Going back in time...Impossible?

[Dudecrush8]

I'm of the oppinion that anything's possible if you try, but some things are just really hard to do :

 

 

 

So yes its possibe, just work on it :) .

 

 

 

I see a thread thats about to become really interesting in the near future.

[i_trollz_u]

Yes, the theory that you can travel FORWARD in time by moving faster than the speed of light is most likely correct. I believe Albert Einstein actually supported it.

 

 

 

I honestly do not know whether it would be possible to go back in time; I would hazard a guess at it would be impossible but I don't know for sure. But assuming you managed to go back in time, i bellieve you CANNOT change the present or future. I don't believe in any time paradox or the overly used example of being able to kill your own grandfather. First of all, there is almost no chance of you being able to even get the chance to kill your own grandfather. He could not be home, he could be on vacation, the possibilities are endless. But making another assumption, lets say you do confront him and you have a gun ready to shoot him. You know that something really bad is going to happen when you shoot him. Everyone will be telling themselves it is an EXTREMELY bad idea to shoot their grandfather because they fear a paradox, it would be morally wrong, you'd be dooming yourself, and you have absolutely no gain out of doing it so no one will actually shoot their own grandfather; thus not altering the future.

[Kashi]

Time travel paradoxes are pretty mindmelting...

 

 

 

Let's say you want to know what it's like to commit a murder. You take a time machine trip back to some random city somewhere in time, kill, and come back. Then you go back to five minutes before the murder and stop yourself. Will you still have the experience?

 

 

 

Simple answer: You will find it impossible to stop yourself once you already commited

 

the murder, because you never stopped yourself in the first place. Watch 'The Time Machine'

 

(though the part I'm referring to isn't in the book). The one chief Morlock tells The Hero that

 

he can't go back in his Time Machine! to stop his girlfriend from dying, because,

 

if not for her death, he would've never built the Time Machine! in the first place.

 

In Harry Potter and the Prisoner of Azkaban, Harry doesn't go back in time and save himself

 

from the Dementors, he is saved by himself the first time around, then the going back

 

fits neatly together with it.

 

 

 

 

 

There are NO PARADOXES in time travel.

[assassin_696]

Reb's addressed some of these points well enough, i'll respond to others if I feel like I can

 

 

 

My friend and I were discussing an interesting topic on time travel. I'm not in a Physics course yet, so I'm not sure if any of this is even right, but here goes.

 

 

 

I just thought speed and time are related. Speed is really a measurement of time. See, after 70 or 80 years, people usually die. So the time for a human life is at the speed of 70-80 years... Or say you run 10 kilometers in an hour.... that's 10km/h.

 

 

 

Not quite, speed is a measurement of time with respect to distance, i'm sure you know the formula (s = d/t), so speed isn't a measurement of time.

 

 

 

But they are related. Brian Greene explains the relation nicely with this little idea (forgive my shoddy adaptation, it's how I sometimes think of it intuitively).

 

 

 

• Speed is dependent on two things, time and distance. Suppose you have a certain amount of energy, call it 100 units, which you can either spend on "time" or "distance". If you spend all 100 units of your energy on time, you won't go anywhere (distance is zero) but time will flow optimally quickly. If you want to go somewhere you have to spend more energy on distance, so you increase your speed at the expense of the rate of flow of time. So your units of energy are spread equally though all 4 dimensions (time included), with most of your energy going into travelling through the time dimension. The faster you go in the spatial dimensions (distance) the slower you go through the time dimension. Because you have a limited amount of energy when you expend all your energy travelling in one spatial motion you'll reach the speed of light, but no time will pass. Hence photons are ageless, they do not experience time.
   
   
   
  So Einstein took this idea and said that everything is moving at the speed of light all the time, it just depends in which dimension the movement is happening.

 

 

 

Wow, this thread is just in time, because I came up with an interesting question earlier today: If we see into the past when we look at stars, because of the time it takes the light to reach us, would time appear to speed up as we got closer to them because the light is reaching us faster than it did before, and we are moving towards it faster?

