Unless you are a person that has a strong belief in religion you probably accept that the universe was created billions of years ago in an event called the big bang. No, it isn’t just a super awesome sitcom. The Big Bang is thought by scientists to have created everything. But what is it? Hopefully, our timeline will help fill in some (not all) of the blanks.
How the theory arose
Up until the twentieth-century scientists pretty much agreed that the universe was infinite. They thought it didn’t have an ending or beginning that it just “was”. However, a couple of scientists helped squash that idea. Firstly Einstein helped us to develop a better understanding of gravity and then Hubble discovered that galaxies were accelerating away from each other. This coupled with the discovery of cosmic background radiation in the 60’s all but confirmed that at one point in the history of the universe it had a beginning, And that’s where the Big Bang theory comes into play.
Something from nothing
It sounds like some kind of scam, doesn’t it? And actually, the very start of the universe is something that scientists have not been able to explain. You see all the laws that govern how the universe works are contained within the universe. So before it existed, the laws of it didn’t exist either. So therefore pretty much all of our clever stuff can’t figure out what happened. More on this later, let’s look at what happened after the big bang
The Universe started as an infinitely dense minuscule “thing” (not a scientific term) and very quickly expanded to the size of a football. It is important to note that the big bang wasn’t an explosion. It was the universe expanding rapidly, everywhere. And it wasn’t expanding into anything, the universe is literally everything, it doesn’t have any edges, because it is everything. If your brain hurts now, don’t worry that’s normal.
During this period the universe was about the size of a football. Because it had so much “stuff” in such a small space it was ridiculously hot. Tiny particles called gluons would come together to form quarks but the quarks would destroy each other creating more gluons. It was really too hot for anything particularly useful to form
Hadron Lepton era
At this point, the universe had expanded to a billion kilometres. Due to this increase, the temperature dropped rapidly. Due to this decrease in temperature quarks were able to form hadrons, particles like protons and neutrons. All this happened within one second of the big bang!
The universe quickly expanded to 100 billion kilometres and as before this led to a much cooler universe. Don’t get me wrong it was still pretty toasty at 10 billion degrees Celsius. But never-the-less at this temperature neutrons were more readily able to degrade into protons. This made it possible for the first atoms to form, Hydrogen. At this point, the universe was filled with countless particles and huge amounts of energy.
In terms of the origins of our universe, it took forever to get to the opaque era (roughly two minutes!) at this point the universe had cooled dramatically so lots of atoms were able to form. The infant universe had already become fairly stable and electrically neutral.
It would take a whopping 200 million years for the stars to form. Which seems like a long time, however, put into context the universe is estimated to be 13 billion years old. So it actually wasn’t that long.
Back to the start
What happened before the big bang we may never know. Finding a theory that unifies everything and could reveal the start of the universe is the holy grail of science. Let’s hope that one day it gets discovered.