Physicist Stephen Hawking is widely considered the smartest person in the world. You may think someone with his brain wouldn't waste his time dealing with something as illogical as time travel. Well, not only does he spend time on it, he thinks time travel is actually possible.
In an article in London's Daily Mail, Hawking, describing himself as a "physicist, cosmologist and something of a dreamer," admits the scientific community might scoff at his ideas:
Time travel was once considered scientific heresy. I used to avoid talking about it for fear of being labelled a crank. But these days I'm not so cautious.
Hawking writes that in science fiction movies, some crazy time machine speeds through a tunnel through the fourth dimension, thus traveling back or forward in time. Far-fetched, yes, writes Hawking, but not out of the realm of possibility.
Physicists have been thinking about tunnels in time too, but we come at it from a different angle. We wonder if portals to the past or the future could ever be possible within the laws of nature. As it turns out, we think they are. What's more, we've even given them a name: wormholes. The truth is that wormholes are all around us, only they're too small to see.
But there in lies the problem -- the size of these wormholes:
Unfortunately, these real-life time tunnels are just a billion-trillion-trillionths of a centimetre across. Way too small for a human to pass through - but here's where the notion of wormhole time machines is leading. Some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter.
So that is the challenge -- making the wormhole bigger. Even then, you'd need a really, really fast vehicle.
There's a cosmic speed limit, 186,000 miles per second, also known as the speed of light. Nothing can exceed that speed. It's one of the best established principles in science. Believe it or not, travelling at near the speed of light transports you to the future.
To put that into perspective, the fastest manned vehicle in history was Apollo 10, which reached 25,000 mph. A time traveling vehicle would have to go 2,000 times faster than that.
So perhaps we can't build our own time machine. Hawking's point is that it is theoretically possible. And what would Hawking do if he could go back in time?:
If I had a time machine I'd visit Marilyn Monroe in her prime or drop in on Galileo as he turned his telescope to the heavens.
Spoken like a true genius.