H. Beam Piper touched on this in his first “Paratime” story. In this, there’s one time line that has learned how to transition to other time lines, and they use this to search for useful resources and technology. But when they’re coming back to their own time line, it has continued to split, so they see a “broadening of the bands”, where every time line is “theirs”, just slightly different based on choices made while they were away.
He kind of drops this idea later on, because of the implication.
Why? We already know the universe is infinite. This just means that it’s even MORE infinite than we thought; but since all infinities are the same size, it doesn’t actually change a thing.
I was thinking about starting a topic on Time Travel movies and found this thread. So I figured I’d toss my two cents in. Regarding the “blue widget” paradox, I’d recommend a novel called Split Second by Douglas Richards. He resolves the “paradox” by saying that the universe simply adjusts to compensate for the extra widget. It goes off from there.
As for the “other Marty” question in BTTF, this is my take. There was another Marty who left from the Lone Pine mall, being a better driver than “original” Marty he didn’t hit the pine. Having read his dad’s SF stories, he was more aware of the possibility of time paradox so he kept a low profile. He didn’t even warn Doc Brown about being shot by terrorists. So what happened to him? He disappeared when Marty I went “home” and took his place.
But one theory I’ve heard is that time travel is inherently self-negating.
Let’s say that time travel is really easy. Building a time machine is as easy as building a toaster. So people are constantly traveling in time and causing changes in the past and future by their actions. The time lime is in a constant state of chaos because of all of these individual changes.
But with these billions and billions of changes occurring, at some point events will line up in such a way that time travel will never have been invented. No matter how simple time travel is, there is some chain of improbable events which led to it not happening.
And the second we arrive at the universe without time travel, all changes stop. Because in this one unlikely universe, there is no time travel around as a means to cause any further changes. We can’t undue the non-invention of time travel so we are frozen forever in the universe without time travel.
" If the universe of discourse permits the possibility of time travel and of changing the past, then no time machine will be invented in that universe."
I read something recently, possibly even on this board, which said the lack of time travelers is proof that time travel is impossible, or that the human race kills itself off before we can invent it.
There’s other possibilities. Such as, traveling into the past causes the universe to split into two timelines, or traveling back in time causes you to land in an alternate past, or the past no longer exists so you end up in a void/dead, or you can’t change the past so any time travelers that exist can’t reveal their existence. And others, authors have been coming up with ideas on the subject for a long time.
So the lack of time travelers is evidence, not proof.
As pointed out at the beginning of the thread, time travel (at least what is meant by that in fiction, 99.999% of the time) does not actually make sense, so there is not necessarily anything that you missed to follow. A common trope, though, is the “causal loop” like in “Chronocrimes” and “All You Zombies”, where one can no longer separate cause from effect.
Another interesting read is Robert Charles Wilson’s “Las Year” in which gateways are established to the past, but the minute you arrive it becomes an alternate past. Basically the present folks treat the past like an exploitable third world country until the past folks catch on and then the gateway is blown. (BTW, if you’ve never read any RCW, I’d recommend him highly.)
That’s basically the same plot as “Mozart in Mirrorshades” by Bruce Sterling. The future invades 1700s France to steal everything they can get their hands on.
Even if that were so, we can’t prove that the timeline we are in, now, is the “final” one, the one with no time travel. Time travel may be possible, and tomorrow someone will time travel and delete our timeline out of existence. And replace it with another one, where some obscure German named Hanz Schmidt became head of the Nazi party. And in 80 years/no time at all, that will be changed again. And we’ll never know, having been “never-existed” away. But right now, we are here. Let’s make the best of it.
Yeah, but if you’re going to play that game, then maybe the simulation gets reloaded with TIME_TRAVEL=y environment variable set, and future people start showing up[1]. All that we can say is right now, in this universe, as far as we are aware, there is nobody jumping around in time. Movement through time for macro particles is always forward, and linear, even if relativity might change the speed.
Back to fiction, I recently read Kaliane Bradley’s The Ministry of Time, and it was enjoyable. It is more about the human aspects of time travel than technology or paradoxes. What exactly would it take to acclimate someone from the 16th century to live in the 21st? It straddles the scifi, thriller, and romance genres, without being solidly in any of them.
