Time Travel is Science Fiction

[paddoboy]

In Einstein's special theory of relativity, there is no such thing as "time" in the singular. Time passes differently for different observers, depending on the observers' motion. The prime example is that of the two hypothetical twins: One of them stays at home, on Earth. The other journeys into space in an ultra-fast rocket, nearly as fast as the speed of light, before returning home:

Afterwards, when the twins are reunited on Earth, the travelling twin is markedly younger, compared to her stay-at-home sibling. The exact age difference depends on the details of the journey. For example, it could be that, aboard the space-ship, two years of flight-time have passed - on-board clocks and calendars show that two years have elapsed, and both spaceship and travelling twin have aged by exactly that amoung of time. On Earth, however, a whopping 30 years have passed between the spaceship's departure and its return. Just like all other humans on the planet, the twin on Earth has aged by 30 years during that time. Seeing the two (ex?) twins side by side, the difference is striking.

So far, so strange, but undoubtedly real. Space-travel with speeds close to that of light may be unfathomably far beyond the reach of current technology. But sending elementary particles on round trips in a particle accelerator at 99.99999 percent of light speed is routine. The result is in precise agreement with the predictions of special relativity - the "inner clock" of such a travelling particle runs much slower than that of a particle of the same species that remains at rest (cf. the page The relativity of space and time in the section Special Relativity ofElementary Einstein).

http://www.einstein-online.info/spotlights/Twins
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I would try and explain it further Motor Daddy, but like your twin river, you are not really interested in an answer, other then to fuel your own inadequacies and misinterpretations.
If you disagree with SR, write up a paper refuting it, gather your evidence via the scientific method, and get it peer reviewed.
Best of luck!

 

[Motor Daddy]

I would try and explain it further Motor Daddy, but like your twin river, you are not really interested in an answer, other then to fuel your own inadequacies and misinterpretations.

I asked you a direct question. Are you refusing to answer?

 

[paddoboy]

No, you don't get it.

The reason this thread is so long is because of people who don't want to address the hard parts of the science and just dismiss it on prejudice. Or, in the case of Farsight, who want to use the rejection of time travel as evidence that their own pseudo-theories are correct.

Time travel is an element of science fiction. It is not likely that we can actually do anything like that fiction. Yet many physicists have outlined plausible scenarios where something similar to time travel is possible and there is no definitive argument against these scenarios.

Worth repeating again. For the dummies!!

 

[Landau Roof]

Well, here I was supporting the title remark of this thread, and then yesterday - I traveled back in time!

Two days ago a guy at work called and said I was wanted on a film set as an extra. So yesterday at the crack of dawn I find myself miles from nowhere in the desert at a fake train station. I was given 1940's style clothes to wear, right down to an overcoat and some Ben Franklin specs. A modern engine (but not that modern) pushed up an old-style engine-less train engine and 1940s' style car. We were so far out that no one's mobile worked. So it really was 1940! Okay, this wasn't really time travel, but it sure as sugar felt like it. Every now and then some yob of a crew member would interrupt the feel of the 1940s by bursting in in his bright-colored down jacket and jeans and his ridiculous 'baby shoes' of multicolored plastic. What I am trying to say is how amazing and wonderful it is how quickly the human mind and eye adjusts. I realy felt like I was in 1940, and all my brain had to say was , 'Of course, of course. It's 1940. Just look around! Don't be stupid' The thing was, I and everyone else felt just dandy strutting around in our 1940s clothes. The anachronistic crew looked like lost children - who else would wear such bright colors?

I know the 1940s were horrible times. They were still feeling like the Great Depression was never going to end (my father says they ate nothing but oatmeal from 1930 to 1938, and they stole that when they could) the whole world was at war, millions were being exterminated in Hitler's death camps, and I'll stop right there because surely that's all horrible enough to make my point,. Them was dark days, but man, they knew how to dress!

I was warm and cozy as well as cutting a fine figure in my wool and felt duds, and so was everyone else, while the crew looked like toddling morons as they half-froze in their modern clothes. It just took a few minutes to feel that our little world was the real one, and though we knew the modern world was a bus ride away, we pitied it. What a fashion disaster the 21st century is. It really is a shame we cant turn back the clock. I had always thought that all old styles looked ridiculous. You can wear your coolest outfit, and in twenty years time everyone will howl with laughter at your photos, but not so the 1940s! Our clothes gave us dignity and gravitas. Aye, we were poor and at war, but at least we knew how to dress and we had some class back then.

