DETECTING THE DARK UNIVERSE
Observations tell us dark matter and dark energy exist, but how do you find something you can’t see or feel?
WORDS COLIN STUART
© Sanford Underground Research Facility
DID YOU KNOW?
American astronomer Sinclair Smith found evidence of dark matter in 1936
E
arth, wind, fire and water. The ancient Greeks thought they had the universe all sewn up… except they didn’t. As scientific understanding progressed, we learnt that it’s atoms that make up the world around us. And yet more recently the goalposts moved again. It now seems that atoms make up just five per cent of the universe. That’s it.
The first inkling that the universe wasn’t quite as it seemed came as far back as 1933. Swiss physicist Fritz Zwicky was gazing at galaxies in the Coma Cluster and noticed its thousand or so galaxies were moving far too fast. Even when he added up all the stars and gas in the cluster, there didn’t seem to be enough gravity to be pulling the galaxies around at such a great speed. He guessed that there must be something else, hidden from view, that contributed, calling his shadowy substance ‘Dunkle Materie’ – German for dark matter.
By the 1970s the mystery remained unsolved, but the evidence continued to mount. Astronomer Vera Rubin, looking at the Andromeda Galaxy, realised that she was seeing impossible stars: ones rotating so fast around the galaxy that they should be flung out into the void, not bound in a neat orbit. She looked for the same phenomenon elsewhere, and by 1980 she had spotted it in over 100 other galaxies.
LUX’s cylindrical detector was immersed in 272,550 litres of ultra-pure water to protect it from background radiation
Did you know?
Fritz Zwicky also coined the term ‘supernova’ in 1934