A real Time Machine.

[kotss]

No, the speed of light and sound are two different things. Sound propogates sound waves and light
propogates electromagnetic waves. Sound requires a medium to propogate, hence why there is no sound
in the vacuum of space. (Not enough hydrogen particles packed densely enough to propogate the sound.)
Light does not require a medium to propogate and actually the speed does change based on the index of refraction of the medium. The major difference is the speed of light in vacuum cannot be exceeded by
any matter that has rest mass. The reason is the amount of energy/force required to get the mass even
close to the speed of light. Photons exist only when traveling at c. They have no rest mass and do
not exist at rest.


In order for your fantasy theorey to work you would also have to counteract the time spent in acheiving
your FTL speeds, unless you have instantaneous speed capabilities. The time spent accelerating to get
close to c would cause time dilation and you would actually begin travelling into the future
(relativistically). This would have to be factored into the calculations.
If you use instantaneous acceleration or ultra high acceleration, how do you counteract the incredible
g-force created by accelerating the mass. The occupants would be liquified in an instant.

Assuming all the "technical problems" could be overcome, then yes I believe you could view the light
waves that originally left earth from the past, you would also have to catch them close to earth as the
propogation of the wave would cause it to collide with other light waves and you have interference.
This would cause destruction or amplification of the images and would distort them in ways unknown.

As I understand the physics of today, the speed of light is something that cannot be achieved by matter.
Only photons can do this.








*c = speed of light in vacuum.

 

[beansbaxter]

first of all, isn't the speed of light supposed to me a maximum theoretical speed for anything? besides, i'd equat the slowing down of (relative) time to the calming of particles as temp approaches 0 Kelvin. u can't have particles more slow than not moving right? at that point u'r at 0. so u can theorize all u want about how particles would gain negative movement as the temp dipped below 0, but that can never happen. besides, even if we said the subject WOULD experience a reversal of time, it wouldnt be what we generally think of as time travel, like what we see in movies. the subject may go back in time but it's still in a different position from in the past as it continues to travel where it's going right? so it's not like u could go back and relive your life or make different decisions. you could maybe get back to earth X years younger if your trip was circular but u'd have lost all your memories too, so what's the point? basically, it would be pretty useless. i guess if u just want to extend ur life by 10years it would be good for that, but how many people would trade their memories for another 10 years? wouldnt that be like throwing those 10 years away anyway? i guess if u had a really bad 10 years... Anyway, that's all dependant on teh idea that reversing time (a better term than "time travel" or "going back in time") is possible to begin with, which i find unlikely.

the other problem with that is our measure of time is just that, a measurement of a physical property...you could no more reverse time than you could put the cork back in the bottle of the Hiroshima bomb......even as 'time' expands for people moving quickly, it still goes along at the same rate for everything else. just accelerating that item faster than speed of light won't do squat for the rest of everything.the time "reversal" would only happen for that one person,a nd it would be their perception....not reality. and really, once they got up to that speed, where time slowed down for them, time is flying so fast elsewhere that they would not know anyone or anything when and if they ever returned anyway.... but that return time would not be *before* they left, it would be a great deal of time AFTERWARDS

 

[wkwong]

why would you lose your memory? just because you going "going back in time" everything is relative to you and you would be experiencing time normally, therefore, no lost of your memory.

as argued in this thread, time is a 4th dimension webbed into the the other 3 dimensions that we can currently perceive. temperature is not the same thing and shouldn't be compared with in time. i'm not saying that for sure time travelling.

there are theories of particles that are travelling faster than the speed of light. i think someone mentioned them earlier in this thread.

technically, if they were to travel near the speed of light, without going over c, time would slow down considerably. if that case, they would return at a time after their departure. however, we are saying that time might possibly be reversed by travelling faster than c.

honestly, i think it'd be a little more complicated than that (not that the task isn't already complicated enough)

 

[Joerg]

Kotss i mentioned in my post that i know light and sound are completely different but its easy to relate sound to light in this sense simply becuase we have and are very capable of breaking a sound barrier.

What i want to know is how the speed of ligth has anything to do with time travel. Like i pointed out you could in theory view a different time period with the use of travel at speeds faster than light but in a sense that i just like our peering into the nights sky seeing dead stars. But looking at the stars is by no means time trave which is why i want to know how the speed of light relates to time travel.

As for traveling faster than light i would say that if that becomes possible then i see no reason we couldnt go far beyond that.

 

[DouglasAdams]

why is it that some of you include the caveat "present understanding of physics" (or words to that effect) whereas the rest are like the old Catholic Church and the Flat Earth Society.
what we think of as "laws", i.e. nothing can travel faster than the speed of light, are just based on theories and these could very easily change.

