Asked by: C Sheridan, Southhampton
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.