Your response doesn't make very much sense, but as far as it goes:

You might want to rethink that one...

If we're speaking strictly theoretically, my objection to time travel is that it requires the Earth to be a fixed reference point--which it's not (contrary to what the early church scholars believed). Think about it this way: you're travelling forward through time right now (at the rate of 1s/s. Duh), but you're also travelling through SPACE, and at a rather high velocity.

If you take into account the Earth's rotational speed about it's axis, the speed of the Earth moving around the Sun, the Sun's rotation relative to the Milky Way, the expansion of the universe...

If you moved 1 minute back in time (without accounting for your movement in space), you'd end up in deep space as the earth and the universe hurtled away from you. And without a fixed point of reference, there's no way to do the math to figure out where you'd have to move in space.

 

That's true, but I am sure that in the "infinite" future, people would be able to adjust the time-turner to transport them to another reference point. Or they could just put on a form of protection(maybe there is a charm?)when they travel to the past, and use some sort of future propulsion method to take them to Earth.
Remember, time is infinite, so there has to be infinite ways for people to be able to get here in the present.

 

We actually cannot say if time is infinite. We don't really know if space is infinite either.

I mean, if both are infinite, then it can be concluded that everything exists.

As the universe expands infinitely, and as time goes on infinitely, then the number of situations possible is also infinite. It's how we exist – the right circumstances all came together – a temperate planet, a lightning bolt, elementary particles conveniently placed (if you subscribe to that idea of creation) at the precise moment.

I mean, if you consider both time and space as infinite, then everything gets a little wacky. One or both have to be finite (or at least, at some point, looping in a circle; some exchange must take place). If both are infinite, then, well... we may as well suspend all rational thought.

As for time-travel. Well, you're traveling through time at the greatest speed when you're not moving at all, so then how does time move backwards? Running at the speed of light stops time (regardless of the direction), so that's out.

It'd have to be some combination of the two (not moving and moving). Or something totally radical. I can't even come up with an idea.

 

Or the concept of time-travel simply is impossible. Time itself could very well be infinite but only if it stays linear.

 

Sorry to put on my pendantic "physicist killjoy" hat, but this statement isn't true. Even if the universe were infinite and, say, a new universe were tessellated throughout space every 20 billion light years (far enough away that nothing there could causally affect occurrences in this universe since the Big Bang), you wouldn't have "every possible universe" occurring unless everything in the universe happened to be quantized.

The reason for this is a pretty simple application of transfinite number theory. Imagine space isn't inherently quantized (described by a discrete set of numbers, such as the integers or rational numbers). If I have a single, non-quantized state, e.g., imagine that the position of the clementine on my desk is in one of a continuum of different possible locations, then there is an uncountable infinity of possible states of the clementine. But the aforementioned infinite tessellation of the multiverse produces only a countable infinity of different universes. Therefore, there is an uncountable infinity of universes not realized.

It's a simple matter to prove that at least something in the universe isn't quantized. (Ionize a hydrogen atom--the electron will exist in a continuum quantum state). Q.e.d. and all that jazz.

It is clear that either the universe has a creation event (a Big Bang or equivalent) or our fundamental understanding of the nature of electromagnetic theory and thermodynamics, the two most solidly verified theories in physics, is fundamentally flawed: Go out at night. Look at the sky. If the universe were infinite and filled with stars, then the sky would be light, not dark. (This is Olbers's Paradox. Google it). I'm simplifying here, but if you dig into this deeply, you will find that one has to go to really contrived lengths to find a resolution of this paradox that doesn't involve an expanding universe with a creation event.

It's actually more weird than that. If you are moving, then time intervals (say the time between "ticks" of a second hand) of a clock outside your moving frame (e.g., a watch on an observer standing on the ground) slow compared with the clock in your frame. But the same can be said for the observer on the ground: comparing your moving clock's ticks with his, he finds that in his reference frame, your clock's ticks take longer than his. This is the magic of relativity: Both are actually "true"--there is, in fact, no paradox associated with the different observations of the universe.

Who is "right" you ask? You would have to slow down (or speed up the other observer) and find out. Or, you could send a message, which takes finite time to propagate. Only then can you sort out the relative frames and figure out who aged more.

I'm not doing the subject justice and for that I apologize. (Feel free to PM me if you would like elaboration).

It's actually possible within Einstein's general theory of relativity to come up with spacetime geometries containing wormholes, where one has what's called "closed time-like loops". (In fanfiction terms, this means being able to violate causality and, in principle, to go back in time to affect the present). The general problem with these solutions is that they are unstable--one cannot transport matter or energy through a wormhole without causing it to collapse. This is one of the things that Nightmares of Futures Past got right. (Harry only sent back his soul and magic, which ostensibly don't have mass or energy).

My apologies to the community for the long-winded, probably boring post.

 

How is time travel possible?

The Flux Capacitor is what makes time travel possible.

Like, duh.


Note: This thread needs more Emmawatts.