Shining new light on dark matter In the 1930s, astronomers
discovered that many galaxy clusters observable from Earth have
a much stronger gravitational field than they should have given
their predicted mass. Further astronomical observations only
added to this puzzle. After much consideration, it was concluded
that something mysterious called dark matter must be involved.
Dark matter is in all respects invisible and can only be
detected by its gravitational effect on normal matter. If this
new theory was right then dark matter would make up most of the
mass of the universe. However, in February three scientists
claimed that dark matter was not necessary and in fact by
slightly altering Einstein's equations for general relativity
they could account for the acceleration. Not everyone was
convinced by the new explanation though, and now new evidence
has been put forward in support of dark matter through studying
the "bullet" galaxy cluster with the Chandra X-ray telescope.
The cluster was created when two separ