Could the universe have a dark side, complete with its own force, a zoo of particles and even a shadow version of the Milky Way?
"Could there be a mirror world where interesting things are going on?
The way stars and galaxies move shows there is more mass present than we can see. To account for this, 80 per cent of the universe's matter must be dark. The trouble is the stuff stubbornly refuses to interact with ordinary matter, except through gravity, so has not been conclusively detected.
