Does the fact that we can only measure the two-way speed of light undermine the axiom of invariance?What if we shine a laser to east and another to west, will they arrive at the same time?Can we measure the speed of light in one direction?Do the particles that were found to break the speed of light really break Einstein's theory of relativity?Why does the speed of light in vacuum have no uncertainty?Speed of light that is traveling away from the observerMichelson-Morley experiment revisited under the light of special relativityHow can we show that the speed of light is really constant in all reference frames?Speed of light invariance (once again)Can the constancy of the speed of light in vacuum be derived from a deeper theory?The implications of Einstein's first lawWhy is light speed the only constant speed?Is speed of light is the only way to measure time
How to ignore kerning of underbrace in math mode
Sankey diagram: not getting the hang of it
Value of a binomial series
Defining the standard model of PA so that a space alien could understand
Ingress filtering on edge routers and performance concerns
Make 24 using exactly three 3s
Construct a word ladder
Is it truly impossible to tell what a CPU is doing?
Can a British citizen living in France vote in both France and Britain in the European Elections?
Does this strict reading of the rules allow both Extra Attack and the Thirsting Blade warlock invocation to be used together?
Why were helmets and other body armour not commonplace in the 1800s?
Can I connect my older mathematica front-end to the free wolfram engine?
Why are GND pads often only connected by four traces?
How did NASA Langley end up with the first 737?
Find the three digit Prime number P from the given unusual relationships
Efficient Algorithm for the boundary of a set of tiles
How to cut a climbing rope?
Count Even Digits In Number
I know that there is a preselected candidate for a position to be filled at my department. What should I do?
What is the function of the corrugations on a section of the Space Shuttle's external tank?
When the Torah was almost lost and one (or several) Rabbis saved it?
How to patch glass cuts in a bicycle tire?
Can I summon an otherworldly creature with the Gate spell without knowing its true name?
Are black holes spherical during merger?
Does the fact that we can only measure the two-way speed of light undermine the axiom of invariance?
What if we shine a laser to east and another to west, will they arrive at the same time?Can we measure the speed of light in one direction?Do the particles that were found to break the speed of light really break Einstein's theory of relativity?Why does the speed of light in vacuum have no uncertainty?Speed of light that is traveling away from the observerMichelson-Morley experiment revisited under the light of special relativityHow can we show that the speed of light is really constant in all reference frames?Speed of light invariance (once again)Can the constancy of the speed of light in vacuum be derived from a deeper theory?The implications of Einstein's first lawWhy is light speed the only constant speed?Is speed of light is the only way to measure time
$begingroup$
When we measure the speed of light we get the same answer in all directions. This is taken to undermine the aether or absolute motion hypothesis and give support to the proposal that the speed of light is invariant, from which derives the theory of special relativity.
But doesn't the fact that we only measure speed of light 'there and back' undermine this conclusion? Wouldn't we expect this result through an aether?
special-relativity speed-of-light
edited May 18 at 23:48
Qmechanic♦
109k122061277
asked May 18 at 20:24
AndrewAndrew
605
$endgroup$
add a comment |
$begingroup$
When we measure the speed of light we get the same answer in all directions. This is taken to undermine the aether or absolute motion hypothesis and give support to the proposal that the speed of light is invariant, from which derives the theory of special relativity.
But doesn't the fact that we only measure speed of light 'there and back' undermine this conclusion? Wouldn't we expect this result through an aether?
special-relativity speed-of-light
edited May 18 at 23:48
Qmechanic♦
109k122061277
asked May 18 at 20:24
AndrewAndrew
605
$endgroup$
2
$begingroup$
Hi @Andrew, you said “Wouldn't we expect this result through an aether?”. Actually, no, if you work out the math the two way speed of light is not isotropic in a standard aether theory.
$endgroup$
– Dale
May 19 at 2:49
$begingroup$
Why do you think we can only measure "there and back"? For instance, one of the first measurements of the speed of light was made by noting variations in the timing of eclipses of Jupiter's moons, which would seem to involve measuring only the "back" reflection of the sun's light: google.com/…
$endgroup$
– jamesqf
May 19 at 5:58
$begingroup$
@jamesqf Wikipedia says that although Rømer's measurement of Jupiter's moons seems to give a one-way speed, careful analysis shows that those calculations assume that the travel speed is isotropic. However, I must confess I don't fully understand the arguments given on that page.
$endgroup$
– PM 2Ring
May 19 at 10:03
2
$begingroup$
Careful analysis shows that Rømer's measurement says nothing about the one-way speed of light. physics.stackexchange.com/questions/456243/…
$endgroup$
– Albert
May 19 at 10:43
add a comment |
$begingroup$
When we measure the speed of light we get the same answer in all directions. This is taken to undermine the aether or absolute motion hypothesis and give support to the proposal that the speed of light is invariant, from which derives the theory of special relativity.
But doesn't the fact that we only measure speed of light 'there and back' undermine this conclusion? Wouldn't we expect this result through an aether?
special-relativity speed-of-light
edited May 18 at 23:48
Qmechanic♦
109k122061277
asked May 18 at 20:24
AndrewAndrew
605
$endgroup$
When we measure the speed of light we get the same answer in all directions. This is taken to undermine the aether or absolute motion hypothesis and give support to the proposal that the speed of light is invariant, from which derives the theory of special relativity.
But doesn't the fact that we only measure speed of light 'there and back' undermine this conclusion? Wouldn't we expect this result through an aether?
special-relativity speed-of-light
special-relativity speed-of-light
edited May 18 at 23:48
Qmechanic♦
109k122061277
asked May 18 at 20:24
AndrewAndrew
605
edited May 18 at 23:48
Qmechanic♦
109k122061277
asked May 18 at 20:24
AndrewAndrew
605
edited May 18 at 23:48
Qmechanic♦
109k122061277
edited May 18 at 23:48
Qmechanic♦
109k122061277
edited May 18 at 23:48
Qmechanic♦
109k122061277
109k122061277
asked May 18 at 20:24
AndrewAndrew
605
asked May 18 at 20:24
AndrewAndrew
605
asked May 18 at 20:24
AndrewAndrew
605
605
2
$begingroup$
Hi @Andrew, you said “Wouldn't we expect this result through an aether?”. Actually, no, if you work out the math the two way speed of light is not isotropic in a standard aether theory.
$endgroup$
– Dale
May 19 at 2:49
$begingroup$
Why do you think we can only measure "there and back"? For instance, one of the first measurements of the speed of light was made by noting variations in the timing of eclipses of Jupiter's moons, which would seem to involve measuring only the "back" reflection of the sun's light: google.com/…
$endgroup$
– jamesqf
May 19 at 5:58
$begingroup$
@jamesqf Wikipedia says that although Rømer's measurement of Jupiter's moons seems to give a one-way speed, careful analysis shows that those calculations assume that the travel speed is isotropic. However, I must confess I don't fully understand the arguments given on that page.
$endgroup$
– PM 2Ring
May 19 at 10:03
2
$begingroup$
Careful analysis shows that Rømer's measurement says nothing about the one-way speed of light. physics.stackexchange.com/questions/456243/…
$endgroup$
– Albert
May 19 at 10:43
add a comment |
2
$begingroup$
Hi @Andrew, you said “Wouldn't we expect this result through an aether?”. Actually, no, if you work out the math the two way speed of light is not isotropic in a standard aether theory.
$endgroup$
– Dale
May 19 at 2:49
$begingroup$
Why do you think we can only measure "there and back"? For instance, one of the first measurements of the speed of light was made by noting variations in the timing of eclipses of Jupiter's moons, which would seem to involve measuring only the "back" reflection of the sun's light: google.com/…
$endgroup$
– jamesqf
May 19 at 5:58
$begingroup$
@jamesqf Wikipedia says that although Rømer's measurement of Jupiter's moons seems to give a one-way speed, careful analysis shows that those calculations assume that the travel speed is isotropic. However, I must confess I don't fully understand the arguments given on that page.
$endgroup$
– PM 2Ring
May 19 at 10:03
2
$begingroup$
Careful analysis shows that Rømer's measurement says nothing about the one-way speed of light. physics.stackexchange.com/questions/456243/…
$endgroup$
– Albert
May 19 at 10:43
2
2
$begingroup$
Hi @Andrew, you said “Wouldn't we expect this result through an aether?”. Actually, no, if you work out the math the two way speed of light is not isotropic in a standard aether theory.
$endgroup$
– Dale
May 19 at 2:49
$begingroup$
Hi @Andrew, you said “Wouldn't we expect this result through an aether?”. Actually, no, if you work out the math the two way speed of light is not isotropic in a standard aether theory.