I thought it funny and maybe a bit pathetic in the 1970s when my old grandad, who was by no means rich, never left home without a neck tie and a hat and dress shoes. I thought he should just wear jeans, sandals and a T-shirt. Now, I understand that he was already a grown man in the 1940s and would have been embarrassed to dress like I did in the 1970s. I must have looked like a shipwrecked sailor to him.

(Beat back the Huns! Buy war bonds)

 

[Billy T]

Yes, and it is equally as useless to point out that people can arrive at the same event (or at adjacent events) by different means. Your reasoning is not getting any better.

Nor is that the evidence I offered for Sergei only aging slower, not time traveling.

Instead, I noted the he was gone for 10 Earth years, continuously experienced and (No discontinuous jump in time, as that would be "time travel" not "slower aging.") and was then 40 years old when he reunited with Ivan his "stay at home identical twin brother, who had age at Earth's normal rate so was 70 years old when they embraced at the same time and place. Ivan has shaken Sergei's hand 40 earth years earlier just before Sergei put on his space suit, when both were age 30.

Summary: Two brothers shake hands at same time and place, obviously, then both experienced the normal steady biological processes that ages them, one by 40 years and the other by 10 years, due to time dilation. Then when reunited, they embrace, at the same time and place. The both traveled to arrive at the "embrace instant" one by bus and the other by space craft. Neither time traveled (as that term is used in science fiction of the OP) but both just normally aged by biological processes, one aging 25% as fast as the other due to time dilation.

I do not think that calling time dilation time travel is useful.

Well that is some progress towards understanding what happened.

It is, however, far more useful and correct than calling it the slowing of the aging process.

I think we agree that every four days of Ivan's steady aging process, Sergei aged only one day. Neither experienced any "jump in time." In fact the ONLY difference was that Sergei aged four times more slowly than Ivan did. - Any reasonable person would call that "slower aging."

People who reject the reality of SR's time dilation, might accept that at the "embrace instant" one twin is 30 years older than the other, but suggest this happened because at the end of every 24 earth hours Sergei was placed in suspended animation for three earth days to reduce the weight of food needed for the trip by 75%. That would, I believe, be a more reasonable POV than claiming Sergei "time traveled" to the "embrace instant" as neither experienced any discontinuity in their biological rate of aging, nor "jumps in time."

.... If someone wrote a science fiction story where one twin got into a device and immediately met his or her twin twenty years in the future, it would not do to argue that it was not a time travel story because the twins met again.

I completely agree! If that discontinuous "jump in time" is experienced, then certainly it is OK to refer to that as "time travel" - The only plausible way for that to happen is via "suspended animation and re-animation" as all other ways are either impossible or prohibitedly expensive. (Kim Thone & Hawkins agree that any time machine will instantly explode when turned on.

As for time travel via "worm holes," note they are made only with more "exotic mater" than is know to exist AND in a nearly "flat" space time are under tremendous forces trying to collapse them. - Why none exist except as unstable theoretical solutions to GR equations. For another example of a valid but unstable solution to SR (and even Newton's) equations, consider: A configuration of 10 perfect spherical and uniformly dense bowling balls with one exactly above the other vertically in a gravitational field. That configuration is "permitted by the laws of GR."

In the case of time dilation, there is a different amount of time on different paths to the same event.

I agree.

So while it is much less interesting "time travel" than what one expects from science fiction, it certainly highlights that time behaves differently according to SR than our ordinary understanding.

No, time travel is when Jack sets out on a time travel trip at t = 0 and arrives at some point of time when Jacks time, Tj is either Tf or Tp (where the subscript refer to future & past) when every body else has arrived at t = Tn (where the "n" subscript refers to the now moment all experience.) If Jack's Tj is also Tn, then no time travel has occurred. Only if Tj is NOT Tn does time travel occur. Or one can take the POV, as I do, that when Jack arrives with every body else, to Tn, all have "time traveled" at the same uniform rate. I.e. We are ALL traveling into the future, except for those who died before it arrived to be Tn.

PS, Yes it is beyond the ordinary understanding of most, but I have believed it for more than 55 years, so it seem perfectly natural to me - I. e. that is just the way "nature is." Like wise I am not bothered by a single photon being reflected by two metal mirrors that are 10Km apart, and instantly ejecting, with its full energy,* an electron from one of the metal mirrors. etc.

* less the "work function" energy of the metal surface, of course.

 

[PhysBang]

Nor is that the evidence I offered for Sergei only aging slower, not time traveling. I noted the he was gone for 10 Earth years, continuously experienced and (No discontinuous jump in time, as that would be "time travel" not "slower aging.")

In your particular fantasies time travelers might experience discontinuities, but this is not a requirement of the genre. And if we are merely calling time dilation "time travel", then this will also be continuous.

