SHAKESPEARE had it right, even in ways he couldn't have imagined. For centuries, scientists have indeed been making much ado about nothing - and with good reason. Nothing, or rather what we've long taken to be nothing, may be the key to understanding everything from why particles have mass to the expansion of the universe. As explored in this special issue of New Scientist (see "The nature of nothingness"), nothing is a rich and subtle subject whose biography is far from finished.
The modern story of nothing began with a thought experiment dreamed up by Isaac Newton. Imagine two identical rocks, tied together with a string, whirling around their common centre. The string pulls taut. But, Newton asked, how would we explain the taut string if the rocks were spinning in an otherwise empty universe? Since motion is relative, and the rocks aren't moving relative to one another, what sets the benchmark for their motion? Newton concluded that the answer had to be, well, nothing: the string pulls taut because the rocks are moving relative to empty space itself.