The Kardashev Scale (page 3-6)
Oobleck: Solid, Liquid, or Both? (page 6-7)
Formation of Hydrogen in the Early Universe (page 8-9)
Superfluidity (page 10-12)
The Physics (and Chemistry) Behind Fireworks (page 12-17)
What is the Shape of the Universe? (page 17- 19)
Evidence for the Big Bang (page 19 - 21)
The Kardashev scale is a method of measuring a civilisation’s level of technological advancement based on the amount of energy it can use. It is a scale which classifies hypothetical extraterrestrial civilisations and generally, it divides into three types of civilisations. The method of measuring was proposed in 1964 by a Soviet astronomer called Nikolai Kardashev, but as time progressed, physicists such as Carl Sagan and Michio Kaku have adopted this idea and brought forth their own interpretations. The scale was originally published in a five-page paper called “Transmission of information by extraterrestrial civilisations.” It strongly focused on calculating how powerful a light signal from any point of the universe would need to be for radio scientists at the time to detect it.
Nikolai KardashevKardashev was born into a family of professional revolutionaries who worked with the Bolsheviks in 1932, just after what many would call the golden age of physics. In 1978, he started a project called the Space Very-Long-Baseline-interferometry (VLBI) mission Radio Astron. This
mission covered more than thirty years and was finally launched in 2011. It uses a global network of radio dishes as one radio telescope the size of the earth. The VLBI method was used in 2019 and 2022 by the Event Horizon Telescope to capture the black hole images. The main goal of the mission was originally to study astronomical objects with an angular resolution of up to a few millionths of an arc second. On top of this, Kardashev is thought to have predicted the existence of pulsars1 in his papers before they were originally discovered.
On the Kardashev scale, there are three main categories simply typed I, II, and III. The overall status of a given civilisation is the product of two things: energy and technology. The better the technology, the more energy a civilisation can harness.
1. Type I is described as a “technological level close to the level presently attained on the Earth.”
2. Type II as “a civilization capable of harnessing the energy radiated by its own star.”
3. Type III as “a civilisation in possession of energy on the scale of its own galaxy”
The Earth’s current status is a Type I civilisation on the Kardashev sphere, whereas a civilisation with a working Dyson Sphere2 a structure harvesting its
1 A pulsar is a highly magnetised neutron star that emits beams of electromagnetic radiation out of its magnetic poles
2 A Dyson Sphere is a hypothetical megastructure that completely encompasses a
star's light would qualify as type II. The scale is only concerned with energy consumption on a cosmic scale and since the 1960s, the scale has had a few extensions proposed beyond the three originally defined by Kardashev. Scientists such as Carl Sagan believe our civilization has a rank more like 0.7 since we have not harnessed the equivalent of the entire energy of the Earth.
Energy development for Type I, as defined by Kardashev, is limited to one planet and the civilisation has to be able to harness all the energy available. Energy sources such as Nuclear Fusion, geothermal power, and other renewables are a given. The energy required to be at a Type I civilisation implies the conversion of about 2kg of matter to energy per second. An equivalent energy release could theoretically be achieved by fusing around 280kg of hydrogen into helium per second. As well as this, antimatter in large quantities would prove a mechanism to produce power on a scale several magnitudes above the current level of technology. The collisions would release four orders of magnitude greater than fission and two orders greater than fusion. Renewable energy would have to be through solar power, wind, biofuel, or hydroelectricity;
star and captures a large percentage of its power output
but, there is no feasible way with Earth’s current technology to use the equivalent of the Earth’s total absorbed solar energy as this could only be done by completely coating the surface with man-made structures.
The energy development for Type II is that the civilisation has managed to harness the power of their local sun. An example strategy for this is to construct a Dyson Sphere or a Swarm around it. The civilisation is y to have colonised multiple planets in their solar system and use the same constructions created by a Type I civilization but applied to a large number of planets in multiple planetary systems. Another means of harnessing energy would be to feed a stellar mass into a black hole and collect photons (light particles) emitted by the accretion disk, reducing a black hole’s angular momentum known as the Penrose Process, this process, may however only be possible for a Type III civilization to achieve.
Energy development for a Type III civilisation would use the same techniques employed by a Type II civilisation but applied to all possible stars of one or more galaxies and they would be able to gather the energy released from a supermassive black hole which exists at the centre of most galaxies. Another method of capturing energy would be through gamma-ray
bursts or quasars3 , if a civilisation could capture this energy, they would have an energy source comparable to small active galaxies.
