Saturday, October 22, 2011

Time Travel

"Gosh that takes me back... or is it forward? That's the trouble with time travel, you never can tell."  - Dr. Who, The Androids of Tara

Since the days of H.G. Wells (and probably before that) dreamers, idealists and lovers of science fiction and fantasy have speculated about the possibility of travelling backward in time; revisiting people, places and events that have gone, or at least changed. 

The very concept immediately raises several questions.  If it were possible to go back in time, could we only do so as passive observers or, as Charles Dickens put it, "shadows" that could watch history unfold without being able to affect it, or might we be able to interact with the past and possibly change the outcome of events?  If this were possible, all sorts of paradoxes come into play.  If we could change the outcome of historical events, would it not also change the future?  Might we find, upon returning to our own time, a radically changed world?  What if we were to meet an earlier version of ourselves, or somehow prevent our parents, grandparents, or any of our ancestors, for that matter, from conceiving the children that they did.  Would we suddenly disappear?

These questions have been amply considered by a myriad of fictional works (and that's only counting the Star Trek series!) but it's still fascinating to ponder on the nature of time, and how it works.  This is not just the province of dreamers and science fiction writers.  Much less fanciful and more learned intellects, such as Albert Einstein and Dr. Stephen Hawking (to name but two well-known examples) have theorized on the subject.

Einstein put forth the remarkable premise that time is relative to each of us, and is affected by speed.  The faster we go, the more slowly time passes.  If you could travel at, or near, the speed of light, theorized Einstein, several thousand years might seem as only a single year to you.  You could traverse the galaxy for one year (or, at least, half a light year's worth of it, allowing for time to return) and, upon returning, you'd find that the Earth, and everyone on it, had aged considerably more than you.

Dr. Stephen Hawking agrees with Einstein's theory and concedes that it makes it possible to travel forward in time if we could only go fast enough.  He asserts, however, that it would not be likewise possible to travel backward in time, because it "violates a fundamental rule that cause comes before effect."

I realize that I'm going out on a limb here, disagreeing with an intellectual giant the likes of Dr. Hawking, but I'm going to do so anyway.  I suggest that travelling backward in time would not violate the "fundamental rule that cause comes before effect", because there is no direct relationship between time and events.  Allow me to explain using something that I like to call the "Garden Hose Analogy".

Using a garden hose as an analogy to explain what time is and how it works is by no means an original idea of mine.  It's been used before, often to explain the concept of "SpaceTime", which brings physical space into the equation, suggests a relationship between space and time, and generally makes the whole concept very weird and confusing. 

My analogy is a simpler one, focusing only on time and leaving space out of it, in the interest of simplicity.  Think of time as a garden hose, and events as the water running through it.  The hose itself is always there, and certainly it's possible to travel through it in either direction (assuming you're small enough), but the water passes through it but once, and is gone.  You could certainly go from the hose's end to its source (effectively travelling "backward" through it), but you'd never find the water that had passed through it before.  It's gone.  There is no connection between the water and the hose, save that the hose acts as a conduit through which the water flows.

By the same token, I believe that we make the mistake of mentally linking time and events when, in fact, there is no direct relationship between the two.  Time, like the hose, is a conduit and it may be possible to traverse it in any direction, but events, like the water, come and go.  You might be able to revisit Kittyhawk in 1903, but you'd never meet Orville and Wilbur Wright.  They're not there anymore.  They have passed through the conduit of time, and are gone.

But what if the water is still flowing?  Surely we would still find water there.  True, but it wouldn't be the same water, it would be new water, which brings us to the ironic possibility of future events unfolding in the past; a strange concept at first blush, but not so strange if you accept the premise of there being no direct link between time and events.

And what about travelling forward in time?  What if we were to move down the garden hose in the same direction as, but faster than, the flowing water.  Then we would find nothing, because the water hasn't arrived yet.  We would be in a void, of sorts, until we slowed down and waited for the water (or events) to catch up to us.

And how do I reconcile these concepts with those of scientists much more learned than I?  Well, let's apply my analogy to Einstein's theory.  If a bit of the water suddenly flowed much faster than the main body, it would travel down the hose more quickly.  In so doing, it would arrive at the end of the hose long before the rest of the water.  Put another way, the main body of water would "age" much more by the time it reached the end of the hose, than the bit which sped up.  So the analogy still works.

These are the sorts of thoughts that flow through the inscrutable mind of the Halmanator, as he stands in his back yard, idly watering his flower bed, on a midsummer's evening.

"But surely it's late October!" I hear you protest.

What can I say?  Apparently the water flows through my hose somewhat more slowly than through yours.