Koda (4) from Canada asks: Where do atoms come from?

This is a huge question – stretching back nearly 14 billion years! But first: let’s remind ourselves of what atoms are. These are the basic building blocks of everything in our universe (except for energy). The ancient Greeks thought atoms couldn’t be divided into any smaller pieces, but we now know that they’re made up of particles called protons, neutrons and electrons. And these in turn are made up of even tinier particles called quarks.

So, how were they created?

When the universe began with the Big Bang, 13.7 billion years ago, everything was super hot, dense and chaotic. After just a few seconds, it was cool enough for quarks and electrons to form. Everything kept on cooling, until a few minutes later quarks were able to join forces to build protons and neutrons. But whenever protons and neutrons tried to join with electrons, they were blasted apart by all the other particles bouncing around in the heat – it was still hundreds of millions of degrees. It took another 380,000 years before the universe cooled down enough for the first stable atoms to form. Those were mostly hydrogen and helium, and they became the ingredients for the very first stars.

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