THERE'VE been some pretty strange theories to explain the identity of the missing mass that must exist to make the Universe behave the way it does. Now there's another one: the lost mass is made of echoes from the hidden dimensions of space.
One reason physicists seriously contemplate the possibility that higher dimensions exist is because of superstring theory. This is the best candidate for a "theory of everything", and it says that there are six extra space dimensions in addition to the three of space and one of time that we know.
We can't see or move in these extra dimensions. And they must be minuscule. If they were any more than a fraction of the size of an atom, we would have detected signs of them already. But if they exist, physicists say there must be a whole load of extra particles out there too.
These are known ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content.