EVERYTHING astronomers have learnt about the Universe they have squeezed
painstakingly from the electromagnetic radiation that pours down to our
planet from space. But astronomers have come to realise that the Universe
has played a cruel trick on them. There is much more out in the Universe
than meets the eye. We now know that luminous matter – the matter that emits
electromagnetic radiation which we can detect with optical telescopes, radio
dishes and so on – makes up a mere 10 per cent or less of the total mass
of the Universe. No one knows the nature of the ‘dark matter’ that makes
up the other 90 per cent.
In laboratories all over the world, the search for dark matter is hotting
up. For the group that first identifies the Universe’s major constituent
there will be instant fame and the chance to shake physics and cosmology
to their foundations. For one thing, the dark matter will have been crucially
important in the formation of the Universe’s large-scale structures, such
as galaxies. There are many possible candidates for the dark matter, such
as faint stars called brown dwarfs, black holes and ‘jupiters’. But it is
the possibility that the dark matter consists of exotic subatomic particles,
such as photinos or neutrinos or monopoles – that has excited experimental
physicists. Any search for these particles is a huge gamble, but it is a
gamble many are willing to take.
A striking feature of many experiments looking for dark matter is that
they are small, relatively cheap and can be carried out in a laboratory
by a small team in a few years. This is…
