Time traveler caught on film in 1920?

I don't see anything at all in her hand, but it begs the question of why a time traveller would attempt to use a cell phone in the 1920's. What is it going to connect to?

And talking into her hand for no reason?

No, I disagree. Relativity makes the notion of time travel not only possible, but inevitable. The notion of time travel to the future is that you experience the passage of a certain amount of time, but everyone else experiences the passage of a much larger amount of time. The notion of time travel into the past is that you experience time in a backward direction, but everyone else experiences it in a forward direction.All of these things are experimentally-verified consequences of general relativity.

We have experimental evidence of creating negative curvature of space, and general relativity indicates that this is the same thing as backwards time travel.

Right. And so, if I take ten minutes but the world around me spins forward for ten years due to a time dilation effect from speed or high gravity, that's functionally time travel to the future. Similarly, if a closed timelike curve loops you around to the beginning of the curve, that's time travel too.We live in a universe where "time travel", to some points in the future and perhaps some in the past, is a physical possibility. But my guess is that the engineering is prohibitive (to say the least.) Further, my guess is that at the very moment that anyone creates a time machine (or, well, will, since I don't think anyone has done it yet), someone from the future pops out of it to kill them. Otherwise we'd be up to our balls in time tourists all over the place. Ok, I don't understand what you're trying to say at all, not least of which because you're trying to measure time with speed, which makes no sense at all. But suffice to say that speed-related time compression is very much a real thing, and accelerating at great speed to take advantage of dilated time to "arrive in the future" - that is, experience a short passage of time while the rest of the universe experiences a great passage of time - is experimentally verified. Time is a very real component of the universe; it's a characteristic of the spacetime which the universe is comprised of. Yes, but general relativity is the theory of which closed timelike curves are a consequence.

I play WoW.With my wife.Who I bang.

No, you're literally bending time by bending spacetime. See? It's right there in the name. Your bending your personal time relative to the time experienced by someone not accelerating. But you're going a longer distance that the person in the nonaccelerating reference frame, because you're accelerating and they're not. Via closed timelike curves. Right. And as you traverse a closed timelike curve, you experience your own time going in a forward direction - the watch on your wrist ticks from 12:00 to 12:01 - but time outside of the curve is experienced in a backwards direction - the clock on the wall ticks from 12:00 to 11:59.Time travel into the past, in other words. It's a permissibile solution to the Lorentz transformations in general relativity. Not precisely true. Time is experienced differently as a result of acceleration. Time is perceived differently as a result of speed. The difference I'm eluding to is the difference between observing a timepiece in your own frame of reference and observing a timepiece in someone else's frame of reference.To illustrate - if you and I have synchronized watches, and you accelerate to near the speed of light and then come back, your watch is behind mine, because you've "traveled into the future"; you've experienced less passage of time than I have. If you and I have synchronized watches and you pass me on the Starlight Express at a constant rate of speed, then when you look at my watch, you see it ticking slower than your own. But when I look at your watch, I see it tick slower than mine. No, you're right, the Twin Paradox is not how someone travels backwards in time, it's how someone travels forward in time. Closed timelike curves are how someone could theoretically travel backwards in time. Don't get confused, I'm talking about two separate phenomena but both are consequences of general relativity. Conveniently, everything in the universe except for spacetime has mass.

I think I see where you're getting hung up. That doesn't make time travel impossible, because nobody wants to travel backwards in "universal time." They want, generally, to travel backwards or forwards in time relative to something else, like the rest of the world. This is permissible under general relativity as I've explained.

No, time is actually bent by gravity, that's why the have to calibrate GPS satellites to correct for the distorted time we experience on the surface of the Earth. Completely wrong. You're just making things up, now. Closed timelike curves exist as a necessary consequence of general relativity, so by definition they can't exist where general relativity doesn't apply. The quantum scale is precisely the very last place we should expect to see a closed timelike curve, because that's precisely where general relativity is the least descriptive.One example of a macroscale closed timelike curve would be a wormhole where one mouth has been accelerated to near the speed of light (say, by rotation.) Passing through such a wormhole would allow you to observe yourself emerging from one mouth of the wormhole before you'd actually entered the other. There's no way to bypass it if the conjecture is true (by definition, because the conjecture is merely "time-travel is impossible on any but sub-atomic scales.") If the conjecture is false, then it's not necessary to bypass it. No, a description of what a closed timelike curve is. I'm sorry you didn't understand it, but maybe you need to read up on your Lorentz transformations. Photons in motion have mass as a consequence of their velocity. So what's stopping you?

But there isn't anyone on Alpha Centauri.

What would who see what?

Yes, quite sure. That's the consequence of general relativity; standing at rest on the Earth's surface is equivalent to accelerating at 9.8 m/sec/sec. In general relativity gravity and curved spacetime are equivalent. We can only speculate on the consequences of a theory of quantum gravity, because we don't have one. Thus you're free to suggest that a theory of quantum gravity will necessarily preclude time travel into the past, and I'm free to respond that in general relativity as we currently understand it, travel into the past is permissible under certain (practically impossible) circumstances. Currently, so is a full theory of quantum gravity.

You match velocity and acceleration with the Planet Earth. That puts you into the same reference frame.AbE: Let me expand your question and correct it, somewhat - as a consequence of these timelike curves, the best you can do is get back to the origin of the curve. So, in 1929, you create a "time machine." Later, in 2010, you step into the machine. You experience time continue in a forward direction - your watch ticks from 12:00 to 12:01 - but when you get out of the machine, you're at the origin of the timelike curve, in 1929. You don't have to do anything to "get into their reference frame", you're already sharing a reference frame with the Earth of 1929 because the exit of your time machine has always been in the same reference frame as Earth in 1929.Edited by crashfrog, : No reason given.

They'd see whatever was going on around Alpha Centari, because that's where they are. What on Earth could you possibly be asking? What would what be "in relative to someone in [Alpha] Centarui"? Seriously, Oni, you're making precisely zero sense with these questions.

I'm not CS. I never said that it was not the speed as well, but it's a matter of settled fact that clocks desynchronize down on Earth compared to a high altitude due to the difference in proximity to a gravity source. That's absolutely true, it's been measured by a number of space probes, and it's a consequence of the equivalence of acceleration and gravity. No, again, they're equivalent. Look, Oni, these are elementary matters that are covered in Brief History of Time as well as other books. I am, and do. This is not at all the issue. The issue is you continuing to make dunderheaded characterizations of general relativity because of a lack of knowledge on your part. I mean you didn't even know what a Lorentz transformation was. Well, no. It's conjectured to have "chronology protection", and it's assumed that a theory of quantum gravity will uphold that conjecture (because why else aren't we up to our tits in obnoxious American time tourists?) But that's not known. And until it is you have only a conjectural basis to assert that travel into the past is a physical impossibility, instead of just an incredibly difficult engineering problem (which is the conclusion of a number of physicists.) LOL! Yes, that's exactly right, Oni - I'm a member of the powerful Time Travel Lobby trying to put one over on people, just like the oil industry or Big Tobacco. Well, it's a good thing a comedian showed up to educate us all on general relativity.What a tool you've become, lately. Maybe, but unlike you I'm not prepared to draw conclusions from theories that don't yet exist.Edited by crashfrog, : No reason given.