Speed of light is limited by what?

[Bobby]

First of all, why can't physicists speak simple english? Secondly, while I agree that the two observers will measure time differently, you have not described a physical property of light or space that causes this to happen. Thus, you have not addressed the issue at hand. Thirdly, look up postulate or axiom in the dictionary and you'll find that they refer to an ASSUMPTION. And you know what you get when you ***-U-ME.

 

First of all, why can't physicists speak simple english?

 

Physicists can talk in everyday language if they want to, and if the discussion is about everyday events, they do so. The Universe, however, is somewhat more complicated than everyday events. Also, much of the physical Universe can best be described in mathematical terms.

 

 

Secondly, while I agree that the two observers will measure time differently, you have not described a physical property of light or space that causes this to happen.

 

 

Sound energy always travels at the same speed in the same medium. Depending on the direction of the sound, the sound waves become higher or lower pitched, but the speed doesn't vary. Light in a vacuum acts almost exactly the same way. Depending on the direction of the light source the length of the light wave will be stretched or shortened, but the light will still have the same speed.

 

T1 = T2 ( 1 + gh/C^2) is an equation from General Relativity. This equation says that time runs slow in a gravitational field. It appears to me that space and time are so closely related to gravity that space and time may very well turn out to be the way we measure changes in gravitational fields. If this is true, then your questions about the physical properties of the Universe which limits the speed of light would be the nature of gravity.

[Bobby]

Time is not defined by clocks, though. Observer A's clock would be “discalibrated” by the addition of perpendicular (y) distance to the oscillating path (x) of the particle. The particle's path changes from lateral oscillation to a zigzag, therefore the actual distance from reflector to reflector changes when the clock starts moving, hence a slower oscillation.

 

 

You are correct. Time is not defined by clocks, but is measured by clocks. I believe it may have been Einstein that said "Time is that thing measured by clcoks and distance is that thing measured by rulers."

 

Observer A can correctly say "this is what I measure from my frame of reference". Observer A cannot correctly say "this is what observer B will measure."

[wazzuuup]

This is just a thought. Light is the fastest speed we know of, traveling at roughly 300,000 km/s. According to SR, anything that travels faster would in fact be traveling backwards in time. So if there would indeed be jinn particles (faster-than-light particles), we wouldn't be able to see them since we are traveling forwards in time, and not backwards, with them.

[EWright]

This is just a thought. Light is the fastest speed we know of, traveling at roughly 300,000 km/s. According to SR, anything that travels faster would in fact be traveling backwards in time. So if there would indeed be jinn particles (faster-than-light particles), we wouldn't be able to see them since we are traveling forwards in time, and not backwards, with them.

 

I've heard mention of traveling backward in time if you exceed the speed of light, but assumed it was science fiction and not actually predicted by SR. Can anyone else confirm that this is an actual prediction of the theory and if so expand on why please.

 

Let us direct the discussion now to the following website's diagrams and description of relative motion and time: http://www.geocities.com/ResearchTriangle/System/8956/Bondi/intro.htm

 

I take issue with some of the math/ideas presented here, which stem from SR. But before I point them out, can you all say that you agree with the circumstances presented on the page?

[Southtown]

You are correct. Time is not defined by clocks, but is measured by clocks. I believe it may have been Einstein that said "Time is that thing measured by clcoks and distance is that thing measured by rulers."

 

Observer A can correctly say "this is what I measure from my frame of reference". Observer A cannot correctly say "this is what observer B will measure."

Only because he has a faulty clock design. What if they both used analog wrist watches?

[Bobby]

This is just a thought. Light is the fastest speed we know of, traveling at roughly 300,000 km/s. According to SR, anything that travels faster would in fact be traveling backwards in time. So if there would indeed be jinn particles (faster-than-light particles), we wouldn't be able to see them since we are traveling forwards in time, and not backwards, with them.