As mentioned earlier, Michio Kaku is a theoretical physicist who speaks on the Kardashev scale. Alongside this, he works on string field theory and is currently pursuing Einstein's research to unite the four fundamental forces. Kaku estimates that we may be anywhere from 100 to 200 years away from graduating into a type I civilization on the Kardashev scale.
Furthermore, Carl Sagan was a pioneer in physics history, understanding that if the countless stars in the universe are suns, they will have their own planets. He also considered how planets may have habitable moons such as Titan and Europa and that Venus has an atmosphere which enhances the greenhouse effect, making it the hottest planet in the solar system. He was also a pioneering scientist in SETI (Search for ExtraTerrestrial Intelligence). Sagan’s main argument to do with the Kardashev scale was that the categories represented too vast of leaps in energy consumption and so he proposed dividing each Type into smaller categories (Type 1.1, 1.2, etc).
3 A Quasi Stellar Object with an extremely luminous active nucleus powered by a supermassive black hole
Carl Sagan
Sagan's involvement in SETI was incredibly important. In this scientific search, scientists monitor electromagnetic radiation for signs of transmissions from civilisations on other planets. The first scientific meeting of the SETI institute had ten attendees including Frank Drake and Sagan who used the Drake equation to speculate that the number of civilisations was roughly between 1,000 to 100 million civilizations in the Milky Way galaxy This scientific investigation began shortly after the advent of the radio in the early 1900s, and efforts internationally have been going since the 1980s. The first telescope designed specifically for SETI use was the Allen Telescope Array, which is a radio telescope array of which the first 42 elements have been constructed and are capable of conducting searches every day.
Finally, the James Webb Space Telescope is most recent modern day telescope which has the purpose of “help[ing] scientists understand how we got herehow, from the tangle of molecules, stars, galaxies, black holes, and planets that populate the universe, the ingredients necessary for life emerged and combined to make this place called
Earth” (per National Geographic). The telescope cost $10 billion and is too big to fit inside one of the worlds biggest rockets, the Ariane 5, without being folded up and will see the universe primarily in infrared light. The sensitivity of the telescope will help it directly observe alien worlds, although this was not the primary purpose of the telescope. In 1989, when the concept of the James Webb was conceived, planets orbiting other stars (exoplanets) had not yet been discovered. John Grunsfeld, a former NASA astronaut and STScI (Space Telescope Science Institute) deputy director said that the “James Webb is sold as studying galaxies, but i think the greatest discovery may be a habitable Earth-like exoplanet That’s what’s going to blow everybody away. ”
With modern technology rapidly increasing, the capturing of two black holes, and the innovations in space
Alexia Noirot UVI-5
Oobleck is one of those things we would make and play with as kids. A simple mixture of water and cornstarch creates a liquid suspension but when a force is applied (i.e from one's hand pressing down or squeezing it) the liquid feels and behaves as a solid.
travel from companies such as SpaceX, the amount of time for our civilization to grow to a type 1 civilization on the Kardashev Scale may be within the lifetime of a child born tomorrow
Oobleck is an example of a non-newtonian fluid. A Newtonian fluid is one which maintains a constant viscosity at any given temperature. Viscosity is a measure of a fluid's resistance to flow. A fluid that is highly viscous has a high resistance and flows slower than a low-viscosity fluid. An example of a high viscous fluid would be honey, whereas a low-viscosity fluid could be water. A non-newtonian fluid does not have a constant viscosity.
In physics stress and strain are talked about a lot in regards to materials. Stress is the force that is applied to the body, and strain is the effect the body feels as a result of the stress. For example: hitting a hammer against a sheet of metal. The force applied by the hammer creates stress and the result of that is described as strain (possible deformation of the metal). Newtonian fluids don’t respond much to stress. Imagine hitting a pool of water with a hammer, the water simply goes around the hammer, it does not resist the stress applied and it is essentially unchanged. The water does not resist the force of the hammer and does not show any signs of strain.
Non-newtonian fluids change their viscosity or flow behaviour under stress. A sudden application of a force (stress) can cause the material to get thicker and act as a solid or in some cases become less viscous. Removing the stress will allow the material to return to its original state. In the case of oobleck, its viscosity or resistance to flow increases with an applied stress. This type of behaviour is called dilatant or shear thickening.
How come this happens with oobleck:
The explanation for this strange behaviour lies in the shape of the cornstarch molecule. Cornstarch can dissolve in hot water, as the heat disrupts the bonds and makes them soluble. Cornstarch consists of long chains of starch molecules that don’t dissolve in cold or room temperature water. As a suspension mixture, solid particles spread through the water without dissolving - this is key to its properties. When a sudden force is applied to oobleck, the starch grains rub against each other and lock into position. The phenomenon is when shear thickening occurs and it basically means particles in a dense suspension resist further compression in the direction of shear. When oobleck is at rest, the high surface tension (the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as insects to float on a water surface without becoming even partly submerged) of water causes water droplets to surround the starch granules. Water acts as a liquid cushion or lubricant, allowing the grains to flow freely. The sudden force pushes the water out of the suspension and jams the starch grains against each other.