And, again, it is wholly incorrect to call this "slower aging". I see you are back to rejecting time dilation. Ah, well, these salad days last only so long.

to reunite with Ivan his "stay at home identical twin brother,

Again, not good evidence, since time travelers in many stories reunite with people.

Neither time traveled (as that term is used in science fiction of the OP)

That is definitely not true, since the evidence is that they did travel through time in the sense of relativity theory in a way that the OP rejects.

Any reasonable person would call that "slower aging."

Any reasonable person who wanted others to reject time dilation. The connotations of merely referring to age give us the equally science fiction idea that people can enjoy more of their life by traveling fast.

If that discontinuous "jump in time" is experienced, then certainly it is OK to refer to that as "time travel"

Again, some discontinuity does not seem to be required for time travel.

- The only plausible way for that to happen is via "suspended animation and re-animation"

Suspended animation is clearly not time travel, as it presumably relies on the standard operation of physics over time.

 

[Billy T]

... I see you are back to rejecting time dilation. Ah, well, these salad days last only so long. ...

You need some very strong glasses. I have been a believer in the reality of time dilation (and the other side of the GR coin, called "length contraction") for at least 55 years - quite possible believed that before you were born and I have never ceased to believe in both these aspects of GR.

I looked up your "Join date" (October 2012) so can confidently say I was here posting about both SR effects 8 year before you even joined.

My lunch time - perhaps more reply later.

 

[PhysBang]

I think we've discovered a new fallacy! The prima posta: I was posting on this subject earlier, so my position is correct.

I don't care how long you have been misrepresenting time dilation, just that you are.

 

[OnlyMe]

This debate seems to be getting out of hand. It boils down to a difference of opinion as to what the deffinition of Time-Travel should be.

Billy has been consistently saying that he believes the definition should be limited the Scifi definition that involves an individual moving between separate, time frames of reference, without a continous experience of the elapsed time from frame to frame... Like a jump in one's own frame of reference, either forward or backward in time.

PhysBang and paddoboy, have been (I believe with some variation) been supporting the idea that the definition of time travel should imclude the effects of time dilation on an individual's leaving one frame of reference and returning in a maner that when comparring clocks traveling with the individual and left at rest at the starting point wind up disagreeing, when brought back together. Essentially saying that time differences associated with time dilation should be defined as time travel.

What seems to me disturbing is that lately it has been being suggested, that if you do not call time dilation time-travel, you are denying time dilation, which is a crap argument. I tend more toward Billy's position, than the idea that time dilation is time travel. Unless as I have mentioned earlier you want to include waking up in the morning, as time-travel.

As I began this post, the discussion is getting out of hand. Both sides have been adequately presented and both have merit. But both are also opinion! There is no fixed definition that all will agree with... And the difference of opinion as to what the definition should be has begun to affect aspects of argument that have no real connection with the underlying disagreement.

 

[Beer w/Straw]

Do you agree with Farsight?

 

[Billy T]

I think we've discovered a new fallacy! The prima posta: I was posting on this subject earlier, so my position is correct.

No you said I had cease to believe in time dilation. I was only pointing that was very unfounded / false claim you made I posted about it 8 year before you joined and did not waver in my believe it (and closely related length contractions) were true in the last 55 years. Time dilation is why cosmic ray daughter muons and others, including people, that travel much farther than is possible even at the speed of light when the duration of their travel is measured by Earth based clocks.

My refusing to call the time dilation that slow the rate of cosmic ray muon aging, so they can "live" much longer by earth based clocks etc. "time travel" is not misrepresenting time dilation, but seems to be your POV.

You apparently have the false idea that those muons are "time travelers" rather than correctly understand that they almost all do not decay before transiting ~ 100,000 meters to the surface of the earth is due to time dilation.

I don't care how long you have been misrepresenting time dilation, just that you are.

 

[PhysBang]

The problem with Billy T's position is not that he calls time dilation time travel. I don't think that time dilation is properly called time travel.

No, the problem with Billy T is with the way that he presents arguments and the way that he characterized time dilation.

On argument:
To say that something isn't time travel because the time traveler ended up where someone else was is ludicrous. To say that something isn't time travel because it used a different method to get where someone else arrived because of another method is ludicrous. To say that something isn't time travel because the traveler did not experience a discontinuity is ludicrous.

On position:
To say that time dilation is equivalent to a difference in aging is incorrect. For one thing, it gives the impression that a given amount of time was experienced but not as much biological process occurred. This is not the case.

To say that time travel into the future is equivalent to being frozen or otherwise having one's biological processes temporarily halted is also incorrect. Time travel involves the movement of all physical processes from one event to another in a manner that they would not otherwise be moved. For a frozen objects, physical processes proceed as they normally do for any frozen object.

