other is an effective morning sickness treatment. The problem arose because the molecule tested was obtained from biological sources and only contained one enantiomer; the one that treats morning sickness. However, when the drug was chemically synthesised, a ‘racemic’ mixture was produced, which contains a 50:50 ratio of the two enantiomers. Whilst these chemicals have the same chemical composition, enzymes can distinguish the different enantiomers and respond differently to them. Enantiomers present a big problem in terms of chemical synthesis, especially when making medicines. In some cases the dose simply has to be increased, while for others the enantiomers must be separated or chemically converted into a single enantiomer. One tiny difference has the potential to cause a dramatic change! OK

Stepped-drum Calculators to Math Grenades

How much do you know about the development of the calculator? Today we see calculators as a useful feature on our phone. Yet when they were first invented, they were considered to be technological masterpieces, accomplishing calculations in a fraction of the time that would leave even the greatest mathematicians hunched over their desks for days.

The mathematician and philosopher Gottfried Leibniz developed the concept of stepped-drum calculators (also known as Leibniz’s wheel) as early as 1673. This involved a cranked system, which coupled a counting wheel with ten different sprockets and cogs of varying sizes to give an output in decimal representation. Invented in the 1870s by Baldwin and Odhner, separately, the pinwheel mechanism built on Leibniz’s concept to further improve the mechanical calculator. Both the steppeddrum and pinwheel calculators performed multiplication and division by successive addition and subtraction, while the Millionaire calculator, 1893, was the first direct multiplication machine.

A standout mechanical calculator is the Curta, often referred to as the ‘Math Grenade’, as it resembles the shape of a stereotypical hand grenade. This pocket-sized creation was the first portable calculator. It was developed in the 1930s by Curt Herzstark, an Austrian engineer. Curta calculators were widely considered the best portable calculators available until they were displaced by electronic calculators in the 1970s. KB

Why Position Matters

Enantiomers are molecular mirror images of each other. This means they have the same chemical composition, however their bond positions are reflected in such a way that the two molecules can no longer be superimposed. This can confer different biological properties to each molecule.

These chemical differences can be experienced in the kitchen. One of the major essential oils in citrus fruit is limonene, which comes in two different enantiomers. The R form of limonene is responsible for the smell of oranges and the S form for lemons. One small change in positions of the atoms causes a drastic change in how we perceive the chemical. It is worth giving them a sniff!

A more extreme example of the effect of enantiomers is thalidomide, a drug which was historically used to treat morning sickness. One thalidomide enantiomer causes birth defects and high infant mortality rates, whilst the other is an effective morning sickness treatment. The problem arose because the molecule tested was obtained from biological sources and only contained one enantiomer; the one that treats morning sickness. However, when the drug was chemically synthesised, a ‘racemic’ mixture was produced, which contains a 50:50 ratio of the two enantiomers. Whilst these chemicals have the same chemical composition, enzymes can distinguish the different enantiomers and respond differently to them. Enantiomers present a big problem in terms of chemical synthesis, especially when making medicines. In some cases the dose simply has to be increased, while for others the enantiomers must be separated or chemically converted into a single enantiomer. One tiny difference has the potential to cause a dramatic change! OK