And so to conclude, oobleck can act as both liquid and solid depending on its environment. Kind of cool no?
Hydrogen is probably one of the most important elements on our planet followed by Carbon and Oxygen. Binding with Oxygen we get water, binding with carbon we get many of the organic molecules that make up our body. About 90% of the atoms and 75% of elemental mass of the universe is hydrogen.
But why are we concerned with knowing how much hydrogen there is in the universe? What does it matter to us?
The large abundance (amount) of Hydrogen in the universe has puzzled astrophysicists for many years, but it is the Big Bang Theory that can explain this large abundance.
The big bang theory states that the universe started out in a very hot, dense state (perhaps infinitely hot and infinitely dense) and has been expanding ever since. Immediately after the big bang, the universe was too hot and too dense for elements to form. Hydrogen didn’t appear until the universe had expanded and subsequently cooled enough for the first protons and neutrons, and later simple atoms, to form. Between about 10^-12 (ten to the
power of minus twelve) and 10^-6 seconds after the Big Bang, neutrinos, quarks, and electrons formed. These are part of the Standard model: a model used by physicists to show every fundamental particle known to mankind of which further particles are made of. For example, quarks are part of the standard model but protons are not because they are made of quarks (two up quarks and one down quark, written uud) and likewise neutrons are made of two down quarks and one up quark (udd) - to read more about this check the article linked at the bottom. As the universe cooled, the quarks condensed into nucleons (protons and neutronscomponents of the atomic nucleus). This process is similar to the way that steam condenses to liquid droplets as water vapour cools. Protons and Neutrons began forming, from around 10^-6 to 1 second after the big bang. Within about three minutes, the Universe cooled enough to around 1 trillion degrees Kelvin, the quark plasma cooled to a Hadron gas where protons and neutrons could fuse to form hydrogen and some helium nuclei, this is called nucleosynthesis. But after about 20 minutes, nucleosynthesis ended and no further nuclei could form.
The problem at this point was that electrons couldn’t stay in orbit around any atomic nucleus because of the immense heat and radiation still flooding the universe. Shortly after any neutral atoms would form (neutral atoms contain the same number of protons and electrons, and thus carry no
overall charge), they were knocked apart again by energetic radiation. Finally, after 380,000 years or so, the universe had again expanded and cooled enough for conditions to favour electrons staying in orbit around atomic nuclei. This is when recombination occurred neutral hydrogen (and helium) finally appeared because they could “recombine with” (hold on to) electrons without easily losing them to stray radiation.
The majority of the helium in our universe is Helium 4, this is its most stable isotope. The vast majority of this was formed through the recombination of electrons with pre-existing helium nuclei. However, large amounts of new helium is being created by nuclear fusion of hydrogen in stars. It takes four hydrogen atoms to fuse into each Helium nucleus. Fusion is a difficult process to mimic on earth but the conditions on stars, like our Sun, is perfect The stellar core is around 14 million Kelvin, a substantial energy barrier of electrostatic forces must be overcome before fusion can occur. The repulsive force between two positive protons must be overcome, this requires lots of energy and pressure which is provided by the conditions on the Sun and sun like stars. Hydrogen ‘burning’ initiates the energy source of stars and leads to the formation of Helium.
Immense amounts of energy is released from the process of fusion. The process releases energy because the total mass of the resulting single nucleus is less than the mass of the two original nuclei. The leftover mass becomes energy. Probably the most well known equation in physics - E=mc2 - can be used to describe this. ‘M’ denotes the missing mass in the helium nuclei, ‘c squared’ denotes the speed of an electromagnetic wave (3 x 10 ^8 squared, equal to 9 x 10^16) and ‘E’ is the energy that any mass has at rest If E and m are proportional, c^2 is the proportionality constant which describes how a tiny amount of mass can be converted into enormous amounts of energy
In summary, hydrogen was created very early on in the lifeline of the universe. Despite the fact that 380,000 years seems like a huge amount of time, the universe has been around for approx 13.8 billion years. The process of fusion forms helium and all other elements known to mankind. Masses of pressure are needed to force nuclei together and this has not been replicated on earth yet, but once we have figured out how too it has potential to be a massive power source.