 

 

 

I don't know if time would speed up, we'd just see events occurring on that star faster relative to someone left back on Earth.

 

 

 

Ok, it's been a while since I've given any thought to this subject, so I might not be entirely correct here, so please correct me if I'm not.

 

 

 

According to the theory of relativity, when you move at extreme speeds, time "slows down" relative to the "normal" pace of time as perceived from the perspective of those who are not moving at your speed. For them, time is moving normally, and you would take the "normal" amount of time to travel that distance. But to you, time literally flew by, and you may have aged by a year while the rest of the world aged by ten.

 

 

 

My question is this: what do we define as "normal"? What I mean to say is, how can we judge any amount of travel time as normal, when theoretically any travel at all is dilating time to some extent. The only "normal" pace of time is when we are still and not moving at all. Movement at any velocity would be subject to relativity. So, when it took you the "normal" amount of travel time to the outside world, just what is that? Obviously it is much less than your speed, but nonetheless any other travel time would also dilate time.

 

 

 

Bottom line: Since there is no real constant to compare your travel time with the outside world's, the theory of relativity would be fundamentally flawed.

 

 

 

However, I do have a hypothesis, and this seems to me to be likely. I would guess that since any typical method of travel is so slow in comparison to the speed of light, and the speed at which you were traveling, the margin of error is small enough to be regarded as insignificant and simply "rounded" to the "still time", that is to say, the pace of time when you are still, which is constant.

 

 

 

Again, there's a chance that I'm completely off my rocker here, as I haven't touched this in a while and I'm supposed to be studying for exams, none of which are physics :lol: .

 

 

 

Both viewpoints are equally valid, since there is no fixed ether or normal with which everything moves respective to you can't say that I'm the one moving and you're standing still or vice versa, they're both equally valid. Same applies to time. I'll try and expand on this a little later, that wasn't particularly clear.

 

 

 

@Reb, if you want to get really technical, travel backwards in time is theoretically perfectly possible (for waves/particles mind you, we couldn't do it, probably) and in fact is happening all the time according to an interpretation of quantum mechanics called the transactional interpretation link. :wink: It explains the whole EPR paradox thing without requiring anything to travel faster than light, it works quite nicely really.

[Denismage]

IMO you can't "be" in the past, you can only see the past, and that is only if you travel A LOT faster than the light and you can only see planet earth it if you have a good telescope, (Such good telescopes don't exist yet, so it's impossible) since you will be very far away.

 

I hope you get my point.

[Nom]

[The stuff I wrote]

 

 

 

Both viewpoints are equally valid, since there is no fixed ether or normal with which everything moves respective to you can't say that I'm the one moving and you're standing still or vice versa, they're both equally valid. Same applies to time. I'll try and expand on this a little later, that wasn't particularly clear.

 

 

 

That's exactly what I'm saying. What I'm really trying to get at is, how long would your travel actually take to an outside observer? On what speed would it be based? You are traveling for a certain amount of time in your ship or whatever, but how does the outside world perceive that time in relation? There has to be some speed to compare it too, or you wouldn't go anywhere. But there is no constant that you can contrast it with, because we travel at different speeds all the time. Would we see see it as taking as long as a jet would, or a car, or a rocket?

[Rebdragon]

@Reb, if you want to get really technical, travel backwards in time is theoretically perfectly possible (for waves/particles mind you, we couldn't do it, probably) and in fact is happening all the time according to an interpretation of quantum mechanics called the transactional interpretation link. :wink: It explains the whole EPR paradox thing without requiring anything to travel faster than light, it works quite nicely really.

 

Oh, I've read up on some experiments about that, pretty frikkin' weird o_O.

 

 

 

But then again, everything at the quantum level seems to be weird, so it shouldn't be all that surprising :-w .

[fgfuyfyuiuy0]

Time travel paradoxes are pretty mindmelting...

