0.999999999c

[celox]

Is it possible that the speed of light (in vacuum) is 0.999999999c (or some other number of 9's after zero) rather than 1c? Here I define "c" as the universal "speed limit", and obviously not as the speed of light itself. I know that it would have to be so close to c that we would (at least currently) be unable to measure any difference. But by my understanding, something accelerating very close to c (relative to us) would eventually move fast enought that it would seem to move at c from all reference frames, as far as we would be able to measure it.

[biggs]

c is ( c)onstant, usually the speed of light not the universal speed limit. and c is always 1c and does not change (speed of light in a vacuum). if in the future we discover that the number c was slightly different to what we have, then c itself would change, so that c would have to become 1c again. nobody really knows if c is the universal speed limit, it's just that theres nothing faster than it so it's presumed it is. long ago, people thought that sound was the speed limit.

[celox]

Let me clarify how I define c in my post: I define c as the speed at which (if it were possible) any mass would become infinite. Is it possible that the speed of light (and not c as I defined it) is slightly lower (relatively) than the c I just defined? I'm first and foremost interested to know if it is possible by current experimental data, and not whether SR or any other theories allows for it (as current theories may not be 100% accurate).

[timo]

There is no measurement being 100% accurate. So if you make the deviation sufficiently small you should be able to fit any experimental data.

[Ophiolite]

long ago, people thought that sound was the speed limit.

I do not believe there was any time when this was true. By the time it was understood that sound had a speed it was already recognised that light, for example, was faster.

[rajama]

Is it possible that the speed of light (in vacuum) is 0.999999999c (or some other number of 9's after zero) rather than 1c? Here I define "c" as the universal "speed limit", and obviously not as the speed of light itself. I know that it would have to be so close to c that we would (at least currently) be unable to measure any difference. But by my understanding, something accelerating very close to c (relative to us) would eventually move fast enought that it would seem to move at c[/i'] from all reference frames, as far as we would be able to measure it.

 

Isn't there always going to be a reference frame for which you (your ship?) is moving past at walking pace - say, for someone who just stepped out the back, for instance...

 

...or when you say 'all reference frames' do you mean the sub-set which - I would assume, I may be wrong - are occupied by most matter in the universe? I may be entirely off here...

[celox]

There is no measurement being 100% accurate. So if you make the deviation sufficiently small you should be able to fit any experimental data.

That's what I thought as well. If anyone disagrees when it comes to the speed of light, I would be interested in hearing about it.

 

I guess, if true, it would/could mean that photons have rest-mass. Let's say that they have for the argument. What would then be the highest rest-mass of photons and the lowest speed of light that current experiments could allow for?

 

Also, if I am correct that it is possible, is it stupid to believe that photons have a tiny amount of rest-mass (as I currently do)? And why is such a belief stupid? I know that physicists say that the photon has no rest-mass, but could that conclusion be premature?

 

I know I'm not "supposed" to put myself in the photons place, but I would like to do so anyway (until anyone provides a good reason why I should not). From the perspective of the photon, if moving at speed c, everything else would be moving at speed infinite. This means that the photon is everywhere at once (and time would not exist?). Now, I don't see how a set amount of energy can be determined for a photon when it's moving at infinite speed (I would think it would have to be zero or infinite). And should not zero rest-mass times anything be zero as well? I know there are other formulas for finding the energy of photons than for something that has rest-mass, but perhaps those exist only because they are mathematically convenient relative to current theories?

 

Another thing: How can infinite speed and "everywhere at once" be divided into chunks, as it must be for light to not travel at infinite speed from our perspective? I mean, infinite divided by a billion would still be infinite... In general I see the "number" infinite as merly a potential, and as something that can probably never occur in reality (other than as a potential).

 

I'm not saying that light can't possible travel at speed c, I'm only saying that it's not logical to me. I'm not saying that reality has to be logical, I'm just saying that I'm more inclined to believe in a logical theory as long as it may possibly be correct -- I find it more...well, logical.

[celox]

Isn't there always going to be a reference frame for which you (your ship?) is moving past at walking pace - say, for someone who just stepped out the back, for instance...

Sure, but that's not the issue here. The post consens itself with light and photons. There are nobody traveling with the photon, it's simply observed in all the ways we (with current technology and techniques) are able to observe it -- those obervations are my reference frames.

 

...or when you say 'all reference frames' do you mean the sub-set which - I would assume, I may be wrong - are occupied by most matter in the universe? I may be entirely off here...