If this process could be mimicked on earth, it has great potential to solve the clean energy crisis on our hands.
● More information on the Standard model:
https://home.cern/science/phys ics/standard-model
A superfluid is a frictionless or zero viscosity fluid; it flows without any loss of kinetic energy and when it is stirred, it forms vortices (whirlpools) that continue to rotate indefinitely. They will do that because of its frictionless characteristic. Superfluids occur in two isotopes (equal number of protons but different number of neutrons in the nucleus) of helium, He-3 and He-4, when they are liquified to cryogenic temperatures from -150ºc to Absolute Zero (-270ºc). This temperature is where molecular motion ceases to occur.
Superfluids also exhibit the so-called “fountain effect” where a container with a superfluid empties itself
Superfluids are often related in conversation to Bose-Einstein Condensates (BECs). They are similar because a BEC is when a state of matter - that is typically formed when a gas of bosons at very low densities - is cooled to temperatures close to Absolute Zero. A boson is a type of particle that includes the photon as well as atoms such as He-4. These condensates can share a quantum state5 and were first predicted in 1924-1925 by Albert Einstein who was following and crediting Satyendra Bose in the new field which is now known as Quantum Physics. Einstein proposed that cooling bosonic atoms to a very low temperature would cause them to fall/”condense” into the lowest accessible quantum state, resulting in a new form of matter (the Fifth state of matter). The important thing to remember is that not all BECs are superfluids, and not all superfluids are BECs.
spontaneously. Superfluids can also be in perpetual motion as a fountain which can be seen in a video.4
A superfluid creeps up the walls of the cup's wall and comes down on the outside forming a drop. This continues until the cup is empty
The History of superfluidity begins in 1908 when physicist Dr Onnes liquified Helium, which is usually in the state of matter of gas. The melting point of He is -272.2ºC and the boiling point is -268.9ºC. The boiling point is reached before the melting point and so in 1910, Onnes discovered that when Helium was cooled below 2.2ºK, it abruptly stops boiling.
4 https://www.youtube.com/watch?v=UNpKCYZFfDU
5 A quantum state is any of various states of a physical system (such as an electron) that are specified by particular values of attributes (such as charge and spin) of the system and are characterised by a particular energy Merriam-Webster.com
Further, in 1923, Onnes, and another physicist, Dana, measured Helium's specific and latent heat and observed a strange discontinuity in the process which they failed to explain.6 Later, in 1935, Doctors Wilhelm, Misenerand, and Clark measured the viscosity of liquid helium with a torsion pendulum and found that the viscosity sharply decreased below the lambda point. Furthermore, in 1935, Kapitsa also worked on the viscosity of the superfluid below the lambda point Kapitsa had an intuition that He-II had something in common with superconductors, but during his work, he was taken by Stalin to work on the USSR's nuclear arsenal.
Similarly, Lev Landau was also working on superfluids, but he was arrested for being an author of a leaflet criticising the Soviets. Landau was born in Baku and studied at the Leningrad Physico-Technical Institute where he worked among many scientists. He also worked in
6 Keemson and Wolfke were also working on liquid helium, but it was not until 1927 that they identified a transition between the two phases at 2.17ºK and named it Helium-I above it and Helium-II below, the transition was known as the Lambda Line.
Copenhagen under Niels Bohr who is renowned for proposing the theory for the Hydrogen Atom; that Electrons move around a nucleus, but only in prescribed orbits, and if electrons jump to a lower-energy orbit, the difference is sent out as radiation. Landau’s work branches through fluid mechanics and quantum field theory, and a large portion of his papers refer to the theory of the Condensed state. After Kapitsa’s discovery of the superfluidity of liquid Helium, Landau’s research led him to construct the complete theory of quantum liquids at very low temperatures. He consequently won the Nobel Prize in 1962 “For his pioneering theories for condensed matter, especially liquid helium”
Superfluids are also slightly controversial when discussing the Second Law of Thermodynamics (SLT). The law stands as “the entropy of an isolated system always increases”, in other words, as energy is transferred or transformed, more and more energy is wasted. But, Physicist Dr Yongle Yu has found a possible loophole in which entropy actually decreases with time.7 This is because the SLT does not correspond to a built-in rule in Quantum Mechanics, and so Dr Yu argues that it is quantum mechanics rather than the SLT which governs nature. In an equation, it can be shown that superfluid He-4 contradicts the SLT and that it is possible to convert thermal energy in the environment into useful energy.