 

 

 

Let's say you want to know what it's like to commit a murder. You take a time machine trip back to some random city somewhere in time, kill, and come back. Then you go back to five minutes before the murder and stop yourself. Will you still have the experience?

 

 

 

You could go forward in time and kill someone like 300 years later, so the evidence can't blame your future self. That'd be much more easier then going back in time and all.

 

 

 

 

 

The only way I'd find time travel possible (Going to the past), would be that you would have to go back too, physically. So, I don't think you'd make it back far enough when you are a fetus...

 

 

 

Going into the future? You could do that. Increase the speed and then time would speed up and you would end up wherever you wanted to be. The problem? You can't go back. Everything is done with. You could most likely die. I don't think the human body could handle being in a state of motion for too long and then having to get out of it.

[assassin_696]

[The stuff I wrote]

 

 

 

Both viewpoints are equally valid, since there is no fixed ether or normal with which everything moves respective to you can't say that I'm the one moving and you're standing still or vice versa, they're both equally valid. Same applies to time. I'll try and expand on this a little later, that wasn't particularly clear.

 

 

 

That's exactly what I'm saying. What I'm really trying to get at is, how long would your travel actually take to an outside observer? On what speed would it be based? You are traveling for a certain amount of time in your ship or whatever, but how does the outside world perceive that time in relation? There has to be some speed to compare it too, or you wouldn't go anywhere. But there is no constant that you can contrast it with, because we travel at different speeds all the time. Would we see see it as taking as long as a jet would, or a car, or a rocket?

 

 

 

To an outside observer you might appear to go say, 50m in 5s, so your speed is 10m/s. But you might measure your time to be 50m in 6s, so your speed is 50/6 m/s (differences exaggerated). Both speeds are equally valid, they measure yours with respect to their surroundings and their local time, and you measure your speed with respect to your (slightly slower) local time and your surroundings.

 

 

 

You're right, you need a point of reference to measure everything to, but you don't need a fixed point of reference for everyone to measure everything to. Hence, relativity.

[FalconBomba]

Well, think about it. You could never quite reach your own future, by being there your changing the structure of time and space singularities that make up the universe, therby creating a slightly different universe that isn't your home's future but, another dimensions and it would be impossible to return not only because of the distortion of the singularities but of the physical impossibility to move backwards in time.

 

 

 

ps. those things like if you go back in time and kill your parents and therefore you'd never be born, so therefore not be able to kill your parents so you'd be born to kill them. Well the solution is that by distorting the singularities you'd be killing two different people than your own parents, a dimension similar to your own with identical parents but, not exactly the same so therefore you'd still be around.

 

 

 

ppss. I'm not a sci-fi junkie, I've actually researched this stuff and not pulling it out of the crack of my *ketchup*.

[doomy]

Well, I meant if a star somehow moved instantly from like, 1,000,000 light years away to right outside our solar system, we'd be able to see both forms, I would think. :P

 

 

 

Even though it's impossible for that to happen, but yea.

 

 

 

The fastest the star could move is the speed of light.

 

The speed of light is impossible isn't it?

 

Because an object trvelling that speed would gain an infinite mass and therefore require infinite force to keep it accelerating?

[flying_death_bombs55]

I think it is impossible to go back in time for a less-scientific reason, yet it is possible.

 

 

 

You "somehow" go back in time, and somehow change the past, causing you to never build the machine, but someone else does, and it repeats over and over.

 

 

 

Edit: I have thought about this many times, and I am 99.6% sure. the 0.4 means the universe implodes and all of time, space and reality is destroyed :ohnoes:

[DragonFirenze]

Its possible to create a "Time Window" as someone previously mentioned. However its impossible to travel back in time. Some simple evidence: In the billions and trillions of years that time will go on someone would have to have come back to our time by now. Which they havent. Therefore travelling back in time is impossible.

[Harrington]

 

Most theory suggests that it may be possible to move forward in time, but not backwards.

 

 

 

If you want to view the past, you could still do so if we had both of the following...