$endgroup$
– Dale
May 19 at 2:49
$begingroup$
Why do you think we can only measure "there and back"? For instance, one of the first measurements of the speed of light was made by noting variations in the timing of eclipses of Jupiter's moons, which would seem to involve measuring only the "back" reflection of the sun's light: google.com/…
$endgroup$
– jamesqf
May 19 at 5:58
$begingroup$
Why do you think we can only measure "there and back"? For instance, one of the first measurements of the speed of light was made by noting variations in the timing of eclipses of Jupiter's moons, which would seem to involve measuring only the "back" reflection of the sun's light: google.com/…
$endgroup$
– jamesqf
May 19 at 5:58
$begingroup$
@jamesqf Wikipedia says that although Rømer's measurement of Jupiter's moons seems to give a one-way speed, careful analysis shows that those calculations assume that the travel speed is isotropic. However, I must confess I don't fully understand the arguments given on that page.
$endgroup$
– PM 2Ring
May 19 at 10:03
$begingroup$
@jamesqf Wikipedia says that although Rømer's measurement of Jupiter's moons seems to give a one-way speed, careful analysis shows that those calculations assume that the travel speed is isotropic. However, I must confess I don't fully understand the arguments given on that page.
$endgroup$
– PM 2Ring
May 19 at 10:03
2
2
$begingroup$
Careful analysis shows that Rømer's measurement says nothing about the one-way speed of light. physics.stackexchange.com/questions/456243/…
$endgroup$
– Albert
May 19 at 10:43
$begingroup$
Careful analysis shows that Rømer's measurement says nothing about the one-way speed of light. physics.stackexchange.com/questions/456243/…
$endgroup$
– Albert
May 19 at 10:43
add a comment |
5 Answers
5
active
oldest
votes
$begingroup$
The bottom line is that this is the wrong question to ask. You don't ever prove an axiom in physics.
You're not quite right about the ether: while the first order effect cancels out in "there and back again" experiments, the second order effect doesn't, which is why the Michelson-Morley experiment stood a chance of testing for the ether. But Michelson-Morley wasn't the end of ether theory, because you could always add fixes to account for the results. For example, the famous Lorentz contraction in special relativity was originally invented for ether theory; the idea was that flowing ether physically squeezed objects smaller. Einstein just took effects like these more seriously.
Ether theory limped on for another 40 years, getting progressively more complicated as more results came in. Ether was not abandoned because it was disproven by experiments or because special relativity was proven by experiments, because this never happens. It was abandoned by the 1930s it could only explain experiments using tons of epicycles, while special relativity just worked perfectly out of the box.
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
$endgroup$
2
$begingroup$
To be fair, you don't ever prove an axiom. Thus is the nature of axioms.
$endgroup$
– tox123
May 19 at 23:58
4
$begingroup$
While it's true that you don't ever prove an axiom in the mathematical sense, you do attempt to falsify them in science. If, after many attempts to falsify it, you have failed to disprove it, then you may accept it as true. This is known as inductive reasoning, and it would typically be regarded as "proving" the theory in the common, non-mathematical vernacular. (Not to diminish the importance of understanding the difference, but we ought make sure we account for these things when dealing with misunderstandings.)
$endgroup$
– jpmc26
May 20 at 5:45
$begingroup$
@jpmc26 The point is that ether isn’t falsified either. You can almost always add tweaks to avoid falsification, so using that alone is not good enough.
$endgroup$
– knzhou
May 20 at 10:57
$begingroup$
For example, you could even take an extremely weak formulation of the ether which is just identical to GR but picks out some frame as special, without any physical consequences. That is not falsified any more than GR is. We don’t use it because it complicates things for no reason.
$endgroup$
– knzhou
May 20 at 10:59
add a comment |
$begingroup$
There-and-back measurements still show the effect of an aether, because you can compare the results in different directions. For example, there-and-back along the direction of motion would show a different speed from there-and-back across it. This was the approach taken in the Michelson-Morley experiment.
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
$endgroup$
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– Chris♦
May 19 at 16:54
add a comment |
$begingroup$
That the one-way speed of light is not observable plays a large role in keeping various relativistically-correct aether theories alive. Like general relativity, these new aether theories locally reduce to special relativity in the absence of nearby massive objects. Unlike general relativity, these new aether theories have a preferred universal frame of reference, typically a frame co-moving with the cosmic microwave background radiation.
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
$endgroup$
1
$begingroup$
If such theories cannot be ruled out, then why shouldn't they be amongst the respectable opinions that thinkers and researchers may choose to adopt and work with?
$endgroup$
– Steve
May 19 at 0:40
1
$begingroup$
@Steve “Choose to adopt and work with” is not a binary. People make different choices. Lots of people find GR useful; few find The Flying Spaghetti God hypothesis useful. Other theories are in between in popularity, i.e the MOND family. Nor is this decision time-invariant: theories and hypotheses are more and less popular as people show them more or less useful.
$endgroup$
– Bob Jacobsen
May 19 at 1:32
2
$begingroup$
@BobJacobsen, useful for what purpose? Perhaps when working with aether concepts attracts comparisons to the Flying Spaghetti God, you make it dis-useful for professional scientists to adopt such views and perform such work? And my point is to rebut the tone in which David speaks of apparently tenable theories being "kept alive" - the writer's implication being that these theories ought to be dead. Like I say, if they cannot be ruled out, then they are fair game for further scientific enquiry.
$endgroup$
– Steve
May 19 at 1:53
3
$begingroup$
@Steve, general relativity is a simple theory. Its only arbitrary parameter is Newton's gravitational constant. Other viable theories carry additional arbitrary parameters. In the limit that these parameters approach some value, typically zero, these theories become equivalent to general relativity. To date, all observations are consistent with these free parameters taking on the value that makes the alternative theory equivalent to general relativity.
$endgroup$
– David Hammen
May 19 at 2:51
1
$begingroup$
@DavidHammen, that's basically what I said above in my original comment to Bob's answer, that as it stands today (and as it stood in about 1920) Lorentz's aether theory (in its latter form) is equivalent to relativity - they are not mutually exclusive theories. It is only the general philosophical approach and concepts they employ which differ.
$endgroup$
– Steve
May 19 at 9:13
|
show 7 more comments
$begingroup$
The $x$ direction is not any different physically than the $-x$ direction. So light travelling towards $x-> infty$ should travel in the same way it travels towards $x-> -infty$ wether theres an aether or not.
What should make a difference is if we measure the speed of light in the direction the body that emitted the light is moving through the aether and any other direction, for example, the direction perpendicular to this movement to see the difference a bit easier. However no difference in arrival times was measured.
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
$endgroup$
add a comment |
$begingroup$
Round - trip measurement of speed of light says nothing about the one - way speed of light. Effects of Lorentz contraction of moving bodies (MM experiment) and dilation of moving clock (Kennedy Thorndike experiment) had been first introduced in the framework of Lorentz aether theory.
Since the same mathematical formalism occurs in both, it is not possible to distinguish between Lorentz aether theory and special relativity by experiment.
The one-way speed of light is apparently anisotropic, the Sagnac effect (page 42 in this paper) is the best evidence of that.
Remember, that in rotating frames, even in special relativity, the non-transitivity of Einstein synchronization diminishes its usefulness. If clock 1 and clock 2 are not synchronized directly, but by using a chain of intermediate clocks, the synchronization depends on the path chosen. Synchronization around the circumference of a rotating disk gives a non-vanishing time difference that depends on the direction used.
Hence, the one – way speed of light relatively to the Earth surface is anisotropic, and it is very unlikely that one way speed of light is c an all relatively moving inertial frames.
On the simplest example of the floating in a water ships this paper simulates all kinematic effects of special relativity (length contraction, time dilation, relativistic velocity addition, relativistic and transverse Doppler effects, Twin paradox, Bell‘s spaceship paradox, symmetry of observations). Things that may seem quirky and unusual take very simple shape, as soon as "absolute" time and medium had been introduced.
The chapter Transverse Doppler Effect makes clear, that „conditionally moving“ clock ticks slower (transverse redshift) than „conditionally resting“ one , while „conditionally resting“ tick faster (transverse blueshift) than the "moving one". It is clear, that different synchronization procedures (standard isotropic for "stationary") frame and (non-standard anisotropic for "moving" frame) is needed to obtain the same result conducting measurements with the pair of synchronized clocks.
The article on special relativity in Wikipedia teaches, that: "The Principle of Invariant Light Speed – "... light is always propagated in empty space with a definite velocity [speed] c which is independent of the state of motion of the emitting body" (from the preface).[p 1] That is, light in vacuum propagates with the speed c (a fixed constant, independent of direction) in at least one system of inertial coordinates (the "stationary system"), regardless of the state of motion of the light source."