I'm not sure I follow... But anyway, no, that's not what I'm talking about.

[rajama]

Oh yes - sorry, you meant what if light were to travel at a speed in a vacuum infinitesimally close to, but not at c, due to - er - some other property of the vacuum..?

 

I only addressed:

But by my understanding, something accelerating very close to c (relative to us) would eventually move fast enought that it would seem to move at c from all reference frames, as far as we would be able to measure it.

 

Apologies.

[celox]

rajama,

 

No problem, just an indication that I may not have made myself clear enough. Just to clarify further, I'm not talking about a special property of vacuum. I'm talking about the properties of light, and the possibility that they may not be exactly what we think. I here define c as the universal speed limit, and not c as defined by the speed of light (which may or may not be the exact same value).

[BlackHole]

The speed of gravity is also a problem. According to special relativity no useful information can be transmited faster than light but it appears gravity can.

[Johnny5]

Is it possible that the speed of light (in vacuum) is 0.999999999c (or some other number of 9's after zero) rather than 1c? Here I define "c" as the universal "speed limit", and obviously not as the speed of light itself. I know that it would have to be so close to c that we would (at least currently) be unable to measure any difference. But by my understanding, something accelerating very close to c (relative to us) would eventually move fast enought that it would seem to move at c[/i'] from all reference frames, as far as we would be able to measure it.

 

A couple of things.

 

1. There is no such thing as a universal speed limit. You can go as fast as you want, relative to some starting point, within propulsion system limitations.

 

2. c is by definition 299792458 meters per second, i think this was done in the 80's youd have to check. There is no uncertainty whatsoever in the number. Instead, the value of the meter is what is uncertain, as well as the second. You can call the above number "the speed of light" but that is irrelevant.

 

Suppose, for the sake of argument, that a photon moves by you at speed c.

 

And that John is sitting right next to you.

 

How fast will the photon pass by John?

 

Now, Jim is moving away from both you and john, at 10,000 miles per hour, in a spaceship.

 

And that photon is headed Jim's way.

 

How fast will the photon pass Jim?

 

Regards

[[Tycho?]]

The speed of gravity[/url'] is also a problem. According to special relativity no useful information can be transmited faster than light but it appears gravity can.

 

Relativity predicts that gravity moves at c. There have been some experiments done on this, and they agree that gravity seems to move at c.

[celox]

1. There is no such thing as a universal speed limit. You can go as fast as you want, within propulsion system limitations.

I mean speed limit in a relative sense. There is a maximum speed at which something can move relative to us and our measurement of time. When something approach c relative to us, it will require more and more energy to accelerate at the same pace, again relative to us. Eventually it will seem that it's no longer accelerating, because it is so close to c that we are unable to see the difference between c and the moving object. That is how fast I think light might be moving.

 

2. c is by definition 299792458 meters per second, i think this was done in the 80's youd have to check. There is no uncertainty whatsoever in the number. Instead, the value of the meter is what is uncertain, as well as the second. You can call the above number "the speed of light" but that is irrelevant.

Hm, I'm not sure you understand what I'm trying to say. Please read some of my other posts above for some clarification (hopefully) of what I'm trying to say.

 

Suppose' date=' for the sake of argument, that a photon moves by you at speed c.

 

And that John is sitting right next to you.

 

How fast will the photon pass by John?

 

Now, Jim is moving away from both you and john, at 10,000 miles per hour, in a spaceship.

 

And that photon is headed Jim's way.

 

How fast will the photon pass Jim?[/quote']According to Special Relativity the photon would pass by all three of us at speed c. By my argument it may pass by me and John at 0.999999999998c and Jim by 0.999999999999c (I don't know how close it would have to be).

 

I'm not asking these questions because I don't understand SR, I'm asking them because I think that the speed of light might in fact be a bit below c -- by a margin that we are currently unable to measure.

[Johnny5]

According to Special Relativity the photon would pass by all three of us at speed c.

 

 

That is correct. Now does that make sense to you?

[Johnny5]

Let me clarify how I define c in my post: I define c as the speed at which (if it were possible) any mass would become infinite. Is it possible that the speed of light (and not c as I defined it) is slightly lower (relatively) than the c I just defined? I'm first and foremost interested to know if it is possible by current experimental data, and not whether SR or any other theories allows for it (as current theories may[/i'] not be 100% accurate).

 

I understand your question.

 

You are trying to understand things from an SR perspective.

 

Here is the best way to answer you.

