Can the Speed of Light Be Changed and What Does It Mean for Space Exploration?

[quantumdude]

and if i measured the length from 1ft away then i measured it from 200ft away. the measurements would be different.

No, it wouldn't. The measurement of length is a function of the relative speed between the observer and the observed. It has nothing to do with the coordinates of the person doing the observation.

edit to add:

the object is getting smaller right?

The object isn't "getting smaller". If a rod is moving, then it is smaller than it is in its own rest frame. But nothing actually happens to the rod. It's not as though the rod is physically shrinking by some compressive force.

 

[bino]

No, it wouldn't. The measurement of length is a function of the relative speed between the observer and the observed. It has nothing to do with the coordinates of the person doing the observation.

edit to add:



The object isn't "getting smaller". If a rod is moving, then it is smaller than it is in its own rest frame. But nothing actually happens to the rod. It's not as though the rod is physically shrinking by some compressive force.

that just proves my point neither the ship or the lattes is physically getting smaller.

 

[employee #416]

Proves my point also.

 

[pervect]

Yeah, I think the reason why emission and absorption is not constant is that light is absorbed through different densities. If it is absorbed in a material that has a low density, it will be absorbed less, but pass it through a dense material, and it will be absorbed fast. Emission of the photons occurs as a result of absorption.

Our eyes would see Terrel rotation, not Lorentz contraction.

http://www.math.ubc.ca/people/faculty/cass/courses/m309-01a/cook/terrell1.html

 

[employee #416]

I wasn't even talking about contraction. Nowhere in there did i mention Lorentz transformation. I was talking about emission and absorption of photons and that's strictly it.

 

[pervect]

Or maybe you're wrong. Just because opinions contradict with the standard model, doesn't make them wrong. You are unable to use the standard model to counter new theories or opinionated ideas.

He's not wrong.

When opinions are in opposition to observed facts, especially well-observed facts that have been confirmed by a multitude of observers, the opinions are wrong.

Has anything moving at relativistic speeds ever been measured? I'm not saying by equations, but by means of physical rulers.

We see muons reach the Earth's surface.

This is proof of both time dilation (from our point of view), and the Lorentz contraction (from the muon point of view). Otherwise, muons simply wouldn't be able to reach the Earth's surface.

 

[pervect]

that just proves my point neither the ship or the lattes is physically getting smaller.

The length of an object is not the same for a moving observer and a stationary one.

The phrase "physically getting smaller" is unfortunately ambiguous. Measurements made of a moving object *will* show that it's length contracts.

 

[quantumdude]

that just proves my point neither the ship or the lattes is physically getting smaller.

It does not. Your statement that the ship "is physically getting smaller" implies that something is happening[/color] to the ship. That is not the case. The fact of the matter is that there is no single "length of the ship". But in your mind, you are at least tacitly denying this, and so you think that when someone measures a length of the ship that differs from the proper length, that something must have been done to the ship to make it so. But that is not right, because there is in fact nothing special about the so-called proper length, other than the fact that it is the length that is measured when the ship happens to be not moving.

 

[quantumdude]

Proves my point also.

By what twisted logic do you reach that conclusion? Recall that your point was that length contraction is an illusion. Nothing I have said supports that view. Indeed, everything I have said specifically denies it.

 

[employee #416]

Silly Tom! Ok, maybe you were not saying what I thought. All-in-all length contraction is an illusion. Refer to the barn example that bino threw out. The bar up close appears to be normal size, but when you inch away from it, it appears to get smaller. It looses measurement off of height and width from the front view. When you are far away from the barn, it looks fairly small. You know that the true length is not that small. Your eyes are playing tricks on you. Do you agree with that? When something is moving at relativistic speeds, your eyes are unable to measure it anywhere near accurate, so it APPEARS TO CONTRACT, when you know that the true length is still in tact.

 

[quantumdude]

All-in-all length contraction is an illusion.

This is the final time I am going to correct you on this. According to SR, the length of any moving object is really less than the length of the same object when it is stationary. Period.

