So, if it's possible in theory but not in actuality, is it true?
I think the more interesting ideas are about information transfer through space time. Quantum computing and the ideas that while information does require a medium, that medium need not pertain to classical laws of physics. But I'm biased.
Yeah, I think about this a lot. I haven't read Hawking's latest, but from what I understand about relativity, it is theoretically possible to create a place where time has stopped or is moving very slowly, i.e., in a black hole, while time outside is moving normally. This would make travel into the future possible, but it would not make travelling back in time possible. The article seems to say that you can travel to the past. I think it's impossible because of the simple fact that going back in time would mean that a person would have to exist twice. Suppose you went back to a time before you were born. Before you were born, you did not exist. And yet you do exist - there you are in your time machine, existing, even though you don't exist.
But I tell you what - I bet Chuck Norris could travel back in time and roundhouse kick your ass yesterday.
A good friend of mine got his Ph.D. under Mallett at UConn. We discuss these topics fairly frequently, but we understand that the engineering is the big issue, and may never be resolved.
An article in Omni Magazine years ago (anyone remember that?) talked about a method that used controlled black holes to transmit information to the past--but only to the point where the BH-controlling machine existed. So once you built a working model, you might start receiving messages from the future immediately.
That article led off with a phrase like "Give scientists enough time and enough money, and they can build anything."
Once you (the observer) is moving at light speed, time has "stopped" for you. The closer you get to the speed of light, the slower time passes for you relative to the reference (the rest of the population of earth, for example). This seems to have been empirically proven as true.
Just because an idea makes us uncomfortable, or challenges our notions of the nature of existence, doesn't mean that it's impossible.
This isn't much of a problem, if space is dimensional. This seems (to me) to be an odd intellectual sticking point... most of our cosmologies depend upon the idea of something not existing and then existing again. If your problem is that there will be matter and energy created, rather than transformed, that's probably compensated through some other process.
If that isn't what you're saying, then you're really talking about a metaphysical objection, rather than a physical one.
MiketheBear: The article seems to say that you can travel to the past. I think it's impossible because of the simple fact that going back in time would mean that a person would have to exist twice. Suppose you went back to a time before you were born. Before you were born, you did not exist. And yet you do exist - there you are in your time machine, existing, even though you don't exist.
From what I understand (not much), scientists have theories to explain what youre tlaking about, Mike. The first is the Grandfather theory, or something like that. It basically states that if one were to go back in time and find their grandfather, and murder him, that logically your mother or father wouldnt exist, and therefore you could not exist. That is impossible, however, because your grandfather could not be murdered by someone who never even existed--so it completely contradicts itself.
This is explained by the Many Worlds Theory that basically says that each time a person makes any kind of decision, time branches off, like a tree. So with every decision a new branch and a new world are created, with those branches continuing to different ends then other branches. There are infinite branches because there are infinite decisions, so, theoretically, nothing is impossible because there are infinite possibilities.
To wrap up the Grandfather thing, the Many World's Theory solves the issue of the Grandfather theory by stating that the person you killed was not YOUR grandfather. He looked exactly like him, smelled like him, etc etc, but could not possibly be your actual grandfather, because someone cannot be murdered by someone who does not exist.
I can definitely see time travel to the future being possible, cos like someone said, travel close to the speed of light and time slows down for you (has been proven). So I guess you can do what they did in Ender's Game and send some old man out in a spaceship travelling superfast and when he comes back say 5 years have passed for him but 100 has passed for us, kinda thing.
As to the many worlds theory, well, wouldn't we be talking about multiple planes of existence (awesome concept), travelling to those would be impressive.
a) that's not necessarily true. b) time travel to the past may be limited by certain conditions, such as the existence of a "receiver." That is, we might have to have a receiving technology that allows travellers from the future to arrive in our own time.
Nephorm, thanks for the response. The idea of time travel doesn't make me uncomfortable at all. Actually, it does make me uncomfortable but in a good way, if that makes sense. I know that black holes and travelling at light speed, or approaching light speed, slows down time and has been proven. No problem there. But these two means of time travel can only get you to "0" - the point at which time stops. We need to go to "-1" and start going backward.
My objections are both metaphysical (yes Irish, I enjoy philosophy very much) and physical. Physically, if you, nephorm, go back in time, you have, as you said, created a new nephorm - matter has been created. Metaphysically, you have created a new nephorm consciousness (perhaps one that won't have the goofy-grin avatar :-)). Or have you? Who knows, perhaps your idea about a multidimensional universe is the answer. Or maybe it'll work like in "Quantum Leap" (yes, I much enjoyed that show) where it was impossible for Dr. Beckett to travel to a time before he was born.
The idea of sending information back in time seems possible and very intriguing.
The many worlds theory doesn't quite say that it is not your grandfather per say, it does say that your grandfather exists on many different planes of existance, and one of them could in fact involve you coming from some future plane of existance and killing him, obviously, you would cease to exist in that plane of existance in the future, but since you did not originate in that plane everything is ok.
In fact, the many worlds theory proposes that every time a big enough decision is made by you, one which will alter your path in life, a split occurs in which you make all possible decisions and each starts fresh on it's own path, it is not entirely clear why your consiousness follows the path chosen, but again, you never really know if you have consiousnesses that followed different paths that are self aware as you are. It seems like it would be necessary for that to happen for all the splits to life out thier existance. Needless to say, if I ever see myself, I will be pretty surprised.
Right how funny would that be, some scientist invents and makes a time travel system with a sender and reciever, and all of a sudden, he starts getting field trips from the future, "now class, this is Dr so and so, he invented time travel as we know it today, everyone say hi to the good doctor. Ok next in our lesson we'll go see the events that led up to world war 8, now everyone put on thier personal protective shields for this assignment, billy stop touching that."
I actually was reading a lot in to this the other week. I came across and article on some Scottish science site about warp speed being possible in the near future, which got my mind rolling on time travel.
From what I could piece together without knowing much of anything about quantum physics, time travel to the past is widely regarded as not possible, or possible under certain conditions as neophorm said. What are these conditions? Who knows. Most of what I read was so beyond my realm of understanding the answer could have been right in front of me and I would have never known.
The part I really have a problem grasping, is the theory that when moving at the speed of light, time stops, and therefor, you don't age. HOW IS THAT POSSIBLE?! Your body doesn't give a shit about time, your heart is still going to beat, you are still going to breath, cells will continue to divide. You will either be dead or age. Or is that what cryogenic freezing is for? And if so, what would the effects of light speed travel be on the human body if not somehow preserved?