About a century ago, scientists were struggling to reconcile what seemed a contradiction in Albert Einstein’s theory of general relativity.

Published in 1915, and already widely accepted worldwide by physicists and mathematicians, the theory assumed the Universe was static – unchanging, unmoving and immutable. In short, Einstein believed the size and shape of the Universe today was, more or less, the same size and shape it had always been.

But when astronomers looked into the night sky at faraway galaxies with powerful telescopes, they saw hints the Universe was anything but that. These new observations suggested the opposite – that it was, instead, expanding.