 

* FTL travel

 

* Extremely powerful telescopes.

 

 

 

You could jump out to say 60 light years with our FLT drive, then train our telescope on Earth and watch "live" WW2 combat.

 

 

 

LOL, that's about the only way I can think of virtual time travel

 

 

 

Too bad gravitational distortion would mess up the image beyond repair :P .

 

 

 

 

 

 

Current sats' don't seem to have a problem with this. I assume that if we had the technology to overcome faster than light travel and create telescopes that can resolve man sized images from 60 light years away, then we'd also have solved any minor gravity distortions, be it through advanced software or whatever... ;)

[flipflop121]

u actually ahve the first bit mixed up, the faster u get to the speed of light, the slower time is, once u get to the speed of light time stops.

 

i believe einstein said that.

 

 

 

it was proved awhile back when a jet went at mach 7 around the earth for 24 hours (time at the base) apon landing the pilots watch and instruments were actually 4 minuetes behind the earths time. what this says is, the pilot had just delayed himself by 4 mins. (thats like WTF LAG!!!)

 

 

 

however the rate at which time slows is exponential.

 

 

 

Because of this theory tho, it may make space travel to other galaxyies a reality. it would however be extremely difficult to calculte everything

 

 

 

if the ship manages to reach speeds close to the speed of light, they will be in essence "frozen in time" there bodys will actually age at a rate of far less then that of the people on earth. this is what may make space travel a reality, without ageing at normal rates, u are basicly being biochemcially frozen, but can still perform functions and move around.

 

 

 

So, having said that i have a few theories for u to stew over.

 

if i want to go back in time, i need to travel faster then the speed of light.

 

but, will this decrease my age? or will it send me into another paradox. if it does decrease my age, will humans ever need to reproduce again, or can we just keep reversing our biological clock.

 

 

 

the 2nd theory is abit like the first. if we want to go forward in time, then we need to travel slower then the speed of light. or, we can travel at the speed of light (time stops) while we distance ourself earth, we set the date of when we want to decend back into the planet. however the planet will be in the future as we have not aged at all by travelling at the speed of light and causeing our time to stop.

 

 

 

 

 

just thought id screw with ur head more

[DragonFirenze]

STUFF

 

 

 

Erm... I think you're referring to Time Dialation in the first part. Also, you cannot go faster than the speed of light. Period (and dont bring up that junk about the end of light waves catching up to itself again). Even reaching speeds above 70% is incredibly difficult at the moment, although i read something about a theoritical Light Sail being used to accelerate large crafts. Even then its only around 70%. The closest anything has gotten to the speed of light was a gold? particle at CERN being propelled to 99.999% which is insanely fast. But still it didnt reach or go faster than the speed of light. Therefore your theories are rubbish (sorry). And theoritically, even if you COULD go back in time you wouldnt become younger because you would be in your own frame of reference. I dont even get what you're trying to say in your second theory.

[sohkmj1]

Correct me if i'm wrong but speed and time is inversely proportionate or something like that. So if speed increases, time should slow down, yes? Not the other way around ?

[epeeflecher]

Alright, here goes nothing

 

 

 

Yo yo, yea G lets start it off

 

Talk about time

 

It rhymes with ma rhymes

 

My rhymes ryhme with time

 

You go back in time

 

See me when i use to be a mime

 

Say hey dude you gonna play a nerdy game

 

I say yo Joe you gonna be my hunting game.

 

You cant go - mph

 

So you cant go back in time to see me when i use to be a mime.

[M_u_s_ii_X]

Impossible. But if it isnt... there would be billions of me! :thumbsup:

[Rebdragon]

 

Most theory suggests that it may be possible to move forward in time, but not backwards.

 

 

 

If you want to view the past, you could still do so if we had both of the following...

 

* FTL travel

 

* Extremely powerful telescopes.

 

 

 

You could jump out to say 60 light years with our FLT drive, then train our telescope on Earth and watch "live" WW2 combat.

