Why speed of light is measured same regardless of their speed?

[ghwellsjr]

Measuring the speed of light involves physics, so it should be possible to explain the results in terms of physical phenomena. We begin in a fixed frame (of reference), aka the universe. It is motionless (unless someone can find a separate entity to serve as a reference for its motion). The propagation pattern of light is spherical from its origin, with a constant propagation speed of c. A simultaneous 360º multi-photon signal from the center of a circular ring will reflect from the ring and return to the center simultaneously. A clock at the center will record 2t units of time for a path length of 2r units of distance. If the ring moves at constant speed v in the x direction, it causes motion induced phenomena in the form of two complementary effects. The em fields of mass modify themselves from spherical to elliptical with an x radius of r'=r/γ, and the clock at the center runs slower than the static clock with 2t'=2t/γ. Both effects are due to the motion extending the distances for light interactions, and are not detectable by the moving viewer. Since the distance and time units are reduced by the same factor γ, r'/t' = r/t = c. The relations for time t and distance x are the same for all inertial frames because of the scaling by 1/ γ. The γ factor is a consequence of constant light speed, therefore the 1st postulate of SR results from the 2nd.
SR is a theory of measurement and perception. Any viewer of the moving ring will see the reflection events occurring over an interval of space and time. Only the viewer moving with the ring will perceive those events as simultaneous, i.e. as if he is in a rest frame. It’s at this point where Einstein knowing you can’t measure light speed relative to the viewer, DEFINES the time out and back as equal, thus supporting the PERCEPTION of the pseudo rest frame.

Here is an animation depicting your scenario:

https://www.youtube.com/watch?v=dEhvU31YaCw

It is explained in great detail in A graphical explanation of Special Relativity.

I'm not sure I agree with all your statements, such as the "em fields of mass modify themselves from spherical to elliptical" because as you can see from the animation, the fields are always spherical in an inertial frame. You also have to be careful about saying "the distance and time units are reduced by the same factor γ" because the time units are increased (dilated) while the distance units are decreased (contracted). It's the Relativity of Simultaneity that "brings" them together so that they "cancel" each other out. Remember, there is no Length Contraction along the directions perpendicular to the motion and yet the Time Dilation still applies. I think the animation makes it very clear.

 

[phyti]

ghwellsjr

I'm not sure I agree with all your statements, such as the "em fields of mass modify themselves from spherical to elliptical" because as you can see from the animation, the fields are always spherical in an inertial frame. You also have to be careful about saying "the distance and time units are reduced by the same factor γ" because the time units are increased (dilated) while the distance units are decreased (contracted). It's the Relativity of Simultaneity that "brings" them together so that the "cancel" each other out. Remember, there is no Length Contraction along the directions perpendicular to the motion and yet the Time Dilation still applies. I think the animation makes it very clear.

The em fields are the electron clouds surrounding nuclei. Light still propagates in circles. I did say the effects are not detectable by the viewer, thus he interprets the longer time unit as normal, i.e. he slows along with his clock. He thinks/preceives events to be earlier and closer than the static frame.

View attachment reflecting circle.doc

 

[ghwellsjr]

ghwellsjr

The em fields are the electron clouds surrounding nuclei. Light still propagates in circles. I did say the effects are not detectable by the viewer, thus he interprets the longer time unit as normal, i.e. he slows along with his clock. He thinks/preceives events to be earlier and closer than the static frame.

View attachment 58239

Your document and added explanation help, thanks.

 

[Nugatory]

The em fields are the electron clouds surrounding nuclei.

Electron clouds are not em fields, they're a (rather dubious, outside of the pop-sci press) description of the source of these fields. Introducing them into the discussion just obscures the relativistic description, which involves the propagation of em radiation, not its generation.

 

[ghwellsjr]

The 499 seconds would represent the time for light to travel from Sun to Earth... but only if you assume that the speed of light from the Sun to the observer is the same as the speed from the Earth to the observer.

yup. of course it does. same assumption one makes when applying the round-trip two-way SOL measurement to a universal SOL. the assumption is there is nothing different about the vacuum of space between the source and the observer and the vacuum of space of between the reflector and the observer. and (somehow) we make sure that the distances are the same.

When considering the observer at the midpoint between the Sun and the Earth, we all agree that the propagation of the light is divided into three segments:

1) From the Sun to the observer.
2) From the observer to the Earth.
3) From the Earth to the observer.

The observer measures the sum of 2 and 3. The observer assumes that 1 and 3 are the same. The observer then concludes that the sum of 2 and 3 is the same as the sum of 2 and 1. So the observer measures the round-trip time for the light to go from him to the Earth and back and calls it the time for the light to go from the Sun to the Earth, which is what I said in post #32:

You are just measuring the round-trip time it takes for light to travel from the midpoint to the Earth and back and calling it the one-way time it takes for light to travel from the Sun to the Earth. Isn't that obvious?

