Without all the empty space, how big would the Universe be? © Getty Images

Without all the empty space, how big would the Universe be?

If we crammed all the atoms in the universe together, so that every single nucleus was touching, how much room would it all take up?

Asked by: C Sheridan, Southhampton

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It’s said atoms are largely empty space, comprising protons and neutrons one million-billionth of a metre across with electrons circling in orbits over 100,000 times larger. Quantum theory shows this model is misleading, with atoms being much fuzzier entities. But ignoring this, astronomers estimate there are roughly 1080 atoms in the visible Universe. Crammed together, with their nuclei touching, they’d make a ball that would fit inside the Solar System.


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