Team finds 'proof' of dark matter
An interesting article is at:
http://news.bbc.co.uk/2/hi/science/nature/5272226.stm
Dark matter - which does not emit or reflect enough light to be "seen" - is thought to make up 25% of the Universe.
By contrast, the ordinary matter we can see is believed to make up no more than about 5% of our Universe.
The other 70% is dark energy.