7 https://arxiv.org/pdf/1611.02566.pdf
Researchers at the Argonne Laboratory say that they have found a loophole to show that entropy does decrease on a microscopic scale and only in the short term. These researchers studied the H-theorem on a quantum scale, more is explained:
https://www.sciencealert.com/physicis ts-say-they-ve-found-a-way-to-break-th e-second-law-of-thermodynamics The ultimate goal is to develop scientific models that unify quantum mechanics with gravity This is known as Grand Unified Theory, where all forces are “unified”, since quantum mechanics already unifies three of the four known fundamental interactions which are the Electromagnetic, Weak, and Strong. This can be seen through Superfluid Vacuum Theory (SVT), where the fundamental physical vacuum is viewed as a superfluid or a Bose-Einstein Condensate. In space, dark matter and particles are substances that flow with zero friction, and SVT could explain how atoms move at similar temperatures in space. Currently, researchers are looking at nebulas with high energy x-rays and gamma rays with hopes that changes in the radiation as it travels to Earth will prove the theory of the Superfluidity of space.
Alexia Noirot UVI-5
Fireworks are one of those things that people see and think ‘oh that's so cool!’ but have you ever wondered about how they work?
The source of most fireworks is a small tube called an aerial shell that contains explosive chemicals. All the lights, colours, and sounds of a firework come from these chemicals. The aerial shell is made of gunpowder and small bits of explosive compounds, known as stars, are contained around them. Stars are round pellets ranging in size from a pea to a golf ball and they are responsible for the colour of the firework. There are six main ‘ingredients’ for a successful firework:
● A fuel source
● An oxidising agent
● A reducing agent
● A regulator
● A colouring chemical
● A binding agent
I will talk about each of these separately to describe their purpose in the fireworks.
A superfluid fountain:
The Fuel source:
The most common fuel source for fireworks is gunpowder. It consists of potassium nitrate (75% by weight), charcoal (15% by weight), and sulphur (10% by weight). Charcoal is just a compound of carbon.
Oxidising Agent:
Firstly, the oxidising agents. The three main oxidising agents used in fireworks are: nitrates, chlorates and perchlorates. In the name ‘oxidising agent’ one can assume that their main purpose is to provide oxygen for another chemical or reaction. We know that oxidising agents are the chemical which is reduced (reduction is the gain of electrons), and so they help the other chemical become oxidised (lose electrons by taking electrons from them.
Each oxidising agent has its respective redox equation:
(X denotes the ion the oxidsing agent is bonded too, this is general and not specific to the compound)
Nitrates:
XNO3 —> XNO2 + ½ O2
Chlorates:
2XClO3 —-> 2XC l + 3O2
Perchlorates:
XClO4 —-> XCl + 2O2
nitrate compound used. Avogadro’s Constant (6.02 x 10^ 23) is used to define the number of compounds/molecules in one mole. Chlorates are the most effective oxidising agent in firework manufacturing. The reason being: Chlorates retain the perfect amount of oxygen at the point of explosion, which creates the most impressive combustion. Alternatively, perchlorates retain even more oxygen, but have improved chemical stability – making them less likely to explode. Nitrates use only one-third of their oxygen potential, resulting in an underwhelming firework explosion.
Reducing agents:
Now that we’ve talked about oxidising agents, it only seems right to talk about their partners: the reducing agents.
The most common reducing agents are sulphur and charcoal (compound of carbon) When ignited, these materials react with oxygen (produced from the oxidising agent) to create sulphur dioxide and carbon dioxide, respectively These gases fuel the firework through its path of travel, prior to explosion.
S + O2 —--> SO2
C + O2 —--> CO2
Chlorates are the most effective oxidising agent, they produce 3 moles of oxygen for every two moles of the chlorate compound. Alternatively, nitrates are the worst oxidising agent, producing only half a mole of oxygen for every mole of the
The two equations can also tell us the standard enthalpy change of combustion for carbon and sulphur. Standard enthalpy change of
combustion is defined as ‘the enthalpy change when one mole of a compound is completely combusted in oxygen under standard conditions (298 degrees Kelvin and 100KPa of pressure) As we know, combustion is an exothermic reaction so heat energy is given out by the system.
ΔH= 394 kJ mol 1 for carbon
ΔH=-297kJ mol-1 for sulphur
The reaction of carbon is more exothermic than sulphur, therefore more heat energy is released during the combustion of carbon.
faster. One would change this depending on how high up in the sky the firework is designed to explode.
The Colouring Chemical: (arguably the best bit of this article and the only physics-y bit)
The part everyone has been waiting for: how do fireworks get their colour? To put it simply, the answer lies in the flame tests we all learnt in GCSE chemistry But to explain how these flame colours arise, a little bit of particle physics is required.