I want to say something about your further comments in the above quote regarding the assumption that "there is nothing different about the vacuum of space between" segment 1 and segment 3. If you had said segment 1 and segment 2, I would agree but the issue is whether segment 3 is the same as either segment 1 or segment 2 and if we ask the question about whether there is any difference between segment 2 and 3 then we don't have to "make sure that the distances are the same" because there is only one distance.

Now we get down to the crux of the issue: are the light travel times for segment 2 and 3 equal? Einstein says that we have no way of knowing unless we define them to be equal and that is what his second postulate does and that is the point I was making in post #22.

Now to continue:

Unfortunately, the experiment you described does not suffice to establish that those speeds are the same. So you cannot claim (based on that setup) that the 499 seconds represents the time for light to travel from Sun to Earth.

first of all, i was not really describing an experiment. i was simply refuting want ghwells said, specifically regarding a stopwatch.

Here's what I said in post #22 regarding a stopwatch:

As I just pointed out in a previous post, you cannot measure the one-way speed of light. In Special Relativity, we define it to be c. So even if the pilot were stationary at the Sun, he still cannot measure how long it takes for light to get to the Earth. In the same way, we cannot measure how long it takes for the light to get from the Sun to the Earth. There is no possible measurement that allows us to start a stopwatch when some light leaves the Sun and stop it when the light arrives at Earth and yields a measurement of 8 minutes and 19 seconds.

In the situation where the observer is at the midpoint between the Sun and the Earth, we all agree that the observer does not start the stopwatch when the light leaves the Sun nor does he stop it when the light arrives at Earth. Instead, he starts it some unknown and unmeasured delayed time after the light leaves the Sun and he stops it some unknown and unmeasured delayed time after the light leaves the Earth.

In your scenario, these two unknown and unmeasured delayed times are even larger but still he does not start the stopwatch when the light leaves the Sun nor does he stop the stopwatch when the light arrives at Earth. So how are you "simply refuting want ghwells said, specifically regarding a stopwatch"?

Please keep in mind that I never said, nor did I ever imply, that the measurement that the observer makes at the midpoint or any other position equidistant from the Sun and the Earth will be anything other than 499 seconds, only that it is not a measurement of the time that it takes for the light to go from the Sun to the Earth. Rather, in Special Relativity, we define that time to be equal to that measurement.

 

[ghwellsjr]

you know, Michaelson-Morley could not claim the absence of aether based on the negative result of the experiment. perhaps the aether moves around with the Earth as the Earth revolves around the sun, that would account for the negative result.

You're right and that's exactly a possibly that they did consider and they proposed repeating the experiment at the top of a mountain where the presumed drag of the aether by the Earth might be reduced. You can read about it at the beginning of the Supplement to their paper, On the Relative Motion of the Earth and the Luminiferous Ether:

It is obvious from what has gone before that it would be hopeless to attempt to solve the question of the motion of the solar system by observations of optical phenomena at the surface of the earth. But it is not impossible that at even moderate distances above the level of the sea, at the top of an isolated mountain peak, for instance, the relative motion might be perceptible in an apparatus like that used in these experiments. Perhaps if the experiment should ever be tried in these circumstances, the cover should be of glass, or should be removed.

but it's an unreasonable assumption. so maybe M-M didn't prove anything. maybe, for the flat-earthers, the aether still is out there, and it moves around with the experimental platform which is why we just cannot measure our motion through it.

Of course they proved something, at least they provided evidence of something, which is you can't measure an aether wind. Lorentz, et al, provided an explanation of why they couldn't measure an aether wind even if there were an absolute stationary aether that the Earth was moving through (and not dragging with it).

when making the round-trip two-way SOL measurement it may seem reasonable that the time of travel is longer in one direction than the other because we might be moving through the aether in nearlythe same direction (maybe another reason why M-M set up a perpendicular path).

No, that's not any reason why they set up a perpendicular path. They rotated the experiment so a few seconds later each path covers the same direction as a perpendicular path would. The reason they set up a perpendicular path is because two parallel paths would both be measuring the same round-trip time. Read the link I provided in post #91 for the reason why they set up perpendicular paths.

however, for the case i outline, as the paths to the observer get longer and longer (yet somehow we guarantee they remain equal in length) the assumption of a difference in speed along those paths gets less and less reasonable because the two directions are virtually the same. and (if you could pull it off, and i never said how one could set that up) it would measure precisely what ghw says cannot be measured with a stopwatch.

After what Samshorn has said in post #89, do you withdraw this claim? If not, you need to rebut his argument.

 

[phyti]

Electron clouds are not em fields, they're a (rather dubious, outside of the pop-sci press) description of the source of these fields. Introducing them into the discussion just obscures the relativistic description, which involves the propagation of em radiation, not its generation.

We are considering the EM exchange between electrons, responsible for their separation. Motion extends distances for light/photon interactions, which alters field strength. EM fields are deformable and will adjust, which provides a process for length contraction, other than magic.