Caution! Before reading further, please review the definition of ‘tongue in cheek’.
Time travel is a staple of science fiction, and with good reason. The paradoxes are delicious to contemplate.
And somewhat related, already there is quite a lot of interest building about the total eclipse of the sun that is due to be visible over a wide swath of the United States on August 21, 2017. I will be in Oregon and already have my fingers crossed that there will be no clouds.
Is such a thing possible? The answer depends on which way you are going—forward or back.
If you go forward, yes, time travel is possible. According to special relativity, we observe the clocks of someone moving relative to us as running more slowly. This fact leads to what is called the twin paradox. One brother blasts off into space while the other remains behind. Each sees the clock of the other running slower. After, say, may years, the spacefarer returns to visit his earth-borne sibling. So, which is now the younger?
It is the traveler who is younger. Among other places, the reason is explained here. In the reference, the stay-at-home twin ages twenty years while the traveler ages sixteen. Effectively the traveler has traveled four years into the future.
Going backwards presents paradoxes too. The classic is to figure out what happens when someone goes back in time and kills his own father before he is born. Physicists say that backwards time travel clearly is impossible. It allows things like the death of a father to happen before they can be caused—by among other things the birth of the murderer. A more folksy argument is ‘If backward time travel is possible, then how come we don’t meet any of the travelers?’
Well, think about it for a moment. Maybe, just maybe, an effect does not always have a cause occurring first and we just have not figured this out yet. And backwards time travelers certainly would be briefed not to do anything stupid. If they were really careful, everything would be OK.
But being careful can be a hard thing to do. Consider fashion, for example. It is changing all the time. Even with the internet, keeping track of the coming and going of fads is not easy. And maybe the time travel machines are not very precise. One might want to visit the sixties but arrive in the twenties instead. As soon as the traveler stepped outside of his machine, he would be immediately spotted as being very much out of place.
For women time travels this is indeed a problem, but for men there is a work around—tuxedos. Yes, men’s fashion does change too, but much more slowly than it does for women. A tux from the twenties might well pass in the sixties with little or no comment.
This means that if you indeed are looking for evidence of time travelers, going to the opera or Nobel Prize ceremonies would be a good thing to do.
There can be other visitors among us as well. Consider the phenomenon of a solar eclipse.
First of all, for such a tiny planet as our Earth, our moon is relatively enormous. From anywhere on the surface, it is one of the two biggest sights in the solar system. That alone is worth the visit of alien tourists.
But the fanstasic thing is that, in addition, the moon is precisely the right distance away from the sun so that a total eclipse can occur. No mere transit across the blazing solar disk, no overlap that is wasted. The moon is blocks out all of the sunlight except for a tiny ring around the edge.
This has got to be an astronomical rarity. What are the odds of such a thing happening? There very well may be no other instance in our entire galaxy. Visiting the Earth during a solar eclipse has got to be on the alien top ten list of things to do.
So, If you have a change to be in the path of totally, please follow up on it. You might see the best of all. There right before your eyes, dressed in a tuxedo, a time traveling alien.
Time travel and eclipses (well, occultations) are an element of The Archimage’s Fourth Daughter.
© 2019 Lyndon M. Hardy