Regulators are often made from various metal powders and are essential to firework safety As the technical term "regulator" suggests, by adding small amounts of metal to the firework mix, the speed of the explosive reaction can be regulated, the inclusion of metal creates a slower burn and thus, a delayed explosion. Regulators make all the difference in fireworks as one doesn't want the explosion to occur by the ground but rather when the shell is at the top of its trajectory The regulator acts as a ‘stopper’ and prevents the actual explosive part from touching until it has all reacted. The size of the metal chunks can alter the rate of explosion. By using larger chunks, it takes longer for all the regulators to react and the path to essentially be ‘clear’ for the actual firework part to combust. In contrast, using smaller chunks/powdered metal results in the rate of ration of the regulator is faster and so the combustion of the firework is
Electrons are held in quantum shells around the nucleus of an atom. We refer to the first shell as the ‘ground state’ of n=1, the following shells are denoted n=2, n=3 and so on. When electrons are bombarded with energy (from for eg a flame) they absorb the energy and become excited. When excited, electrons jump to a higher energy level. Once at the higher level, they become de-excited as the electron wants to return to the ground state as it is more energetically stable. Upon falling, the electron re-emits the energy that it previously absorbed. This energy leaves the atom as light (or a photon). Light can be modelled as a particle with each particle of light (photon) holding energy (E) equal to Planck’s constant
(h) times frequency (f). We can write this in the equation E=hf. From gcse waves, we know that the speed of any wave ( c) is equal to the frequence times the wavelength (Λ): c=fΛ, by rearranging for f and substituting back into the first formula, we get: E=hc/Λ. So each photon of light contains this amount of energy When the electron absorbs this, it rises to a higher state. And as it falls back down, it releases that amount of energy. The colours we see are related to the wavelength of the photon emitted. From the electromagnetic spectrum (EM spectrum) we can decipher what colour the photon will be: red having a wavelength of approx 650 nm, and blue having a wavelength of approx 350 nm. The rest of the colours fall in between. But how come different elements give different colours? The spacing between quantum shells is specific to the element in question. The different spacing of energy levels means that a different amount of energy will be released per element And so, different elements produce different colours when their electrons are excited.
The Binding Agent:
the composition together. Dextrin is a water-soluble binder.
Now that we know how all the little bits work inside the firework, it’s time to put them together and find out how the whole thing goes from a shell in the ground to colours in the sky. The explosion of a firework happens in two steps: The aerial shell is shot into the air, and then it explodes in the air, many feet above the ground. To propel the aerial shell into the air, the shell is placed inside a tube, called a mortar, which is often partially buried in sand or dirt A lifting charge of gunpowder is present below the shell with a fuse attached to it. When this fuse, called a fast-acting fuse, is ignited with a flame or a spark, the gunpowder explodes, creating lots of heat and gas that cause a buildup of pressure beneath the shell. Then, when the pressure is great enough, the shell shoots up into the sky
After a few seconds, when the aerial shell is high above the ground, another fuse inside the aerial shell, called a time-delay fuse, ignites, causing the bursting charge to explode. This, in turn, ignites the black powder and the stars, which rapidly produce lots of gas and heat, causing the shell to burst open, propelling the stars in every direction.
Binders are used to hold what is essentially the mixture of the firework together in a paste like mixture. The most commonly used binder is known as dextrin, a type of starch which holds
During the explosion, not only are the gases produced quickly, but they are also hot, and they expand rapidly, according to Charles’ Law (v1/t1 = v2/t2), which states that as the temperature of enclosed gas increases,
the volume increases, if the pressure is constant The loud boom that accompanies fireworks is actually a sonic boom produced by the expansion of the gases at a rate faster than the speed of sound! If the stars are arranged randomly in the aerial shell, they will spread evenly in the sky after the shell explodes. But if the stars are packed carefully in predetermined patterns, then the firework has a specific shape.
The mental picture of the universe many of us have is an infinite expanse with no shape, but is this a true perspective?
Our universe is smooth and homogeneousin other words, everywhere in the universe will have a similar average density of luminous matter and will look the same at any instant in time - because of this, the variety of possible shapes the universe can hold will be limited There are two main theories for the shape of the universe: either that it is flat or spherical.
