Relativity Question *waves at TheEngineer*

Quote from: Gulliver on July 19, 2007, 06:05:38 PM

Quote from: TheEngineer on July 19, 2007, 03:31:34 PM

His own source proves him wrong, so it must be that the article, in its entirety no less, is now out of context.   But prior to this realization, the article was just fine, in its entirety, no less.

Still waiting on that quote from Einstein that "gravity as a force does not exist". Still waiting on your proof that Nature is an observer. Still waiting on any proof that the 1998 AIP web page is wrong about Nature sending info FTL. I will consider your geodesics explanation, but still haven't seen any evidence that Einstein thought we should stop treating gravity as a force in all cases.

Um, I don't recall anyone saying that we should stop treating gravity as a force in all cases.  I recall TheEngineer saying that gravity is a fake force.  There's a difference.  We can treat it like a force when we're dealing with it, but that doesn't make it a force.

You and I agree about gravity. TheEngineer, though, claims that Einstein said "gravity as a force does not exist." and that this arises from a shift of FoR.
See, for example:

Quote from: Trekky0623 on July 07, 2007, 10:24:36 AM

Does not acceleration require a force?  That force is gravity.

Actually, no.  We are in a non inertial frame of reference, thus, by definition, Newton's first two laws don't apply.  Since we perceive ourselves as not accelerating, we transform our frame of reference into an inertial one.  This transformation gives rise to fictitious forces, namely, gravity.

Yes, gulliver, but that acceleration only exists if you think of spacetime being Euclidean.  When you think of it not being Euclidean, as GR describes, no force is necessary for that 'gravity'.

EDIT:  Also, TheEngineer never said to not treat it as a force, he just said it isn't a force.

EDIT2: Changed 'space' to 'spacetime'

You and I agree about gravity. TheEngineer, though, claims that Einstein said "gravity as a force does not exist."

I'm sure he didn't say that specific quote (Einstein).

It's true that TheEngineer did say that, but he's clearly wrong or he meant that Einstein's work revealed that conclusion. Since TheEngineer is rarely wrong, I'm guessing it's the latter.

Yes, information transfer at FTL speeds is strictly prohibited by GR.  Things can move at FTL speeds, but they can't tell us they are doing so.  This would cause all kinds of problems with causality, so there is usually a very neat mathematical solution as to why information can't be transfered at FTL speeds.  Such as a tachyon detector:  It would be able to detect the incoming tachyon, but it would also emit an exact copy of that tachyon, thus losing the information.

What if FTL particles are reduced in speed to c?

Quote from: TheEngineer on July 17, 2007, 11:48:13 AM

Yes, information transfer at FTL speeds is strictly prohibited by GR.  Things can move at FTL speeds, but they can't tell us they are doing so.  This would cause all kinds of problems with causality, so there is usually a very neat mathematical solution as to why information can't be transfered at FTL speeds.  Such as a tachyon detector:  It would be able to detect the incoming tachyon, but it would also emit an exact copy of that tachyon, thus losing the information.

What if FTL particles are reduced in speed to c?

Not possible. The existence of FTLs relies on them always being faster than light. In other words, by definition, they are always moving superluminally.

What if FTL particles are reduced in speed to c?

That would require an acceleration to c, which is prohibited.

So are you saying superliminal particles like tachyons cannot be distorted nor decelerated to  or lower than c when transversing through a medium?

So are you saying superliminal particles like tachyons cannot be distorted nor decelerated to  or lower than c when transversing through a medium?

Yes.

Quote from: The Kommunist on July 20, 2007, 08:20:22 AM

So are you saying superliminal particles like tachyons cannot be distorted nor decelerated to  or lower than c when transversing through a medium?

Yes.

I think I disagree, on a technicality. (This is really hypothetical stuff.) c[/c] is the speed of light in a vacuum. A very energetic tachyon traveling through a very dense medium could very well travel more slowly than c[/c], but never as slow as light would travel in the same medium (which is what I think Fritz meant).

Quote from: The Kommunist on July 20, 2007, 08:20:22 AM

So are you saying superliminal particles like tachyons cannot be distorted nor decelerated to  or lower than c when transversing through a medium?

Yes.

I think I disagree, on a technicality. (This is really hypothetical stuff.) c[/c] is the speed of light in a vacuum. A very energetic tachyon traveling through a very dense medium could very well travel more slowly than c[/c], but never as slow as light would travel in the same medium (which is what I think Fritz meant).

Thank you.  This simple demonstration shows that the current GR theory needs revisions in its definitions.

