Questions on General Relativity

I was doing some research on faster than light propulsion (Science Fiction-ish research) and I came across this GREAT SITE that explained a whole manner of sci-fi mistakes that authors sometimes make when writing futurish technology.

www.projectrho.com...

when I stumbled upon this little tidbit of information:


www.projectrho.com...

Relativity proves that FTL travel is identical to Time travel (to help your research, the technical term for time travel is "Closed timelike curve")

And I couldn't for the life of me understand *WHY* the speed of light is the same in all reference frames...

Or why faster than light travel = time travel.

Anyone have any insight on this one?

-Edrick

Relativity prooves nothing of the sort. Sounds like some bad info on that site

The only way time travel and FTL are remotely close are in a causality type thing: You travel out, can stop and look back and see yourself at home prepping to leave. Thus from perspective you are 'back in time'. However this is not time travel anymore than watching a TV recording is time travel.

reply to post by lordtyp0

Relativity prooves nothing of the sort. Sounds like some bad info on that site

It is highly possible, but I thought that I would throw this one out there... i'm not particularly well versed in general or special relativity.

The only way time travel and FTL are remotely close are in a causality type thing: You travel out, can stop and look back and see yourself at home prepping to leave. Thus from perspective you are 'back in time'. However this is not time travel anymore than watching a TV recording is time travel.

Yeah, you are talking about the light speed delay, and the "Picard Manuver".


I was more interested in the "Light speed is the same in all reference points" which does not make sense at all.

Thanks for responding though

-Edrick

[edit on 23-2-2010 by Edrick]

reply to post by Edrick

I was more interested in the "Light speed is the same in all reference points" which does not make sense at all.

I am rather tired atm, but it sounds like the part that makes it all relative

Basically, the speed of light is a constant. If you are traveling on a train and shoot a gun, the bullets velocity is whatever feet per second said bullet is-to those on the train. If you are on the train and shoot at something stationary, it would be the FPS of the bullet + the train momentum.

The speed is relative to the observer/impacted reference point.

Light however is constant, it doesn't accelerate more on a train regardless of observers onboard or if you shine it at a tree that is passing by.

At least, thats what it sounds like, I am tired like I said


EDIT: Bit of a ramble:


Was thinking about this the other day. The whole time/space thing. The analogy that popped into mind about the relationship of the two would be the ocean (space) and it's temperature (time).

You have all the volume with influences of temperature. You cannot have water without temperature being an element. In a similar manner "Time" is a mathematical description of the state of the universe at any given 'snapshot'.
So like temperature in extremes determines the state of matter in regards to the ocean, and whether something is survivable etc.. Time is a designation on similar conditions in space. You cannot 'time travel' because time is a description and nothing more. The only way to go 'back in time' would be to reset all matter.


If that makes sense, I am kind of rambling

[edit on 24-2-2010 by lordtyp0]

Because of Lorentz symmtery.

The laws of physics are the same in all reference frames.

reply to post by lordtyp0


What I have gathered so far in regards to light speed being the same in all reference frames, is that as your velocity approaches C (light speed) your internal time, and length (in the direction of travel) shrinks, so that even though, relative to you, light is moving a different speed, your measurement of distance over time (speed) of the photon will always agree on C.

This, however, violates basic logic, in that your measurement of time is only "Skewed" in this fashion depending upon your relative velocity to the photon in question....

So that at .5 C, you see a photon traveling parallel to you a going C, because your time frame is "Halved", but a photon traveling opposite your direction, but also parallel, would necessarily be measured as moving at 150% C, because of your time dilation.... unless your time frame is ALSO increased at the same time it is decreased.

This means, that ALL photons are moving faster than C, relative to the difference in perspective between US (the observer), and our time dilation from the perspective velocity of another photon traveling in an opposite direction.

It just does not make sense.

-Edrick

[edit on 24-2-2010 by Edrick]

reply to post by Edrick


You make an interesting point with the light travelling in the opposite direction. Not trying to be rude but I'm sure somebody else has tackled this and you must be wrong somehow but again, you make a good point!

I have a reasonable grasp on this subject so I'll have to think about this one.

reply to post by OZtracized

Not trying to be rude but I'm sure somebody else has tackled this and you must be wrong somehow but again, you make a good point!

