The Big Bang saw the creation and ionisation of the universe. The ionisation of a particle occurs when the particle becomes charged, essentially meaning it is ‘ready’ to react with other particles. The initial ionisation of the universe occurred when neutral hydrogen gas (a proton and an electron) became ionised (the electrons are stripped, leaving a positively charged proton). This ionised gas went from smoothly distributed, to slowly collapsing in different areas to become the highly structured galaxies and clusters of galaxies we have today.
Astrophysicists classify the initial blanket of gas as a ‘smooth’ universe, compared to what we now live in, which is the ‘clumpy’ universe. Imagine that that layer of gas is a pillow. When you add marbles (stars) into it, it becomes clumpy. The more you add, the more rigid it becomes. This is similar to what happened in our universe, but the fabric of the pillow became the marbles themselves.
In the beginning, only a few stars began to form at a very slow rate, but there was a tipping point – where these stars gave way to a rapid spur of supernova all over the universe, which is what we call the Epoch of Reionisation.
So how did astrophysicists discover this? Well, as the universe expands, the stars move away from us. The light they emit appears to ‘shift’ to the red end of the electromagnetic spectrum. Red Shift acts similarly to the sound of an ambulance that changes in frequency as it speeds past you. But in this case, it’s the light from the star. So by probing (measuring) the distance between two points over time, scientists can understand almost everything about the stars; including their origin.
But it’s not just stars that can be measured by this technique. It’s also pulsars (magnetised neutron stars) and even entire galaxies!
Paul Geil, the animator/developer of the 3D data cube, further explains the concept of Red Shift: “We can look at an object’s spectrum and work out how much that light has elongated due to the expansion of the universe.”