Apparently, according to the article, there is at least one "special stationary frame" where speed of light is isotropic and some others, where the speed of light is anisotropic.
answered May 19 at 9:44
AlbertAlbert
952310
$endgroup$
2
$begingroup$
The Sagnac effect is most emphatically not evidence for light speed anisotropy. The Sagnac effect is predicted by special relativity which assumes isotropy. To claim that it demonstrates anisotropy is only evidence that you do not know your facts enough to produce a credible answer! -1
$endgroup$
– Dale
May 19 at 10:49
1
$begingroup$
Especially for YOU I have posted the links to the Sagnac effect explanation in Gron's paper (it is written black on white there, that in rotating frame speed of light is anisotropic ) and the link to Einstein synchronization in Wikipedia. Could you please be so kind to clean your glasses and read it again? Or maybe you think that the Earth does not rotate? These views are out to date, I am afraid to say.
$endgroup$
– Albert
May 19 at 11:00
1
$begingroup$
That the speed of light is anisotropic in a rotating reference frame does not imply that it is evidence for light speed anisotropy. For something to be evidence of a hypothesis it must not only be predicted by a hypothesis but also it must be not predicted by the alternative hypothesis. The Sagnac effect is equally predicted both a non-isotropic and an isotropic hypothesis. Therefore it is not evidence of either
$endgroup$
– Dale
May 19 at 11:10
1
$begingroup$
Another minus one. The Sagnac effect is not evidence that the one-way speed of light is anisotropic in inertial frames. It is evidence that the one-way speed of light is anisotropic in rotating frames, which of course are not inertial. The Sagnac effect is fully consistent with special relativity. If this observed fact was inconsistent with special relativity, we wouldn't be teaching special relativity any more. It would instead be yet another idea tossed on the "oops, that turned out to be wrong and useless" pile of failed theories, just like the many failed theories of heat.
$endgroup$
– David Hammen
May 19 at 15:24
1
$begingroup$
@Dale, agreed, excuse me on that point. I think when I wrote I attributed Albert's apparent mis-paraphrasing of you, to your own actual words. As long as we are all now agreed that there is no conclusive evidence either way, and the one-way speed may or may not be constant, then that is the state of current science on the question. Special relativity is a theory that treats the one-way speed as constant (without establishing the fact by any experiment), other theories are tenable which do not treat the one-way speed as constant.
$endgroup$
– Steve
May 19 at 19:22
|
show 13 more comments
Your Answer
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "151"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f480938%2fdoes-the-fact-that-we-can-only-measure-the-two-way-speed-of-light-undermine-the%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
5 Answers
5
active
oldest
votes
5 Answers
5
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
The bottom line is that this is the wrong question to ask. You don't ever prove an axiom in physics.
You're not quite right about the ether: while the first order effect cancels out in "there and back again" experiments, the second order effect doesn't, which is why the Michelson-Morley experiment stood a chance of testing for the ether. But Michelson-Morley wasn't the end of ether theory, because you could always add fixes to account for the results. For example, the famous Lorentz contraction in special relativity was originally invented for ether theory; the idea was that flowing ether physically squeezed objects smaller. Einstein just took effects like these more seriously.
Ether theory limped on for another 40 years, getting progressively more complicated as more results came in. Ether was not abandoned because it was disproven by experiments or because special relativity was proven by experiments, because this never happens. It was abandoned by the 1930s it could only explain experiments using tons of epicycles, while special relativity just worked perfectly out of the box.
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
$endgroup$
2
$begingroup$
To be fair, you don't ever prove an axiom. Thus is the nature of axioms.
$endgroup$
– tox123
May 19 at 23:58
4
$begingroup$
While it's true that you don't ever prove an axiom in the mathematical sense, you do attempt to falsify them in science. If, after many attempts to falsify it, you have failed to disprove it, then you may accept it as true. This is known as inductive reasoning, and it would typically be regarded as "proving" the theory in the common, non-mathematical vernacular. (Not to diminish the importance of understanding the difference, but we ought make sure we account for these things when dealing with misunderstandings.)
$endgroup$
– jpmc26
May 20 at 5:45
$begingroup$
@jpmc26 The point is that ether isn’t falsified either. You can almost always add tweaks to avoid falsification, so using that alone is not good enough.
$endgroup$
– knzhou
May 20 at 10:57
$begingroup$
For example, you could even take an extremely weak formulation of the ether which is just identical to GR but picks out some frame as special, without any physical consequences. That is not falsified any more than GR is. We don’t use it because it complicates things for no reason.
$endgroup$
– knzhou
May 20 at 10:59
add a comment |
$begingroup$
The bottom line is that this is the wrong question to ask. You don't ever prove an axiom in physics.
You're not quite right about the ether: while the first order effect cancels out in "there and back again" experiments, the second order effect doesn't, which is why the Michelson-Morley experiment stood a chance of testing for the ether. But Michelson-Morley wasn't the end of ether theory, because you could always add fixes to account for the results. For example, the famous Lorentz contraction in special relativity was originally invented for ether theory; the idea was that flowing ether physically squeezed objects smaller. Einstein just took effects like these more seriously.
Ether theory limped on for another 40 years, getting progressively more complicated as more results came in. Ether was not abandoned because it was disproven by experiments or because special relativity was proven by experiments, because this never happens. It was abandoned by the 1930s it could only explain experiments using tons of epicycles, while special relativity just worked perfectly out of the box.
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
$endgroup$
2
$begingroup$
To be fair, you don't ever prove an axiom. Thus is the nature of axioms.
$endgroup$
– tox123
May 19 at 23:58
4
$begingroup$
While it's true that you don't ever prove an axiom in the mathematical sense, you do attempt to falsify them in science. If, after many attempts to falsify it, you have failed to disprove it, then you may accept it as true. This is known as inductive reasoning, and it would typically be regarded as "proving" the theory in the common, non-mathematical vernacular. (Not to diminish the importance of understanding the difference, but we ought make sure we account for these things when dealing with misunderstandings.)
$endgroup$
– jpmc26
May 20 at 5:45
$begingroup$
@jpmc26 The point is that ether isn’t falsified either. You can almost always add tweaks to avoid falsification, so using that alone is not good enough.
$endgroup$
– knzhou
May 20 at 10:57
$begingroup$
For example, you could even take an extremely weak formulation of the ether which is just identical to GR but picks out some frame as special, without any physical consequences. That is not falsified any more than GR is. We don’t use it because it complicates things for no reason.
$endgroup$
– knzhou
May 20 at 10:59
add a comment |
$begingroup$
The bottom line is that this is the wrong question to ask. You don't ever prove an axiom in physics.
You're not quite right about the ether: while the first order effect cancels out in "there and back again" experiments, the second order effect doesn't, which is why the Michelson-Morley experiment stood a chance of testing for the ether. But Michelson-Morley wasn't the end of ether theory, because you could always add fixes to account for the results. For example, the famous Lorentz contraction in special relativity was originally invented for ether theory; the idea was that flowing ether physically squeezed objects smaller. Einstein just took effects like these more seriously.
Ether theory limped on for another 40 years, getting progressively more complicated as more results came in. Ether was not abandoned because it was disproven by experiments or because special relativity was proven by experiments, because this never happens. It was abandoned by the 1930s it could only explain experiments using tons of epicycles, while special relativity just worked perfectly out of the box.
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
$endgroup$
The bottom line is that this is the wrong question to ask. You don't ever prove an axiom in physics.
You're not quite right about the ether: while the first order effect cancels out in "there and back again" experiments, the second order effect doesn't, which is why the Michelson-Morley experiment stood a chance of testing for the ether. But Michelson-Morley wasn't the end of ether theory, because you could always add fixes to account for the results. For example, the famous Lorentz contraction in special relativity was originally invented for ether theory; the idea was that flowing ether physically squeezed objects smaller. Einstein just took effects like these more seriously.
Ether theory limped on for another 40 years, getting progressively more complicated as more results came in. Ether was not abandoned because it was disproven by experiments or because special relativity was proven by experiments, because this never happens. It was abandoned by the 1930s it could only explain experiments using tons of epicycles, while special relativity just worked perfectly out of the box.
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
answered May 19 at 12:54
knzhouknzhou
49.9k12136244
49.9k12136244
2
$begingroup$
To be fair, you don't ever prove an axiom. Thus is the nature of axioms.
$endgroup$
– tox123
May 19 at 23:58
4
$begingroup$
While it's true that you don't ever prove an axiom in the mathematical sense, you do attempt to falsify them in science. If, after many attempts to falsify it, you have failed to disprove it, then you may accept it as true. This is known as inductive reasoning, and it would typically be regarded as "proving" the theory in the common, non-mathematical vernacular. (Not to diminish the importance of understanding the difference, but we ought make sure we account for these things when dealing with misunderstandings.)
