Written by Carmelo Amalfi Monday, 31 August 2009 13:41
BEND me, shape me … time and space have never been the same since Einstein raised the possibility of physically travelling back and forward in time.
Until his relativistic views emerged as the new physics of the 20th century and beyond, scientists, thinkers and science fiction writers let the human imagination run wild with the most elusive phenomena in the universe - time. But what is it? Where is it? When is it?
The space-time continuum described by Einstein is four dimensional.
The three dimensions of space include width, breadth and depth, which can all be measured. The fourth dimension is time, which we cannot see or touch. Time is experienced.
We feel ourselves passing through the dimension of time. And if you could move fast enough, it can also take years off your life.
Take a ship fast enough to reach the nearest star and return in 10 or 20 Earth years - everyone will be 10 or 20 years older, or dead, but you will have hardly aged.
Frequent flyers experience this effect each time they travel above the planet. Flying from Perth to London will shave off a few billionths of a second relative to people on the ground. Every second counts and atomic clocks have measured this effect.
What is still beyond us is travelling to the distant past - say to the Jurassic jungles or birth of life on Earth.
Maybe the time machine cannot be used before its manufacture date, limiting time tours to the immediate past, for example yesterday or last year when Barack Obama was elected as the US president and the Large Hadron Collider was switched on.
Trickier is getting to the future.
This is no problem for science fiction writers - time-travelling astronauts have already reached Earth’s future when apes have taken over the world and the Statue of Liberty is buried in sand.
In The Time Machine, its 19th century hero ends up travelling 800,000 years into the future where people are divided into warring races.
However, for theoretical physicists, time machines will have to move at near-light speeds to achieve any noticeable leaps from the ‘present’.
Guy Micklethwait, Australian National University associate lecturer at the Department of Physics and PhD researcher at the Centre for the Public Awareness of Science in Canberra, says travelling forward in time is possible but physically going back in time is speculative science.
And tricky.
He says that theoretical physicists are occupied with using ‘wormholes’ and other possible time travel techniques to move between dimensions of time. Whether or not they can build machines that actually work is another matter for another century.
“That hasn’t stopped filmmakers,” he says, adding that films inspired audiences to hope that one day they would be able to travel in time, just as people once dreamed of a rocket reaching the Moon.
