Didymus

That's a pretty long list of citation with no explanation. I'm not going to look them up one by one. Find one experiment which conclusively shows the uniformity of the speed of light. Not a list of textbooks that make the claim by quoting people who subscribe to the theory...I don't care about popular opinion. Do you know of a single experiment that you can summarize? If it has such a long history, you must know one or two that can be functionally explained... Not just a couple names listed saying "we proved this, trust us." That's a pretty long list of citation with no explanation. I'm not going to look them up one by one. Find one experiment which conclusively shows the uniformity of the speed of light. Not a list of textbooks that make the claim by quoting people who subscribe to the theory...I don't care about popular opinion. Do you know of a single experiment that you can summarize? If it has such a long history, you must know one or two that can be functionally explained... Not just a couple names listed saying "we proved this, trust us."

Of course not. Like the tones in sound, color is perceived by a change in frequency. Frequency being a function of wavelength vs. The speed at which these waves pass by (or that you pass by these waves). If you're on a train and pass anything making a constant sound, it will seem to switch to a lower pitch when you pass it because, when approaching it, your speed relative to that wave is higher and thus the frequency is higher.... The wave doesn't care that you're there. When you pass, the wavelength stays the same, but the tone will go down relative to your speed away from the source of that sound. (i use a moving reference frame instead of a moving source to account for a stationary medium). Basic elementary school physics. But when we see celestial objects traveling away from us, their light spectrum will be shifted toward a lower frequency. Objects moving toward us will have their entire spectrum shifted toward a higher frequency. ... The simple solution would be that this light is doing it's thing, not caring who is observing it. It's wavelength is what it is... And we see the frequency change because we're moving relative to it and thus it is approaching us at a speed other than C, depending on our speed relative to it's source. SR Dictates that light moves at a constant speed in all frames of reference and thus the speed of the wave can not be altered. This is why the wavelength must be changed, which is the whole point of the theory of spacial dilation. The down side is that if the speed of light is constant and already at this maximum speed... Time is already stopped and space is already infinitely compressed from it's frame of reference.... Then why would our motion relative to it cause it to experience "more compressed space?" It doesn't hold water. Swanson... You ask for evidence... The Doppler effect is more than sufficient. SR is the one with the burden of proof to overthrow logic.... Without basing this proof on an experiment where this light is absorbed and re-emitted from a new source.

Oh, what a stirring counterpoint. My entire viewpoint on life has now changed now that some anonymous poster claims that some anonymous experiment proved it one time. .... Mind sharing any details? I'm not talking aether wind....

It stands to reason that the function of light being produced expels it at a certain speed, thus light would move at a constant speed relative to it's source. I've yet to see convincing evidence that shows a single object capable of simultaneously moving through different levels of compressed space depending on how different observers may be moving... I.e. the Doppler effect's change in frequency being explained as a change in wavelength as opposed to speed relative to that wave. A given photon will have a different redshift based on your speed relative to it's source... Pretty obvious that this light is moving slower relative to us than blueshifted light.

No point beating that horse anymore. Your faith is quite strong, so, next problem: time dilation supposedly happens due to relative speed, agreed? And neither frame of reference is preferred over the other. Do you agree with both points? I.e. you don't assert that time dilation is some inertial aspect of the acceleration process?

If we agree on units of length from the frame of reference of the earth. Total distance traveled (the circumference of the earth)/(7 LY) at a speed relative to that frame of reference of (the speed of the plane)/(.99c). This trip was accomplished in (51 nanoseconds less than "ground time")/(6 years less than "ground time"). If the H&K trip actually covered the same journey in 51 nanoseconds less than would be measured from an outside observer... it doesn't matter that this is because "space seems to have shrank" ... it legitimately made the trip in less time. For this to be true, the corresponding example would hold equally true. If the idea that the space craft only perceived 1 year should be discounted... then so should the idea that the plane experienced 51 fewer nanoseconds. If the spaceship didn't "really" travel 7 lightyears in 1 year because the earth's frame of time is preferred... then neither did the H&K experiment. If it is legitimate to mix the spacial frame at rest and the temporal frame in motion... it must be in all cases. That's the whole "repeatable and falsifiable" part. The math is self-defeating because it imposes limitations, then breaks it's own limitations unless we change the definition of everything in physics to accommodate this one theory. If I say that I am the tallest man in the world, and provide a formula which proves that anything which SEEMS taller than me is actually just an inch shorter, but existing in expanded space correlating to the amount that they appear taller. Every time someone points out an inconsistency I could easily claim that this simply appears to be inconsistent because of the expansion of space around objects that appear taller than me... and that I can not be directly compared to people because of false simultaneity. I can then test this formula by finding a person or object that appears taller than me, adjusting it per this formula and proving conclusively that the results are exactly as the formula predicts! Think this will catch on? Of course not. But, this is simply time dilation with a few details swapped out.

