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John Glenn Saturday, 7 November, 1998, 18:05 GMT
Space age
Take a trip to eternal youth
At 77, John Glenn is now the oldest man to have left the Earth's atmosphere.

But if you are worried about getting old then a speedy trip to the stars may just help.

It will not make you live any longer but, in the eyes of the friends you left back on Earth, you will appear to have "stretched" time.

Travelling close to or at the speed of light slows down time - so says Albert Einstein's Special Theory of Relativity.

What actually takes years and years on the Earth is experienced as much less for the person on the move.

Relatively speaking that is.

So set off travelling near the ultimate speed limit, light, on a journey that would take decades and you may return to find that much more time has passed on the Earth.

And don't expect to see your loved ones alive.

However, travelling fast enough for the effects of "time dilation" to show itself is not possible at the moment. Only Paramount (the film company that makes Star Trek) knows how to do it.

So near and yet so far

Part of the problem is the vast distances in between the stars.

Travelling at the speed of light it takes just over a second to get to the Moon, eight minutes to the Sun, five hours to the most distant planet and four YEARS to get to the nearest star.

At the moment out most distant space probes are about eight light-hours away, having travelled in space for more than two decades.

At this rate it will take hundreds of thousands of years to get to the nearest star.

Warp factor

What is needed, scientists say, is a fundamentally new way of propelling spacecraft. Today's conventional chemical rockets are just not powerful enough.

The "warp drive" popularised in Star Trek is an interesting idea. The principle is simple. Einstein's theory says you cannot travel faster than the speed of light in normal space. So take the space with you and you can travel much faster than light.

The problem is that warping space around a spacecraft and then propelling it through the universe seems to require fantastic amounts of energy, far more than mankind could muster.

Origami travel

Another possibility, though rather far-fetched, is the folded space idea.

On a flat piece of paper the shortest route between two points is a straight line. But if you take the paper and fold it so the points touch then the shortest point is in fact through the paper.

Perhaps the same thing is possible in reality; taking a short cut through space in a "wormhole", a tunnel through the conventional dimensions of space.

Many scientists believe that wormholes could exist but they would be very small and not last very long so they would be useless to send a spaceship through even if it could survive the forces - then of course there is the question of coming back!

So travelling to distant stars seems out of the question at the moment.

Perhaps the best way to do it is to wait for an alien spaceship to land on Earth and ask the occupants how they did it.

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