Time Travel is Very Unlikely, and Rather Unnecessary
First of all, I am not an expert on time travel, nor do I know anybody who is working on the subject of human time travel as is in so much current science fiction. I also haven’t heard any speculative physics talks on it. I’m writing this purely off the top of my head.
The science fiction movies and serials that are massive on premium channels always transport wholely dressed humans without twisting an eyebrow. The targets are to precise locations. Not to outer space or the center of the earth. My first subject was going to suggest a Time Travel Police Force to trace down such travelers. They probably are coming with very good humanitarian intent, or very selfish intent.
Unmentioned in most of the science fiction is that just being transported to the same spot in space years before or in the future is without doubt going to leave you in empty space, far from anything. First of all, the earth rotates at about 1,000 miles an hour, or once per day. Then, the earth revolves around the sun at 67,000 miles per hour, or once per year. The sun revolves around the Milky Way at 514,000 miles per hour, or a revolution every 230 million years. Being off by a second in the latter, leaves you 143 miles away from your target, in outer space or inside the earth. You also have to match exactly the galactic, orbital, and rotational speed or end up colliding with something when you arrive! Now, the Milky Way is speeding through the Universe at 1.3 million miles per hour also, but to a large extent, everybody in our past and future has such a similar speed.
Because of the difficulty in exactly matching position and velocity, there are two modes of time travel that would be preferred. One way is to be placed into the atmosphere, with a parachute. The preferred target area to avoid cities and avoid being far out at sea, would be a well monitored desert landscape, so you could get picked up by people who would not be shocked at your arrival. Area 51 in Nevada would be the preferred area. If the time traveler could use a small aircraft, it would have to have very high speed to match the velocity of the target atmospheric area, and could then be over the ocean. That is quite similar to the high speed UFOs seen by Navy pilots all of the time. Just pointing these things out.
Now, lets get speculative about the motive of a time traveler. The standard humanitarian movitation of a time traveler is to kill Hitler. I have lived about 80 years, and during my lifetime, the history of the world has not dramatically changed because suddenly everything I remember of the Second World War and its consequences became out of match with history or the current memory of the world. Also, 75 million people killed in that war and their offspring did not suddenly appear. Hence, there weren’t any humanitarian visitors that have occurred yet.
The next speculative visitor would be someone out to become a billionaire knowing the companies to form or to invest in. Such people have well known pasts, and nobody has just appeared out of nowhere. That could be topped by a really narcissistic traveler who felt that being a billionaire was not enough, but that they had to rule the greatest economic country in the world. They would of course cover up their past, and have no scruples about telling 30,000 lies while in office. Hmmm.
Now for some more physics. The older science fiction had the time traveler annihilating their younger selves to avoid a time paradox. As we showed with Antman converting to bug sized, the E = m c^2 of the human body is equivalent to exploding all of our nuclear weapons at one point and time. That obviously hasn’t happened, nor does it make sense. Such an annihilation would occur if antiparticles met particles, but people are just particles, not antiparticles. More recent science fiction does not have that happening. After all, we are now untroubled by many people becoming political clones of our past President. Hmmm.
Then there are the giant wormhole connections with entrances and exits through black holes. But when people or anything go into a black hole, they are elongated by tidal forces since black holes start at just a few miles in size, and they would not survive. The black hole would of course not just sit there quietly, but would devour the earth.
If you had to simply send a message that a pandemic was about to occur, you could do it microscopically, if you knew exactly where to pipe it into a computer chip on a broadcast network. Of course, there were many researchers who knew it could occur, and nevertheless their research to prepare for it was cut. Our last President even cut out the small agency set in place to give us warning about a pandemic. Even now, a year and a half into the pandemic, with either 600,000 or 900,000 US deaths, and with all of the communications and free speech the US has, we cannot convince 40% of adults to get vaccinated and highly protected. So much for the humanitarian approach. We are also spending the summer experiencing serious effects of climate change, despite warnings over the last 50 years. We also live under a nuclear threat that can instantly destroy all of civilization, destroy future crops, and release damaging radiation for years. Nobody knows how to stop that. The future could tell us how we are fools not to dismantle that now, after such an annihilation, but advanced science would not exist then to construct a time machine, were it possible at all.
We also don’t need to travel forward in time to warn people in the future of what is going to occur because of our actions. It already has occurred, and they will hopefully understand where we failed and how to correct it for themselves.
