Everything you have ever touched — every mountain, ocean, star, and galaxy visible through any telescope — is made of the 5% of the universe that physicists can actually account for. The other 95% has no name beyond ‘dark’, and no confirmed identity at all.

NASA’s current summary rounds the balance sheet to 5 per cent ordinary matter, 27 per cent dark matter and 68 per cent dark energy. Ordinary matter is often called baryonic matter because almost all its mass resides in protons and neutrons, which physicists classify as baryons. The relative heights and positions of its acoustic peaks reveal how much ordinary matter and total matter were present. Dark matter is unseen, not unsupportedStars far from galactic centres orbit too quickly for the gravity of visible material alone. Dark matter and dark energy are not two shades of one substance.