Fire up the DeLorean, Marty... because time travel exists!
Party invitations to visitors from the future have yet to be answered, but the science proves it’s possible
IT WAS a party with an unusual open invitation – anyone from the FUTURE welcome. Sadly, the convention for time travellers, held in 2005 at the Massachusetts Institute of Technology in America, was something of a flop. No one turned up. Equally disappointing was the plaque put up in Perth,WesternAustralia, inviting adventurers from the future to meet at noon on March 31 that year. Again, it was a dismal no-show.
Even a bash held by the redoubtable Professor Stephen Hawking in Cambridge in 2009 resulted in zero attendees from the future. But we shouldn’t take this as proof time travel doesn’t exist – even if shows like Doctor Who or The Time Machine seem unbelievable. In fact, it isn’t at all surprising when you understand how the real thing differs from fiction.
There is nothing in the laws of physics that prevents journeys through time, at least in theory. Albert Einstein’s relativity theories showed how time travel is possible, though it’s only with the technology of the 21st century and beyond that it will finally become a reality.
But before anyone rushes out to buy a DeLorean, and tries to emulate Michael J Fox’s adventures playing Marty McFly in Back To The Future, real time travel is very different from TV and film. If you want to build your own Tardis, the first essential is to realise that travelling forward in time is entirely different from – and a whole lot easier than – travelling backwards.
We all head into the future. Just wait a few minutes, and there you are. But far more is possible.What Einstein showed with his special theory of relativity is that time and space are not separate things. When we move in space, we also influence the flow of time.
For anything moving, time slows down. The faster you travel, the stronger the effect. So travellers in a fast-moving spaceship will get back home to find that they have slipped into the Earth’s future. Even walking across the room or taking a plane flight produces a tiny time shift. If you crossed the Atlantic weekly for 40 years, you would move 1/1000th of a second into the future.
Our best time machine to date is doing better than this though. It’s called Voyager 1.
This was one of a pair of NASA probes sent out past Jupiter and Saturn into deep space in 1977.
Over its 44 years in space, Voyager 1 has travelled around 1.1 seconds into the future.
The two essentials to forward time travel are how fast you go and how long you keep moving.There’s no sudden jump in time, like in Doctor Who. And that’s where our technology has to develop. As yet, the fastest a human being has ever travelled was on Apollo 10 in 1969. The astronauts got up to speeds of around 25,000 miles per hour.
But their time travelling was tiny because they only managed this over a few days and, impressive though this sounds, it is actually extremely slow.
The important speed to match up against is the speed of light – around 186,000 miles per second.The closer a traveller gets to light speed, the more time slows down.TheApollo astronauts didn’t come close, only going around 0.000037 of light speed.
But in theory, any time journey can be made if the ship moves fast enough.
Imagine, for instance, there were twins, Lucy and Zoe, aged 25. Lucy stays on Earth, but Zoe takes off in a spaceship and travels for 10 years at 99 per cent of the speed of light.When Zoe gets back to Earth, she is 35. But she will arrive in time for her twin’s 85th birthday party. The problem with getting up to that kind of speed is that it would take a whole load of energy. But the more fuel on board the ship, the more energy it takes to move it. About the only possible fuel to make time travel feasible is antimatter. This weird substance was featured in the Dan Brown novel Angels And Demons, but reality is stranger than fiction. Antimatter is made up of different particles to the atoms that make up everyday stuff.
When antimatter particles come into contact with ordinary matter, they combine to produce pure energy. A few tons of antimatter would be enough to power a time machine into the future.
ANTIMATTER not only exists, it is made in a number of labs around the world – but only a few millionths of a gram are produced each year. Although it’s not impossible to push up production, it would be immensely expensive to make enough. A better option might be not to carry the fuel at all.
This is the idea behind a scheme designed to send tiny probes to our nearest neighbouring star. Called Breakthrough Starshot, the international initiative aims to power
‘Backward time travel is also possible... but a whole lot harder than going forwards’
spacecraft up to 0.2 times the speed of light by blasting them with lasers. Although light seems insubstantial, it does produce a small push which, over time, can accelerate the ships to great speed.The same approach may eventually power a time machine.
Whatever technology is used, travelling forwards is only half the story.
Part of the fascination of time travel is seeing the past – and even a visit to the future would not be complete if the traveller couldn’t get back to their own time.
The good news is that backward time travel is also theoretically possible, but a whole lot harder than going forwards.
Going into history makes use of Einstein’s other theory of relativity, the general theory. This shows how matter distorts time and space, producing the effect we call gravity.
In theory, the right kind of warp in spacetime can enable a journey into the past. The trouble is, it would involve engineering far beyond anything currently possible.
Typical technologies for backward time travel either need the use of a wormhole – a theoretical bridge between two points in space and time – or constructing a cylinder from a stack of ultra-dense neutron stars and rotating it at high speed. Sadly, that’s not going to happen any time soon. But it is with backward time travel that things would get really interesting, and not just by sending back next week’s lottery results.
Imagine, for example, someone visited the past and accidentally killed one of their parents before the time traveller was conceived. Then the traveller wouldn’t exist. But if they didn’t exist, then the accident would never have happened. So they would exist… It’s a genuinely mind-bending concept.
TAKE another example. Say someone took the music for the Beatles album Sergeant Pepper’s Lonely Hearts Club Band back to 1965, before the album was thought of, and gave it to the Beatles. All they would need to do was record the album. But then, who wrote it?
Although there’s no time-travel involved, this scenario mirrors the plot of the Richard Curtis romantic comedy, Yesterday, starring Himesh Patel as a struggling musician who suddenly finds himself the only person on Earth who’s ever heard of the Beatles – and becomes famous after taking credit for their songs. Some scientists think this kind of weird outcome of backward time travel means it will never be possible.
In reality, even if such a time machine was built, it almost certainly couldn’t be used to reach 1965, because a side effect of the way these devices work would mean it couldn’t travel back before the point in time it was first created. But no one can be sure.
Real time travel is very different from what we see on screen.
Yet it’s still quite amazing that time travel is a real thing. It’s happening everywhere on a small scale as moving objects make tiny shifts in time.
Even the GPS satellites used for satnav, which are orbiting ultra-accurate clocks, have to have their data corrected for their journeys through time. If they didn’t, GPS would drift away from being accurate by several miles a day.
Time travel is more than fiction – it’s part of the fabric of reality.
10 Short Lessons In Time Travel by Brian Clegg (Michael O’Mara, £9.99) is out now. Call Express Bookshop on 01872 562310 or order via www.expressbookshop.co.uk UK postage and packing is £2.95