$endgroup$
– jpmc26
May 20 at 5:45
$begingroup$
@jpmc26 The point is that ether isn’t falsified either. You can almost always add tweaks to avoid falsification, so using that alone is not good enough.
$endgroup$
– knzhou
May 20 at 10:57
$begingroup$
For example, you could even take an extremely weak formulation of the ether which is just identical to GR but picks out some frame as special, without any physical consequences. That is not falsified any more than GR is. We don’t use it because it complicates things for no reason.
$endgroup$
– knzhou
May 20 at 10:59
add a comment |
2
$begingroup$
To be fair, you don't ever prove an axiom. Thus is the nature of axioms.
$endgroup$
– tox123
May 19 at 23:58
4
$begingroup$
While it's true that you don't ever prove an axiom in the mathematical sense, you do attempt to falsify them in science. If, after many attempts to falsify it, you have failed to disprove it, then you may accept it as true. This is known as inductive reasoning, and it would typically be regarded as "proving" the theory in the common, non-mathematical vernacular. (Not to diminish the importance of understanding the difference, but we ought make sure we account for these things when dealing with misunderstandings.)
$endgroup$
– jpmc26
May 20 at 5:45
$begingroup$
@jpmc26 The point is that ether isn’t falsified either. You can almost always add tweaks to avoid falsification, so using that alone is not good enough.
$endgroup$
– knzhou
May 20 at 10:57
$begingroup$
For example, you could even take an extremely weak formulation of the ether which is just identical to GR but picks out some frame as special, without any physical consequences. That is not falsified any more than GR is. We don’t use it because it complicates things for no reason.
$endgroup$
– knzhou
May 20 at 10:59
2
2
$begingroup$
To be fair, you don't ever prove an axiom. Thus is the nature of axioms.
$endgroup$
– tox123
May 19 at 23:58
$begingroup$
To be fair, you don't ever prove an axiom. Thus is the nature of axioms.
$endgroup$
– tox123
May 19 at 23:58
4
4
$begingroup$
While it's true that you don't ever prove an axiom in the mathematical sense, you do attempt to falsify them in science. If, after many attempts to falsify it, you have failed to disprove it, then you may accept it as true. This is known as inductive reasoning, and it would typically be regarded as "proving" the theory in the common, non-mathematical vernacular. (Not to diminish the importance of understanding the difference, but we ought make sure we account for these things when dealing with misunderstandings.)
$endgroup$
– jpmc26
May 20 at 5:45
$begingroup$
While it's true that you don't ever prove an axiom in the mathematical sense, you do attempt to falsify them in science. If, after many attempts to falsify it, you have failed to disprove it, then you may accept it as true. This is known as inductive reasoning, and it would typically be regarded as "proving" the theory in the common, non-mathematical vernacular. (Not to diminish the importance of understanding the difference, but we ought make sure we account for these things when dealing with misunderstandings.)
$endgroup$
– jpmc26
May 20 at 5:45
$begingroup$
@jpmc26 The point is that ether isn’t falsified either. You can almost always add tweaks to avoid falsification, so using that alone is not good enough.
$endgroup$
– knzhou
May 20 at 10:57
$begingroup$
@jpmc26 The point is that ether isn’t falsified either. You can almost always add tweaks to avoid falsification, so using that alone is not good enough.
$endgroup$
– knzhou
May 20 at 10:57
$begingroup$
For example, you could even take an extremely weak formulation of the ether which is just identical to GR but picks out some frame as special, without any physical consequences. That is not falsified any more than GR is. We don’t use it because it complicates things for no reason.
$endgroup$
– knzhou
May 20 at 10:59
$begingroup$
For example, you could even take an extremely weak formulation of the ether which is just identical to GR but picks out some frame as special, without any physical consequences. That is not falsified any more than GR is. We don’t use it because it complicates things for no reason.
$endgroup$
– knzhou
May 20 at 10:59
add a comment |
$begingroup$
There-and-back measurements still show the effect of an aether, because you can compare the results in different directions. For example, there-and-back along the direction of motion would show a different speed from there-and-back across it. This was the approach taken in the Michelson-Morley experiment.
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
$endgroup$
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– Chris♦
May 19 at 16:54
add a comment |
$begingroup$
There-and-back measurements still show the effect of an aether, because you can compare the results in different directions. For example, there-and-back along the direction of motion would show a different speed from there-and-back across it. This was the approach taken in the Michelson-Morley experiment.
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
$endgroup$
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– Chris♦
May 19 at 16:54
add a comment |
$begingroup$
There-and-back measurements still show the effect of an aether, because you can compare the results in different directions. For example, there-and-back along the direction of motion would show a different speed from there-and-back across it. This was the approach taken in the Michelson-Morley experiment.
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
$endgroup$
There-and-back measurements still show the effect of an aether, because you can compare the results in different directions. For example, there-and-back along the direction of motion would show a different speed from there-and-back across it. This was the approach taken in the Michelson-Morley experiment.
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
answered May 18 at 20:38
Bob JacobsenBob Jacobsen
6,1801021
6,1801021
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– Chris♦
May 19 at 16:54
add a comment |
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– Chris♦
May 19 at 16:54
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– Chris♦
May 19 at 16:54
$begingroup$
Comments are not for extended discussion; this conversation has been moved to chat.
$endgroup$
– Chris♦
May 19 at 16:54
add a comment |
$begingroup$
That the one-way speed of light is not observable plays a large role in keeping various relativistically-correct aether theories alive. Like general relativity, these new aether theories locally reduce to special relativity in the absence of nearby massive objects. Unlike general relativity, these new aether theories have a preferred universal frame of reference, typically a frame co-moving with the cosmic microwave background radiation.
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
$endgroup$
1
$begingroup$
If such theories cannot be ruled out, then why shouldn't they be amongst the respectable opinions that thinkers and researchers may choose to adopt and work with?
$endgroup$
– Steve
May 19 at 0:40
1
$begingroup$
@Steve “Choose to adopt and work with” is not a binary. People make different choices. Lots of people find GR useful; few find The Flying Spaghetti God hypothesis useful. Other theories are in between in popularity, i.e the MOND family. Nor is this decision time-invariant: theories and hypotheses are more and less popular as people show them more or less useful.
$endgroup$
– Bob Jacobsen
May 19 at 1:32
2
$begingroup$
@BobJacobsen, useful for what purpose? Perhaps when working with aether concepts attracts comparisons to the Flying Spaghetti God, you make it dis-useful for professional scientists to adopt such views and perform such work? And my point is to rebut the tone in which David speaks of apparently tenable theories being "kept alive" - the writer's implication being that these theories ought to be dead. Like I say, if they cannot be ruled out, then they are fair game for further scientific enquiry.
$endgroup$
– Steve
May 19 at 1:53
3
$begingroup$
@Steve, general relativity is a simple theory. Its only arbitrary parameter is Newton's gravitational constant. Other viable theories carry additional arbitrary parameters. In the limit that these parameters approach some value, typically zero, these theories become equivalent to general relativity. To date, all observations are consistent with these free parameters taking on the value that makes the alternative theory equivalent to general relativity.
$endgroup$
– David Hammen
May 19 at 2:51
1
$begingroup$
@DavidHammen, that's basically what I said above in my original comment to Bob's answer, that as it stands today (and as it stood in about 1920) Lorentz's aether theory (in its latter form) is equivalent to relativity - they are not mutually exclusive theories. It is only the general philosophical approach and concepts they employ which differ.
$endgroup$
– Steve
May 19 at 9:13
|
show 7 more comments
$begingroup$
That the one-way speed of light is not observable plays a large role in keeping various relativistically-correct aether theories alive. Like general relativity, these new aether theories locally reduce to special relativity in the absence of nearby massive objects. Unlike general relativity, these new aether theories have a preferred universal frame of reference, typically a frame co-moving with the cosmic microwave background radiation.
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
$endgroup$
1
$begingroup$
If such theories cannot be ruled out, then why shouldn't they be amongst the respectable opinions that thinkers and researchers may choose to adopt and work with?
$endgroup$
– Steve
May 19 at 0:40
1
$begingroup$
@Steve “Choose to adopt and work with” is not a binary. People make different choices. Lots of people find GR useful; few find The Flying Spaghetti God hypothesis useful. Other theories are in between in popularity, i.e the MOND family. Nor is this decision time-invariant: theories and hypotheses are more and less popular as people show them more or less useful.
