The cosmic landscape of time that explains our universe’s expansion

Imagine looking out over a beautiful vista. The sun glances off the snowy peaks of distant mountains, a river winds through rolling hills. There is something wonderful about beholding the contours of a majestic landscape.

It might not be obvious when you look at the night sky, but the universe has a landscape of its own – filaments of galaxies separated by near-empty voids. We have long known this much. But now one group of cosmologists is taking things further and proposing that the universe possesses not just a landscape, but a timescape, too. The idea is that the very flow of time varies from place to place.

To say this goes against the grain would be an understatement: we have always thought that on large scales, time runs at the same speed throughout the universe. But in this picture – known as timescape cosmology – there are large patches of the universe where time has been ticking for billions of years longer than we usually assume.

It may sound strange, but what entices some physicists is the simple elegance of this idea. There is no freaky physics involved, it springs naturally from established theory. “It is part of the structure of general relativity,” says its inventor David Wiltshire at the University of Canterbury in New Zealand. “It’s just not a part of the…