 

[Billy T]

... Both sides have been adequately presented and both have merit. But both are also opinion! There is no fixed definition that all will agree with... And the difference of opinion as to what the definition should be has begun to affect aspects of argument that have no real connection with the underlying disagreement.

Yes. As I have several times stated the argument is a semantic one; However, I don't think any Ph.D. in physics describes the arrival at the surface of Earth as "time travel" by the muons instead of proof of time dilation. In fact in any good physics course, even at the undergraduate level, those muons are always cited as PROOF that SR's time dilation is real and never called "time travel."

 

[Billy T]

... I don't think that time dilation is properly called time travel. ...

Good, as What SR predicts is "time dilation" Others interprete it as time travel.

will read rest of you post later - I am with limited time -falling behind in needed replies one to you, soon I hope.

 

[krash661]

This debate seems to be getting out of hand. It boils down to a difference of opinion as to what the deffinition of Time-Travel should be.

Billy has been consistently saying that he believes the definition should be limited the Scifi definition that involves an individual moving between separate, time frames of reference, without a continous experience of the elapsed time from frame to frame... Like a jump in one's own frame of reference, either forward or backward in time.

PhysBang and paddoboy, have been (I believe with some variation) been supporting the idea that the definition of time travel should imclude the effects of time dilation on an individual's leaving one frame of reference and returning in a maner that when comparring clocks traveling with the individual and left at rest at the starting point wind up disagreeing, when brought back together. Essentially saying that time differences associated with time dilation should be defined as time travel.

What seems to me disturbing is that lately it has been being suggested, that if you do not call time dilation time-travel, you are denying time dilation, which is a crap argument. I tend more toward Billy's position, than the idea that time dilation is time travel. Unless as I have mentioned earlier you want to include waking up in the morning, as time-travel.

As I began this post, the discussion is getting out of hand. Both sides have been adequately presented and both have merit. But both are also opinion! There is no fixed definition that all will agree with... And the difference of opinion as to what the definition should be has begun to affect aspects of argument that have no real connection with the underlying disagreement.

is age directly related to time ?

 

[krash661]

Good, as What SR predicts is "time dilation" Others interprete it as time travel.

will read rest of you post later - I am with limited time -falling behind in needed replies one to you, soon I hope.

i move highly fast, time slows down.
is age directly related to time ?

 

[Motor Daddy]

i move highly fast, time slows down.

What do you mean when you say you move fast? Do you mean that you move a greater distance per second than if you were moving slower?

You do realize that a fast runner in the 100 meter dash takes less time to travel 100 meters than a slow runner. If he takes 10 seconds to cross the finish line, and the slowest runner takes 20 seconds to cross the finish line, what do the faster runners do during the time they cross the finish line until the time the slowest runner crosses the finish line? The fastest runner has to wait 10 seconds while the slowest crosses the line. In 20 seconds the fastest runner ran 100 meters and then waited for 10 seconds. The slowest runner ran 100 meters in 20 seconds.

 

[krash661]

i don't understand how one can say time doesn't exist, that it's just motion.
but then say time dilation slows time down.
funny.

 

[krash661]

What do you mean when you say you move fast? Do you mean that you move a greater distance per second than if you were moving slower?

You do realize that a fast runner in the 100 meter dash takes less time to travel 100 meters than a slow runner. If he takes 10 seconds to cross the finish line, and the slowest runner takes 20 seconds to cross the finish line, what do the faster runners do during the time they cross the finish line until the time the slowest runner crosses the finish line? The fastest runner has to wait 10 seconds while the slowest crosses the line. In 20 seconds the fastest runner ran 100 meters and then waited for 10 seconds. The slowest runner ran 100 meters in 20 seconds.

is age directly related to time ?

 

[Motor Daddy]

i don't understand how one can say time doesn't exist, that it's just motion.
but then say time dilation slows time down.
funny.

No answers? You claim time slows down if you run fast, but that's BS! A runner runs 100 meters in 10 seconds. If he was faster he would run the 100 meters in 9 seconds. Time didn't slow down, the faster a runner runs in the 100 meters the less time the runner takes to compete the task. Time ticked as usual.

 

[krash661]

No answers? You claim time slows down if you run fast, but that's BS! A runner runs 100 meters in 10 seconds. If he was faster he would run the 100 meters in 9 seconds. Time didn't slow down, the faster a runner runs in the 100 meters the less time the runner takes to compete the task. Time ticked as usual.

yeah,(shakes head) typical. you know exactly what i'm saying.
again, is age directly related to time ?