Refer to the barn example that bino threw out. The bar up close appears to be normal size, but when you inch away from it, it appears to get smaller. It looses measurement off of height and width from the front view. When you are far away from the barn, it looks fairly small. You know that the true length is not that small. Your eyes are playing tricks on you. Do you agree with that?

Yes.

When something is moving at relativistic speeds, your eyes are unable to measure it anywhere near accurate, so it APPEARS TO CONTRACT, when you know that the true length is still in tact.

Wrong. First of all, the two situations are not analogous. The apparent shrinking of an object with increasing distance is a bonafide optical effect. Length contraction in SR is not. Second, I have already told you that this has nothing to do with human eyes or human minds. Lifeless mechanical or electronic sensors would register the result predicted by SR. And third, there simply is no "true length" of any object. The length of an object varies with its state of motion.

 

[ArmoSkater87]

employee, by denying length contraction, you are denying time dilation, and therefore you are wrong because time dilation has been physically measured. Precise atomic clocks have been placed in airplanes and observed after a day of flight and apparently the time had been dilated. Not only that...but the amount of time that was dilated fit the model of time dilation exactly. T = T_0 / sqrt(1-v^2/c^2)

 

[employee #416]

Heh, don't babble to me about what I'm denying and what I'm accepting. In the end, you are right though.

Time contraction is also an illusion. Time only seems slower at high velocities, because our eyes can't measure things as fast as it can moving at non-relativistic speeds. This lag in the eye's calculation gives the illusion that time is running slower. This may not be relevant, but I'll take a stab at it. Turn on a strobe light. How does everything look in motion? Slower than it actually is, eh? Our eyes are tricked. We measure things only if visible. If things go in and out of visiblity the eye measure slower than normal. This is an illusion, but we know that time is the same, right?

How can we rely on equations, that are derived from methods our eyes use for measurements? Our eyes do not measure everything accurately. If something is too fast for our eyes to measure, our eye distorts it. If an object is not moving, our eye is not accurate in measuring any dimension of that object. It's all estimated, until a tool for measuring is pulled out for clarity.

An object has a length of 100cm. It is traveling at relativistic speeds. Let's make that speed .95c. It appears to be shorter or is shorter? I'd go with the former. Length does not just disappear into thin air. The true length will ALWAYS be there. The time experienced by that moving object is the same as a person in a difference reference frame. It just seems slower.

Haha, just saw your post Tom Mattson.

This is the final time I am going to correct you on this. According to SR, the length of any moving object is really less than the length of the same object when it is stationary. Period.

No, I'm going to correct you. It only appears to be shorter. The physical length of an object traveling at relativistic speeds is always there.

By true lenght, I'm referring an object measured while on the ground or table.

Second, I have already told you that this has nothing to do with human eyes or human minds. Lifeless mechanical or electronic sensors would register the result predicted by SR.

They are measruing wrong. No length is lost due to motion. That's just stupid. Magically that length returns when an object is decelerated to non-relativistic speeds. No, it was always there. I'm pretty sure this has to do with the human eye. TRIANGLES! The whole formula is derived from the transformation of triangles. I'm pretty sure if you were to mess with it, you could get at the method the human eye uses to measure things.

Why is it an eye trick? Ok, take an object with two points. The point at the head end is point A, while the point at the back end is point B. This object, at rest, has a length of AB. Give this object a velocity that is non-relativistic, and your eyes notice no drastic affects in measuring the length. Give it relativistic speeds, and your eyes notice a huge difference. When it tries to calculate the distance from A to B it is smaller than what the distance is at rest. When point A crosses the eye, almost immidiately point B crosses the same path A has just crossed. Thus making measurment SEEM contracted. No length contraction is taking place.

This is probably all jumbled up...I have school in 2 hours and I haven't slept, so whatever.

 

[ArmoSkater87]

Time contraction is also an illusion. Time only seems slower at high velocities, because our eyes can't measure things as fast as it can moving at non-relativistic speeds. This lag in the eye's calculation gives the illusion that time is running slower. This may not be relevant, but I'll take a stab at it. Turn on a strobe light. How does everything look in motion? Slower than it actually is, eh? Our eyes are tricked. We measure things only if visible. If things go in and out of visiblity the eye measure slower than normal. This is an illusion, but we know that time is the same, right?