 

[gamefreakgcb]

Originally posted by: Joerg
Ok excuse me if im just being stupid here but it seems to me that people are making a mistake when they relate time tavel to the speed of light. The speed of light is in this case alot like the speed of sound. For example an asteroid hits and you see the explosion before you here it right?

Ok so now for the purpose of relating this to light lets just assume that sound never disipates. So now you could in theory sleep through the english lesson then travel faster than sound for the length of the lesson then stop and listen to it as the sound arrives at that point. Make sense?

Ok so now lets just speed it up 600,000x and call it light ofcourse the properties and everything are different and sound and light really have nothing to do with each other but for this purpose it works out fine. Anyways now lets say you build somethign that can travel faster than the speed of light and lets say signifigantly faster simply becuase we want to be able to do this and come back in time for lunch.

So your history project on ancient egypt is due. You jump in your faster than light craft and you shoot away from earth. Going at twice the speed of light you can see back one year for every one year of travel that means that to do this in one hour and go back 5000 years we need to be going somewhere around 87.6million times the speed of light to do this in one hours time. Ok so we have traveled our 5000 lightyears away from earth and we went alot faster than light so we arrive before the egyptians built the great pyrimids. Ok so the pyrimids are still built and we cant change that but we can see them being built only becuase the light or the image of them being built just now got to us.

I know really confusing but basically we only beat light not time itself. So in theory we could go back and watch something happen even a million years after it happened we just need to go faster than light and catch that image.

Ok so natures memories are stored as an image but the acctual matter would be there it would be a hallogram if you will. Sort of an empty image like peering into the the sky knowing that some of those stars are no longer there.

Ok now lets says that true time travel were possible by means of black holes or something my question is what happens when you create mass in that time frame you visit? One of the simplest laws in physics is that mass cannot be created or destroyed.

And again im only in highschool if my ideas are very flawed just tell me where im going wrong.

Not a big techhead but that was a the best explanation I've read in this thread. You cannot go and reverse time as of now but you maybe able to experience it by jumping ahead of light. But then you'd need to be in many different places to see the many different spectrums of light that have left one place since the light that left off the pyramid will keep on spreading and spreading as it goes further and further in space. Also you'd need one hell of equipment to filter that light of any interference it might have recieved in the way and lets not forget obstacles in between the point of origin and the place where you go in a vehicle traveling at 87.6 million times the speed of light and that speed keeps on increasing every second you're living ATM. So for now this is like discussing the aircraft with the primates a few millions or possibly billions of years ago with dinosaurs . I hope I didnt confuse too many people here or got this off-topic or anything.

 

[evilmantis]

Pick up a quantum physics textbook and you will see your reason. The speed of light is not so much a velocity as a constant, a theoretical limit. Don't think of it as a setting on a speedometer -- think of it as a limit which is unreachable by objects with mass. Do you know what asymptotic limits are? It's when you can keep getting closer and closer, but never get there. Example: if you start with the number 1 and cut it half, how many halves will it take to get to zero? Answer : you never will. 1 -> 0.5 -> 0.25 -> 0.125 ->.....
You can keep cutting it in half, but you will never reach zero. It's a limit, not final result.

Not to be insulting, but I think you really need to understand what the speed of light is and how it plays into relativity and quantum physics before you can understand what some of the posters are talking about.

 

[gamefreakgcb]

Originally posted by: evilmantis
Pick up a quantum physics textbook and you will see your reason. The speed of light is not so much a velocity as a constant, a theoretical limit. Don't think of it as a setting on a speedometer -- think of it as a limit which is unreachable by objects with mass. Do you know what asymptotic limits are? It's when you can keep getting closer and closer, but never get there. Example: if you start with the number 1 and cut it half, how many halves will it take to get to zero? Answer : you never will. 1 -> 0.5 -> 0.25 -> 0.125 ->.....
You can keep cutting it in half, but you will never reach zero. It's a limit, not final result.

Not to be insulting, but I think you really need to understand what the speed of light is and how it plays into relativity and quantum physics before you can understand what some of the posters are talking about.

Yeah hence my last statement there. Very very few will actually be able to understand whats being talked about here and I think Im not one of those few yet. Heck I just turned 18 and just beginning to understand life and Im having a hard time with keeping up with my studies and I'm now supposed to be in physical therapy for my back problem for a few months . Hope you guys figure something out (very very very very unlikely BTW) but kudos to you guys.

