School Presentation on Quantum Physics

Note from mum:
This is Jacques' English homework. He has to choose a subject of interest (any subject), and prepare a presentation. The presentation itself is on Power Point slides. I put them together here so that the reader can read them together with the pictures. Have a nice journey into Jacques' world....!

Quantum physics is the study of particles, their behaviour and everything about the quantum world.

The atom was first thought up by Democritus, the Greek philosopher, who had believed that everything was made up of tiny building blocks which he named ‘atomos’, meaning indivisible. It is the smallest part of an element which ‘defines’ that element. It consists of electrons and a nucleus, consisting of protons and neutrons. The electrons can only orbit the nucleus in set shells. Proportionately the space between the electrons and nucleus are so massive that if we were to take that space out of the whole human race, then all 6.8 billion of us would be no bigger than a sugar cube.

Protons and neutrons are not the smallest particles; in fact the proton is rather large relative to most particles. Within the proton and neutron there lay three quarks; there are two up quarks and one down quark in a proton whilst the neutron is made up of two down quarks and one up quark.
There are six types of quarks, as you can see on the board, which makes up most matter in the universe. Quarks belong to a group called elementary particles which consist of, literally, the smallest particles and are the main building blocks of the universe.
Gluons, photons and the w and z bosons are the four force carriers; photons mediate light, gluons sticks particles together whilst the w and z boson mediate the nuclear weak force, which causes radiation.
The three neutrinos are thought to be the main ingredient of dark matter, a virtually invisible and ‘ghostly’ form of matter which makes up about 90-95% of the universe. These neutrinos travel near the speed of light (300,000km/s), they have a neutral charge and almost always pass through regular matter making them extremely difficult to detect even though the Earth is bombarded by millions of tons every day!

Every particle has an antiparticle which has exactly the same mass and spin but with an opposite charge. The Universe is almost exactly symmetrical in the quantum world and so this brings up the question: why is there more matter than there is antimatter in the Universe presently? The answer lays in CP violation, charge conjugation and parity violation, which basically states that this symmetry is only a rough approximate.

In 1894 Max Planck began to work on the problem of black body radiation; how the intensity of the electromagnetic radiation (radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, x-rays and gamma rays) emitted by a black body (an idealised perfect absorber of electromagnetism) depends upon the frequency of the radiation hitting it. There were experiments made to explore this problem but there were no theories on the outcome of the experiments.

Then in 1899 Planck came up with the ‘Planck black-body radiation law’ which shows the spectrum of black-body radiation. From this he had to lead to the theory that electromagnetic energy can only exist in a quantised or particle form which he called quanta, later to be named by Einstein as photons. This then began quantum physics, leading to a century of huge leaps in quantum theory and earned him the reputation of being the Father of Quantum Physics. Max Planck then won a Nobel Prize in 1918 for the discovery of the energy quanta.

Einstein, as you all know, came up with the General Theory of Relativity which states that the fabric of space time is curved by bodies of mass, which causes gravity, and that time and space aren’t as linear as first thought; they can be shortened when one is travelling near the speed of light and that time and space are not universally uniform but are relative. For example the time for a commuter waiting for a train is different to someone on a train speeding past because the quicker someone is time begins to shrink and shrinks faster nearer the speed of light. This theory allows us to be able to understand the universe better and make sense of some seemingly random anomalies.

He also postulated Special Relativity (E=MC2) which states that light has a constant speed which therefore is an exception of General Relativity so light will seem to travel at the same speed to both the waiting commuter and the one on the train.

Einstein, Planck, de Broglie, Bohr and others to name a few, also contributed on wave-particle duality; an attempt to collaborate the wave and particle like behaviours of photons which concluded with the theory that light is both. They used experiments such as the double-slit experiment; light is shone through two parallel slits onto a screen creating an interference pattern due to the wave properties of light.