You are not understanding what I am talking about. I mean AFTER the airplanes fly for a day, the clock that was on it is compared to the one that was on the ground. So you are saying when we look at these two clocks next to each other, the difference somehow is an illusion?? Not to mention that the difference magically with illusions fits the model.

How can we rely on equations, that are derived from methods our eyes use for measurements? Our eyes do not measure everything accurately. If something is too fast for our eyes to measure, our eye distorts it. If an object is not moving, our eye is not accurate in measuring any dimension of that object. It's all estimated, until a tool for measuring is pulled out for clarity.

An object has a length of 100cm. It is traveling at relativistic speeds. Let's make that speed .95c. It appears to be shorter or is shorter? I'd go with the former. Length does not just disappear into thin air. The true length will ALWAYS be there. The time experienced by that moving object is the same as a person in a difference reference frame. It just seems slower.

Once again, like Tom said...this has nothing to do with your eyes, we arent the ones observing the length contraction, its the electronic sensors. I guess the sensors are tricked by their sillicon chips right?? We only observe the data from the sensors, or are the computer screens also an illusion that makes us think that there is contraction going on?? Wait, what if you print the data out, I am sure the paper deflects the light in such a way that the numbers printed on the paper change before they enter our eyes. Ahh...those damn illusions, don't you just hate them??

No, I'm going to correct you. It only appears to be shorter. The physical length of an object traveling at relativistic speeds is always there.

By true lenght, I'm referring an object measured while on the ground or table.

Humm...you keep saying this without any actualy evidence or data. Its funny to see you say something that is consistent with all observations is wrong and an illusion, and yet you have nothing to actually support your arguement. And please don't quote again with something that has to do with our eyes and illusions.

They are measruing wrong. No length is lost due to motion. That's just stupid. Magically that length returns when an object is decelerated to non-relativistic speeds. No, it was always there. I'm pretty sure this has to do with the human eye. TRIANGLES! The whole formula is derived from the transformation of triangles. I'm pretty sure if you were to mess with it, you could get at the method the human eye uses to measure things.

Why is it an eye trick? Ok, take an object with two points. The point at the head end is point A, while the point at the back end is point B. This object, at rest, has a length of AB. Give this object a velocity that is non-relativistic, and your eyes notice no drastic affects in measuring the length. Give it relativistic speeds, and your eyes notice a huge difference. When it tries to calculate the distance from A to B it is smaller than what the distance is at rest. When point A crosses the eye, almost immidiately point B crosses the same path A has just crossed. Thus making measurment SEEM contracted. No length contraction is taking place.

This doesn't help your case at all and doesn't counter any part of what Tom said in the quote you quoted. Your argument again has to do with the way the eye sees things, which is not the case. We don't know length contraction is true because we observe with our EYES something moving at relativistic speeds. I mean...WTF? We can't even make out details on a car moving by on a highway...and that's like 60mph, oh soooo relativistic isn't it?!?

Anyways...you can't use "illusions with eyes" as a way to defend your case because your eyes only play a role in reading data on a computer or a piece of paper.

Btw...Tom, take it easy, I know the rage you are feeling from such arguements, I feel the same way.

 

[russ_watters]

Minor nitpick - these two statements contradict each other:

If something is measured to be shorter, then it is shorter. Measurements are what tell us what is real.

...there is no "real" length of objects.

I know what you mean, but I think it may be less confusing to others if the second statement read 'every measured length of objects is "real."' You mean there is no single real length and a bunch of illusions.

 

[russ_watters]

Time contraction is also an illusion. Time only seems slower at high velocities, because our eyes can't measure things as fast as it can moving at non-relativistic speeds. This lag in the eye's calculation gives the illusion that time is running slower.

How do our eyes effect the tick rate of clocks on GPS satellites?

They are measruing wrong.

Explain this: are you saying that every scientist who accepts the validity of Relativity is wrong? Are you saying every scientist who uses it is wrong?