Cool. Now apply rule #1 to Hafele-Keating. The entire experiment that "proves" SR is entirely based on the premise you're now saying is faulty. The planes went from a frame stationary to the ground clock, to an inertial frame (back and forth quite a few times for each leg of their journey)... and then when they stopped, they'd actually traveled the entire distance and actually experienced less time. If you are to put your faith into this experiment, it would then extend that a person traveling at .99C for 1 year and then stop would actually have traveled about 7 lightyears in 1 year. If mixing frames in this way is invalid, then the Hafele-Keating experiment is equally invalid.

GR states that all objects traveling through space travel in straight lines. Even the earth orbiting the sun... that's a straight line. Through curved space.

For this one, I will agree with the orthodox interpretation of things: There is no "negative speed." Direction is irrelevant. Whatever effects relative speed has, it's the same moving toward or away from an object. ... where this gets interesting is under the theory that time dilation may be activated by a given object's acceleration as opposed to relative velocity. Both have their faults, of course... but the problem with claiming that "acceleration" is what starts to slow time down is that when that object decelerates... this would simply be acceleration in the opposite direction. To your question, per the theory: He sees an object 7 lightyears away. When he starts moving between these two objects at a speed of .99c, the entire universe will seem to contract (in the direction of travel) by a factor of 7, and thus, the distance between these two objects (while moving at this speed) will seem to only be 1 LY. If he stops at any point in the process... the universe will seem to stretch back into it's former state, increasing the gap between the two points to 7 LY. If he resumes travel in either direction... it shrinks again. Of course, that's when the second part of the above illustration kicks in. What if a second person is traveling in this same craft... but is interested in some meteor or second ship that should be near that spot in 7 years. Say this object is moving at .1C either toward or away from you. Depending on what you're measuring your relative speed against, the entire universe may be contracted by significantly different factors... for two people on the same ship, depending on what object they're thinking of. ... hence, the problem with the claim that relative speed causes spacial contraction in the first place. But, without it, the Doppler effect would have to be acknowledged as evidence against the constant of C.

Hafele-Keating is the most common experiment people I've talked to have brought up. Definitive evidence of time dilation. Essentially Atomic clock on the ground vs. atomic clocks on a jet, flies around the world... clock reads different (and by the predicted amount). We know that these clocks can not be made inaccurate, therefore after traveling, the fact that this clock has a few missing nanoseconds is hard evidence of SR. It's assumed that these clocks have legitimately experienced the entire flight through a shorter period of time. Hense, the example in the first post of this thread... same situation, except with a longer distance and higher speed. Pick a point 7 light years away. Travel toward that point at .99C. According to your clock, you can stop after 1 year, look behind you and have traveled 7 light years. If time dilation is correct, the speed of light can not be a limit. To dismiss the above illustration is to dismiss Hafele-Keating by the same logic. Of course, for swanson, the thought experiment is a bit like Schrodinger's cat... the whole intention is to illustrate the illogical implications of the Hafele-Keating experiment. You asked what inherent flaws are in the test so many people have put their faith into: 1: it has the implications of the illustration in the original post of this thread. 2: The plane was flying along an unspecified path at an unspecified average altitude at an unspecified speed... The only thing documented about the altitude is that the aircraft's altitude was considered negligible and not included in the predicting formula. True, the GR implication of a few miles is only a fraction of a percent... but consider the scale of their results! less than 180 billionths of a second over a period of a quarter million seconds. The negligible amount is larger than their results. 3: In order to get the math right, GR had to be taken into consideration, thus the distance of the ground clock from center of gravity. They wanted to test this ratio.... and in order to prove the math they were testing... the used that same formula to adjust the results... to prove the formula. This circular reasoning doesn't jump out at anyone? The fact that the clocks had to be adjusted by this expected amount indicates that, after the trip, these clocks were still in sync... and were only out of sync by the expected amount BECAUSE they were artificially adjusted to "simulate the clock being at the center of the earth" in order to account for GR. 4: (This one, I admit can be taken a number of ways. This one has so many variables, I very well may be missing something simple) For the SR calculations, the rotational speed of the earth was taken into account... but not the orbital speed. One could say "but the plane is moving with the earth, so the orbital speed doesn't change anything." ... However, to the same extent, the plane was traveling with earth's rotation. The only SR change relative to the ground clock would be actual ground speed. I've seen some attempt to explain it as an object on a marry-go-round... Objects farther from the center will be traveling faster because they're traveling a larger circumference during each revolution. However, this is only relative to an outside, preferred frame of reference... which we were trying to -disprove- ... not rely upon. On any marry-go-round, put screws in at any distance from the center, and spin it at any speed... even though each will have a different ground speed, none of these screws will have a speed relative to each other. If we're to accept a preferred frame of reference that would account for rotational speed, then there's no real reason not to account for orbital speed as well. 5.... then, even if everything was done appropriately and the readings weren't adjusted assuming the formula's correctness to prove itself correct... All we have is a reading no way to isolate the variable to conclude that "the relative speed of one clock to the other" is what caused the discrepancy .. let alone that it was an alteration of time as opposed to an alteration of some function of the clock itself. If I want to set a bigfoot trap... and set meat outside my backdoor, postulating that if an adult, male bigfoot is in the area, he'll eat it... and it turns up gone the next day... I still have to prove it wasn't because of a dog or cat or bird or raccoon or any other simple explanation. Likewise, a result like this doesn't conclusively show that it was relative speed (as opposed to any other variable) that caused time (as opposed to any physical property of the clock) to alter by this amount.

