We've all seen time machines in films and TV. But will
scientists ever be able to build one? And if they do build one,
will it be as cool as the TARDIS?
Flying faster than light
Scientists haven't worked out how to make a time machine yet.
But they have worked out how to slow down time.
Einstein's
theory of relativity says that if you're travelling very fast
compared a friend who is stationary, time will pass slower for
you.
Scientists tested this by putting a very accurate clock on an
aeroplane. This clock was synchronised with an identical clock on
the ground. After several long distance flights, the clock on the
plane was running slower than the clock on the ground. But it was
slower by less than a billionth of a second.
Travelling fast can slow down
time for you, compared to someone standing still
The same thing happens with GPS satellite clocks. GPS satellites
zoom around the Earth at 14,000 kph and lose 7 microseconds off
their clocks daily, relative to clocks on Earth. The GPS clocks
have to be reset daily.
If you could fly at the speed of light, you would be moving
through time much more slowly than someone on the ground. But we
can't travel that fast yet!
Theoretically, if you could fly faster than the speed of light,
you might be able to travel backwards in time. So far, nothing has
been able to travel faster than light, not even those
pesky neutrinos.
If we could travel faster than
the speed of light, we might be able to travel back in
time
What about wormholes?
Some scientists think that wormholes could allow us to travel in
time. Wormholes are a "shortcut" through spacetime. Think of
spacetime as a piece of paper. Fold that piece of paper in half.
What's the quickest way to get from one side to the other?
The quickest way is to travel in a straight line through the
paper, instead of going all the way round. If spacetime in our
universe is folded, then wormholes could be used to take shortcuts
through space.
Wormholes are a shortcut through
space
If wormholes do exist, humans would probably disintegrate if we
went through them. Some scientists think that the bit of you that
went in first would accelerate so fast compared to the bit of you
that went in last that your atoms would stream off into space!
Most scientists think that wormholes don't exist. We haven't
seen any yet. However, some physicists are convinced that wormholes
are out there, we just haven't found them. Perhaps one day
wormholes will let us take shortcuts through spacetime, just like
Thor.
Will we ever travel in time?
You can never say never in science. Einstein's theory of
relativity does allow for the possibility of time travel in our
universe. But at the moment, most scientists think that time travel
is unlikely. The practical problems of time travel are probably too
difficult to solve.