FROM THE EDITOR
COVER: ANDY POTTS THIS PAGE: BERNARD LEONARDO, GETTY IMAGES X2, ALAMY
Dark matter really is an awkward thing to explain to anyone who doesn’t follow science. Even if you do follow science, it still sounds kind of silly when you try and make sense of it. Any attempt to do so usually ends up sounding something like this:
“So, as far as we can tell, normal matter – the stuff that makes atoms, planets and stars, as well as mundane things like tables and chairs – only accounts for one-fifth of the physical ‘stuff’ in the Universe. The rest of it, the other 80 per cent of all matter everywhere, is something we call dark matter. Why dark? Because we’ve never actually seen it. Not only is it invisible, but it’s also totally intangible – at least, it is as far as we’re concerned. In fact, while you read this, millions of particles of dark matter will probably pass through your body without so much as an ‘excuse me’. So how do we know it’s there? Well, when we look out at other galaxies, our current understanding of the Universe and the way it works suggests that they shouldn’t exist. They’re spinning so fast that, strictly speaking, they should have torn themselves apart, hurling their contents out into the void like a Catherine wheel. And yet, something is holding them together. Something that’s providing the gravity needed for galaxies to hang onto their innards. That something is what we call dark matter.”