Elfmotat, your absence will not be missed. Not everyone who disagrees does so out of ignorance. I've pointed out legitimate inconsistencies and missed variables in the popularly accepted experiments. If you have nothing of value to add beyond "but this book says I must stay strong in my faith" ... please, feel free to move on. Some of those questions being: People are using the "lightclock tests" as proof... everywhere I've seen, this has been a poorly thought out idea rather than anything functionally tested. If this is to remain "proof" ... specifically when was this functionally tested? In what way has anyone tested the uniformity of the speed of light from actual moving sources? i.e. without beginning the experiment by causing the light to be re-emitted from an object stationary relative to the rest of the experiment (such as bouncing the light off of a mirror)? I agree people have done many experiments and supported their theory with quite a bit of pretty math... I propose that nearly every such experiment is inherently flawed because they're only measuring light with each mirror as a source, only showing that this light is moving at a constant speed relative to it's source rather than in "every frame of reference." Cool story. I've read through the list of aether wind experiments you provided. None of them conclusively prove anything about time dilation or light's speed being constant from moving reference frames. Sometimes, it's acceptable to combine frames of reference (i.e. atomic clocks on jets) where the clocks (adjusted by the formula being tested) happen to exactly match the formula being tested after they've flown around the world. Other times, you yourself have said that it's inappropriate to combine frames of reference, when we realize that, based on this math, a person traveling .99c for one year will end up 7 light years away. Perhaps I can be more specific... you claim that it has "quite a lot of experimental confirmation." ... Can you cite/explain a single experiment supporting any aspect of relativity that can actually stand up to basic critical thinking. Something that doesn't have glaring inherent flaws that corrupt the whole experiment... like all of the aether wind ones you listed previously?

1: I'm curious where you got the "108x10-13" figure? In one calculation it's added to meters/second, in another it's added to km/second. Doesn't seem to be a ratio based on anything. 2: It doesn't look like any actual experimentation was done. You're giving VERY specific numbers based on what you anticipate the thought experiments would look like... yet not relying on the logic behind the thought experiment... but the numbers from the results of the thought experiments... which you set arbitrarily.

"What scientific evidence is there that takes into account the following variables...." "This is nonsense, Buy a textbook, don't waste our time" "You don't understand." Very insightful answers. Keep in mind, though, that this is a science forum. If you don't want to waste your time actually digging in and questioning things, why are you here? If your mind is already made up and you have no interest in considering other possibilities, and seem to be offended when others offer alternative explanations... what are you doing here? Science is not about reaffirming your unquestioning loyalty to the accepted theory... einstein was the one who described such a thing as a sign of great intellectual weakness. That the single greatest failure in how americans view education is how we preach the doctrine that will be accepted and any sign of questioning this doctrine is looked down upon. Science is the art of seeking better/simpler explanations for how the universe works. ... I'm rather disappointed.