 

[silverpig]

Originally posted by: evilmantis
Pick up a quantum physics textbook and you will see your reason. The speed of light is not so much a velocity as a constant, a theoretical limit. Don't think of it as a setting on a speedometer -- think of it as a limit which is unreachable by objects with mass. Do you know what asymptotic limits are? It's when you can keep getting closer and closer, but never get there. Example: if you start with the number 1 and cut it half, how many halves will it take to get to zero? Answer : you never will. 1 -> 0.5 -> 0.25 -> 0.125 ->.....
You can keep cutting it in half, but you will never reach zero. It's a limit, not final result.

Not to be insulting, but I think you really need to understand what the speed of light is and how it plays into relativity and quantum physics before you can understand what some of the posters are talking about.

The speed of light doesn't really have much to do with quantum physics. It shows up but you can have non-relativistic quantum just fine. In QM the speed of light is just some number... a conversion factor really. It's relativity where the speed of light becomes important. Of course you can apply relativity to QM to come up with quantum electrodynamics/chromodynamics, but that's much more advanced than you'd find in an intro quantum text. All of this time travel talk is relativity. Special relativity for "go fast here and you'll see yoru clock go slower" and general relativity for the black holes and other phenomena.

 

[wkwong]

Originally posted by: evilmantis
Pick up a quantum physics textbook and you will see your reason. The speed of light is not so much a velocity as a constant, a theoretical limit. Don't think of it as a setting on a speedometer -- think of it as a limit which is unreachable by objects with mass. Do you know what asymptotic limits are? It's when you can keep getting closer and closer, but never get there. Example: if you start with the number 1 and cut it half, how many halves will it take to get to zero? Answer : you never will. 1 -> 0.5 -> 0.25 -> 0.125 ->.....
You can keep cutting it in half, but you will never reach zero. It's a limit, not final result.

Not to be insulting, but I think you really need to understand what the speed of light is and how it plays into relativity and quantum physics before you can understand what some of the posters are talking about.

the key word there is "theoretical." true, based on current physics laws, we definitely cannot travel at the speed of light. but they also said it was impoosible to teleport an atom before, and we know we broke that rule. i'm not sure if we can ever break the speed of light, but i'm not going to just say "it can't be done" and leave it at that. i'm sure everyone else who is pro-time travel feels the same way

 

[gamefreakgcb]

Originally posted by: wkwong

Originally posted by: evilmantis
Pick up a quantum physics textbook and you will see your reason. The speed of light is not so much a velocity as a constant, a theoretical limit. Don't think of it as a setting on a speedometer -- think of it as a limit which is unreachable by objects with mass. Do you know what asymptotic limits are? It's when you can keep getting closer and closer, but never get there. Example: if you start with the number 1 and cut it half, how many halves will it take to get to zero? Answer : you never will. 1 -> 0.5 -> 0.25 -> 0.125 ->.....
You can keep cutting it in half, but you will never reach zero. It's a limit, not final result.

Not to be insulting, but I think you really need to understand what the speed of light is and how it plays into relativity and quantum physics before you can understand what some of the posters are talking about.

the key word there is "theoretical." true, based on current physics laws, we definitely cannot travel at the speed of light. but they also said it was impoosible to teleport an atom before, and we know we broke that rule. i'm not sure if we can ever break the speed of light, but i'm not going to just say "it can't be done" and leave it at that. i'm sure everyone else who is pro-time travel feels the same way

Correct, our current knowledge about the universe and time and all relative things isnt up to the par where we can start working out the equations needed for time travel, also our current level of technology makes it impossible to travel at the speed of light, infact we're barely anywhere near it, I dont know if NASA's test flight scheduled this week to break the Mach 10 barrier was successful or not. We may have broken that limit for traveling into space but to reach the speed of light or hyperspace or slipstream space or whatever you want to refer to it as is still quite a bit far away. So I will conclude my rambling by saying that this is a feasible task but not for a few generations atleast, and if time travel becomes a reality, well then we should start expecting someone from the future then? Ok now Im moving in another direction as I say this but if time travel were to become reality, wouldnt we have someone from the future here now? As it is with everything in the world, there are "Bad Guys" in every field, then time travel should be no different right? Even if it was to be decided that Time Traveling to past is illegal and a deatch panelty or whatever, the bad guys will do it just for the hell of it right? I mean even today, what field of knowledge is completely free from these things?? OK I will stop now.

 

[stinkynathan]

I don't necessarily see any of this as time travel though. Of course, in a definitive sense of the word, it really is time travel, but.....