$endgroup$
– Bob Jacobsen
May 19 at 1:32
2
$begingroup$
@BobJacobsen, useful for what purpose? Perhaps when working with aether concepts attracts comparisons to the Flying Spaghetti God, you make it dis-useful for professional scientists to adopt such views and perform such work? And my point is to rebut the tone in which David speaks of apparently tenable theories being "kept alive" - the writer's implication being that these theories ought to be dead. Like I say, if they cannot be ruled out, then they are fair game for further scientific enquiry.
$endgroup$
– Steve
May 19 at 1:53
3
$begingroup$
@Steve, general relativity is a simple theory. Its only arbitrary parameter is Newton's gravitational constant. Other viable theories carry additional arbitrary parameters. In the limit that these parameters approach some value, typically zero, these theories become equivalent to general relativity. To date, all observations are consistent with these free parameters taking on the value that makes the alternative theory equivalent to general relativity.
$endgroup$
– David Hammen
May 19 at 2:51
1
$begingroup$
@DavidHammen, that's basically what I said above in my original comment to Bob's answer, that as it stands today (and as it stood in about 1920) Lorentz's aether theory (in its latter form) is equivalent to relativity - they are not mutually exclusive theories. It is only the general philosophical approach and concepts they employ which differ.
$endgroup$
– Steve
May 19 at 9:13
|
show 7 more comments
$begingroup$
That the one-way speed of light is not observable plays a large role in keeping various relativistically-correct aether theories alive. Like general relativity, these new aether theories locally reduce to special relativity in the absence of nearby massive objects. Unlike general relativity, these new aether theories have a preferred universal frame of reference, typically a frame co-moving with the cosmic microwave background radiation.
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
$endgroup$
That the one-way speed of light is not observable plays a large role in keeping various relativistically-correct aether theories alive. Like general relativity, these new aether theories locally reduce to special relativity in the absence of nearby massive objects. Unlike general relativity, these new aether theories have a preferred universal frame of reference, typically a frame co-moving with the cosmic microwave background radiation.
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
answered May 19 at 0:06
David HammenDavid Hammen
34.3k759111
34.3k759111
1
$begingroup$
If such theories cannot be ruled out, then why shouldn't they be amongst the respectable opinions that thinkers and researchers may choose to adopt and work with?
$endgroup$
– Steve
May 19 at 0:40
1
$begingroup$
@Steve “Choose to adopt and work with” is not a binary. People make different choices. Lots of people find GR useful; few find The Flying Spaghetti God hypothesis useful. Other theories are in between in popularity, i.e the MOND family. Nor is this decision time-invariant: theories and hypotheses are more and less popular as people show them more or less useful.
$endgroup$
– Bob Jacobsen
May 19 at 1:32
2
$begingroup$
@BobJacobsen, useful for what purpose? Perhaps when working with aether concepts attracts comparisons to the Flying Spaghetti God, you make it dis-useful for professional scientists to adopt such views and perform such work? And my point is to rebut the tone in which David speaks of apparently tenable theories being "kept alive" - the writer's implication being that these theories ought to be dead. Like I say, if they cannot be ruled out, then they are fair game for further scientific enquiry.
$endgroup$
– Steve
May 19 at 1:53
3
$begingroup$
@Steve, general relativity is a simple theory. Its only arbitrary parameter is Newton's gravitational constant. Other viable theories carry additional arbitrary parameters. In the limit that these parameters approach some value, typically zero, these theories become equivalent to general relativity. To date, all observations are consistent with these free parameters taking on the value that makes the alternative theory equivalent to general relativity.
$endgroup$
– David Hammen
May 19 at 2:51
1
$begingroup$
@DavidHammen, that's basically what I said above in my original comment to Bob's answer, that as it stands today (and as it stood in about 1920) Lorentz's aether theory (in its latter form) is equivalent to relativity - they are not mutually exclusive theories. It is only the general philosophical approach and concepts they employ which differ.
$endgroup$
– Steve
May 19 at 9:13
|
show 7 more comments
1
$begingroup$
If such theories cannot be ruled out, then why shouldn't they be amongst the respectable opinions that thinkers and researchers may choose to adopt and work with?
$endgroup$
– Steve
May 19 at 0:40
1
$begingroup$
@Steve “Choose to adopt and work with” is not a binary. People make different choices. Lots of people find GR useful; few find The Flying Spaghetti God hypothesis useful. Other theories are in between in popularity, i.e the MOND family. Nor is this decision time-invariant: theories and hypotheses are more and less popular as people show them more or less useful.
$endgroup$
– Bob Jacobsen
May 19 at 1:32
2
$begingroup$
@BobJacobsen, useful for what purpose? Perhaps when working with aether concepts attracts comparisons to the Flying Spaghetti God, you make it dis-useful for professional scientists to adopt such views and perform such work? And my point is to rebut the tone in which David speaks of apparently tenable theories being "kept alive" - the writer's implication being that these theories ought to be dead. Like I say, if they cannot be ruled out, then they are fair game for further scientific enquiry.
$endgroup$
– Steve
May 19 at 1:53
3
$begingroup$
@Steve, general relativity is a simple theory. Its only arbitrary parameter is Newton's gravitational constant. Other viable theories carry additional arbitrary parameters. In the limit that these parameters approach some value, typically zero, these theories become equivalent to general relativity. To date, all observations are consistent with these free parameters taking on the value that makes the alternative theory equivalent to general relativity.
$endgroup$
– David Hammen
May 19 at 2:51
1
$begingroup$
@DavidHammen, that's basically what I said above in my original comment to Bob's answer, that as it stands today (and as it stood in about 1920) Lorentz's aether theory (in its latter form) is equivalent to relativity - they are not mutually exclusive theories. It is only the general philosophical approach and concepts they employ which differ.
$endgroup$
– Steve
May 19 at 9:13
1
1
$begingroup$
If such theories cannot be ruled out, then why shouldn't they be amongst the respectable opinions that thinkers and researchers may choose to adopt and work with?
$endgroup$
– Steve
May 19 at 0:40
$begingroup$
If such theories cannot be ruled out, then why shouldn't they be amongst the respectable opinions that thinkers and researchers may choose to adopt and work with?
$endgroup$
– Steve
May 19 at 0:40
1
1
$begingroup$
@Steve “Choose to adopt and work with” is not a binary. People make different choices. Lots of people find GR useful; few find The Flying Spaghetti God hypothesis useful. Other theories are in between in popularity, i.e the MOND family. Nor is this decision time-invariant: theories and hypotheses are more and less popular as people show them more or less useful.
$endgroup$
– Bob Jacobsen
May 19 at 1:32
$begingroup$
@Steve “Choose to adopt and work with” is not a binary. People make different choices. Lots of people find GR useful; few find The Flying Spaghetti God hypothesis useful. Other theories are in between in popularity, i.e the MOND family. Nor is this decision time-invariant: theories and hypotheses are more and less popular as people show them more or less useful.
$endgroup$
– Bob Jacobsen
May 19 at 1:32
2
2
$begingroup$
@BobJacobsen, useful for what purpose? Perhaps when working with aether concepts attracts comparisons to the Flying Spaghetti God, you make it dis-useful for professional scientists to adopt such views and perform such work? And my point is to rebut the tone in which David speaks of apparently tenable theories being "kept alive" - the writer's implication being that these theories ought to be dead. Like I say, if they cannot be ruled out, then they are fair game for further scientific enquiry.
$endgroup$
– Steve
May 19 at 1:53
$begingroup$
@BobJacobsen, useful for what purpose? Perhaps when working with aether concepts attracts comparisons to the Flying Spaghetti God, you make it dis-useful for professional scientists to adopt such views and perform such work? And my point is to rebut the tone in which David speaks of apparently tenable theories being "kept alive" - the writer's implication being that these theories ought to be dead. Like I say, if they cannot be ruled out, then they are fair game for further scientific enquiry.
$endgroup$
– Steve
May 19 at 1:53
3
3
$begingroup$
@Steve, general relativity is a simple theory. Its only arbitrary parameter is Newton's gravitational constant. Other viable theories carry additional arbitrary parameters. In the limit that these parameters approach some value, typically zero, these theories become equivalent to general relativity. To date, all observations are consistent with these free parameters taking on the value that makes the alternative theory equivalent to general relativity.
$endgroup$
– David Hammen
May 19 at 2:51
$begingroup$
@Steve, general relativity is a simple theory. Its only arbitrary parameter is Newton's gravitational constant. Other viable theories carry additional arbitrary parameters. In the limit that these parameters approach some value, typically zero, these theories become equivalent to general relativity. To date, all observations are consistent with these free parameters taking on the value that makes the alternative theory equivalent to general relativity.
$endgroup$
– David Hammen
May 19 at 2:51
1
1
$begingroup$
@DavidHammen, that's basically what I said above in my original comment to Bob's answer, that as it stands today (and as it stood in about 1920) Lorentz's aether theory (in its latter form) is equivalent to relativity - they are not mutually exclusive theories. It is only the general philosophical approach and concepts they employ which differ.
