Author(s): Brian Clegg
All the matter and light we can see in the universe makes up a trivial 5per cent of everything. The rest is hidden. This could be the biggest puzzle that science has everfaced.
Since the 1970s,astronomers have been aware that galaxies have far too little matter in them toaccount for the way they spin around: they should fly apart, but somethingconcealed holds them together. That 'something' is dark matter - invisiblematerial in five times the quantity of the familiar stuff of stars and planets.
By the 1990s wealso knew that the expansion of the universe was accelerating. Something, nameddark energy, is pushing it to expand faster and faster. Across the universe,this requires enough energy that the equivalent mass would be nearly fourteentimes greater than all the visible material in existence.
Brian Clegg explainsthis major conundrum in modern scienceand looks at how scientists are beginning to find solutions to it.