 

If SR is correct then it is necessary for the mass of a photon to be zero, hence the photon could travel at c, it wouldnt have to be slightly less. But this answer is predicated on the "if SR is correct".

 

But also note that many conceptual problems are created by the basic assumption of SR, which is that the speed of light is c in all inertial frames.

 

Go back to the John and Jim example, and explain to me (within the context of SR) the resolution.

[celox]

That is correct. Now does that make sense to you?

If the photon travels at speed c, yes. However, I think it makes more sense that the photons travels slightly below c (because of the logical problems I outlined in a previous post).

 

I understand your question.

 

You are trying to understand things from an SR perspective.

No' date=' I'm not. I'm trying to understand things from experimental data, regardless of [i']SR[/i] or any other theories. I wan't to know how possible it is that the speed of light may not be exactly c.

 

Here is the best way to answer you.

 

If SR is correct then it is necessary for the mass of a photon to be zero' date=' hence the photon could travel at c, it wouldnt have to be slightly less. But this answer is predicated on the "if SR is correct".[/quote']Yes, I know. What I'm suggesting is that SR may not be 100% correct -- that we can't be entirely certain that the rest-mass of a photon is in fact zero. Could this be the case (based on experimental evidence alone, and not SR)?

 

But also note that many conceptual problems are created by the basic assumption of SR, which is that the speed of light is c in all inertial frames.

I agree, so I question the validity of SR.

 

Go back to the John and Jim example, and explain to me (within the context of SR[/i']) the resolution.

Which resolution? My speculations are not within the context of SR (only experimental data), and can not be correct if SR is entirely accurate.

[Johnny5]

 

Which resolution? My speculations are not within the context of SR (only experimental data)' date=' and can not be correct if [i']SR[/i] is entirely accurate.

 

Ok then you're fine.

 

 

Maybe I should say more than just that...

 

 

Suppose your speculation is correct.

 

Then i can switch reference frames, and the same photon is moving faster than .99999c.

 

Speed is relative.

[BlackHole]

'']Relativity predicts that gravity moves at c. There have been some experiments done on this, and they agree that gravity seems to move at c.

 

In 2003 they announced that the speed of gravity is c but i think there was experimental bias. The issue is not completely solved yet.

[celox]

Ok then you're fine.

As in there are no current experimental evidence that would invalidate my theory?

 

Suppose your speculation is correct.

 

Then i can switch reference frames' date=' and the same photon is moving faster than .99999c.

 

Speed is relative.[/quote']Yes you can, however the speed would always be sub-c.

[Johnny5]

As in there are no current experimental evidence that would invalidate my theory?

 

Yes you can' date=' however the speed would always be sub-[i']c[/i].

 

No, I don't think you understand. In one frame a specific photon has one speed, in another frame the same photon has a different speed.

 

Speed is relative.

[celox]

In one frame a specific photon has one speed' date=' in another frame the same photon has a different speed.

 

Speed is relative.[/quote']That's right. In one reference frame the photon might move at 0.999999999c, in another it might move at 0.999999995c. The speed could theoretically be zero point any number of figures (from a frame of reference), but never 1c -- because then the mass of the photon would become infinite (remember that in my speculations the photon has rest-mass).

[swansont]

The speed of gravity[/url'] is also a problem. According to special relativity no useful information can be transmited faster than light but it appears gravity can.

 

 

No. Gravity waves travel at c. Van Flandern is misrepresenting or misinterpreting the physics.

 

There are other speed of gravity threads.

 

Speed of gravity faster than light?

How fast is gravity?

 

Kopeikin's experiment isn't the only one. There are binary pulsar orbital decay observations, too.

[swansont]

That's right. In one reference frame the photon might move at 0.999999999c, in another it might move at 0.999999995c. The speed could theoretically be zero point any number of figures (from a frame of reference), but never 1c -- because then the mass of the photon would become infinite (remember that in my speculations the photon has rest-mass).

 

If EM radiation doesn't travel at c, Maxwell's equations don't work: you don't satisfy the wave equaton. I think we can safely say that radio waves are still waves even if the car is in motion.

[BlackHole]

No. Gravity waves travel at c. Van Flandern is misrepresenting or misinterpreting the physics.

 

There are other speed of gravity threads.

 

Speed of gravity faster than light?

How fast is gravity?

 

Kopeikin's experiment isn't the only one. There are binary pulsar orbital decay observations' date=' too.[/quote']

 

I also think gravity must propagate at c in vacuum, otherwise mass-energy conservation would be violated (locally).