Euclidean space is a 2D or 3D space in which the rules of Euclidean geometry apply, for example angles in a triangle sum to 180° and all right angles are congruent Euclidean space could either be flat (as shown in Fig. 1) or manipulated into other forms, an interesting one being the flat torus shape (Fig. 2). This is a rather special shape as there are some instances where,
although the light is travelling in a straight line, it would seemingly be going in a circle around the universe to end up where it started This is because the topology has been distorted when creating the curved structure Theoretically, if you faced one of these directions and there was nothing obstructing the light’s path, the light emitted from behind you would travel around the universe along that straight line until it met your eyes and you would see the back of yourself (Fig 3) You would, however, only be able to notice this phenomenon if the universe was small enough that over the period of time the light has taken to reach your eyes you are able to recognise what it is you are looking at, as by that point the image you are seeing may be from so long ago that the universe looks drastically different now Since spotting copies of ourselves in the universe is imaginably very difficult, scientists have been attempting to find repeating features in the universe by closely analysing the cosmic microwave background radiation (CMBR) left over from the Big Bang.
Rather than Euclidean space our universe may instead be spherical We are all familiar with 2-spheres, such as a football or the earth, however, a 3-sphere is an object with 3 dimensions that folds to form the boundary of a sphere in 4D. Life in a 3-sphere is hard to imagine as it would be vastly different from life in flat space. Nevertheless you can try to picture what it would be like by considering yourself to be a 2D being living in a 2-sphere. This sphere would be your entire universe so you wouldn’t be able to access or even see
the surrounding 3D space. Just as in a flat universe, the light will travel in straight lines but since you are in a sphere they would actually be circles around the sphere
(Fig 4) Another visual occurrence that would happen to a 2D inhabitant of a
2-sphere would be as follows Imagine yourself at the north pole and someone walking away from you towards the south pole As they approach the equator they will appear to get smaller since your visual circle is expanding and they take up a smaller percentage of it Yet, unusually, as they pass the equator and enter the southern part of the sphere they would appear to get bigger since your visual circle shrinks (Fig. 5). Furthermore, if no one was at the south pole you would see yourself as the light coming off you will travel all the way around the sphere until it returns to you Now, as you may have noticed, we do not see ourselves when we look to the universe nor do we see celestial objects increasing in size as they move away. But, as with the flat torus, just because we don’t see it, that doesn’t mean it can’t exist Perhaps In closing, most evidence indicates a flat universe Despite this, when considering the colossal scale of the universe it could also be easy to conclude that maybe we can only see a very small portion of the universe, which appears to have no curvature, but when knitted together with the multitude of other pieces beyond our view an interesting curved shape is revealed. So perhaps it is more apt to finish by saying that our observable universe is almost undoubtedly flat, but beyond that it is impossible to tell the circumference of the spherical universe is so large that it is greater than the observable universe In a spherical universe the geometry we are so familiar with would be distorted, for example the angles in a triangle would seem to sum to greater than 180° since straight lines would become curved and create a “puffy” triangle For this reason we can test whether the universe is curved or not. By measuring each cold and hot spot in the universe its diameter across and its distance from the earth are known, allowing us to form three sides of a triangle From here the angle the spot subtends from the sky can be
measured so that we can see whether the lengths and angles fit a spherical universe or not. The majority of research suggests that the universe is flat, however there are scientists who have contradicted this theory however it is largely thought that their evidence was as a result of statistical flukes
In closing, most evidence indicates a flat universe. Despite this, when considering the colossal scale of the universe it could also be easy to conclude that maybe we can only see a very small portion of the universe, which appears to have no curvature, but when knitted together with the multitude of other pieces beyond our view an interesting curved shape is revealed. So perhaps it is more apt to finish by saying that our observable universe is almost undoubtedly flat, but beyond that it is impossible to tell.
Introduction:
The Big Bang Theory is the theory used to explain the creation of the universe It states that the universe started in a hot, dense state and has been expanding ever since Some suggest that it could have been infinitely hot and infinitely dense. Up until the 1930s, astronomers thought that the universe was infinitely large and static but since, new theories have been produced to suggest otherwise This essay will discuss the relevant theories that support the Big Bang Theory: Galactic Redshift, Hubble’s Law, Cosmic Microwave Background Radiation, Dark Energy and Hydrogen to Helium Abundances
Observing Galactic Doppler Shift can be done through analysing absorption/emission spectra from distant galaxies A reference spectrum is used against the observed one to calculate the difference in wavelength This can be used to calculate how much redshift is present from the galaxy.
This supports the Big Bang Theory because if the universe was not expanding, no redshift would be present The fact that redshift is observable in these spectra shows that the galaxy or star being observed is moving away from us on Earth It also shows that the galaxy is moving away from us at an increasing rate If we on earth and the galaxy far away were moving at the same velocity, there would be no relative speed between us and so no redshift would be observed. Since we do observe redshift, the galaxy must be moving at a higher velocity than us so it must be accelerating at an increasing rate.