Thank you.

And I have absolutely NO QUALMS about being wrong on this one.. I'm just trying to understand it...

But everywhere I have looked, noone seems to want to tackle this problem, and give me a straight answer.

IF you find a reasonable answer... PLEASE let me know... like, for my sanity, ya know?

-Edrick

reply to post by Edrick


The only answer I can think of to this question is "nothing can move faster than light speed and the speed of light is constant so the light travelling in the other direction can only be travelling at light speed".

There, that's your answer now shut up and stop questioning Einstein........

reply to post by OZtracized

There, that's your answer now shut up and stop questioning Einstein........

NEVER!


(Shakes tiny fist in the air)

-Edrick (Also, Second line)

The damning thing about special and general relativity is that they have been proven over and over again. Einstein assumed that the speed of light is constant in all frames of reference so it has been included in all the equations and the predictions have turned out to be correct every time.

Now as to why? It goes further than the general relativity into the nature of the universe. It has been said that particles are actually trapped light rays.

If a particle goes faster than the speed of light, the time becomes an imaginary number in the equations. It is termed "time-like".

It's people like you that insist on questioning nearly perfect physics.

You are almost as annoying as that guy who questioned Newton. Newtonian physics reigned supreme for a couple of hundred years and some fool had to find one tiny flaw.

What was his name? It started with E........ I think he was Austrian.......

reply to post by OZtracized


Actually Einstein didn't destroy Newtonian physics. Yes, he questioned it but he presented a better theory over it. We still use Newtonian physics today, even in rocket science.

The proof is in the pudding.

reply to post by Deaf Alien


Very true but if you read my post I never said he did. Newtonian physics is still widely used it just doesn't apply in every situation.

Possibly Einstein will suffer the same fate.

reply to post by OZtracized


Possibly. If someone invents a better theory, it will be *over* einstein theory, unless there is another theory that totally demolishes his theory and still have the same predictions and more.

Another damning thing is that the relativity theory is still being used in quantum mechanics.

It's not being used in quantum physics! At least not with any logical answers. That is the thorn in the side of modern physics. The two DO NOT work together.

A new theory doesn't have to prove Einstein wrong, it just has to explain things better in certain situations (did you say that in your post?).

[edit on 25-2-2010 by OZtracized]

reply to post by OZtracized


That may be true. There have been many attempts but with some successes.

Early attempts to merge quantum mechanics with special relativity involved the replacement of the Schrödinger equation with a covariant equation such as the Klein-Gordon equation or the Dirac equation. While these theories were successful in explaining many experimental results, they had certain unsatisfactory qualities stemming from their neglect of the relativistic creation and annihilation of particles. A fully relativistic quantum theory required the development of quantum field theory, which applies quantization to a field rather than a fixed set of particles. The first complete quantum field theory, quantum electrodynamics, provides a fully quantum description of the electromagnetic interaction.

The speed of light is still constant everywhere.

reply to post by OZtracized

A new theory doesn't have to prove Einstein wrong, it just has to explain things better in certain situations (did you say that in your post?).

Yes that's what I said. Like I said, someone might bring up a theory that totally destroys Einstein theory and still have the same predictions and better.

Originally posted by Deaf Alien
reply to post by OZtracized

 

A new theory doesn't have to prove Einstein wrong, it just has to explain things better in certain situations (did you say that in your post?).

Yes that's what I said. Like I said, someone might bring up a theory that totally destroys Einstein theory and still have the same predictions and better.

Yeah, I'm starting to see the need for that more and more if we are to further our understanding of quantum phenomenon... not to mention gravity.

Ah, Geez... Gravity....

-Edrick

I am sorry but I disagree. You should always question EVERYTHING.

I am a theoretical physics student and I know that although there are many fundamental laws that have been proven to be true, there are also many many problems with physics.

I always question a scientific fact no matter how well-accepted it is. People that accept everything they are told as true just get sucked into the dogma and this is how religion continues to manipulate.

People like Einstein and Newton thought outside the box, they did not accept what society dictated, and they did not accept the scientific paradigms of their day, AND THIS IS WHY THEY CREATED BEAUTIFUL WORKS OF ART!

Wake up!