Swanson... which of these are anything more than an aether drift experiment? These show quite well that light moves at a constant speed relative to it's source (each mirror). Doesn't give any logical confirmation of time's mutibility... let alone that this explanation is more viable than a physical change that is "real" in all inertial frames. You say: "There is no mechanism to slow these rates. You have to have atomic systems and nuclear systems and subnuclear particle interactions — all with different coupling strength — affected in an identical fashion. There is nothing in the models that would allow for this." Yet, you seem to have come to the same conclusion and accepted it as fact... that these subnuclear particle interactions are somehow defined by the flow through a fabric of time as opposed to time being a way to universally describe an order of operations. That leap of faith is what I question. The experiments you listed seem to all be a bunch of remakes of Michelson-Morley....

So, you say that there is 0 evidence for a preferred frame of time and thus, the idea of high speed causing physical change to be unorthodox. This implies that time as an inalterably fabric has been sufficiently proven to override the more intuitive concept of time being an abstract concept rather than a universal, yet inconsistent fabric. Other than the observation of muons, the clocks on a plane and the GPS lag, what evidence has been collected that time is alterable? Not thought experiments. What numbers support it that don't have a much simpler physical explanation? I.e. why are the rates of atomic transitions considered able to tell time "more accurately" than time itself? When we see atomic transitions happen at a slower rate on jets or satellites or muons... What evidence is there that time changes in stead of those rate of change in atomic states?

Change the. Cockroach's name to schrodinger and you've got a deal.

To delta: logical correlation, but not proportional to this conversation. If time expansion and space contraction were proportional, we would see no time dilation because the two would cancel eachother out. If time dilation were to be a viable explanation for the results of the "atomic clocks on a plane" test, when the aircraft landed, the clocks would be synchronized again. To IM... If you're going to use the light clock idea as proof... When/where/how was it actually tested? As a thought experiment, it's no more valuable than "imagine a photon traveling toward a pair of objects a lightyear away at the point of emission. For C to be a constant, that light must hit both simultaneously regardless of where in the universe each object travels during that year." The light clock idea misses a number of obvious variables.... First off, the path that the light will take isn't longer or shorter based on how the observer is moving... If the train is moving, light bouncing 90 degrees to each mirror (for the W path) will fall off track as the train moves the length between the point of emission and the edge of the mirror. Light that continues bouncing along that perceived "straight path" will in fact be traveling at an angle relative to the speed of the train as is described for how the observer on the ground sees the light. Second.... There have been "real experiments" to "prove a constant speed of light from moving sources... Guess what the first step is.... Taking that incoming, redshifted light.... And bouncing it off of a mirror stationary relative to the rest of the set up. ... And guess how light bounces. It's absorbed and reemitted... Thus completely nullifying the experiment because as soon as the light hits that first mirror, the mirror is now the source of that light, so of course it will travel at a constant speed.... Because they're using stationary sources. Please... If anyone knows of an evidence where these variables were taken into account... Please tell me. I'be read a lot of studies and so far the best explanation I've got is ".... Well... These people are scientists... I'm sure they thought of that." And that is the faith of religion. Not science.

And, therefore if there is no such thing as a constant space or time, then by definition, there can be no constant speeds (light). The more hoops people jump through to protect light's status as a constant, the more it disproves itself. You can't have a constant measurement of two things that are, each, unconstant (change in position in space over a period of time).