GPS satellites have their clock tick rates calibrated according to Relativity prior to launch. This allows the clocks to stay in sync with clocks on the ground. How is this possible if the scientists are screwing up? Dumb luck?

As others have noted, you can program a computer to do all of this for you and give you the answer: how can human eyes affect the operation of computers?

employee #416, do you realize the implications of what you are saying? Its absurd. This whole issue boils down to you refusing to accept reality at face value because you don't like how reality is.

 

[bino]

i understand what each of you is saying. both sides make very good points. some sides better points than others. you have to keep in mind that the length contracts only from the point of view of the stationary object. that's where the disagreement comes from. the ship looks shorter because it is shorter from the point of view of the lattes. the measurements from the equipment are correct from their point a view. the measurement are taken from a point in time. at that point in time the ship will measure to be shorter than its real length. but from the point of view of the ship it length has not changed so the equipment on the ship will say that same thing that it is in fact the same length as when it was stopped. it all matters on the point of view.

 

[Nenad]

hence the name 'relativity'

 

[quantumdude]

Heh, don't babble to me about what I'm denying and what I'm accepting. In the end, you are right though.

The only one here babbling is you.

Time contraction is also an illusion. Time only seems slower at high velocities, because our eyes can't measure things as fast as it can moving at non-relativistic speeds. This lag in the eye's calculation gives the illusion that time is running slower. This may not be relevant, but I'll take a stab at it. Turn on a strobe light. How does everything look in motion? Slower than it actually is, eh? Our eyes are tricked. We measure things only if visible. If things go in and out of visiblity the eye measure slower than normal. This is an illusion, but we know that time is the same, right?

I repeat: Our eyes have nothing to do with it. When time dilation is measured in muon decay, the time of creation is recorded, and the time of decay is recorded. The particle lives longer in the lab frame than it does in its rest frame. And no, the decay is not too fast for the equipment.

Particle phyisicists use time dilation every day to prolong the lifetime of unstable particles so that they can study them. But once again, here you are, the arrogant, ignorant internet bozo, thinking that you know better than the people who work with it every day, when you have never even studied it once.

How can we rely on equations, that are derived from methods our eyes use for measurements? Our eyes do not measure everything accurately. If something is too fast for our eyes to measure, our eye distorts it. If an object is not moving, our eye is not accurate in measuring any dimension of that object. It's all estimated, until a tool for measuring is pulled out for clarity.

Our eyes don't take the measurements in modern physics. Why are you ignoring me?

An object has a length of 100cm.

Correction: An object has a length of 100cm in its rest frame.

It is traveling at relativistic speeds. Let's make that speed .95c. It appears to be shorter or is shorter?

It is shorter in the frame of the person watching the object fly by. It is still 100 cm in its rest frame.

I'd go with the former.

No one cares what you would go with. All experimental confirmations of SR contradict you.

That's why you are a crackpot.

Length does not just disappear into thin air.

The universe is not oblgated to behave according to your preconceived notions.

The true length will ALWAYS be there.

Correction: There is no "true length" of any object.

The time experienced by that moving object is the same as a person in a difference reference frame. It just seems slower.

No, it is slower.

No, I'm going to correct you.

Again, your arrogance is absolutely staggering. What on Earth makes you think you know anything about this? You have very clearly not studied it.

It only appears to be shorter. The physical length of an object traveling at relativistic speeds is always there.

Wrong. There is no preferred frame of reference, and so there is no true "physical length" of an object. You are just clinging to a faulty view of space and time that was used by Newton and is now known to be false.

By true lenght, I'm referring an object measured while on the ground or table.

That is called the proper length, but there is nothing special about it. The idea of the length of an object has no meaning apart from specifying its state of motion.

They are measruing wrong. No length is lost due to motion. That's just stupid.

Oh, well now I'm convinced.

I'll just scrap all of those experimental tests of relativity because, "that's just stupid".

Learn to formualte an argument, kid.

Magically that length returns when an object is decelerated to non-relativistic speeds. No, it was always there.

Wrong. The length contraction formula applies at all speeds, not just relativistic speeds.