 

 

The part of the relativity equations referenced above contain the mathematical phrase 1 / SQRT ( 1 - V^2/C^2). As V approaches C, the equation approaches 1 / 0. Many people take this to mean that 1 / 0 is infinity, but it is not. What the equation says is "As Velocity approaches the Speed of Light, the relativistic effects become greater and greater.

 

If you stayed awake in high school algebra, you might remember complex numbers. A complex number is any number containing the imaginary number i where i means the square root of -1. In the equation 1 / SQRT (1 - V^2/C^2), if V becomes greater than C the only thing that happens is you now have a complex number, and complex numbers DO NOT, I repeat, DO NOT mean you would be traveling back in time.

[Bobby]

I've heard mention of traveling backward in time if you exceed the speed of light, but assumed it was science fiction and not actually predicted by SR. Can anyone else confirm that this is an actual prediction of the theory and if so expand on why please.

 

Let us direct the discussion now to the following website's diagrams and description of relative motion and time: http://www.geocities.com/ResearchTriangle/System/8956/Bondi/intro.htm

 

I take issue with some of the math/ideas presented here, which stem from SR. But before I point them out, can you all say that you agree with the circumstances presented on the page?

 

 

It isn't even good science fiction. I doubt that time travel is possible, but if it is, it is not because of the SR equations. At V greater than C, the SR equations simply become complex numbes.

 

I could not access the web site you gave. What does it say?

[Bobby]

Only because he has a faulty clock design. What if they both used analog wrist watches?

 

 

An observer can only say what he sees. He cannot say what another observer sees.

[Southtown]

An observer can only say what he sees. He cannot say what another observer sees.

Right. HAHA But wasn't CraigD trying to illustrate that time passed differently for two observers with clocks that distort with motion? Am I just missing the point entirely? LOL

[EWright]

Sorry Bobby, I apparently can not access the site via the link either, and now I am at home instead of at work where I was posting from throughout the day. I'll have to get back to that tomorrow at work as I have much more valuable things to do with my time when I am at home (This is why you get more posts from me on the weekends) :eek:

 

I do believe you are mistaken in your description of imaginary numbers. SQRT of -1 = i, but v/0 = 0. Generally equations that result in dividing by zero are ruled out by scientific folk. But apparently if Einstein says its OK in this one case, it must be OK. And it does, it seems to me, mean that the photon travels an infinite distance while experiencing zero time. LOL, what a crock. Again, this is because Einstein CHOSE to zero things out at c for simplicity's sake, it is NOT REALITY.

[Southtown]

Sorry I meant to post a fix for that a while ago.

 

http://www.geocities.com/ResearchTriangle/System/8956/Bondi/intro.htm

[CraigD]

First, EWright, let me say I take no offense at your criticism of my reasoning, and find your positions interesting and insight-provoking, and your manner spirited yet polite. I hope that, thought exchanging ideas, we and the others on scienceforums can reach new insights and understandings.

...I do agree with you that both observers will measure time differently. I was not making any argument contrary to this. My position is that there are no physical properties of light that actually cause this to happen.

The critical point that I’m trying to make is that there is a property, unique to light (to be precise, unique to all fundamental, boson interaction forces, of which electromagnetic radiation is one), that causes this effect to happen. That quality is the one demonstrated by the Michelson-Morley experiment – its speed is independent of the motion of its source, or the motion of the device measuring its speed.

 

This quality is truly unique. Particles such as cannon balls and electrons – even ones moving close to the speed of light - don’t have it. Waves such as ocean waves and sound waves don’t either. Prior to the MM experiment, there was no reason to expect that light would have such a counterintuitive quality. Whether a particle or a wave (prior to around 1924, it was thought that light must be one or the other, but not both) – there was no reason to believe that light was different than either cannon balls or ocean waves, other than being much faster. It was entirely reasonable to believe that, given a sufficiently pure vacuum and a sufficiently powerful projectile-thrower, one could throw a projectile much faster than the speed of light.

