Time Travel

I'm always always late for everything but last week I came early? Relativity speaking like.
 
Jim Tolmie's Underpants said:
Where does he say it can't exist? He clearly states "Backwards time travel is theoretically possible by several different methods using general relativity. " If it's theoretically possible, by definition, it can't "viloate the laws of physics."
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It absolutely violates the law of physics.

Firstly we need to understand what this is referring to. The usual reference is to Godel who showed that the field equations in GR would allow something to arrive before it left, in a Universe where all matter is rotating. This is not a Universe that exists which is why it was "theoretically possible" but not "possible".

Others have tried to tie GR into backwards travel using string theory and all of them start with the preface of "imagine a Universe like ours but where you can do X; given these axioms it is possible using GR calculations". Again, all of this is fine but we don't live in a Universe where you can do X which is why backwards time travel is still an impossibility.
 
Damocles said:
It absolutely violates the law of physics.

Firstly we need to understand what this is referring to. The usual reference is to Godel who showed that the field equations in GR would allow something to arrive before it left, in a Universe where all matter is rotating. This is not a Universe that exists which is why it was "theoretically possible" but not "possible".

Others have tried to tie GR into backwards travel using string theory and all of them start with the preface of "imagine a Universe like ours but where you can do X; given these axioms it is possible using GR calculations". Again, all of this is fine but we don't live in a Universe where you can do X which is why backwards time travel is still an impossibility.
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how do you know we cant do x and how do you know that the laws of physics are equal throughout the (our) universe, bottom line to the question is no one knows and that's simply down to humans not having the intelligence to create such a machine to enable this
 
Surely we just have to develop a way of travelling really fast outside the earth's atmosphere. I thought we were working on this anyway in order to reach planets further afield. If you can blitz it to a far off planet and back in say 10 years, by the time you get back it would be, say, 20 years on in earth's time. That's time travel isn't it ?
 
BimboBob said:
I think if you buy one of the cars that were made in Northern Ireland with tax payers money, find a friendly but slightly weird but not in a paedo way professor, get a small and slightly shaking man who thinks he can act but in reality all he does is run around like an ex-leper and then invent some y shaped light box then time travel is possible.
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Yay !! - FOUR pages before a veiled reference to a flux capacitor - I was getting worried Blues - I was starting to believe it wasn't possible - daft I know but.............
 
Hamann Pineapple said:
Surely we just have to develop a way of travelling really fast outside the earth's atmosphere. I thought we were working on this anyway in order to reach planets further afield. If you can blitz it to a far off planet and back in say 10 years, by the time you get back it would be, say, 20 years on in earth's time. That's time travel isn't it ?
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I think most are referring to the BTTF type as in arriving at a certain point in history in the same location as you left. There'd have to be an infinite number of time zones though. It's less likely than Phil Jones presenting X Factor.
 
I read a fantastic novel years ago about three students who invented a time machine. They went back to the time of the nativity to see if it was true. And guess what? They agreed they needed to land their time machine outside Bethlehem to avoid scaring the locals and ended up scaring the shit out of some shepherds instead who thought they were angels. So there weren't actually three wise men, just three students from California. Gold, frankincense and myrrh were actually some change, an inhaler and something else I can't remember.

It was a really interesting premise. I read it aeons ago and can't remember what it was called.
 
Jim Tolmie's Underpants said:
Where does he say it can't exist? He clearly states "Backwards time travel is theoretically possible by several different methods using general relativity. " If it's theoretically possible, by definition, it can't "viloate the laws of physics."
Click to expand...

Damocles said:
It absolutely violates the law of physics.
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No it doesn't. I don't know why you keep disagreeing with scientists who know a lot more about this than you do.

The general theory of relativity allows the so-called closed time-like curves which allow backwards time travel, at least in principle.

http://www.sciencechannel.com/tv-shows/through-the-wormhole/could-we-go-back-in-time-2/
 
Jim Tolmie's Underpants said:
No it doesn't. I don't know why you keep disagreeing with scientists who know a lot more about this than you do.

The general theory of relativity allows the so-called closed time-like curves which allow backwards time travel, at least in principle.

http://www.sciencechannel.com/tv-shows/through-the-wormhole/could-we-go-back-in-time-2/
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Because you're misunderstand what they're saying and taking it mean something else. I'm in total agreement with them because I know the math that they're doing, it's your interpretation of what they're saying that I'm disagreeing with. CTCs are a consequence of GR in specific circumstances. None of these circumstances exist.
 
marco said:
how do you know we cant do x and how do you know that the laws of physics are equal throughout the (our) universe, bottom line to the question is no one knows and that's simply down to humans not having the intelligence to create such a machine to enable this
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Because physics is an evidence based pursuit, and the laws of the Universe are equal everywhere because local laws makes absolutely no sense at all

The bottom line is just because you don't know something doesn't mean that nobody knows something.
 
Physics bamboozles, i will get to thinking about time travel after i work out why, if the world spins at about 1000 mph, why when i stand still my face isn't covered in Gnats.
 
talkativesprout said:
Physics bamboozles, i will get to thinking about time travel after i work out why, if the world spins at about 1000 mph, why when i stand still my face isn't covered in Gnats.
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We're almost in December you daft ****. No Gnats around at this time of year.
 
marco said:
its certain i don't know everything and have never declared so, but i'm pleased for you however you MAY be wrong


http://www.sciencedaily.com/releases/2010/09/100909004112.htm
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This again is somebody misinterpreting what that actually says. One thing researchers always do is make their discoveries sound Earth shattering because it alerts the mainstream press which gives them exposure which is what all scientific institutes crave; the paper itself is somewhat less ground breaking.

I'll grab a comment from elsewhere which may explain this better as electromagnetism is essentially still magic to me:

In physics, a coupling constant, usually denoted g, is a number that determines the strength of the force exerted in an interaction. Usually, the Lagrangian or the Hamiltonian of a system describing an interaction can be separated into a kinetic part and an interaction part. The coupling constant determines the strength of the interaction part with respect to the kinetic part, or between two sectors of the interaction part.

It is called constant because of historical reasons. It is a number that enters in the expansion to a mathematical series of a calculation of cross sections using Feynman diagrams, when we assume the interaction to be small to allow for a converging series expansion. It was neat that in electromagnetic diagrams it was a real constant, alpha.

There is no reason though to expect that the nice expression for alpha is also the exact expression needed in the final form of the Feynman series expansion of the cross section.

It was realized that the coefficients of the series had a calculable energy dependence. Look for the format in the link, page 9.

Thus alpha is not changed. The running is on the coefficient of expansion, quite legitimate, versus the energy for which the expansion is made. Physicists who have taken a course on this have no problem with the definition.
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talkativesprout said:
I stand corrected and bow to your superior Gnat knowledge....though gnats would have to fly 100mph just to stay still :)
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It is a mystery though mate. If the Earth is indeed spinning so fast, why when I jump over our little garden fence don't I land in the miserable cunts garden at the end of the street?
 
stony said:
It is a mystery though mate. If the Earth is indeed spinning so fast, why when I jump over our little garden fence don't I land in the miserable cunts garden at the end of the street?
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The question that bends a few minds is if you get on a plane that's flying against the Earth's rotation why don't you travel the speed of rotation (~1000mph) + flight speed.
 
Damocles said:
The question that bends a few minds is if you get on a plane that's flying against the Earth's rotation why don't you travel the speed of rotation (~1000mph) + flight speed.
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Is it god helping us? and as soon as we get far enough away from earth he thinks 'fuck it, if they don't wanna be here I'm not helping them any more'
 
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