The whole thought- versus real-experiment distinction is a red herring; I don't know why Tach brought it up. The only reason RoS can't be tested is that the correctness of Einstein clock synchronization cannot be verified. No matter how you frame an experiment (and Einstein's thought experiments are no exception), at some point you have to talk about an observer seeing two spacelike-separated events as simultaneous. And there is no way to say for sure that two events are simultaneous without a system of synchronized clocks that could measure that simultaneity.
Is relativity of simultaneity measurable?
- Thread starter Pete
- Start date
The whole thought- versus real-experiment distinction is a red herring; I don't know why Tach brought it up. The only reason RoS can't be tested is that the correctness of Einstein clock synchronization cannot be verified. No matter how you frame an experiment (and Einstein's thought experiments are no exception), at some point you have to talk about an observer seeing two spacelike-separated events as simultaneous. And there is no way to say for sure that two events are simultaneous without a system of synchronized clocks that could measure that simultaneity.
Neddy Bate
Valued Senior Member
I agree the "thought- versus real-experiment distinction" is a non-argument, but that's all Tach has left. He can't argue "E-Sync is just a convention" while at the same time claiming "OWLS is isotropic," as you well know, and have argued effectively. But he does not seem to understand how those two arguments contradict each other, which is why I asked him about Einstein's thought experiment (which does not rely on E-Synch, but does rely on OWLS isotropy).
Thank-you. As I'm casually lurking I'm confused on how OWLS being isotropic isn't sufficient to E-synch clocks. I also haven't read through all of the links but some I cannot understand how testing for the TWLS in all directions would not be sufficient for proving the isotropy of OWLS.
This is an error that you keep repeating.
Let me try one last time to dispel your errors:
In order to measure OWLS you do not need E-synch, what you need is either:
1. a pair of synchronized clocks (if you keep reading the Stanford page you have been cherry-picking) you will get to the paragraph on "Slow clock transport", physicists have been using this method for quite a while, I pointed this out to you many posts ago
or
2. no clocks at all. Modern measurement of OWLS do not use any clocks, as I explained to you 4 times already. I already gave you two papers as reference, you obviously have not read the references or you stubbornly refuse to accept that they show that you are wrong. Here is one more reference, I suggest that you read it:
Evenson, KM; et al. (1972). "Speed of Light from Direct Frequency and Wavelength Measurements of the Methane-Stabilized Laser". Physical Review Letters 29 (19): 1346–49. Bibcode:1972PhRvL..29.1346E. doi:10.1103/PhysRevLett.29.1346
You clearly do not understand this subject, I recommend that you do some serious reading before you come back, I provided you with a lot of information, try to understand it.
The information that I gave you demonstrates that the experiment cannot be performed as a REAL experiment. This is why no self-respecting experimentalist has ever tried to perform a RoS test. This is also why Ros "tests" are absent from the list of SR tests. So, your question falls in the category: "if my grandmother had wheels would she be a trolleybus?"
OWLS isotropy is tested differently, doesn't require "testing TWLS in all directions". See here.
The problem shared by you (and to a much greater extent by Neddy Bate and Fednis48 ) is that you do not understand the experimental foundations of SR. I provided quite a few references throughout this thread as well as explanations as to how experimental physicists deal with the issue. I will let you guys figure out things all by yourselves.
The basis for this answer comes indirectly from one of Tach's earlier links. I think it was a Wiki reference...
As long as we can only measure the speed of light in the context of a two way light path, one led could be instantaneous and the 1/2 c, and the measured two way speed of light would still be the same as if both legs were c. So a simple measurement of TWLS in all direction still only tells you what the average speed of light was, not that OWLS is equal to TWLS.
Neddy Bate
Valued Senior Member
You're welcome! As you said earlier, E-synch is just a convention based on a conventional definition of simultaneity. As such, E-Synch can be used whether OWLS is isotropic or not. However, if OWLS is "truly" isotropic, then E-Synch goes beyond being just a convention, and tells us "true" simultaneity, (whatever that might mean).
Even if TWLS is shown to be isotropic after testing in many directions, it is still possible that the light was faster on one leg of one of the tests, and slower of the other leg of one of the tests. The faster and slower speeds could sort of cancel out, masking the effect, resulting in isotropic TWLS without isotropic OWLS. I think that is the reasoning, anyway.
OK, I get this, but the details would be fleshed out as we did the experiment in different directions...the math isn't very complicated
Neddy Bate
Valued Senior Member
Why can't Einstein's thought experiment be performed as a real experiment? Start with a long train, traveling along a straight length of track. Instead of hoping for lighting bolts to strike simultaneously in the ground frame, flash two bulbs at the same time. Let one be co-located with the front of the train, and the other be co-located with the rear of the train. The light from those bulbs will take some time to travel to the midpoint of the train, and by that time, the train will have moved such that M' is not longer located in the same place as M. Done.
Neddy Bate
Valued Senior Member
Let's say that the east-to-west light speed is fastest, and the west-to-east speed is slowest. I guess you are saying that the north-to-south speed would not necessarily come out to be the average of the east-to-west and west-to-east speeds? Yes, that makes sense. But if it did come out to be the average, (somehow), then you would find isotropic TWLS without isotropic OWLS.
You just repeated the same error Fednis48 made with his naive "eram experiment". He'll explain it to you
Neddy Bate
Valued Senior Member
You just repeated the same error Fednis48 made with his naive "eram experiment". He'll explain it to you
Umm, yeah, there's nothing wrong with the Eram experiment either. Give it up, Tach. Tell me why I can't flash two bulbs near a moving train, or else admit the experiment can be done.
Only that you'd measure zero Ros. In all frames. Neddy , you are on your way for this year Nobel prize nomination.
OK so according to the link, here's the issue:
I understand the premise but I do not understand how it would be possible, mathematically. BTW...no one here is going to like hearing this but...Motor Daddy's version of reality falls within this "large class of theories".wiki said:
In my naive understandings, anything exhibiting a regular oscillatory or cyclic phenomenon can be considered a "clock" process by which other processes can be "timed" etc. So a laser light having frequency of cycles must be by definition its own "clock" process, yes? So when this "frequency" (inherent clock rate) is used to calculate a wavelength relationship to arrive at a light "speed" value, then the light frequency itself is a clock being used in this calculation? So why do you say "there is no clock used" in this referenced experiment?
Why are you running away and evading, as usual? Playing games again? Answer the post properly or admit you do not understand that a "clock process" of some sort or other are involved either intrinsically or extrinsically in such "speed" timing/calculating experiments whether you realize it or not?
Neddy Bate
Valued Senior Member
Wrong. At the time when I flash the two bulbs simultaneously in the ground frame, the observers M and M' are co-located. By the time the light from the flashes reaches M simultaneously, the train passenger at M' has moved away from M in the same direction that the train is moving. Therefore M' will see the light from the front of the train first, even though M sees both lights at the same time. Hence, RoS.
In the Eram experiment, the light reaches the AND gate simultaneously in all frames, but it could not have been EMITTED simultaneously in all frames, as Fednis showed you mathematically. Hence, RoS.
But what you measure is $$T'_A-T'_B=0$$
Like I said, you have your nomination pretty much locked up.