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Author: Subject: Can we travel back in time really?
jack44556677
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[*] posted on 15-3-2019 at 02:59


Definitely a physics question.... I've been musing on this for a long time. Below is the idea of a professor from UConn to talk to his dead father again.

Assuming time ISN'T adequately described by thermodynamic change, and thus requires some sort of omniscient observer recording all things in order to allow for such a "backup" to be restored.

Here's the setup : If you buy measured time relativity, i.e. the experiment with the atomic clocks, one on the rocket and one at home - then there might just be a way.

Because the clock moving at 25,000mph relative to the "stationary" one on earth is moving that much closer to the speed of light, the speed at which the clock runs is slightly slower when compared to the clock at home. This is a highly dubious experiment for a variety of reasons, but let's go ahead and say it proves everything Einstein ever thought right, from now until infinity.

That is still just travel into the future, but it demonstrates that you can change the passage of time by changing your speed relative to a somehow "ir-relative" speed of light.

Here's the rub : From the mathematics, speed isn't the only thing that can alter the flow of time relative to earth. So can gravity / energy density. Assuming black holes are real, and actually what we think they are, they are a good example. As things are sucked into the event horizon, or rather as they approach it, they slow down (appear to slow down from our observational reference) and at "infinite" gravity/energy density you get a "tear" and time stops completely. AFAIUI Hawking was instrumental in mathematically describing why time does NOT stop at the even horizon and why all black holes evaporate eventually, but I digress. Still with me? Long story short (and if this was a physics forum I would have left little to none of the above) - if you send light or something moving very close to it into or nearby an energy/gravity concentration, from your perspective it would slow down until it vanished from your sight. It is this vanishing point that may hold the key to time travel, if such a thing there be. If you imagined the light as a clock, whose face you could always see and read (even after it vanishes) ... one of the potential mathematical solutions involves the light moving backwards towards the origin and the clock hands moving backwards (from your, relatively stationary, perspective).

The Uconn professor hoped to use this principle with a powerful array of lasers focused on a very small area of space (high energy density) and some sort of charged particle or light sent into it in pulsed / information carrying ways in the hopes that results from future testing of the machine might be measurable in the present. Of course this device would only be useful for information transfer, and only SINCE the time travel telegram facility was first built.

Fun stuff.

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Sulaiman
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[*] posted on 15-3-2019 at 06:11


https://www.youtube.com/watch?v=N0qDy0T5WXM



CAUTION : Hobby Chemist, not Professional or even Amateur
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MrHomeScientist
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[*] posted on 15-3-2019 at 06:22


jack44556677, you seem distrustful of relativity and black holes. Why do you think clocks running slower is "dubious"? GPS satellites wouldn't work without clock corrections based on relativity. Atomic clocks in space have been shown to run slower than atomic clocks on Earth. You can observe cosmic ray muons in a cloud chamber on Earth despite these muons not having a long enough lifespan to reach the surface, because time is slowed down for them. I've seen these myself, just the other day.

Black holes certainly exist, they're just hard to observe (they're black, after all). We can observe stars near the galactic center orbiting a gigantic mass that occupies a small volume and doesn't emit light; a black hole fits that quite nicely.

Do you have alternative explanations for these phenomena?
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Mothman
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[*] posted on 16-3-2019 at 07:50


Man I'm not high enough for this thread, lemme go grab my *other* glassware.

Funny thing is it's still chemistry equipment because I'm that much of a nerd. 14/20 blaze it!




You can be happy
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jack44556677
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[*] posted on 9-4-2019 at 21:09


@MrHomeScientist - At this point in my life I would say I am distrustful, generally, regardless of subject or object.

I am a fellow lover of cloud chambers, and my ex does the muon experiment for every undergrad that goes through the basic physics lab course (though she doesn't use a cloud chamber, which is a bummer).

I do have grave doubts, as Tesla and many others did/do, about Relativity writ large - including but not limited to: relative time and black holes.

Large non-luminescent mass/gravity/"dark energy"/"dark matter"/"fill in the blank made up term to keep circling the big bang standard cosmological drain without repentance or humility" do exist in the observable universe. Though obviously we only "know" it is there by making observations of visible phenomena and inferring the rest, we observe matter being affected by the invisible and declare the invisible this and that. Do I have a better suggestion as to what it is than the interpretation that Einstein himself thought was a purely mathematical misunderstanding/misapplication of his theories? Short answer, No. Do I think it is reasonable to continue to doubt that such things exist until there is experimental evidence that can support it (extra-ordinary claims and all that...)? Short answer : Yes. Sagan fought the oort cloud tooth and nail for the same reasons, and he was right to. Looking for the universe in our models/equations is almost always counter-productive, and leads further into fantasy and supposition. The black hole fitting "nicely" isn't coincidence, it is evidence of a failing cosmological model desperate for anything to keep propping it up (dark energy and matter come to mind most prominently). We continue to have very little, if any, physical evidence that black holes can or do exist.