$endgroup$
– Steve
May 19 at 9:13
$begingroup$
@DavidHammen, that's basically what I said above in my original comment to Bob's answer, that as it stands today (and as it stood in about 1920) Lorentz's aether theory (in its latter form) is equivalent to relativity - they are not mutually exclusive theories. It is only the general philosophical approach and concepts they employ which differ.
$endgroup$
– Steve
May 19 at 9:13
|
show 7 more comments
$begingroup$
The $x$ direction is not any different physically than the $-x$ direction. So light travelling towards $x-> infty$ should travel in the same way it travels towards $x-> -infty$ wether theres an aether or not.
What should make a difference is if we measure the speed of light in the direction the body that emitted the light is moving through the aether and any other direction, for example, the direction perpendicular to this movement to see the difference a bit easier. However no difference in arrival times was measured.
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
$endgroup$
add a comment |
$begingroup$
The $x$ direction is not any different physically than the $-x$ direction. So light travelling towards $x-> infty$ should travel in the same way it travels towards $x-> -infty$ wether theres an aether or not.
What should make a difference is if we measure the speed of light in the direction the body that emitted the light is moving through the aether and any other direction, for example, the direction perpendicular to this movement to see the difference a bit easier. However no difference in arrival times was measured.
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
$endgroup$
add a comment |
$begingroup$
The $x$ direction is not any different physically than the $-x$ direction. So light travelling towards $x-> infty$ should travel in the same way it travels towards $x-> -infty$ wether theres an aether or not.
What should make a difference is if we measure the speed of light in the direction the body that emitted the light is moving through the aether and any other direction, for example, the direction perpendicular to this movement to see the difference a bit easier. However no difference in arrival times was measured.
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
$endgroup$
The $x$ direction is not any different physically than the $-x$ direction. So light travelling towards $x-> infty$ should travel in the same way it travels towards $x-> -infty$ wether theres an aether or not.
What should make a difference is if we measure the speed of light in the direction the body that emitted the light is moving through the aether and any other direction, for example, the direction perpendicular to this movement to see the difference a bit easier. However no difference in arrival times was measured.
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
answered May 18 at 23:06
Juan Pablo ArcilaJuan Pablo Arcila
868
868
add a comment |
add a comment |
$begingroup$
Round - trip measurement of speed of light says nothing about the one - way speed of light. Effects of Lorentz contraction of moving bodies (MM experiment) and dilation of moving clock (Kennedy Thorndike experiment) had been first introduced in the framework of Lorentz aether theory.
Since the same mathematical formalism occurs in both, it is not possible to distinguish between Lorentz aether theory and special relativity by experiment.
The one-way speed of light is apparently anisotropic, the Sagnac effect (page 42 in this paper) is the best evidence of that.
Remember, that in rotating frames, even in special relativity, the non-transitivity of Einstein synchronization diminishes its usefulness. If clock 1 and clock 2 are not synchronized directly, but by using a chain of intermediate clocks, the synchronization depends on the path chosen. Synchronization around the circumference of a rotating disk gives a non-vanishing time difference that depends on the direction used.
Hence, the one – way speed of light relatively to the Earth surface is anisotropic, and it is very unlikely that one way speed of light is c an all relatively moving inertial frames.
On the simplest example of the floating in a water ships this paper simulates all kinematic effects of special relativity (length contraction, time dilation, relativistic velocity addition, relativistic and transverse Doppler effects, Twin paradox, Bell‘s spaceship paradox, symmetry of observations). Things that may seem quirky and unusual take very simple shape, as soon as "absolute" time and medium had been introduced.
The chapter Transverse Doppler Effect makes clear, that „conditionally moving“ clock ticks slower (transverse redshift) than „conditionally resting“ one , while „conditionally resting“ tick faster (transverse blueshift) than the "moving one". It is clear, that different synchronization procedures (standard isotropic for "stationary") frame and (non-standard anisotropic for "moving" frame) is needed to obtain the same result conducting measurements with the pair of synchronized clocks.
The article on special relativity in Wikipedia teaches, that: "The Principle of Invariant Light Speed – "... light is always propagated in empty space with a definite velocity [speed] c which is independent of the state of motion of the emitting body" (from the preface).[p 1] That is, light in vacuum propagates with the speed c (a fixed constant, independent of direction) in at least one system of inertial coordinates (the "stationary system"), regardless of the state of motion of the light source."
Apparently, according to the article, there is at least one "special stationary frame" where speed of light is isotropic and some others, where the speed of light is anisotropic.
answered May 19 at 9:44
AlbertAlbert
952310
$endgroup$
2
$begingroup$
The Sagnac effect is most emphatically not evidence for light speed anisotropy. The Sagnac effect is predicted by special relativity which assumes isotropy. To claim that it demonstrates anisotropy is only evidence that you do not know your facts enough to produce a credible answer! -1
$endgroup$
– Dale
May 19 at 10:49
1
$begingroup$
Especially for YOU I have posted the links to the Sagnac effect explanation in Gron's paper (it is written black on white there, that in rotating frame speed of light is anisotropic ) and the link to Einstein synchronization in Wikipedia. Could you please be so kind to clean your glasses and read it again? Or maybe you think that the Earth does not rotate? These views are out to date, I am afraid to say.
$endgroup$
– Albert
May 19 at 11:00
1
$begingroup$
That the speed of light is anisotropic in a rotating reference frame does not imply that it is evidence for light speed anisotropy. For something to be evidence of a hypothesis it must not only be predicted by a hypothesis but also it must be not predicted by the alternative hypothesis. The Sagnac effect is equally predicted both a non-isotropic and an isotropic hypothesis. Therefore it is not evidence of either
$endgroup$
– Dale
May 19 at 11:10
1
$begingroup$
Another minus one. The Sagnac effect is not evidence that the one-way speed of light is anisotropic in inertial frames. It is evidence that the one-way speed of light is anisotropic in rotating frames, which of course are not inertial. The Sagnac effect is fully consistent with special relativity. If this observed fact was inconsistent with special relativity, we wouldn't be teaching special relativity any more. It would instead be yet another idea tossed on the "oops, that turned out to be wrong and useless" pile of failed theories, just like the many failed theories of heat.
$endgroup$
– David Hammen
May 19 at 15:24
1
$begingroup$
@Dale, agreed, excuse me on that point. I think when I wrote I attributed Albert's apparent mis-paraphrasing of you, to your own actual words. As long as we are all now agreed that there is no conclusive evidence either way, and the one-way speed may or may not be constant, then that is the state of current science on the question. Special relativity is a theory that treats the one-way speed as constant (without establishing the fact by any experiment), other theories are tenable which do not treat the one-way speed as constant.
$endgroup$
– Steve
May 19 at 19:22
|
show 13 more comments
$begingroup$
Round - trip measurement of speed of light says nothing about the one - way speed of light. Effects of Lorentz contraction of moving bodies (MM experiment) and dilation of moving clock (Kennedy Thorndike experiment) had been first introduced in the framework of Lorentz aether theory.
Since the same mathematical formalism occurs in both, it is not possible to distinguish between Lorentz aether theory and special relativity by experiment.
The one-way speed of light is apparently anisotropic, the Sagnac effect (page 42 in this paper) is the best evidence of that.
Remember, that in rotating frames, even in special relativity, the non-transitivity of Einstein synchronization diminishes its usefulness. If clock 1 and clock 2 are not synchronized directly, but by using a chain of intermediate clocks, the synchronization depends on the path chosen. Synchronization around the circumference of a rotating disk gives a non-vanishing time difference that depends on the direction used.
Hence, the one – way speed of light relatively to the Earth surface is anisotropic, and it is very unlikely that one way speed of light is c an all relatively moving inertial frames.
On the simplest example of the floating in a water ships this paper simulates all kinematic effects of special relativity (length contraction, time dilation, relativistic velocity addition, relativistic and transverse Doppler effects, Twin paradox, Bell‘s spaceship paradox, symmetry of observations). Things that may seem quirky and unusual take very simple shape, as soon as "absolute" time and medium had been introduced.
The chapter Transverse Doppler Effect makes clear, that „conditionally moving“ clock ticks slower (transverse redshift) than „conditionally resting“ one , while „conditionally resting“ tick faster (transverse blueshift) than the "moving one". It is clear, that different synchronization procedures (standard isotropic for "stationary") frame and (non-standard anisotropic for "moving" frame) is needed to obtain the same result conducting measurements with the pair of synchronized clocks.