<snip>
Thank you.  This simple demonstration shows that the current GR theory needs revisions in its definitions.

No shit Sherlock! 

Quote from: Fritz Zwicky on July 20, 2007, 08:30:24 AM

Quote from: The Kommunist on July 20, 2007, 08:20:22 AM

So are you saying superliminal particles like tachyons cannot be distorted nor decelerated to  or lower than c when transversing through a medium?

Yes.

Quote from: Gulliver on July 20, 2007, 02:15:56 PM

I think I disagree, on a technicality. (This is really hypothetical stuff.) c[/c] is the speed of light in a vacuum. A very energetic tachyon traveling through a very dense medium could very well travel more slowly than c[/c], but never as slow as light would travel in the same medium (which is what I think Fritz meant).

Thank you.  This simple demonstration shows that the current GR theory needs revisions in its definitions.

The current GR theory needs more revisions than that. It is simply a model of gravitation which is better able to predict the effects of gravity than Newton's gravity. In this model, there are many problems (things which happen on a very small scale do not agree with GR).

I think that 99% of the posters on here referring do GR do not understand GR as well as they claim. (I'm not claiming that I understand it either, as I do not!)

I think that 99% of the posters on here referring do GR do not understand GR as well as they claim. (I'm not claiming that I understand it either, as I do not!)

How can these two statements go together?

Quote from: andrews on July 21, 2007, 02:26:13 PM

I think that 99% of the posters on here referring do GR do not understand GR as well as they claim. (I'm not claiming that I understand it either, as I do not!)

How can these two statements go together?

I am not a physicist, and I have not read books or papers on GR, but I have taken a course in Differential Geometry, I am soon to take a course in GR, and I know a relativist quite well, and we talk about GR a little bit. I am not a stupid person!

Gravity is the reason that objects fall to the Earths surface, whether it is a force or not. To my understanding, the theory of GR assumes that the universe is a 4D manifold which is curved by mass, and objects follow geodesics on this manifold, which happen to cause them to move towards sources of mass. Either way, it pulls things downwards, so it is irrelevant to us whether it is a force or not.

I am not a stupid person!

No one said you were.

Gravity is the reason that objects fall to the Earths surface

Gravitation is the reason objects fall to the Earth's surface.  This is not a force, in GR.  So yes, it does matter.

Quote

Gravity is the reason that objects fall to the Earths surface

Gravitation is the reason objects fall to the Earth's surface.  This is not a force, in GR.

This is exactly what I said, so I am done arguing this point.

Quote from: TheEngineer on July 21, 2007, 04:22:59 PM

Quote

Gravity is the reason that objects fall to the Earths surface

Gravitation is the reason objects fall to the Earth's surface.  This is not a force, in GR.

This is exactly what I said, so I am done arguing this point.

No, you said gravity. He said gravitation. They are different.

gravity and gravitationare interchangeable just like we can say kilograms or pounds when we really mean Newtons or Slugs, I really do not see you guys going to the butcher and ordering 2 Newtons of beef, and no gravity(gravitation) is not a force but it is a cause of a force.

gravity and gravitationare interchangeable just like we can say kilograms or pounds when we really mean Newtons or Slugs, I really do not see you guys going to the butcher and ordering 2 Newtons of beef, and no gravity(gravitation) is not a force but it is a cause of a force.

"In scientific terminology gravitation and gravity are distinct." - Source

Typically, physicists will look at photons as waves for your thought argument. This allows them to ignore their mass. They will then look at them as particles when they need them to have mass. Basically we have the newtonian vs quantum laws that we pick and choose from. This is evidence that we have a flaw in our model at a more elementary level.

Photons do not have mass. They have momentum...

Quote from: cbarnett97 on July 22, 2007, 03:36:26 AM

gravity and gravitationare interchangeable just like we can say kilograms or pounds when we really mean Newtons or Slugs, I really do not see you guys going to the butcher and ordering 2 Newtons of beef, and no gravity(gravitation) is not a force but it is a cause of a force.

"In scientific terminology gravitation and gravity are distinct." - Source

This is a useless argument. I'm sorry if I didn't use the word gravitation when I meant gravity. While reading/writing this forum, I don't really think much about scientific terminology as it is not particularly scientifically accurate.

This is a useless argument. I'm sorry if I didn't use the word gravitation when I meant gravity. While reading/writing this forum, I don't really think much about scientific terminology as it is not particularly scientifically accurate.

You're forgiven. Just, if you want to avoid useless arguments, it helps to use the appropriate terms. It disallows people from attacking your sentence formation and use of inaccurate words as evidenced by the last few posts.