In a column for noted scientific journal The Daily Mail, accomplished physicist Stephen Hawking – who’s been more at ease talking about out-there topics of late — writes an instructive DIY guide to time machine construction. Though he admits to past concerns that he’d be “labelled a crank” in stodgier scientific circles for his explorations into time travel, he now admits to an open fascination with the subject.
The Daily Mail headline (“STEPHEN HAWKING: How to build a time machine”) and dek (“All you need is a wormhole, the Large Hadron Collider or a rocket that goes really, really fast”) may oversell the piece a bit, but its value is as a popular science primer. Like his remarks about alien overlords, if Hawking has to give some writers easy misconstruable headlines and pop-up jokes in exchange for a lively debate about science (and publicity for his new TV show, Stephen Hawking’s Universe, which debuts on May 9th), so be it.
From the piece:
…But the story’s not over yet. This doesn’t make all time travel impossible. I do believe in time travel. Time travel to the future. Time flows like a river and it seems as if each of us is carried relentlessly along by time’s current. But time is like a river in another way. It flows at different speeds in different places and that is the key to travelling into the future. This idea was first proposed by Albert Einstein over 100 years ago. He realised that there should be places where time slows down, and others where time speeds up. He was absolutely right. And the proof is right above our heads. Up in space.
This is the Global Positioning System, or GPS. A network of satellites is in orbit around Earth. The satellites make satellite navigation possible. But they also reveal that time runs faster in space than it does down on Earth. Inside each spacecraft is a very precise clock. But despite being so accurate, they all gain around a third of a billionth of a second every day. The system has to correct for the drift, otherwise that tiny difference would upset the whole system, causing every GPS device on Earth to go out by about six miles a day. You can just imagine the mayhem that that would cause.
The problem doesn’t lie with the clocks. They run fast because time itself runs faster in space than it does down below. And the reason for this extraordinary effect is the mass of the Earth. Einstein realised that matter drags on time and slows it down like the slow part of a river. The heavier the object, the more it drags on time. And this startling reality is what opens the door to the possibility of time travel to the future.
For a future Daily Mail exposé: Does time travel give you cancer?