The article on special relativity in Wikipedia teaches, that: "The Principle of Invariant Light Speed – "... light is always propagated in empty space with a definite velocity [speed] c which is independent of the state of motion of the emitting body" (from the preface).[p 1] That is, light in vacuum propagates with the speed c (a fixed constant, independent of direction) in at least one system of inertial coordinates (the "stationary system"), regardless of the state of motion of the light source."
Apparently, according to the article, there is at least one "special stationary frame" where speed of light is isotropic and some others, where the speed of light is anisotropic.
answered May 19 at 9:44
AlbertAlbert
952310
$endgroup$
2
$begingroup$
The Sagnac effect is most emphatically not evidence for light speed anisotropy. The Sagnac effect is predicted by special relativity which assumes isotropy. To claim that it demonstrates anisotropy is only evidence that you do not know your facts enough to produce a credible answer! -1
$endgroup$
– Dale
May 19 at 10:49
1
$begingroup$
Especially for YOU I have posted the links to the Sagnac effect explanation in Gron's paper (it is written black on white there, that in rotating frame speed of light is anisotropic ) and the link to Einstein synchronization in Wikipedia. Could you please be so kind to clean your glasses and read it again? Or maybe you think that the Earth does not rotate? These views are out to date, I am afraid to say.
$endgroup$
– Albert
May 19 at 11:00
1
$begingroup$
That the speed of light is anisotropic in a rotating reference frame does not imply that it is evidence for light speed anisotropy. For something to be evidence of a hypothesis it must not only be predicted by a hypothesis but also it must be not predicted by the alternative hypothesis. The Sagnac effect is equally predicted both a non-isotropic and an isotropic hypothesis. Therefore it is not evidence of either
$endgroup$
– Dale
May 19 at 11:10
1
$begingroup$
Another minus one. The Sagnac effect is not evidence that the one-way speed of light is anisotropic in inertial frames. It is evidence that the one-way speed of light is anisotropic in rotating frames, which of course are not inertial. The Sagnac effect is fully consistent with special relativity. If this observed fact was inconsistent with special relativity, we wouldn't be teaching special relativity any more. It would instead be yet another idea tossed on the "oops, that turned out to be wrong and useless" pile of failed theories, just like the many failed theories of heat.
$endgroup$
– David Hammen
May 19 at 15:24
1
$begingroup$
@Dale, agreed, excuse me on that point. I think when I wrote I attributed Albert's apparent mis-paraphrasing of you, to your own actual words. As long as we are all now agreed that there is no conclusive evidence either way, and the one-way speed may or may not be constant, then that is the state of current science on the question. Special relativity is a theory that treats the one-way speed as constant (without establishing the fact by any experiment), other theories are tenable which do not treat the one-way speed as constant.
$endgroup$
– Steve
May 19 at 19:22
|
show 13 more comments
$begingroup$
Round - trip measurement of speed of light says nothing about the one - way speed of light. Effects of Lorentz contraction of moving bodies (MM experiment) and dilation of moving clock (Kennedy Thorndike experiment) had been first introduced in the framework of Lorentz aether theory.
Since the same mathematical formalism occurs in both, it is not possible to distinguish between Lorentz aether theory and special relativity by experiment.
The one-way speed of light is apparently anisotropic, the Sagnac effect (page 42 in this paper) is the best evidence of that.
Remember, that in rotating frames, even in special relativity, the non-transitivity of Einstein synchronization diminishes its usefulness. If clock 1 and clock 2 are not synchronized directly, but by using a chain of intermediate clocks, the synchronization depends on the path chosen. Synchronization around the circumference of a rotating disk gives a non-vanishing time difference that depends on the direction used.
Hence, the one – way speed of light relatively to the Earth surface is anisotropic, and it is very unlikely that one way speed of light is c an all relatively moving inertial frames.
On the simplest example of the floating in a water ships this paper simulates all kinematic effects of special relativity (length contraction, time dilation, relativistic velocity addition, relativistic and transverse Doppler effects, Twin paradox, Bell‘s spaceship paradox, symmetry of observations). Things that may seem quirky and unusual take very simple shape, as soon as "absolute" time and medium had been introduced.
The chapter Transverse Doppler Effect makes clear, that „conditionally moving“ clock ticks slower (transverse redshift) than „conditionally resting“ one , while „conditionally resting“ tick faster (transverse blueshift) than the "moving one". It is clear, that different synchronization procedures (standard isotropic for "stationary") frame and (non-standard anisotropic for "moving" frame) is needed to obtain the same result conducting measurements with the pair of synchronized clocks.
The article on special relativity in Wikipedia teaches, that: "The Principle of Invariant Light Speed – "... light is always propagated in empty space with a definite velocity [speed] c which is independent of the state of motion of the emitting body" (from the preface).[p 1] That is, light in vacuum propagates with the speed c (a fixed constant, independent of direction) in at least one system of inertial coordinates (the "stationary system"), regardless of the state of motion of the light source."
Apparently, according to the article, there is at least one "special stationary frame" where speed of light is isotropic and some others, where the speed of light is anisotropic.
answered May 19 at 9:44
AlbertAlbert
952310
$endgroup$
Round - trip measurement of speed of light says nothing about the one - way speed of light. Effects of Lorentz contraction of moving bodies (MM experiment) and dilation of moving clock (Kennedy Thorndike experiment) had been first introduced in the framework of Lorentz aether theory.
Since the same mathematical formalism occurs in both, it is not possible to distinguish between Lorentz aether theory and special relativity by experiment.
The one-way speed of light is apparently anisotropic, the Sagnac effect (page 42 in this paper) is the best evidence of that.
Remember, that in rotating frames, even in special relativity, the non-transitivity of Einstein synchronization diminishes its usefulness. If clock 1 and clock 2 are not synchronized directly, but by using a chain of intermediate clocks, the synchronization depends on the path chosen. Synchronization around the circumference of a rotating disk gives a non-vanishing time difference that depends on the direction used.
Hence, the one – way speed of light relatively to the Earth surface is anisotropic, and it is very unlikely that one way speed of light is c an all relatively moving inertial frames.
On the simplest example of the floating in a water ships this paper simulates all kinematic effects of special relativity (length contraction, time dilation, relativistic velocity addition, relativistic and transverse Doppler effects, Twin paradox, Bell‘s spaceship paradox, symmetry of observations). Things that may seem quirky and unusual take very simple shape, as soon as "absolute" time and medium had been introduced.
The chapter Transverse Doppler Effect makes clear, that „conditionally moving“ clock ticks slower (transverse redshift) than „conditionally resting“ one , while „conditionally resting“ tick faster (transverse blueshift) than the "moving one". It is clear, that different synchronization procedures (standard isotropic for "stationary") frame and (non-standard anisotropic for "moving" frame) is needed to obtain the same result conducting measurements with the pair of synchronized clocks.
The article on special relativity in Wikipedia teaches, that: "The Principle of Invariant Light Speed – "... light is always propagated in empty space with a definite velocity [speed] c which is independent of the state of motion of the emitting body" (from the preface).[p 1] That is, light in vacuum propagates with the speed c (a fixed constant, independent of direction) in at least one system of inertial coordinates (the "stationary system"), regardless of the state of motion of the light source."
Apparently, according to the article, there is at least one "special stationary frame" where speed of light is isotropic and some others, where the speed of light is anisotropic.
answered May 19 at 9:44
AlbertAlbert
952310
edited May 19 at 19:17
answered May 19 at 9:44
AlbertAlbert
952310
answered May 19 at 9:44
AlbertAlbert
952310
answered May 19 at 9:44
AlbertAlbert
952310
952310
2
$begingroup$
The Sagnac effect is most emphatically not evidence for light speed anisotropy. The Sagnac effect is predicted by special relativity which assumes isotropy. To claim that it demonstrates anisotropy is only evidence that you do not know your facts enough to produce a credible answer! -1
$endgroup$
– Dale
May 19 at 10:49
1
$begingroup$
Especially for YOU I have posted the links to the Sagnac effect explanation in Gron's paper (it is written black on white there, that in rotating frame speed of light is anisotropic ) and the link to Einstein synchronization in Wikipedia. Could you please be so kind to clean your glasses and read it again? Or maybe you think that the Earth does not rotate? These views are out to date, I am afraid to say.
$endgroup$
– Albert
May 19 at 11:00
1
$begingroup$
That the speed of light is anisotropic in a rotating reference frame does not imply that it is evidence for light speed anisotropy. For something to be evidence of a hypothesis it must not only be predicted by a hypothesis but also it must be not predicted by the alternative hypothesis. The Sagnac effect is equally predicted both a non-isotropic and an isotropic hypothesis. Therefore it is not evidence of either
$endgroup$
– Dale
May 19 at 11:10
1
$begingroup$
Another minus one. The Sagnac effect is not evidence that the one-way speed of light is anisotropic in inertial frames. It is evidence that the one-way speed of light is anisotropic in rotating frames, which of course are not inertial. The Sagnac effect is fully consistent with special relativity. If this observed fact was inconsistent with special relativity, we wouldn't be teaching special relativity any more. It would instead be yet another idea tossed on the "oops, that turned out to be wrong and useless" pile of failed theories, just like the many failed theories of heat.
