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The Big Bang
Transcript of The Big Bang
In 1915 Albert Einstein Proposed his 'Special Theory of Relativity', in which he induced what is now the most recognised (and probably least understood) equation of all time.....
This equation was amazingly revolutionary. Up until this point in time, it was believed that matter and energy were two completely separate entities. Einstein's theory however, was that matter and energy were different forms of the same entity and could in fact interchange. This idea of changing matter into energy would later be put into practice to develop the most devastating weapon ever produced by man kind....The atom bomb.
What is the Big Bang Theory?
The "Big Bang" is the term given to what is currently the most widely accepted scientific model for the origin and evolution of the Universe. This model has supplanted other models such as the Steady State theory proposed by Hoyle, Bondi and Gold in the 1940s. Indeed it was Fred Hoyle who coined the term "big bang" as a derisory one in an interview in the 1960s.
In the Big Bang theory the Universe comes into existence, creating time and space. Initially the Universe would have been extremely hot and dense. It expanded and cooled. Some of the energy involved was turned into matter. Current observations suggest an age for the Universe of about 13.7 billion years.
The current success of the big bang model relies on several key areas of observational evidence and predictions.
What Led to the Theory?
Scientists such as Friedmann and Hubble had proven that the Universe was in fact expanding. Now other scientists began to hypothesise what the past Universe may have looked like. It was reasoned that if the Universe was expanding, in the past it must have been contracted into a single point. Was there any evidence to support this?
Cosmic Background Radiation
By observing very distant galaxies (which are therefore very old galaxies as the light which traveled from them has taken amazing lengths of time to get to us) scientist were able to predict the original temperature of the early Universe. This figure was given as approx. 3000 K (K being degrees Kelvin, an absolute scale for temperature). Given the observed rate of expansion, they went on to predict that the energy given off from the big bang should have cooled to around 3 K. There was no evidence to prove this however.
Penzias and Wilson
In 1965, Arno Penzias and Robert Wilson accidentally discovered the Cosmic Background Radiation which had alluded physicists for years. The most amazing thing about the discovery was the fact that it showed that the radiation was indeed around 3 K, just as predicted by earlier scientists using maths alone.
Events after the Big Bang
Using Einsteins theory, scientists were then able to investigate exactly how energy can transfer into matter and matter into energy. This led them to develop theories of how the Universe came into existence.
Our current understanding of physics allows us to model events in the Universe nearly, but not quite, back to the moment of the big bang. Significant developments in our understanding of the very early Universe are due to advances in high-energy particle physics and particle accelerators such as those at CERN. According to the "Standard Model" of particle physics we now know that all the matter around us is composed of combinations of only a few fundamental particles. These twelve particles fall into two families, quarks and leptons.
Fundamental particles, the building blocks of the Universe
Quarks are the particles that group together to form hadrons. Hadrons made of three quarks in turn are called baryons. The most familiar baryons to us are the protons and neutrons that comprise the nuclei of the atoms in our bodies and the rest of the Universe. A proton comprises two up quarks and one down quark, whilst a neutron has two down quarks and only one up quark. If you study the following table you will see that quarks have charges that are fractions of the charge of an electron, e. Hence the overall or net charge of a proton = 2 × (+2e/3) - 1 ×(-1e/3) = +1e and the overall charge of the neutron is 0.
Leptons include three charged particles, the electron, muon and tau particle. Each of these has an associated neutrino particle that is neutral.
Together these twelve particles are the building blocks of matter. Interestingly though, each of them has a corresponding antiparticle. These differ only in having the opposite charge but have the same mass as the corresponding matter particle. These antiparticles collectively are known as antimatter.