Q&A WITH A FAST RADIO BURST EXPERT

A significant amount of the Universe's matter from the Big Bang is missing. Now scientists believe they've found it hiding between galaxies

- Liam Connor

What is normal or 'ordinary' matter?

When astronomers talk about normal matter, we're referring to baryons. By that, we just mean 'the stuff of atoms' - things like protons and neutrons.

How did we find out some of the Universe's ordinary matter was missing?

We can see leftover light from the Big Bang; we call this the cosmic microwave background radiation or CMB. Fluctuations in the CMB give us a snapshot of how things were around 400,000 years after the Big Bang - a kind of 'baby photo' for the Universe, which tells us how much matter there was, both normal and dark. All those atoms should still be here 13.8 billion years later. But, if you count the stars and planets and dust you can see with your telescope, you'll find a significant amount of matter appears to be missing.

Where did you find this missing matter?