Time travel, while not entirely impossible according to Albert Einstein's theory of relativity, is so fraught with paradoxes and uncertainties it will likely never happen. The concept is tantalizing for many in and out of the scientific community, but the obstacles we would have to overcome, at least when attempting to tunnel to the past, are so huge it's hard to believe even the most ingenious minds on Earth can make it a reality.

We are all time travellers in a sense, going in one direction towards the future. Like Isaac Newton said, time is like an arrow. Once fired it goes just one way. In my mind that's the way it should be. I can understand why somebody would want to travel back into the past to prevent some horrible tragedy or correct mistakes they have made. But, as the late author and astronomer Carl Sagan once said, history as we know it would become an experimental science. The records which reflect past events would be changing by the minute. The past is the past and it cannot be altered.

Stephen Hawking also made a convincing statement which seemed to refute the possibility of time travel. He asked why visitors from the future haven't appeared or made contact with us. Some would claim 21st century humans would not be interesting to those who originated from a date in the future, but this argument rings hollow. They couldn't interact with anybody from this time, because their world would not be the same.

We know for certain that to build a device capable of delivering us backwards in time would take a marvelous feat of engineering, which at this point is beyond our abilities. There is still the nagging question about what to use as fuel for a time machine. Somehow we will have to figure out how to harness the power of a black hole, or locate a wormhole in deep space and manipulate the properties of this galactic phenomenon to transport ourselves to the past.

You should consider this very carefully. Imagine you wanted to go back to 1941 to prevent the destruction of Pearl Harbour, and were successful. So, you decide to go back to where you came from. Sounds simple, right? Well, not really. You can't go back to where you came from because the attack on Pearl Harbour never took place, and therefore your actions will have created an alternate universe.

If we could change the past so easily, we might not be here to observe it. But we are watching what unfolds day after day, and year after year.

Learn more about this author, Scott Hayden.
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