I'm pretty sure this has to do with the human eye.

I've already told you this is wrong, so the question is, why the hell are you persisting in it?

TRIANGLES! The whole formula is derived from the transformation of triangles.

You are hopeless.

First, you ask me for a link that contains the derivation of these phenomena, and I gave it to you. You have obviously not even looked at it, because it very clearly shows how the Lorentz transformation is derived from the postulates of relativity and Maxwell's electrodynamics.

"TRIANGLES!" Pfffft. Get a clue.

I'm pretty sure if you were to mess with it, you could get at the method the human eye uses to measure things.

I'm absolutely sure that you have no idea of what you're talking about.

Why is it an eye trick?

It isn't an eye trick.

Ok, take an object with two points. The point at the head end is point A, while the point at the back end is point B. This object, at rest, has a length of AB. Give this object a velocity that is non-relativistic, and your eyes notice no drastic affects in measuring the length. Give it relativistic speeds, and your eyes notice a huge difference. When it tries to calculate the distance from A to B it is smaller than what the distance is at rest. When point A crosses the eye, almost immidiately point B crosses the same path A has just crossed. Thus making measurment SEEM contracted. No length contraction is taking place.

Wrong. Look at the Lorentz transformation, and you'll see no reference is made to human eyes, human minds, or the means of measurement.

You keep posting this same garbage, and I keep telling you that it is not reflective of relativity at all. Why do you do that? It is just not rational. You say that you want to be a member of this Forum, and you know that we do not allow unsubstantiated nonsense here. So why is that all you ever post? It makes no sense.

 

[quantumdude]

Minor nitpick - these two statements contradict each other: I know what you mean, but I think it may be less confusing to others if the second statement read 'every measured length of objects is "real."' You mean there is no single real length and a bunch of illusions.

OK, I'll explain.

If something is measured to be shorter, then it is shorter. Measurements are what tell us what is real.

And this is what is "real": The length of an object is depends on its state of motion relative to an observer. It is not a determinate quantity until its state of motion relative to an observer is specified.

...there is no "real" length of objects.

Meaning that since the length of an object is determined by its state of motion relative to an observer, and since there is no preferred reference frame, it cannot be said that the length measured in any reference frame is any more "real" than that measured in any other frame. All reference frames have an equally valid experimental point of view.

 

[Nereid]

Note: some people *think* they may have found a change in the fine structure constant. This hasn't been widely accepted, and the magnitude of the supposed change is very small - on the order of .001 percent. Not enough to fuel any visions of "galactic superhighways" even if it is true (and it's probably just a very small measurment error of some sort).

AFAIK, there are two types of observation which have been done, to see if alpha is varying over cosmological time (roughly, billions of years) - Oklo and astronomical. The former refers to a natural reactor, in uranium ore in Africa; from an analysis of the decay products, alpha has been shown to be constant to 1 part in 10 million, over a billion years or three. The astronomical observations are of several kinds; the most accurate - in several senses - show that alpha has not changed by more than 1 part in ~100,000, over ~10 billions years. There were some earlier studies, with lower accuracy, which could be interpreted as evidence for a small time variation; these observations used a technique that requires a rather long chain of calculations and many inputs (so the results were always in some doubt).

employee #416, I see that you have a different opinion from many other posters here; can you point to experimental evidence that supports your opinion? In particular, how are the muon decay experiments, and the actual functioning of the GPS system consistent with your opinion? No hand-waving please, just the numbers and the math.

 

[Alkatran]

Oh fun fun, crackpot smashin time

Heh, don't babble to me about what I'm denying and what I'm accepting. In the end, you are right though.

Time contraction is also an illusion. Time only seems slower at high velocities, because our eyes can't measure things as fast as it can moving at non-relativistic speeds. This lag in the eye's calculation gives the illusion that time is running slower. This may not be relevant, but I'll take a stab at it. Turn on a strobe light. How does everything look in motion? Slower than it actually is, eh? Our eyes are tricked. We measure things only if visible. If things go in and out of visiblity the eye measure slower than normal. This is an illusion, but we know that time is the same, right?

