Time Travel is Science Fiction

Sign #37 that you might be a crank -
Most regular posters are on your "ignore" list, but MotorDaddy and Landau are not.
Sign #38 that you might be a crank -
You think Einstein, Thorne, Sagan and Hawking are idiots compared to you.
Sign #39 that you might be a crank -
You denigrate people who "worship the Bible of science" and applaud people with open minds who are not fettered by education.

 

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Sign #632 that you might be a crank -
You ignore Motor Daddy on an internet site.

 

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No I didn't. See post #707 above where I quoted this:

"Eine Krümmung der Lichtstrahlen kann nämlich nur dann eintreten, wenn die Ausbreitungsgeschwindigkeit des Lichtes mit dem Orte variiert."

Einstein was talking about the SR postulate, saying it didn't apply for gravity. That SR postulate was the constant speed of light. Like Don Koks said, Einstein was talking about the variable speed of light:

"Einstein talked about the speed of light changing in his new theory. In the English translation of his 1920 book "Relativity: the special and general theory" he wrote: "according to the general theory of relativity, the law of the constancy of the velocity [Einstein clearly means speed here, since velocity (a vector) is not in keeping with the rest of his sentence] of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [...] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity [speed] of propagation of light varies with position." This difference in speeds is precisely that referred to above by ceiling and floor observers."

 

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The over riding fact on this subject is that the laws of physics and GR in no way forbid the possibility of time travel.
And any sufficiently advanced civilisation could achieve it, even our own.
Both are undeniable facts accepted by all mainstream common sense logical physicists.

 

Trippy, You may beware of Farsight’s claim that Don Koks agrees with him about the speed of light slowing to zero at the event horizon, you probably know Don Koks is referring to the coordinate speed of light, this can be seen from D. Koks book “Explorations in Mathematical Physics: The Concepts Behind an Elegant Language. “

Link here…Use page turner or scroll onwards to 501 when you land on the restricted page.
Note my underlining on the image below, which explains that all this ‘slowing and stopping of light at the horizon is according to Scwarzschild coordinates.
" as far as the coordinates are concerned, it slows to zero as it approaches r = 2M,which thus defines the Scwarzschild horizon..”

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I don't think Farsight is talking about the coordiante speed.

 

Note the thread title. The whole point of understanding time, is this:

When an optical clock goes slower when it's lower, it isn't because time goes slower, it's because light goes slower.

I started a thread on that, only somebody moved it to alternative theories. It would be nice if they could move it back.

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Paddoboy, you know that at least that portion underlined above is not true. And the rest depends on restricting conclusions to the mathematical model... There is no evidence that time travel can occur in any way other than from the present to the future, and even then it is limited by an individual's life span.., and perhaps the clock he/she uses to mark the passage of time.

I would even go as far as to say that there is nothing in the known LAWS of physics that suggests that time travel, other than as described above, is possible. The laws are things which have been demonstrated to be true, as in having been observed... I am not even sure that any extension of a locally confined observation, which could support a law of physics.., to a universal or global context, can be thought of as a LAW of physics...

 

Farsight, optical clocks are not light boxes... And if your little bouncing light boxes had anything to do with anything.., anyone who has programmed a pong game could alter time.

.... Actually it seems more likely that at some point any thread you begin posting in, where you drag the same old arguments in, is in risk of joining Alternate Theories or just being closed.

 

No, they're like atomic clocks, only they use an optical frequencies rather than microwaves.

Those are parallel-mirror light clocks. They're a simplified form of gedanken clock used extensively in relativity. For example it's used in the simple inference of time dilation due to relative velocity.

Come come now, even you know that a parallel-mirror light-clock goes slower when its lower. And that there ain't no time flowing between those mirrors.

 

Come, come now Farsight, even you know there are no real parallel light clocks. They are as you mentioned an imaginary construct, used in hypotheticals. They are not real clocks and thus PROVE nothing!

 

And so does mine: Einstein was referring to the SR postulate, saying it didn't apply when gravity is concerned. The SR postulate of the constant speed of light. Speed. Not some vector-quantity velocity. Einstein knew about mirrors and refraction.

