The most convincing argument that time travel will never be possible is that certain events have transpired that time-travelers obviously would have wanted to prevent, if it were within their power. Since these events have not been prevented, it can be assumed that no one came back to prevent them because time travel isn’t possible. That can be a pretty convincing line of thought. But I have a different theory.
I don’t discount the possibility of time travel. Nor do I ascribe to the belief that time is immutable. However, I have a different hypothesis as to why time-travelers haven’t altered our history.
Time travel stories always involve one or more people moving forward or backward in time, but remaining stationary with respect to our three-dimensional space. If they leave from a parking lot, they will re-appear at the same spot in that same parking lot. It will be at a different time. The parking lot may not be there, it may not have been built yet or it may have been ripped up and replaced with a park or an apartment building, but the traveler will appear exactly where the parking lot used to be.
That’s the bit I have a problem with. The way I see it, the traveler will travel through time but remain stationary with respect to our three-dimensional space. We agree up to that point. However, I would insist that the traveler would remain stationary with respect to the universe, not some local point of reference, such as a parking lot.
The Earth rotates once upon its axis every 24 hours. If our traveler was located in New York and moved forward 12 hours in time, the Earth would continue to spin (one-half revolution), and she would find China under her feet when she re-appeared. Of course, there is more going on than just the rotation of the Earth. The Earth also revolves around the Sun once every 365.256 days. This orbit is approximately 584 million miles. If our traveler moves forward in time 12 hours, the earth would have moved along its orbit roughly eight hundred thousand miles during this same time. Our poor time-traveler would re-appear only to be left sucking vacuum.
Further, our Sun follows an orbit around the Milky Way galaxy. That galaxy is part of a cluster of galaxies that affect each other’s movements. That cluster is part of a super-cluster whose components similarly affect each other. That super-cluster is moving generally away from the center of the universe, the point at which the big bang took place. I won’t even attempt to guess at the combined effect of all of these forces, other than to say that the point on the earth, where our traveler was standing when beginning her 12-hour voyage into the future, must be a very great distance away when she returns to our space-time continuum. Her distance and direction from the center of the universe would remain unchanged, but the Earth, Sun, Galaxy, etc. would have moved away from the point where she was when she started.
Time travel may well be possible, but as I see it the traveler would be in no position, as it were, to affect changes in the timeline.