Maybe things appear to go slower lalalla bu it doesn't matter: The effect is getting larger. The objects continue to move slower/faster through time and the gap between them increases. Think of two clocks, one is stationary and one is moving at near lightspeed. Let's say when they're a lightyear apart, they're synchronized (in the rest frame with Clock 1, of course). By the time Clock 2 meets Clock 1, Clock 2 well have a few extra days, maybe a few extra years, depending on the speed, on it. Is that still an optical illusion? I've never seen an illusion that could rotate a clock hand 360 degrees.

How can we rely on equations, that are derived from methods our eyes use for measurements? Our eyes do not measure everything accurately. If something is too fast for our eyes to measure, our eye distorts it. If an object is not moving, our eye is not accurate in measuring any dimension of that object. It's all estimated, until a tool for measuring is pulled out for clarity.

I can guarantee you they don't use human eyes to measure particles inside a particle accelerator. There's a big slab of matter (metal?) in the way.

An object has a length of 100cm. It is traveling at relativistic speeds. Let's make that speed .95c. It appears to be shorter or is shorter? I'd go with the former. Length does not just disappear into thin air. The true length will ALWAYS be there. The time experienced by that moving object is the same as a person in a difference reference frame. It just seems slower.

Haha, just saw your post Tom Mattson.

No, I'm going to correct you. It only appears to be shorter. The physical length of an object traveling at relativistic speeds is always there.

By true lenght, I'm referring an object measured while on the ground or table.

In a way this is true, an object can never be longer than its proper length.

They are measruing wrong. No length is lost due to motion. That's just stupid. Magically that length returns when an object is decelerated to non-relativistic speeds. No, it was always there. I'm pretty sure this has to do with the human eye. TRIANGLES! The whole formula is derived from the transformation of triangles. I'm pretty sure if you were to mess with it, you could get at the method the human eye uses to measure things.

I like the "TRIANGLES!" remark, which clears up the whole thing for me.
Just so you know, the length is always "there", the problem is that you're looking at the object skewed through time. I'll include a link for a nice explanation of this at the bottom of this post.

Why is it an eye trick? Ok, take an object with two points. The point at the head end is point A, while the point at the back end is point B. This object, at rest, has a length of AB. Give this object a velocity that is non-relativistic, and your eyes notice no drastic affects in measuring the length. Give it relativistic speeds, and your eyes notice a huge difference. When it tries to calculate the distance from A to B it is smaller than what the distance is at rest. When point A crosses the eye, almost immidiately point B crosses the same path A has just crossed. Thus making measurment SEEM contracted. No length contraction is taking place.

But this effect would be reversed if you measured B followed by A, making the object appear longer.

This is probably all jumbled up...I have school in 2 hours and I haven't slept, so whatever.

Don't worry about the lack of sleep, it would be jumbled anyways.

http://casa.colorado.edu/~ajsh/sr/paradox.html

 

[bino]

lets say there is a star 44000 lightyears away. how long will it take to get there going light speed?

 

[Doc Al]

lets say there is a star 44000 lightyears away. how long will it take to get there going light speed?

Assuming that you mean that according to Earth-frame measurements the star is 44000 lightyears away, and that you are sailing by in a rocket at close to c (say 0.99c with respect to the Earth): the distance as seen by you in your rocket frame will be contracted--and it will take you about 6270 years to get there according to your rocket-frame clock.

 

[bino]

how long from Earth's point of view?

 

[Alkatran]

how long form Earth's point of view?

44 000 years, of course. (well, approximately, the Earth is rotating around the sun which is rotating around the galaxy...)

 

[Nenad]

Assuming that you are going at o.99c. In Earth's point of view, they will see your trip takes:
t_o = t\sqrt{1 - v^{2} /c^{2}}
6270y = t\sqrt{1 - 0.99c^{2} /c^{2}}
\frac {6270y}{0.141} = t
t = 44468 years

 

[bino]

does light have mass?

 

[Nenad]

light has no rest mass. It has relativistic mass, and momentum.

 

[bino]

where did you get 0.141?