None of these theories address interaction with the past. Its all well and good that, in theory, we could cruise out in space for $BIGDISTANCE and view what just happened a few minutes ago but we still can not, for example, go back and tell people lottery numbers.

Thats all I have. My math brain is nowhere near big enough to really discuss in this one.

/me sets mode: +lurking stinkynathan

nate

 

[tkeely4777]

Forgive me for my simplicity, but, for a moment, let's just say that, in the the future, time travel has been accomplished...wouldn't....couldn't there possibly be evidence of a bizaar occurrence that potentially fits a description of time travel in our recorded history?

Take the phenomena of Unidentified Flying Objects...I'm not saying that every account of UFOs is proof of time travel, but bear with me and consider this: evidence of UFOs have existed since the Renaissance age, portrayed in paintings and the like....

That's just my opinion.... *shrug*

 

[bsobel]

None of these theories address interaction with the past.

Causality loops and other fun interaction with the past games are easily solved in an infinite multi-verse model.
Bill

 

[Mr. Lennon]

Originally posted by: tkeely4777
Forgive me for my simplicity, but, for a moment, let's just say that, in the the future, time travel has been accomplished...wouldn't....couldn't there possibly be evidence of a bizaar occurrence that potentially fits a description of time travel in our recorded history?

Take the phenomena of Unidentified Flying Objects...I'm not saying that every account of UFOs is proof of time travel, but bear with me and consider this: evidence of UFOs have existed since the Renaissance age, portrayed in paintings and the like....

That's just my opinion.... *shrug*

Many people that say time travel is not possible usually say "wouldnt we have already met someone from the future if it was possible?" Simple, but that is a good question though.

 

[kotss]

I think it is a little bit of arrogance to think that "if time travel existed we would have proof, because
people from the future or past would be visiting us". I would think that you (time traveller) would keep
your existence secret. I personally would keep it secret, because I would want to observe other times.
Letting people from other times know of your existence while visiting them would be counterproductive to
the very reason for time travelling, observing. (Obviously I look at it from the moral standpoint, "evil"
people would want to change history/future for their own desires. Interacting in any meaningful way, I think would lead to problems. BUT, time travel in any significant manner is not possible. The only thing possible is relative travel to the future, with no way back. Unless some new radical theories and validations about the laws of the universe are discovered, time travel will only be possible in one direction , to the future. The only area of study that is not fully detailed is string theorey and that could
lead to explanations of how time travel into the past is possible, but from my readings I have seen no
indication of this. (At least from practical standpoints).

 

[Mr. Lennon]

Originally posted by: kotss
I think it is a little bit of arrogance to think that "if time travel existed we would have proof, because
people from the future or past would be visiting us". I would think that you (time traveller) would keep
your existence secret. I personally would keep it secret, because I would want to observe other times.
Letting people from other times know of your existence while visiting them would be counterproductive to
the very reason for time travelling, observing.

I agree with you on that. Maybe those flying saucers people claim to see are time travelers? Even if time travel were to fall into the wrong hands, it would be seriously very hard to change the inevitable events in history. Heres a quote from Dr. Carl Sagan:

"What if your time traveler had persuaded Queen Isabella that Columbus's geography was wrong? Almost certainly some other European would have sailed west to the new world soon after. There were many inducements: the lure of the spice trade, improvements in navigation, competition among rival European powers. The discovery of America around 1500 was inevitable. Of course, then there wouldn't be any postage stamps showing Columbus, and the Republic of Columbia would have some other name. But the big picture would have turned out more or less the same. In order to affect the future profoundly, a time traveler would have to pick and choose. He would probably have to intervene in a number of events which are very carefully selected so that he could change the weave of history."

 

[Epimetreus]

Several things, though I won't be detailed, as I'm too lazy to look up the appropriate references at the moment:

First, the speed of light may or may not be a constant or a quantity; our current understanding of physics does indicate the former, but since said understanding is only guaranteed to change, swearing on "current theories of physics" like a Bible is just a good way to make yourself a fool in the history books.

Second, there is a certain amount of controversial data that indicates the speed of light may be variable. Obviously this goes against about 100 years of physics, and is, well, controversial, but please do remember that every groundbreaking theory of physics has been, in its time, controversial. Just because we can't prove it yet, or said proof may be dubious, does not mean it's not true.

Third, while reversing entropy has been demonstrated to be unlikely possible(though, again, said demonstrations may be later disproven), the possibility of traveling a closed spacial-temporal loop to a point in the past cannot be discounted, since the correct malformation of the surface of space could possibly have temporal ramafications as well. Highly theoretical, and relies on the generation of energies which are economically not viable, but not necessarily impossible.