$endgroup$
– David Hammen
May 19 at 15:24
1
$begingroup$
@Dale, agreed, excuse me on that point. I think when I wrote I attributed Albert's apparent mis-paraphrasing of you, to your own actual words. As long as we are all now agreed that there is no conclusive evidence either way, and the one-way speed may or may not be constant, then that is the state of current science on the question. Special relativity is a theory that treats the one-way speed as constant (without establishing the fact by any experiment), other theories are tenable which do not treat the one-way speed as constant.
$endgroup$
– Steve
May 19 at 19:22
|
show 13 more comments
2
$begingroup$
The Sagnac effect is most emphatically not evidence for light speed anisotropy. The Sagnac effect is predicted by special relativity which assumes isotropy. To claim that it demonstrates anisotropy is only evidence that you do not know your facts enough to produce a credible answer! -1
$endgroup$
– Dale
May 19 at 10:49
1
$begingroup$
Especially for YOU I have posted the links to the Sagnac effect explanation in Gron's paper (it is written black on white there, that in rotating frame speed of light is anisotropic ) and the link to Einstein synchronization in Wikipedia. Could you please be so kind to clean your glasses and read it again? Or maybe you think that the Earth does not rotate? These views are out to date, I am afraid to say.
$endgroup$
– Albert
May 19 at 11:00
1
$begingroup$
That the speed of light is anisotropic in a rotating reference frame does not imply that it is evidence for light speed anisotropy. For something to be evidence of a hypothesis it must not only be predicted by a hypothesis but also it must be not predicted by the alternative hypothesis. The Sagnac effect is equally predicted both a non-isotropic and an isotropic hypothesis. Therefore it is not evidence of either
$endgroup$
– Dale
May 19 at 11:10
1
$begingroup$
Another minus one. The Sagnac effect is not evidence that the one-way speed of light is anisotropic in inertial frames. It is evidence that the one-way speed of light is anisotropic in rotating frames, which of course are not inertial. The Sagnac effect is fully consistent with special relativity. If this observed fact was inconsistent with special relativity, we wouldn't be teaching special relativity any more. It would instead be yet another idea tossed on the "oops, that turned out to be wrong and useless" pile of failed theories, just like the many failed theories of heat.
$endgroup$
– David Hammen
May 19 at 15:24
1
$begingroup$
@Dale, agreed, excuse me on that point. I think when I wrote I attributed Albert's apparent mis-paraphrasing of you, to your own actual words. As long as we are all now agreed that there is no conclusive evidence either way, and the one-way speed may or may not be constant, then that is the state of current science on the question. Special relativity is a theory that treats the one-way speed as constant (without establishing the fact by any experiment), other theories are tenable which do not treat the one-way speed as constant.
$endgroup$
– Steve
May 19 at 19:22
2
2
$begingroup$
The Sagnac effect is most emphatically not evidence for light speed anisotropy. The Sagnac effect is predicted by special relativity which assumes isotropy. To claim that it demonstrates anisotropy is only evidence that you do not know your facts enough to produce a credible answer! -1
$endgroup$
– Dale
May 19 at 10:49
$begingroup$
The Sagnac effect is most emphatically not evidence for light speed anisotropy. The Sagnac effect is predicted by special relativity which assumes isotropy. To claim that it demonstrates anisotropy is only evidence that you do not know your facts enough to produce a credible answer! -1
$endgroup$
– Dale
May 19 at 10:49
1
1
$begingroup$
Especially for YOU I have posted the links to the Sagnac effect explanation in Gron's paper (it is written black on white there, that in rotating frame speed of light is anisotropic ) and the link to Einstein synchronization in Wikipedia. Could you please be so kind to clean your glasses and read it again? Or maybe you think that the Earth does not rotate? These views are out to date, I am afraid to say.
$endgroup$
– Albert
May 19 at 11:00
$begingroup$
Especially for YOU I have posted the links to the Sagnac effect explanation in Gron's paper (it is written black on white there, that in rotating frame speed of light is anisotropic ) and the link to Einstein synchronization in Wikipedia. Could you please be so kind to clean your glasses and read it again? Or maybe you think that the Earth does not rotate? These views are out to date, I am afraid to say.
$endgroup$
– Albert
May 19 at 11:00
1
1
$begingroup$
That the speed of light is anisotropic in a rotating reference frame does not imply that it is evidence for light speed anisotropy. For something to be evidence of a hypothesis it must not only be predicted by a hypothesis but also it must be not predicted by the alternative hypothesis. The Sagnac effect is equally predicted both a non-isotropic and an isotropic hypothesis. Therefore it is not evidence of either
$endgroup$
– Dale
May 19 at 11:10
$begingroup$
That the speed of light is anisotropic in a rotating reference frame does not imply that it is evidence for light speed anisotropy. For something to be evidence of a hypothesis it must not only be predicted by a hypothesis but also it must be not predicted by the alternative hypothesis. The Sagnac effect is equally predicted both a non-isotropic and an isotropic hypothesis. Therefore it is not evidence of either
$endgroup$
– Dale
May 19 at 11:10
1
1
$begingroup$
Another minus one. The Sagnac effect is not evidence that the one-way speed of light is anisotropic in inertial frames. It is evidence that the one-way speed of light is anisotropic in rotating frames, which of course are not inertial. The Sagnac effect is fully consistent with special relativity. If this observed fact was inconsistent with special relativity, we wouldn't be teaching special relativity any more. It would instead be yet another idea tossed on the "oops, that turned out to be wrong and useless" pile of failed theories, just like the many failed theories of heat.
$endgroup$
– David Hammen
May 19 at 15:24
$begingroup$
Another minus one. The Sagnac effect is not evidence that the one-way speed of light is anisotropic in inertial frames. It is evidence that the one-way speed of light is anisotropic in rotating frames, which of course are not inertial. The Sagnac effect is fully consistent with special relativity. If this observed fact was inconsistent with special relativity, we wouldn't be teaching special relativity any more. It would instead be yet another idea tossed on the "oops, that turned out to be wrong and useless" pile of failed theories, just like the many failed theories of heat.
$endgroup$
– David Hammen
May 19 at 15:24
1
1
$begingroup$
@Dale, agreed, excuse me on that point. I think when I wrote I attributed Albert's apparent mis-paraphrasing of you, to your own actual words. As long as we are all now agreed that there is no conclusive evidence either way, and the one-way speed may or may not be constant, then that is the state of current science on the question. Special relativity is a theory that treats the one-way speed as constant (without establishing the fact by any experiment), other theories are tenable which do not treat the one-way speed as constant.
$endgroup$
– Steve
May 19 at 19:22
$begingroup$
@Dale, agreed, excuse me on that point. I think when I wrote I attributed Albert's apparent mis-paraphrasing of you, to your own actual words. As long as we are all now agreed that there is no conclusive evidence either way, and the one-way speed may or may not be constant, then that is the state of current science on the question. Special relativity is a theory that treats the one-way speed as constant (without establishing the fact by any experiment), other theories are tenable which do not treat the one-way speed as constant.
$endgroup$
– Steve
May 19 at 19:22
|
show 13 more comments
Thanks for contributing an answer to Physics Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f480938%2fdoes-the-fact-that-we-can-only-measure-the-two-way-speed-of-light-undermine-the%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
2
$begingroup$
Hi @Andrew, you said “Wouldn't we expect this result through an aether?”. Actually, no, if you work out the math the two way speed of light is not isotropic in a standard aether theory.
$endgroup$
– Dale
May 19 at 2:49
$begingroup$
Why do you think we can only measure "there and back"? For instance, one of the first measurements of the speed of light was made by noting variations in the timing of eclipses of Jupiter's moons, which would seem to involve measuring only the "back" reflection of the sun's light: google.com/…
$endgroup$
– jamesqf
May 19 at 5:58
$begingroup$
@jamesqf Wikipedia says that although Rømer's measurement of Jupiter's moons seems to give a one-way speed, careful analysis shows that those calculations assume that the travel speed is isotropic. However, I must confess I don't fully understand the arguments given on that page.
$endgroup$
– PM 2Ring
May 19 at 10:03
2
$begingroup$
Careful analysis shows that Rømer's measurement says nothing about the one-way speed of light. physics.stackexchange.com/questions/456243/…
$endgroup$
– Albert
May 19 at 10:43