We know what 4% of the Universe is made of. But what about the rest? 　　There was a time, not so long ago, when science seemed to understand how the universe worked. Everything – us, the Earth, the stars and even exotic-sounding supernovae – was made of atoms which were all created at time-zero: the Big Bang. In between the atoms was nothing, a void: quite literally, 'space'. 　　But ...