My favorite quote on this subject is the following: "The laws of physics do not preclude FTL travel; the laws of economics do."

 

[bradyA]

Hello all.

Several years ago I read a study which claimed that several scientist were able to accelerate certain particles up to 300x the speed of light. This all occured in a vaccum which, to my understanding, was filled with a specific type of gas (cesium I believe). I don't understand all of the ins and out, but assuming this is all true it can lead to a whole range of interesting speculations.

First, I will try to outline what occured in the expirement:

1) a photon was shot from point A
2) it travelled through a tube containing (cesium) gas which accelerated the photon to 300xSpeed of Light

Maybe this diagram will help (I know its shoddy).

What follows is the result of a discussion I had with an astrophysicist about the expirement I've been refering to.

If such a technology were refined enough so that large amounts of data could effectively be sent through a system containing this gas element, it theoretically may be possible to look into the future. Please understand this is all hypothetical and speculatory, so your going to have to use your imaginations a little bit. I should also note that this all gets a little wierd when you flesh it out. Lets say you could use wires with this gas element in them to hook up a video camera to a monitor. Imagine the whole process was streamlined with this type of wire/gas element. The insides of both the tv and camera were constructed with this 'high data transfer' wire. So what we have is an input and output system that all has the potential to move data faster than light speed. So imagine that being the case right now and this system is set up directly in front of you (your computer monitor is connected to a camera and your watching yourself right now). In a typical setting you would wave your hand in front of the camera and you would see your self doing the exact same thing on the screen. Today you might even see a bit of a delay, maybe one tenth to a half second. In our imaginary setup based on the data from this expirement you would wave your hand in front of the camera and the output would be instant. Absolutely no delay. Now imagine that instead of 300x the speed of light we were able to accelerate the data to 1000's x the speed of light. What theoretically may occur is that you would wave your hand in front of the camera yet oddly enough you would have seen that gesture a second or two or three before you did it! Of course the problem is what happens if you saw yourself do somthing on screen and then decided not to do it? That is the big question about time travel anyway.

In any case, I just wanted to chime in and offer my 2 cents. Take if for what it's worth. I didnt bother looking up the article I am refering to. Im sure you could find it on google. I know this is not necessarily about time "travel", but I thought it was related enough.

 

[kotss]

According to Wikipedia.com under the speed of light :

Wikipeida : "Faster-than-light" observations and experiments

Recent experimental evidence shows that it is possible for the group velocity of light to exceed c. One experiment made the group velocity of laser beams travel for extremely short distances through caesium atoms at 300 times c. However, it is not possible to use this technique to transfer information faster than c: the velocity of information transfer depends on the front velocity (the speed at which the first rise of a pulse above zero moves forward) and the product of the group velocity and the front velocity is equal to the square of the normal speed of light in the material.

Exceeding the group velocity of light in this manner is comparable to exceeding the speed of sound by arranging people in a distantly spaced line of people, and asking them all to shout "I'm here!", one after another with short intervals, each one timing it by looking at their own wristwatch so they don't have to wait until they hear the last person shouting.

The speed of light may also appear to be exceeded in some phenomena involving evanescent waves, such as tunneling. Experiments indicate that the phase velocity of evanescent waves may exceed c; however, it would appear that neither the group velocity nor the front velocity exceed c, so, again, it is not possible for information to be transmitted faster than c.

I always will allow for theories to change and understanding of the very nature of the universe can change. But at this current time, observations do meet expected theories in regards to items travelling at
high speeds. In regards to closed time loops utilizing wormholes, this has been speculated upon by
Hawkings among others. The limitation is you cannot proceed any farther back in time than when you first
constructed the loop. Severe limitation in my opinion. Plus the energies needed are huge, and there was
no implication as far I remember of being able to transmit items of "mass", only energy (i.e. photons).

I for one would welcome the ability to travel in time freely, but I also ground myself in reality. I do not
limit myself to this, but it is useful to remember that just because we want something does not mean it
will happen ( I am aware of the corrollary to this). I am also very mindful that our own experiences
might be what form reality. (If you have not read the Dancing Wu Li Masters, then you should, another
good book is Brian Greene's an Elegant Universe also reading some of Hawkings work probably would be
a good idea.) Maybe the dancer can become the dance and vice versa.


A good point to hammer it all home is this: Gravity it is just a theorey, so if I do not like it, I will change it.
Nolw when I jump off this building I will float instead of falling, because that is what I believe will happen,
inevitably the reality of things grabs hold of you and slams you into the ground hard.