As for measured relative time, this is another massive claim requiring massive evidence to justify. I will continue to be a skeptic myself until some physical / mechanical clock is tested, and I don't trust NASA to conduct this science any better than the other inept bureaucratic American government/military institutions. I personally suspect that the speed of light is the universal constant and that it enables the building of a light clock allowing for absolute time and absolute position. One of my relativity thought experiment paradoxes that suggests this is as follows : What happens when, in a space ship, traveling near to the speed of light at constant velocity and you turn on a flashlight in the direction of motion. What do you see? What does your friend on earth see through the window? Rather than allow superliminal light inside the cabin or other such nonsense, I think it is far simpler to just say (imagine) the light comes out slower. This slower light would be the measurement of your speed relative to "absolute stationary" as well as your direction. It is also far simpler (and more sane) to suppose that space travel and orbit affect the function of the atomic clock in this way which requires adjustment, rather than concluding that what has altered is "the very flow of time, itself!!".

@Sulaiman - I don't like that show, but that clip really captures and succinctly conveys something about time travel discussion in general!
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[*] posted on 10-4-2019 at 09:51


Quote: Originally posted by jack44556677  

I do have grave doubts, as Tesla and many others did/do, about Relativity writ large - including but not limited to: relative time and black holes.


No disrespect to Tesla, but by the time SR was published he was already in his 50's. Few scientists have made significant contributions that late in life. Also, he was "merely" an electrical and mechanical engineer so he might not be the best one to listen to.

Reality is that people have been trying to poke hoes in GR for more than a century, and it's still going strong. We know it has it's limits, but within those it's as right as we can measure.

You want observations? GR explains the anomalous perihelion shift for the innermost planets. Gravitational lensing has been used for astronomical observation. We've observed gravity waves, we've even taken a fucking picture of a black fucking hole!!!




We're not banging rocks together here. We know how to put a man back together.
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MrHomeScientist
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[*] posted on 10-4-2019 at 11:02


jack44556677, thank you for the well thought-out and non-emotional response. Far too many people on the internet immediately go nuts when they are challenged.

Quote: Originally posted by jack44556677  
Do I have a better suggestion as to what it is than the interpretation that Einstein himself thought was a purely mathematical misunderstanding/misapplication of his theories? Short answer, No. Do I think it is reasonable to continue to doubt that such things exist until there is experimental evidence that can support it (extra-ordinary claims and all that...)? Short answer : Yes.

Nothing wrong with healthy scepticism! Incorrect math is always a possibility, and theories have been changed, refined, and thrown out as new observations were made. What we have now is our best approximation of how we think the world works, and observations fit the theory to pretty good accuracy for the most part. The problem, I think, is that it's very difficult for the lay person to really understand why a theory works when "behind the curtain" the math and explanations are so convoluted. Hell, I'm a physicist myself and a lot of it goes over my head. But these models and the math behind them are currently the best ones that fit the observations. We can say with a pretty strong degree of certainty that, indeed, this is how the universe works.

Quote: Originally posted by jack44556677  
The black hole fitting "nicely" isn't coincidence, it is evidence of a failing cosmological model desperate for anything to keep propping it up (dark energy and matter come to mind most prominently). We continue to have very little, if any, physical evidence that black holes can or do exist.

Funny that you should post this literally one day before an actual photo of a real black hole was released! It's from radio telescopes so it's false color of course, but the photo is fascinating. The Guardian has some nice graphics that explain why it looks the way it does: https://www.theguardian.com/science/2019/apr/10/black-hole-p...

Quote: Originally posted by jack44556677  
As for measured relative time, this is another massive claim requiring massive evidence to justify. I will continue to be a skeptic myself until some physical / mechanical clock is tested, and I don't trust NASA to conduct this science any better than the other inept bureaucratic American government/military institutions.

They have tested clocks, and observed time dialation on them. Again, GPS wouldn't work at all without accounting for it. Why would the clock being mechanical be any different? They use atomic clocks because they are far more accurate and the effect being measured is so tiny. The innaccuracy of a mechanical wristwatch, for example, would drown out the tiny signal they are trying to observe. Either that, or they'd have to fly that clock around for much, much longer than the atomic clock before a difference could be seen.
Also, you said your wife does the muon experiment regularly, so presumably you have also seen it and understand what's happening. Is that not convincing evidence for time dialation?
Finally, just because NASA is a government organization doesn't mean 100% of its people are bad at their job. These are highly qualified people that are experts in their field; literal rocket scientists. They understand this stuff far better than we do. If you don't trust scientists to do science, who would you prefer to do these experiments?

Quote: Originally posted by jack44556677  
It is also far simpler (and more sane) to suppose that space travel and orbit affect the function of the atomic clock in this way which requires adjustment, rather than concluding that what has altered is "the very flow of time, itself!!".

How exactly do you propose that "space travel and orbit" affects the clock? I'm interested to hear the details. Any good theory needs to be well-defined and rooted in mathematics. It also needs to be able to explain the observations and, ideally, make predictions for new experiments.
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