Is time travel possible?
Travel
To travel is to change your position with time. If I travel North at 50 mph then every hour my coordinates are 50 miles further North. But does it make sense to talk about changing time coordinates with time? We all travel at precisely 1 hour per hour. When people talk about time travel, they generally mean jumping from one time to another. Is this possible? There are various different conceivable ways of travelling through time. There is continuous and discontinuous, forwards or backwards, blind and previewed.
Continuous Time Travel
When we talk about time travel, we generally mean discontinuous jumps through time. Imagine you have a Tardis-like time machine. You get in, set it’s controls for some other time, press go and then get out into another time. If the machine travels continuously through time, then it is present for every moment in time for the next year. Suppose you are travelling forward to the same place, but a year from now. The time machine simply stay in place until you emerge from it a year later, as though it were frozen in time, and you with it. The hope is that nothing happens to the machine during the year, since neither you or the machine and are incapable of responding to intervening events.
Discontinuous Time Travel
Most science fiction depicts time machines a jumping from place to place in space and time. That is, you get in the machine, set the controls, press go, and you disappear from your old time and re-appear in the new time. The question is: where were you and your machine in the intervening time? Even quantum physics does not allow you to be completely removed from space and time – that would violate all sorts of laws of conservation. If you suddenly materialize in a new time, what happens to the matter that was in the place that you take up? If it is pushed aside, this would be a very sharp explosion. If it dematerializes, then conservation laws are violated.
Travelling Blind
Should you time travel, without looking where you are going? Do you just press go and hope for the best? Suppose the space you plan to materialize in has something else in it or is under water? It all seems a bit risky.
Time Preview
Suppose your time machine can preview the time and space where you are going. This would have massive implications. If travelling into the future, there would need to be some way in which the future scenario would be guaranteed. This would require the future to be predetermined, and as we have seen, this cannot happen.
Travelling Into the Past
If we travel into the past then we create duplicates of ourselves. Suppose we decide to move back and hour and sideways by a little distance. This would create, an hour ago, two time machines side by side, and two versions of ourselves. There are two ways of thinking about this. We could just say that this is verifiably impossible because we were there an hour ago and this event evidently did not happen. Alternatively, we could imagine that this does happen. What we observe is the sudden and, at the time unintended, appearance of a second time machine, together with copies of ourselves. Our original selves are now predetermined to wait an hour and then go back in time. Again, physics does not allow this sort of exact predetermination. Either way, travelling into the past is not possible.
Travelling into the Future
Suppose we jump one hour into the future. After an hour there would be two time machines and two copies of ourselves. This would contravene all laws of conservation so is not possible. It would also raise big issues as to which one of us we are.
Prophecy
Prophecy comes from the Greek words pro (forward) and phesein (tell) meaning to tell what is going to happen. An exact prophecy would constrain us to a predetermined future and so would go against nature and any divine plan involving free will. But this does not exclude enigmatic and, to a certain extent cryptic prophecies. These do not constrain free will, because they are not completely understood, especially at the time they were first given. However, they can guide the faithful, and affirm faith when they are realized.
For instance, Isaiah’s prophecy that “a virgin shall conceive and bear a son, who will be called Immanuel” (Isaiah 7:14) would not have been fully understood at the time and might have been misconstrued to be about current events. However, events have shown that this was a powerful prevenience of the incarnation. Thankfully, the prophet just delivered the message, without trying to give an interpretation. The effect of this that this remarkable prophecy has indicated God’s knowledge of future events and encourage people to hope in Him.
Conclusion
We conclude that time travel, as generally understood is not possible. However, prophecy is reasonable and there are plenty of instances to consider and discern.
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