 

If light did not have this property, moving clock would not run slower than stationary ones. In the example I gave, observer B would just observe that the zig-zaging light moved faster. This is just what he observes if the reflecting clock in the example uses an “ordinary” particle, such as a perfectly elastic, friction-free ball (an ordinary, high-temper glass ball comes reasonably close to being one).

For example, time will still be measured differently by two 'observers' if the experiment is conducted deep underground with no light available. (let's say they wear watches and compare later, since there's no light to 'observe' by at the time). Hence, again, it is not a property of light that is responsible for this phenomena. The same thing would happen if there was no light in the universe, and thus we did not have light speed to account for the phenomena.

Practically speaking, it’s hard to imagine any sort of observer without photons. Photons don’t just carry visible light – they carry the magnetic force that keeps the electrons in atoms from flying off into space. However, if the universe had no bosons of any kind, I believe effects like time dilation would still occur, because if a boson existed, it would have the motion-invariant speed quality.

As for agreeing with the posulates of SR, postulates are assumptions by deffinition. You stated that *IF* you accept this postulate, then the argument holds true. I do not disagree with this statement. But I have trouble agreeing with a posulate that grants light universal authority, when it is not a universal quantitiy. …

The postulate of SR – the equivalency principle – is supported by experimental evidence. Postulates strongly supported by evidence have an elevated status – one might even hazard to call them facts.

 

I sense that your discomfort with the speed of light arises because, unlike values such as Pi, e, and the golden ratio, which arise from fundamental arithmetic and geometry, it’s an arbitrary value. Though the nature of physical matter and its dynamics would be very different if the speed of light were one tenth or ten times its observed value, there still would be physical mater, space, and time, and, except for the constants, the laws of Physics would be unchanged. Many respectable theories even propose that the speed of light in a gravity-free vacuum has and is changing.

 

The only thing I can think to say to this discomfort is that the actual value of c doesn’t, ultimately, mater. What’s important is that there’s only one such value. If there were 2 or more families of bosons, each with its own motion-invariant speed, Modern Physics would need to be fundamentally rewritten in ways I can barely imagine.

 

A suggestion, based on my own experience in striving to contribute to Science: before rejecting major parts of mainstream Physics, strive to attain unimpeachable expertise in it. In so doing, you may encounter great surprises, and ultimate come to accept much that you once were moved to reject. If not, the acquired expertise will enable you to state your theories in a powerful, compelling manner.

[Boerseun]

Great post, Craig.

 

Interesting thought:

 

Imagine that we stumbled across the value for Pi without having the faintest idea what its related to. We'd think it weird to have such an arbitrary number, until some time in the future someone says: "Hey, check it out - Pi fits nicely here with them circle thingys... what a coincidence!"

 

In that unlikely example, the result was discovered first. Okay - I know, stupid example - but say, for instance, the speed of light is related to something in relation to something else? Until we figure that out, the value for c will look arbitrary. I wonder...

[CraigD]

Only because he has a faulty clock design. What if they both used analog wrist watches?

I think your speculation, taken a slight step further, raises an interesting question of Particle Physics. I’ve responded to it, and voiced this question in a new thread, ”An experiment to confirm that gravity is a bosonic force”.

[tedoniman]

OK, let's get to the heart of the matter here. The speed of light is limited by what physical property of the physics of the universe???

 

Greetings,

 

Am new to this Forum business. Just signed on. This topic interests me - though for sure I'm not a highbrow. Was originally after some info on the on-line book "The Final Theory". Already looked at some of that thread.

 

As regards the "speed-of-light" item, I've had the same question on my simple mind for some years now - but leaning more towards an answer that might at least in part have been dependent on the properties that existed (were created) in the first few microseconds of creation - as pertaining to the 'big bang' theory.

