Magnetic fields that originated during the earliest moments of the Universe may have been billions of times weaker than the pull of a household fridge magnet, with strengths on the scale of the magnetism produced by neurons in the human brain. Despite being so faint, measurable evidence of these fields can still be detected in the cosmic web, the vast network of structures linking galaxies across the Universe.

This conclusion comes from a study involving about 250,000 computer simulations carried out by researchers at SISSA (the International School for Advanced Studies in Trieste) in collaboration with teams from the Universities of Hertfordshire, Cambridge, Nottingham, Stanford, and Potsdam.