When reading stories regarding time travel, it's always assumed that there will be no displacement in space. Sometimes, there is consideration given to the fact that the geography of a given area might change over long temporal jumps, but it's always assumed that if you leave Chicago in 2007 and move thru time to 1945, you will appear in Chicago in the same spot you left. But this neglects the fact the earth itself is moving. It is rotating about it's own axis at about 1000 miles per hour. It is orbiting the sun at a speed of 66,514 miles/hour. And that the entire milky way galaxy is rotating at about 612,000 miles per hour. Wouldn't a vehicle designed to move in time but not space find itself hundreds of thousands of miles from the earth somewhere out in space? H.G. Well's intrepred time traveler riding a machine that resembled a bicycle, would have been in for quite a surprise.
Yep, and they always assume the elevation of that "one spot" has never changed, either - despite a million years (or whatever) of erosion. Even if they managed to overcome the flaw you pointed out they could still easily arrive inside solid rock or deep within a prehistoric ocean. Please Register or Log in to view the hidden image!
It would seem that the safest way to time travel would be in a space ship. Of course, I suppose you could theorize some BS about how the temporal field is fixated on the gravatational well created by a planet and fixes its position that way. But the funny thing is most SciFi stories don't even bother.
I don't agree with this. If you could make your world-line PERFECTLY time-like (i.e. solely along the `t' direction), then it would be possible. I mean, heck, this is just a minor problem once we've figured out how to travel through time Please Register or Log in to view the hidden image!
There's not a lot of conceptual difference between a time machine and a teleporter. Both take you from one place in space-time to another. So, it's not a big stretch to combine the two - when choosing your destination, you specify both the time and the place... or, you get the machine to figure out where your current location will be at the destination time. But yes... most time travel stories gloss over those kinds of details. But there are exceptions. Doctor Who's TARDIS sets both time and place when travelling. I vaguely recall a novel called Billennium (I think) that also had some spatial compensation. Any story in which there is some device to serve as a destination doesn't need to address that problem.
Could be! Please Register or Log in to view the hidden image! But that's the thing about writers of fiction, they have license to make anything happen that they want. Some make a good effort to at least partially explain their wonderful machines. Others either can't figure out how or just don't want to get bogged down in fine detail.
According to Einstein's theory of Special Relativity, the time machine rider would enjoy the priviledged position of viewing the entire universe in the reference frame as unfolding in terms of Newton physics, which means that the rider would see himself ( or herself ) (or itself ) having no special displacement in time or space. In Special Relativity there is no provision for any observer to see the external frame as happening faster than expected, only slower. So, according to Special Relativity, a time machine rider could only see the universe happening slower than normal, not faster. The time machine rider, if Special Relativity is an accurate description of reality, would age, say 50 years, while traveling 10 years into the future. How can such a thing be proved?
The effect should be opposite to what you have described. Time traveller who uses a fast ship to go to the future would age more slowly than the ones on Earth. Otherwise, he would not be travelling, but the people on Earth would be travelling into his future. ps: I think the readers should assume that the tie machine has some sense about the environment it is travelling through, and can control its position with some accuracy. So for example, it could be so that by default the machine just brings you to the place with the same location relative to Earth, whatever that is defined to be.
I think CANGAS may be referring to SR's prediction that the time traveller would 'see' universal clocks ticking slower than his own clock, the rest of the universe moving in 'slow motion'. That perdiction cannot be correct, of course. If the time traveller watched 50 years pass on Earth, he would have to see the Earth orbit 50 times around the sun, while only 10 years accumilated on his own clock. Some state the traveller would see the Earth orbit the sun only twice during the inertial phase of his journey, and 48 times during the acceleration/decelleration non-inertial phases. That kind of plays havoc with orbital mechanics in the solar system. Or, do you think the Earth will orbit the sun fewer times in one frame of reference than it does in the other?
time travel is impossible, it is pure science fiction nothing more. i cant believe scientists actualy think you might be able to do it someday, its absurd. how can anybody even explain how its possible even in woo woo theory. go back in time and meet yourself as a baby. what happened in the past cannot be lived again or seen. the universe is not some kind of computer software with a hard drive that saves past events. time is not even a real physical aspect of the universe. its something we use as a way to measyre events and motion. peace.
I think most physicists would disagree. Don't they speak of a "time-space continium"? As far as time travel being impossible, you may be right. If it is possible, things could get messy quite quickly.
I think that unles someone posts a time travel thread with a really well explained theory of operation it should automatically be dumped into the hoodooscience bin, or whatever this physics forum calls it.
A well explained theory of operation? So unless we can offer a mathmatical proof showing how a time machine would work, it shouldn't be discussed at all? What kind of attitude is that? I'm no physicist, biology was my major as an undergrad and I also have a doctor of optometry degree (lots of optics, obviously). But it is interesting to discuss areas of science outside of my area of expertise. If I'm way off base, set me right. Or, if hearing a bunch of non-experts talk about your area of expertise offends you, just skip the thread in question.
According to the published rules of this physics forum (as if they have ever been executed fairly ) when a subject cannot be proved it is automatically subject to being put into the hoodooscience bin, where it can be discussed freely until the cows come home.
Well, I did take some physics and seem to recall that time travel is not ruled out by the known laws of physics. So are you saying that discussions of theoretical physics are barred?
Please carefully read my previous post. I do not care what you discuss or try to discuss. My point is that if the published rules of this physics forum are executed honestly and fairly and if a poster has not written a post which proves that time travel is possible, the post/thread is supposed to be tossed out of the real science area. I am sure holding my breath patiently waiting for the monitors to fairly execute their own rules. Please Register or Log in to view the hidden image!
How's this? Time travel has recently been discussed quite extensively in the context of general relativity. Time travel can occur in general relativistic models in which one has closed time-like curves (CTC's). A time like curve is simply a space-time trajectory such that the speed of light is never equalled or exceeded along this trajectory. Time-like curves thus represent the possible trajectories of ordinary objects. If there were time-like curves which were closed (formed a loop), then travelling along such a curve one would never exceed the speed of light, and yet after a certain amount of (proper) time one would return to a point in space-time that one previously visited. Or, by staying close to such a CTC, one could come arbitrarily close to a point in space-time that one previously visited. General relativity, in a straightforward sense, allows time travel: there appear to be many space-times compatible with the fundamental equations of General Relativity in which there are CTC's. Space-time, for instance, could have a Minkowski metric everywhere, and yet have CTC's everywhere by having the temporal dimension (topologically) rolled up as a circle. Or, one can have wormhole connections between different parts of space-time which allow one to enter ‘mouth A’ of such a wormhole connection, travel through the wormhole, exit the wormhole at ‘mouth B’ and re-enter ‘mouth A’ again. Or, one can have space-times which topologically are R4, and yet have CTC's due to the ‘tilting’ of light cones (Gödel space-times, Taub-NUT space-times, etc.) General relativity thus appears to provide ample opportunity for time travel. Note that just because there are CTC's in a space-time, this does not mean that one can get from any point in the space-time to any other point by following some future directed timelike curve. In many space-times in which there are CTC's such CTC's do not occur all over space-time. Some parts of space-time can have CTC's while other parts do not. Let us call the part of a space-time that has CTC's the “time travel region" of that space-time, while calling the rest of that space-time the "normal region". More precisely, the “time travel region" consists of all the space-time points p such that there exists a (non-zero length) timelike curve that starts at p and returns to p. http://plato.stanford.edu/entries/time-travel-phys/