Galactic Redshift: d to This is absolute be treated or a source he avelength light that e observe creases e to the ppler effect The waves are pushed towards the longer wavelength side of the Electromagnetic spectrum and we say that they have been redshifted The faster the relative motion is between the source of the light and the observer results in a higher value for redshift
Hubble’s Law:
Edwin Hubble was the first scientist to suggest that the universe was expanding. He did so by using Type 1a Supernovae to calculate distances to galaxies. Using the redshift calculated from spectra, recessional velocity could be calculated
This can be used to calculate
��/�� = ��/�� redshift and the galaxy's velocity (v) The velocity calculated can then be used to calculate the distance to the galaxy:
�� = ���� and d is the distance to the galaxy
Where H is Hubble’s constant
On a graph showing recessional velocity against distance, a directly proportional relationship was found. The gradient of the plotted graph is Hubble’s constant (65 kms^-1MPc^-1)
Analysing this graph can show us that as the distance to a galaxy or star increases, its recessional velocity increases This supports the Big Bang Theory.
The Big Bang model predicts that at the moment the universe was created, a large burst of short wavelength electromagnetic radiation (probably Infra-Red) was produced in all directions As the universe has expanded (and subsequently cooled) the wavelength of this radiation has been increased out to the microwave region These waves only started propagating once the universe turned transparent They can be detected by a microwave specialised telescope and can be seen to be the same in whichever direction the telescope is pointed at.
CMBR has a perfect blackbody spectrum
This means a continuous spectrum of all wavelengths The peak in this type of curve can be used to calculate the temperature of the universe though Wien's Law. This peak falls into the microwave region of the Electromagnetic Spectrum. The Big Bang Theory suggests the temperature is around 2.7 Kelvin, and CMBR’s Black Body
curve supports this estimate There are small fluctuations in calculated temperatures due to tiny energy density variations which have been present since the early universe.
CMBR also contributes to the cosmological principle, which is the second assumption of the Big Bang Model. This states that the observer’s view of the universe should not depend on the direction of observation or location CMBR can be seen to be homogeneous (every part is the same) and isotropic (everything looks the same in every direction - there is no centre)
Dark
and Matter:
All mass in the universe feels the gravitational force, one of the four fundamental forces in the Universe. This force is always attractive and is only zero at infinity. In theory, this attractive force felt by all objects with mass should slow down the rate of expansion but that is not the case with the universe. Scientists believe that this is due to something they have called Dark Matter which is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Dark Matter is composed of particles that do not emit, absorb or reflect light so cannot be detected by observing electromagnetic radiation. This means that it cannot be directly seen, which makes its existence hard to prove. We can however measure the effect it would have on the universe, its acceleration. Since that is something we deem to be true, dark matter, in principle, should exist
Dark Energy is a form of energy that fills the whole space of the universe, it is thought to be the only energy source
responsible for its acceleration Dark energy has never been directly measured or observed but it is necessary for the universe to continue expanding For the Big Bang model to be true, dark matter and energy must exist
Hydrogen to Helium Abundances: The Big Bang Model predicted a ratio of hydrogen:helium. This was thought to be 4:1, but when measured was actually 3:1 This ratio was formed through the formation of sub–atomic particles
Between about 10^-12 and 10^-6 seconds after the Big Bang, neutrinos, quarks, and electrons formed. As the universe cooled, the quarks condensed into nucleons Protons and Neutrons began forming, from around 10^-6 to 1 second after the big bang. Within about three minutes, the Universe cooled enough to around 1 trillion degrees Kelvin, the quark plasma cooled to a Hadron gas where protons and neutrons could fuse to form hydrogen and some helium nuclei, this is called nucleosynthesis But after about 20 minutes, nucleosynthesis ended and no further nuclei could form.
The problem at this point was that electrons couldn’t stay in orbit around any atomic nucleus because of the immense heat and radiation still flooding the universe. Shortly after any neutral atoms would form, they were knocked apart again by energetic radiation. Finally, after 380,000 years or so, the universe had again expanded and cooled enough for conditions to favour electrons staying in orbit around atomic nuclei. This is when recombination occurred neutral hydrogen (and helium) finally appeared because they could “recombine with” electrons without easily losing them to stray radiation
The majority of the helium in our universe is Helium 4, this is its most stable isotope. The vast majority of this was formed through the recombination of electrons with pre-existing helium nuclei. However, large amounts of new helium is being created by nuclear fusion of hydrogen in stars. It takes four hydrogen atoms to fuse into each Helium nucleus
This provides evidence for the early universe and its constituents and thus is in favour of the Big Bang model.
