Time travel doesn't exist because time travel wiped out the timelines where it did

[Retros_x]

I thought the simple answer is that time travel backwards isn't really possible. Not just in our timeline, but in general.

 

[GreyLord]

I don't believe that time is actually a thing. Change my mind.

That is like saying Height is not actually a thing.

What we see as height is actually a measurement of something in comparison to something else. The way one does it changes. It may be in Feet. It may be in Meters. It may be in Krogospac, but whatever it is measured in, the idea still exists.

The same applies to time. As I see it, time is a measurement of change. If things were static, I think we would not have any measurement of "time" as one would put it. However, as things change, we measure how quickly or slowly that change occurs.

So, if you believe Change is a thing, then you would believe in the idea that time measures.

What I suppose we mean by time travel is the ability to travel to a former state before certain changes occurred.

We are already traveling through time (though we are traveling forward through time) in that we see progressive changes caused by changes previously.

 

[Umbran]

We still couldn't think of any other post-apocalyptic cyborg movies though lol

Kickpuncher!

 

[Umbran]

I thought the simple answer is that time travel backwards isn't really possible. Not just in our timeline, but in general.

In reality? Quite possibly. But also, proving a negative like, "there is no way to travel backwards in time" is incredibly difficult.

 

[Umbran]

Regarding relativity, I thought the point was that physics / physical reality has no preferred frame of reference. Although, curiously, cosmologically, background radiation seems to provide such a frame.

Not quite.

Einstein's Special Relativity tells us, in effect, that there is no inertial frame of reference in which physical laws of the universe differ. If you are looking at two different frames of reference, and you account for the (constant) velocity difference between them, the laws of the universe will be the same in both.

An "inertial frame" is one in which, in the absence of a net force, a body will follow Newton's Laws. Basically, any frame of reference that is itself not accelerating is likely an inertial frame.

 

[Umbran]

That is like saying Height is not actually a thing.

Well...
Since we are talking about weird things like time travel....
If we are, in fact, a hologram or a simulation (two kinda weird, but technically possible cosmologies), then "height" may, in fact, be an illusion.

 

[Maxperson]

This is basically how every game of Chrononauts ends up playing out

You play with them? I eat my cronuts.

 

[Gradine]

 

[GMMichael]

Well, what do you mean by "without any time passing"? Because, if we are thinking of this as spacetime, then time never passes - we pass through time, just like we pass through space.

Which is why I said:

. . . time being part of space, "spacetime," and therefore probably not separately navigable from space?

with which you seemed to disagree. You can't pass through just one or the other. You have to pass through both.

What I suppose we mean by time travel is the ability to travel to a former state before certain changes occurred.

That's a good way to put it. The past isn't a place; it's a state of the same universe we're in now. To go to a previous state would require changing this entire universe or finding another one in the exact same state you're looking for. Except it has just enough room for you drop yourself and your time machine into it.

We are already traveling through time (though we are traveling forward through time) in that we see progressive changes caused by changes previously.

So "how do we time travel" becomes "how do we undo all the changes since 1955?" It's good that we're in an RPG forum for this, because you'd need god-powers to do something like that.

 

[Umbran]

Which is why I said:

with which you seemed to disagree. You can't pass through just one or the other. You have to pass through both.

I guess I wasn't clear.

I, personally, here and now, cannot pass through one without the other. I, personally, here and now, am restricted to motion governed by Einsteinian Relativity. But I, personally, here and now, don't have a time machine.

Time machines, in general concept, can violate Einsteinian Relativity. If we are considering time travel, we are expecting to break those rules, such that, in principle, the movement in space and time are no longer linked, or are linked differently than we know today.

Rather like, right now, I am more or less restricted to movement on the dry parts of the surface of an oblate spheroid called "Earth", at rather low speeds. Put me in a car, and I can go faster. Put me in a boat, and I am not restricted to the dry parts. Put me in an airplane or rocket, and I am no longer restricted to the surface.

That's a good way to put it. The past isn't a place; it's a state of the same universe we're in now. To go to a previous state would require changing this entire universe or finding another one in the exact same state you're looking for.

(emphasis mine) Not even Einsteinian Relativity requires that.