 

 

 

LOL, that's about the only way I can think of virtual time travel

 

 

 

Too bad gravitational distortion would mess up the image beyond repair :P .

 

 

 

 

 

 

Current sats' don't seem to have a problem with this. I assume that if we had the technology to overcome faster than light travel and create telescopes that can resolve man sized images from 60 light years away, then we'd also have solved any minor gravity distortions, be it through advanced software or whatever... ;)

 

That's because there are no other heavenly bodies near them, besides Earth and the Moon, which cause very little gravitational light distortion when the sat's are so close. But you put that thing far enough away, you're going to have enough distortions (stars, black holes, that light isn't going to be traveling in a straight path for 60 straight lyears) and things getting in the way that you'll be lucky to get past the see the Earth as anything more than a blurry dot, let alone actually see what was going on with the little people :P .

 

 

 

Though yes, FTL travel is probably going to be the harder achievement of the two .

[kelem_ryu]

Nothing is impossible.

 

 

 

Two possibilities: Either you stay on your current timeline and your actions result in the future from were you left, or the moment you enter the past generates a new branch of the timeline.

 

 

 

I don't know how you'd do it, but if you really want to, you'll find a way.

 

 

 

 

 

 

And if so, wouldn't time have the same properties as speed?

 

For example, they are both present in this 3D world and the higher speed you are at the faster time goes (that's proven if you go faster than the speed of light you can travel forward in time)

 

 

 

 

Mice for example have a much faster heart rate. So although they only life one or two years, they subjectively may life as long as humans.

[Rebdragon]

 

And if so, wouldn't time have the same properties as speed?

 

For example, they are both present in this 3D world and the higher speed you are at the faster time goes (that's proven if you go faster than the speed of light you can travel forward in time)

 

 

 

 

Mice for example have a much faster heart rate. So although they only life one or two years, they subjectively may life as long as humans.

 

If you're going to say "nothing is impossible", at least act like you understand what you're trying to refute. Geez.

[El_Tigre]

What about this for a paradox?

 

 

 

Say you go back in time, and kill your own grandfather.You would cease to exist right?But, if you didn't exist, you couldn't have killed your grandfather..so he'd still be alive, andyou'd exist, so you would kill him, and you wouldnt exist anymore..... :shock:

It very well might be posible but this is what I was going to say only with a bully and a bike :P

[Kill_Thomas9]

The only reason speed can't be lower than 0 is because speed (or lets say velocity just to make things easier) is just a measure of an object's displacement (or speed) over time (in seconds).

 

 

 

So if v=d/t, the only way to get a negetive velocity is to either have either a negetive distance which is impossible (I will get to the reason in a moment) or a negetive time.

 

 

 

Displacement (or d) is a property created by the space between two points. So if point a were at the coordinates (4,2), and point b were at the coordinates (4,5), then d would be 3. But how would you have a displacement of -3? Even if point a was at (4,2), and point b was at (4,-1), then the displacement of -1 and 2 would still be 3.

 

 

 

So if there is no way to have a negetive displacement, then the only way to have a negetive velocity (v) would be to have a negetive time (t). So according to what I just said, the only reason v can't be negetive is because t can't be negetive. But according to what you said, the only reason t cant be negative is because v can't be negative.

 

 

 

So either time and velocity are the same thing (or at least interchangable), or one of us is wrong. And it's too late for me to think in enough detail to figure out which is the correct conclusion. So if someone could prove one of us wrong, I would appreciate it, because this paradox-like thing is kind of annoying (the fact that velocity and speed seem to be the same thing, while at the same time velocity is a product of the space between two points over the amount of time the object is in motion).

 

 

 

 

 

 

 

Mind... clouded...

[assassin_696]

^^^

 

 

 

Time and velocity are not the same thing. Mathematically one's a vector quantity and the other's scalar, they're certainly not interchangeable. Saying "one day I was travelling at 50m/s on a bearing of 20 degrees" cannot be interchanged with "one day I was travelling at 5 minutes". That's crazy.