The Big Bang Theory: A Guide

Chances are you’ve probably heard of the Big Bang Theory at some point in time. Whether it was from GCSE Science or the sitcom on channel 4 the phrase is certainly thrown about a lot. Yet do you really know what the Big Bang Theory actually represents?

Explaining the Big Bang Theory

The central premise of the Big Bang is that the universe began with a huge explosion, occurring around 10 to 20 billion years ago. Before this event the universe was an extremely compact and hot body yet the Big Bang caused it to expand and cool, which it is still doing now.

The theory states that all matter in existence, from stars to people, originates from that great explosion. Evidence for the Big Bang Theory has been provided in several ways. The first evidence came from Einstein’s Theory of Relativity in 1915, which stated that the universe was either expanding or contracting – not simply remaining constant. All very well, you may say, for a man in a lab to come up with a theory on the universe but what evidence is there to actually support it?

Evidence

There are two main pieces of evidence for the Big Bang Theory. Probably the most well known is ‘redshift’. In 1929 Edwin Hubble made the observation that the light coming from some distant galaxies was shifted towards the red end of the colour spectrum. Since red light has a longer wavelength, and therefore a shorter frequency, this indicated that these galaxies were moving away from us, on earth, and thus supported the idea of an initial ‘Big Bang’. 

Yet, just to make things that bit more complicated, there are some closer galaxies which appear to actually be heading towards us! This is known as ‘blueshift’ as the light goes to the opposite blue end of the spectrum. No need to worry about collisions though, it’ll take a few billion years for them to even get close!

Another extensively researched piece of evidence supporting the Big Bang Theory is ‘Cosmic Microwave Background’. This was initially discovered by accident in 1965. Throughout space there is a uniform amount of microwave background in every direction, known as ‘isotropic radiation’. Scientists argue that these background microwaves are the remains of the initial blast. To put it in simple terms, a left over echo of that original huge explosion.      

Results of the Big Bang

So, the universe is expanding: we know that much. But is that going to carry on forever? Well, scientists have come up with a few theories as to what might happen. It all comes down to the total mass of the universe and its ultimate ‘critical mass’. If the total mass is more than the critical then there will be a ‘Big Crunch’; basically the opposite of the Big Bang. In this model once the universe reaches a certain size it will begin to contract back on itself until it vanishes altogether. If this happens the final result could be yet another ‘Big Bang’ – possibly we are simply in the middle of an endless cycle of ‘Bang’ and ‘Crunch’.

However if total and critical mass ultimately end up equal then the universe will end up slowing down its expansion over a long amount of time, then finally coming to a total stop.

Finally if critical mass exceeds the universe’s total mass then there will be infinite expansion. Debate over the end result is still fairly heated and there are many supporters for each of the different theories.

Ultimately we may never be sure of the universe’s fate until it actually happens (If indeed humanity still exists then!) However as an explanation of its origins the Big Bang theory is currently the theory which has the most support behind it.