More than 13 billion years ago, everything in the Universe was contained inside a singularity tinier than a proton. There were no planets, no stars, and the laws of physics didn’t exist. Then came inflation: the Universe’s growth in that first tiny fraction of a second is comparable to an ant expanding to the size of the Milky Way almost instantaneously.
Three minutes after inflation, things cool down enough for quarks and gluons to combine to form protons and neutrons. That’s when we start to see the nuclei of hydrogen, helium, and lithium emerge – but it’s too hot for them to capture electrons, so all the electrons are flying around freely, smashing into photons, which scatters light making the Universe opaque.
More than 300,000 years later, the Universe FINALLY gets cool enough for atomic nuclei to begin capturing electrons. That means the Universe becomes transparent, and the coolest thing of all is that we can detect light from this era today – it’s the earliest light we’ll ever be able to see.
Over the next 450 million years, the very first stars and galaxies start to form. How far have we come from that tiny singularity 13.8 billion years ago, and how much had to happen just for our little planet, and ourselves, to exist!
Adapted from an article by Fiona McDonald published in Science Alert