Niels Bohr, sometimes know as the Golden Dane, was a Danish physicist who was as well known and looked up to as Einstein and Planck in the 20th Century. He, using Ernest Rutherford’s theorems, hypothesised the idea of electron shells orbiting the nucleus of an atom which meant the characteristics of a chemical is largely determined by the amount of orbiting electrons.

He also predicted electrons being able to travel from a higher-energy state (an electron shell) to a lower-energy state (an electron shell closer to the nucleus) by emitting a photon.

With Werner Heisenberg, they created the Copenhagen Interpretation. This states that any particle does not exist in one state or another but in infinite states of all possible outcomes and is only decided when it is observed. It was collaborated from theories such as Heisenberg’s Uncertainty Principle and ideas from thought experiments such as the double-slit experiment and Schrödinger’s Cat.

A cat is placed beside some radioactive material and a Geiger counter, used to measure radioactivity, which is set up to break a vial of poison if the radioactive material decays. So if the Copenhagen Interpretation is correct, then the material has both decayed and not decayed therefore the vial of poison is both broke and not broke, so the cat is both alive and dead.

Werner Heisenberg was a German theoretical physicist who made great scientific leaps before World War 2 and was one of the leading physicists in the Uranverein (The Uranium club), which was the Nazi attempt to build stronger and better bombs by using nuclear fission.

Nuclear fission is basically when the nucleus of an atom splits into smaller nuclei, free neutrons and photons in the form of gamma rays.

Heisenberg hypothesised the Uncertainty Principle which states that certain pairs of properties (such as velocity and position or time and energy) can only have one property accurately measured while the other is less accurate. So the more accurate one is the less the other property is. For example if a photon’s position is measured its momentum is less accurate.
He, along with Pascual Jordan and Max Born, also gave birth to Matrix mechanics. Matrix mechanics interprets particles as matrices, a form of number arranging which means AB-BA doesn’t always equal zero. They then developed it into what is known as matrix mechanics. Because of this he won the Nobel Prize in 1932 whilst Born received it in 1954.

The LHC (The Large Hadron Collider) is the largest particle collider in the world and is used to collide two beams of protons. It is based in Geneva and was created by CERN, the European Organisation of Nuclear Research. It’s 27 km in circumference and lays deep underground at 50 to 175 metres. Over 10,000 scientists from 100 countries are involved with the LHC as well as universities and laboratories. CERN approved the design of the LHC in 1994 and the four main projects were approved between 1996 and 1998. The cost to make the accelerator was 3.03 billion Euros, they received 0.71 billion towards the experiment and 0.16 billion towards the computing.

It has four main projects: ALICE, ATLAS, CMS and LHCb. CMS and ATLAS were designed as general detectors and are used to find new particles and the Higgs Boson. ALICE was designed to look at the collisions of lead ions. Whilst LHCb is designed to find out why all the antimatter has gone and where to?

Questions and theories which will hopefully be answered because of the LHC are:
· The Higgs boson and the Higgs field; the origins of mass
· Supersymmetry; every particle has a supersymmetric partner which has a spin, a property of particles, different to its partner by a half.
· Extra dimensions
· Whether the four universal forces are manifestations of one single unified force.And why gravity is vastly weaker than the other three universal forces

In 2008 the LHC was finally finished and on the 10th September 2008 it successfully fired the first protons around the whole area in circuits. However on the 19th September one of the magnets holding the protons in circuit broke and lead to a loss of about 6 tonnes of liquid hydrogen which was used to stop the whole thing from overheating. On the 20th November the first low-energy particles were sent around the tunnel after the incident.

And on Tuesday 30th March, the two beams of protons collided at 7 TeV (teraelectronvolts), the highest energy ever produced by a collider, at 13:06 CEST, Central European Standard Time. They will continue colliding protons to make sure the first results are accurate. The results however will require months, years, possibly even decades to analyse and decode.
The LHC will hopefully revolutionise quantum physics by shedding light on old and modern theories.