Introduction: The real nature of what we call ‘time’ is one of the Big Questions. It’s been debated ever since humans evolved thought and language. That puzzlement remains true to the average person today, although ‘time’ has become the professional subject or province of philosophers, metaphysicists, and theoretical physicists, not to forget many a science fiction author! Here’s my two cents worth – ‘time’ is an illusion!
Continued from yesterday’s blog…
Travel through Time? The question remains despite my earlier negation; can you revisit and experience a past event? Can there be an instant (or not so instant) replay? Take the example of the now dispersed ink in the bowl of water. If all the ink bits (particles) were to exactly retrace their movements (that’s just so highly improbable that you’d wait longer than the age of our Universe to actually see it), they would eventually come together as an ink drop. If they now retrace those retraced movements (ditto on the statistical improbability) you get back to the exact same configuration of dispersed ink bits in the bowl of water. You will have witnessed an instant (or not so instant) replay of a past event. You would have in a sense travelled back in time to ‘record’ an event that had already happened. Of course you would have ‘time’ travelled with respect to that specific event and only that event.
Ah, that word ‘record’. Of course you could have filmed the original ink drop to dispersed ink event then watched the film at a later date, but that’s cheating a bit, don’t you think?
Assuming for a moment that time is actually something tangible and that travel through it is possible (that’s in agreement with Einstein’s General Theory of Relativity). Einstein’s Relativity aside, I’d maintain that travel backwards in time is probably nonsense.
If you go back in time with a view to either preventing something from happening or inaugurating something and you succeed, then when you return to your own present time the original motive to go back in time in the first place has ceased to exist. That’s because in your now altered present, there’s nothing motivating you to go back in time and so you don’t, but if you don’t then you couldn’t have changed the past in the first place. That actually suggests that your actions have split the Universe and generated two timelines (or universes), one in which you go back to fix something, and one in which you don’t because there’s nothing that needs fixing.
If you don’t succeed, if you can’t tamper with the past* then it’s all an exercise in futility and so there’s no point being a damn fool about it. If at first you don’t succeed, give up!
If you go back in time just to observe (as historian, scientist or even tourist), your very presence in the past has introduced a change that didn’t previously exist, and any change has a ripple effect which will change, even if only slightly, your own present, in you’re your before-the-fact time travelling present was different to your after-the-fact time travelling present, which could, as we’ll see, generate a paradox. You may not care about the alteration, but other people may not be so happy and laid back with your inadvertent meddling.
But wait a second. Those other people probably wouldn’t know or be aware that anything had altered. Having reset the clock when you went back in time, the ripples would have become part and parcel of their world view, so only you, upon your return (having bypassed all the rippling) would notice the change.
But what if you go back in time only to materialize in front of a speeding train and are killed. Of course that doesn’t affect your ancestors so presumably they still meet and marry and breed and ultimately your born – again – only to go back in time and get hit by that train!
Or, you materialize back in time and so startling someone of that era into failing to notice that train and gets killed. Now say that someone was your father-to-be; your father before he met your mother. Now you have two universes – timelines – again. One timeline is where you went back in time and presumably returned; one in which you were never born.
That’s one of many variations on the ‘grandfather paradox’ which in general has as a plot where you go back in time and somehow prevent your own birth by say, killing your grandfather before he met your grandmother, or in a less gruesome way, prevented them from ever meeting. When I was a teenager I remember writing a short story (never published) where a group of scientists travelled back in time some four billion years to just after the Earth formed and solidified and cooled. One of the scientists was a pipe smoker, and after finishing his smoke, tapped out the pipe ashes into a small puddle of water. Of course that puddle was the very puddle that was to have given rise to that first proto-cell, but the pipe ash polluted the puddle and so that origin of life event never happened, and so back in what would have been the 20th Century, the sun shone down on a sterile planet! The only trouble with the story was that four billion years ago, there was no oxygen in Earth’s atmosphere so one couldn’t smoke. Still, it was the mother of all grandfather paradoxes!
Here’s another time travelling curve ball coming your way. You have a set of coordinates with respect to Planet Earth – latitude, longitude, and altitude. But you also have a set of coordinates with respect to the Moon – lunar latitude, longitude and altitude. You have a set of coordinates with respect to the Sun (solar latitude, longitude and altitude). Ditto Mars, and ditto the nearest star and ditto the centre of the Milky Way Galaxy, etc. In fact, although they change from moment because of relative motions of all the bodies concerned (that also applies to you and Planet Earth since you move around), you have a set of coordinates with respect to every bit of matter in the Universe. The question is, when you time travel, what set of coordinates do you take with you? Where exactly do you end up? It’s taken for granted in works of fiction that its Earth’s coordinates, but is it necessarily so? What if you retain your exact position (relative to where exactly is a mystery) but travel in time. Then presumably when you materialize else-when, the Earth will have moved far away, and there you are flailing around in empty space, breathing a deep vacuum!
So we see that while time travel stories are a staple of the sci-fi authors’ bag-of-tricks – they stir up those little grey cells – there doesn’t appear to be much chance of time travel in any physical reality we know of. Time travel is only a reality in the imagination. We in fact have a version of the Fermi Paradox here. While the Fermi Paradox referred to aliens that should be knocking on our collective doors (“where is everybody?”), if time travel were possible, as astrophysicist Stephen Hawking has so absolutely pointed out, then where are all those gawking time travelling tourists and historians from our future?
*Akin to astrophysicist Stephen Hawking’s Chronology Protection Conjecture which states that there is as yet some undiscovered principle in physics which will make it impossible to travel back in time and thus make the Universe safe for historians.
Further recommended readings about time and time travel:
Carroll, Sean; From Eternity to Here: The Quest for the Ultimate Theory of Time; Dutton , New York
Davies, Paul; About Time: Einstein’s Unfinished Revolution; Penguin Books, London
Gott, J. Richard; Time Travel in Einstein’s Universe: The Physical Possibilities of Travel Through Time; Phoenix , London
Hawking, Stephen & Penrose, Roger; The Nature of Space and Time; Princeton University Press, Princeton , New Jersey
Hawking, Stephen W. et al.; The Future of Spacetime; W.W. Norton and Company, N.Y.; 2002:
Le Poidevin, Robin; Travels in Four Dimensions: The Enigmas of Space and Time; Oxford University Press, Oxford
Lockwood, Michael; The Labyrinth of Time: Introducing the Universe; Oxford University Press, Oxford
Mahid, Shahn (Editor); On Space and Time; Cambridge University Press, Cambridge
Randles, Jenny; Breaking the Time Barrier: The Race to Build the First Time Machine; Paraview Pocket Books, New York
Toomey, David; The New Time Travelers: A Journey to the Frontiers of Physics; W.W. Norton & Company, New York
No comments:
Post a Comment