Yes, he said propagation speed for added emphasis, trying to make it clear that light curves because the speed of light varies with altitude. But obviously it wasn't clear enough.

Well you're wrong again. It was me who emailed Don Koks pointing out a problem in the previous article, which contradicted itself. Because of that, he wrote the new article that I've referred to. Here the quote again:

"Einstein talked about the speed of light changing in his new theory. In the English translation of his 1920 book "Relativity: the special and general theory" he wrote: "according to the general theory of relativity, the law of the constancy of the velocity [Einstein clearly means speed here, since velocity (a vector) is not in keeping with the rest of his sentence] of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [...] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity [speed] of propagation of light varies with position." This difference in speeds is precisely that referred to above by ceiling and floor observers."

Well we're not. And if you doubt me, go and email Don Koks.

No it isn't. Not when Don Koks, the editor of the Baez web site, said Einstein clearly means speed here.

 

But they are employed in relativity, and correctly, because they're an idealized version of the optical clock, which is not hypothetical. See this interview with David Wineland of NIST: "if one clock in one lab is 30cm higher than the clock in the other lab, we can see the difference in the rates they run at". And again: there is no time flowing in these clocks. Just light and things, moving.

 

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The problem here is that when they were first introduced, there were no optical clocks. They (your parallel mirror light clocks) were and are not idealized optical clocks. One is an imaginary tool, used in hypotheticals, the other is real. One (the parall mirror light clock) does at least suggest that the speed of light is involved, the other involves the mechamics of an atom, as it affects the emission of photons... Not the speed of light.

The NIST optical clocks do not measure the speed of light or depend on any change in c. This is a complete misrepresentation of the facts. BTW did that particular reference provide any control, proving that those two optical clocks would function identically when side by side, rather than when located in different labs? And if so why does it take more than one atomic clock to come up with our standard of time?

Seems I have seen some NIST reference that demonstrates that even two otherwise identical optical clocks in the same room vary in their clock rate!

 

A quote from your link...

Even your NIST optical clocks, clock rate can be affected by more than just location in a gravity well. Did your reference include controls for temperature differences or and differences in the magnetic fields each clock was exposed to? Even gravity can change from one location (meaning room or lab) to another depending on the local mass density of the earth... You know, I don't remember seeing a peer reviewed paper on this, but I am sure if one exists it would include even the affect that the electrical wiring in the two labs would have on the clocks... How they determined the difference in altitude, local magnetic fields, temperatures.., how many other variables?

I accept the NIST clock reference as supporting the GR prediction that the two clocks would function differently at different locations in the earth's gravity well. What it does not prove is that the speed of light is anything other than c.

You make claims of fact about conditions that are not only beyond your ability to measure but are beyond mankind's current ability to measure and confirm. That is my biggest concern with your posts. Is the speed of light the same everywhere in the universe? I don't know. All we can do is base what we believe on what we do know, which is that when we measure the speed of light we always get the same answer... And when we use that value as a constant, to interpret what we observe of the distant universe, the conclusions we reach seem to make sense, so until proven otherwise it works for me.

 

All I have ever said is that the laws of physics and GR do not forbid time travel.
Since you raised the concept of evidence for it to be possible, I see the validated concept of time dilation as that evidence.

Again, all I have ever claimed is that the laws of physics and GR do not forbid it.
But again, I offer time dilation as a form of evidence that time travel is possible for any sufficiently advanced civilisation.

Will we ever get to achieve it with macro physical objects?? I don't know, but it has been achieved and is achieved with micro physical particles in Accelerators and illustrated with the lifetimes of muons.
My only other claim is that any sufficiently advanced civilisation could achieve it.
And I stand by that statement, with the emphasis on "sufficiently advanced"

The undeniable facts I refer to are, [1] The laws of physics and GR do not forbid it, and [2]Any sufficiently advanced civilisation could achieve it

 

The point is as I have already said, not one of the professors that were contacted agreed with Farsight's version of things, and one even went as far as to say he should learn some GR.
Any other claims by Farsight are delusional in the extreme.