Photons have no frame of reference now? Then, how exactly can they be a constant? Take the Doppler effect... We move relative to a source of light and see a redshift. Intuitively, we think "we're moving relative to the wave, duh.". However, this violates SR. So, instead of our motion relative to the source adding or subtracting from our speed relative to that light (as would make perfect sense), Einstein states that our additional speed is diluting the space through which light travels and the change in frequency is caused by a change in wavelength rather than relative speed. But, if the photon has no frame of reference how do you suppose it's affected by spacial dilation? ...either way... Fine, photons are cheating. What about galaxies? Hubble's constant. Put dots on a balloon and blow it up. The larger the balloon, the more the dots will accelerate away from one another. This is how we explain the universe expansion accelerating. Larger it gets, the greater the red shift and we can already observe objects that have been shifted WELL out of the visible spectrum, indicating that those rocks with nothing but inertia to propel them are approaching the speed of light relative to us. Once the universe passes the 13.7 billion LY (iirc) mark, objects at that distance will have a rest frame of greater than C relative to us. Even if we assume that both objects will see the other forever frozen in time where they passed that point... All this suggests is that we won't be able to observe them... Not that time or space is being altered in any way for either object... Just because there happens to be another object billions of lightyears away moving at a certain speed relative to it. ... In fact, it stands to reason that the universe may well already exceed this size... But because of the rate of expansion past that point, it can't be detected because light will never reach us because we're already outpacing it. The Doppler effect and Hubble's constant conclusively disprove the idea of SR causing time dilation. The math on a small scale works for GPS... But on a large scale, it's observably wrong. There's a difference between physical changes and changes in how one observer would measure the other. When I close my eyes, I can't observe my phone at ALL! That doesn't mean my phone has stopped existing. If the only changes being made is a change in observation.... That's as useful as closing your eyes and noting that you can't observe things visually at the moment.

I assume this person is indicating that the math is correct, but a simpler explanation exists for how that math functions. Instead of using those numbers to explain a lag in space and time, perhaps this is an equal lag in another, simpler, variable.

If there is no physical change, but only a way to describe what the observer observes... Then the whole thing is a trivial optical illusion. However, if there's a physical change as you describe, that would mean every time a photon travels toward the earth, the earth's speed relative to that photon is C, thus as long as the sun shines, time can not exist and space must be infinitely compressed in any direction from which light travels toward us. One could change the subject to saying that it only explains how we observe the object in relative motion, not any other part of space... Yet light's frequency is readily observable... If any frame of reference between us and photons, as predicted, we should observe all functions of light as instantaneous.

But it can be measurable from a single reference frame, according to the theory. If you set up markers every "lightday" away, and began traveling at .99c, as soon as you reached this speed, the space between them would seem to shrink and you would pass them round very 3 hours (and a few minutes) or so, instead of every 24 hours. Because you know you havn't really shrunk the universe, you would be able to adjust for that illusion and know that you are traveling at about 7C from your perspective. ...unless you believe the rubber pencil trick actually transmitters the pencil just because it appears wobbly.

If this.is the case, is time dilation not just a sort of optical illusion? If no clock experiences change itself, but only appears to change from other points of view?

... basically any test intended to prove time dilation could more simply be explained by a physical change. Specifically cesium clocks running slow and muons decaying slower. The absolute frame in reference being either their speed relative to the medium through which they travel, or if traveling through a vacuum, their speed relative to their source.

ACG, I'm not intending to do anything dishonest. But, to describe one's flow of time as dependant on it's speed relative to another object mandates that each object be experiencing an infinite number of frames of time (and spacial distortion) simultaneously as there are virtually infinite objects in our universe traveling at all sorts of speeds and trajectories. The biggest reason I bring up the "going .99c for 1 year and ending up 7 lightyears away" thing... is because einstein pointed out that there is no preferred frame of reference. It would be equally logical to state that... from the frame of reference of the ship, they are standing still and it is the planet moving toward them at that speed. Thus, to whatever extent the ship experiences time dilation in it's frame of reference, so must the planet it's traveling toward. Thus, this planet systems away would suddenly experience time and space dilation because of some object coming toward it, lightyears away. And, if this is the case, it must also experience time dilation based on every other rock in the universe moving relative to it, completely oblivious of this planet's existence. Some would say that this is reductio ad absurdum, but ... when two objects begin moving relative to each other... how do you define which is to experience time dilation? Unless you assume this is attributed to inertial changes due to acceleration, rather than consistent speed... but that opens an even uglier can of worms. another endlessly more complicated consideration of this illustration.... what if a second passenger is boarding this ship, intending to catch up to a meteor that should pass this point 7 lightyears away... but this meteor is traveling at, say .1C... Depending on which direction a meteor so far away is traveling, the ship's speed relative to his target would change wildly... I'm not doing the actual math at 2 AM (Yes, I am losing sleep over this)... but with the whole (v+u)/(1+((vu)/(c^2)) bit... somewhere between .89c(ish) and a dilation factor well below 7... to adding a few digits behind .99c and making this factor significantly higher. Thus, two people on the same ship would have a different intended targets and thus different relative speed, and thus experience time and space SIGNIFICANTLY differently based on what theoretical point they're thinking of. ... thus the problem mixing objective absolutes with subjective reference frames.