 

In that sense, my reasoning here was analoguous to that pertaining to the creation of a complex organism, a human, for instance, from a single, miniscule cell wherein the even smaller genes determine the properties of the final whole. I keep thinking that the properties of everything which we can detect as existing, now, must have already been determined in toto, by factors existing at the very beginning - including anomalies due to probabilities - assuming that our present universe, or any other type, could have been created in the first place under any other than the precise, original conditions. If so, then that right there implies to me that 'C' could conceivably have been something altogether different.

 

It seems logical, also that, had the singularity (or whatever one might call it) been larger (or smaller), than what caused the 'big bang' and it's resultant properties, then the resultant Velocity constant for EMR, might have, again, been quite different. That's all assuming of course that the 'big bang' (if it ever occurred) could have occurred under any kind of other conditions (different original mass, etc.).

 

Or am I completely out in left field here?

 

Ted / tedoniman

[wazzuuup]

Great post, Craig.

 

Interesting thought:

 

Imagine that we stumbled across the value for Pi without having the faintest idea what its related to. We'd think it weird to have such an arbitrary number, until some time in the future someone says: "Hey, check it out - Pi fits nicely here with them circle thingys... what a coincidence!"

 

In that unlikely example, the result was discovered first. Okay - I know, stupid example - but say, for instance, the speed of light is related to something in relation to something else? Until we figure that out, the value for c will look arbitrary. I wonder...

 

In fact, the value for c has already been applied to many useful relationships. For instance, before Einstein, physicists always measured time in a sacred unit, called the second, different from the unit to measure space. No one suspected the powerful results of using the same unit for both, or of squaring or combining space and time separations when both were measured in meters. Time in meters is just the time it takes a light flash to go that number of meters. And thus the conversion factor between seconds and meters is the speed of light! Such has lead to the Einstein-Poincare discovery in 1905; showing that now two individuals can disagree on separations in space and time; but agree on thet spacetime interval.

 

Furthermore, there is no law of physics (so far I know) that forbids superluminal travel, so the speed of light is perhaps not the limiting speed.The only complication is that nothing can cross the light barrier; thus classifying all objects into three main groups according to their speed limits. The first class is slow moving things of the everyday world around us (you, me, stars, etc). All scientists agree that this class exists.

The second class is one where subatomic particles move only at the speed of light. These particles, like photons or neutrinos, have never been detected to have slowed down or speeded up. The speed of light is a constant due to the fact that time, distance, and mass are not the same for all observers.

The third class is tha tof superluminal objects. called tachyons, that move faster than light. They are accomodated by RT and would never be able to travel slower than the speed of light. Currently, there is no evidence for their existence. But think about it. If a tachyon were appraoching you from a distance galaxy, it would actually look to you like it was with you and then moving away from you. This is because the light, which allows you to see the object, can only move at one speed. Thus the photons showing the object closest to you would have arrived at your eyes first, showing the gradual journey of the tachyon moving away from you. Thus it would, according to the observer, travel backwards in time.

 

My point is that because of the universal property of light to always travel at a constant speed, and all our 'human and invented' notions such as time, distance and mass are directly affected, it is only natural to want to know why the lightspeed has such a massive impact. But if everything could just go faster or slower than the speed of light, our universe probably wouldn't be able to operate. If one object could first travel forwards in time, and then backwards, there would be no arrow of time anymore.

[Bobby]

Great post, Craig.

 

Interesting thought:

 

Imagine that we stumbled across the value for Pi without having the faintest idea what its related to. We'd think it weird to have such an arbitrary number, until some time in the future someone says: "Hey, check it out - Pi fits nicely here with them circle thingys... what a coincidence!"

 

In that unlikely example, the result was discovered first. Okay - I know, stupid example - but say, for instance, the speed of light is related to something in relation to something else? Until we figure that out, the value for c will look arbitrary. I wonder...

 

 

From GR, T1 = T2 (1 + gh/C^2) says that the rate of time depends on the force of gravity.

Does this not say that the speed of light is also determined by the force of gravity?