The problem of our age is that the future isn’t what it used to be.

PAUL VALÉRY (1871-1945)

Time Travel

SHUTTERSTOCK

Worm Holes In Space


According to General Relativity, everything in the Universe is played out on a stage that has three dimensions of space and one of time. This space-time is warped by the mass and energy of the Universe’s contents. Theoretically a large enough concentration of mass or energy can distort time so much that it folds back on itself like a crumpled sheet. These folds were described by Kurt Gödel in 1949 and are known as ‘closed time-like curves’. They ought, at least in theory, to allow us to revisit past moments in history by using an idea developed in 1988 by Kip Thorne and colleagues at the California Institute of Technology, who showed that tunnels through space-time (wormholes), would allow time travel by taking a shortcut from one fold to the next.
 
There are still plenty of obstacles to time-travelling through wormholes. Not least is the fact that the only wormholes we can possibly make with present-day technology are tiny: only subatomic particles would be small enough to travel through them. 

Velocity and gravity both slow clocks down. In orbit 5,900 miles (9500km) above Earth, the low gravity and high velocity cancel each other out.


 

Astronaut Time Travellers


You could say that time travel has already been achieved. Russian cosmonaut Sergei Krikalev has time-travelled 0.023 seconds (23 milliseconds) into the future. It may not be much, but it’s more than any other human has achieved so far. We know this because Sergei holds the world record for time spent in space: 803 days, 9 hours and 39 minutes. He also orbited the Earth (on six different missions) aboard the MIR space station and the International Space Station (ISS) at an average speed of 17,400 mph (28,000 kph).
 
Sergei’s minuscule amount of time travel is made possible by the effect of ‘time dilation’, as predicted by Einstein’s Special Theory of Relativity. The closer you travel to the speed of light, the slower time runs for you compared with someone else who is at rest. In fact, time always runs slightly slower for you when you’re moving, but usually the effect is so tiny that we can’t detect it. However, astronauts zooming around the Earth for long periods experience measurable amounts of ‘time dilation’. Two years for us on Earth was two years minus 20 milliseconds for Sergei Krikalev.
 
That may not be as impressive as what Marty McFly could achieve in a DeLorean travelling at 88 mph (142 kph) in Back To The Future, but that’s because in the real world of relativity, even an orbiting space station is very slow indeed. If an astronaut were able to travel at close to the speed of light, it might take her a minute to reach the nearest star and another minute to get back: that’s just two minutes of her time. But we on Earth would be waiting eight years. In this case, it would be possible to say that she has travelled eight years into the future.

Build It And They Will Come


One of the questions posed by time travel sceptics is: if time travel is theoretically possible, why hasn’t anybody from the future turned up yet? One explanation is that the earliest point anyone in the future could travel back to is the time when the first time machine was invented. This is founded on the idea that one time machine on its own would be as useless as a single tube station - you need one at each end of the journey. According to Irina Aref’eva and Igor Volovich, mathematicians based at the Steklov Mathematical Institute in Moscow, the Large Hadron Collider (LHC) might just turn out to be the device we’ve all been waiting for. If so, then the LHC will be known as the ‘birthplace of time travel’ - a ‘must see’ destination for all future time-travellers.
 
According to Aref’eva and Volovich, the LHC could create wormholes which would allow some form of time travel. Each accelerated particle whizzing round the LHC creates a kind of shock wave in space-time, a gravitational ripple that distorts the space and time around it. Under certain conditions, the colliding gravitational waves might rip a hole in Space and Time.

On June 28 2009, Stephen Hawking threw a party for time-travelers. No one came.

TARDIS stands for Time And Relative Dimension In Space.

Due to tidal friction from the sun and moon, the solar day is lengthening by 1.7 milliseconds each century.

JAMES BALDWIN (1924-87)

The future is like heaven, everyone exalts it, but no one wants to go there now.

The Grandfather Paradox



Stephen Hawking doesn’t believe time travel into the past will ever be possible because of the problem of the Grandfather Paradox. This is a thought experiment in which you travel back in time and kill your own grandfather. Having done this, you ensure that your father will never be born, which means that you will not only suddenly cease to exist, but will never have existed. But as a nonexistent person, you can’t travel back in time to kill your grandfather, so he survives, and so you can be born after all, in which case you can still go back in time and kill your own grandfather…. and so on. This problem remains unsolved.

ALAN MOORE

Machine. Unexpectedly I’d invented a time.

The MWI


One way to get round any awkward paradoxes that forbid time travel into the past was proposed by physicist Hugh Everett III, who first came up with the ‘many-worlds interpretation’ (MWI) of time travel. The MWI says that many universes may co-exist as separate branches following their own timelines, with new branches sprouting off in different directions at every decisive moment where there could be more than one outcome. Therefore, if you were to travel back in time and kill your grandfather, the branch of the universe you left behind would left be unaffected, and you would live on in the new branch (though possibly in prison for murder).

THE DOCTOR (DOCTOR WHO)

People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff.