Time Travel, True or False Options

It's depicted in several movies. Terminator uses technology, The Butterfly effect uses a phychological element, and Superman circles the earth several times to turn back a few minutes to save Lois from an earthquake. Is time travel possible? Magic, technology, speed. What are your thoughts?

Brian Greene in his book "Fabric of the Cosmos" had an interesting thought experiment about time and entropy, thermodynamics that is. The progression from order to disorder that is thermodynamic decay has been called "time's arrow" before, because we can sort the moments in time simply by looking at how high a level of entropy there is. He kind of disproved that though. I don't have the book with me, but here's a paraphrasing of the idea.

Thermodynamics states that there are many possible futures. We could all vaporize in a moment turning into pure quarks, or even vanish entirely, and each of those is one future. But most of the futures have the characteristics of which we're familiar with: increasing entropy, stuff falls down, planets orbit, hearts beat, etc. In fact, the amount of futures that match these characteristics is so vast that there is practically no chance that one of the scant oddball futures would ever occur. That's what we know so far, and that's what we use to tell which part of Hamlet is the beginning and the end, based on how many people are dead.

What happened a moment ago? You remember that, but your memory was a part of that moment. Perhaps your memory was false, and appeared spontaneously just an instant ago, and beforehand the past was different indeed. Maybe 20 milliseconds ago, the universe was nothing but empty space and we all just suddenly came into existence, memories and all, in one incredibly unlikely quantum fluctuation.

The problem with "time's arrow" is, there is no direction in thermodynamics. It's just applying statistics to everyday physics. It works backwards as well as forwards. The chance that the one single past that you remember is the real past is extremely unlikely. It's far more likely that the entire universe just appeared out of the quantum foam moments ago. You wouldn't be able to tell that of course, and the universe would proceed normally from here on. But there are many possible pasts that are far more likely than the one that you remember. And you know the most likely possible past?

It's the future.

Once you do the math, thermodynamics can predict the past macrostate that has the most microstates, and therefore is the most likely to have occured. That prediction is exactly the same as predicting the future, just with a negative time instead of a positive time. The most likely possible past is that we were in the future, proceeding backwards through time to this very moment, doing and thinking everything in reverse until we hit the present, after which we proceed normally back into the future! And every point in the future you consider this thought again, it's more likely that the switch you remember is false, and that the future you are at is now the pivot point.

So the way to put this in perspective is, the Big Bang was a highly unlikely cosmic event. I mean seriously. You got nothing, not even time, and then suddenly you've got enough energy to make all the stars and galaxies in an instant, compressed smaller than a golf ball? Yeah right! Like that's ever going to happen. That's why the "thermodynamic" past is more likely than the real one, because no matter how sensible the past you remember seems to be, the probability of the Big Bang happening is so small it invalidates all that sensibility. If we don't assume that a Big Bang happened, then we can show that the most likely past is a mirror image of the future. If we do assume that a Big Bang happened, then the past you remember is quite certainly the most likely one to have occurred.

Stuff like this makes me realize why time travel is such an absurd idea. We don't want to travel through time; we don't even know what travelling through time means! What we want is to reverse entropy, and all the stories about time travel involve travelling to a state where the universe has a much lower entropy, like before the dinosaurs went extinct. Is it time travel to go see the dinosaurs? I can't say for sure. But I can say it is a reversal of entropy to be able to walk up to something that used to be millions years dead, and now is alive and looking at you hungrily, uh oh...