Talk:One-way speed of light

Thought Experiment - Measuring the one-way speed of light.
Here's a published paper describing a number of thought experiments that lead to a method for synchronizing clocks, and a method for measuring the one-way speed of light.

https://doi.org/10.5539/apr.v10n6p45 Kenneth William Davies (talk) 00:03, 9 July 2022 (UTC)

The length of a meter can be compared experimentally against some other standard of length. Some as in...?
> Since 1983 the metre has been defined as the distance traveled by light in vacuum in 1⁄299,792,458 second. This means that the speed of light can no longer be experimentally measured in SI units, but the length of a meter can be compared experimentally against some other standard of length.

The problem with this sentence is: there are apparently no other actual standards of lenght any more. Around 1955 the USA and UK officially declared the feet to be 0.3048... meter longs, leaving the "heavy lifting" in metrology to the french and their SI conferences. At best, the speed of light could be experimentally compared to the 1970s era "caesium ion meter" definition or the museum-piece "platinum rod meter" (provided the latter item hasn't been melted down yet for its raw precious metal value...) 158.88.16.4 (talk) 10:50, 9 January 2023 (UTC)

One-way ticket to the quantum?
> The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector.

I'm surprised this article doesn't even contain the word "quantum" a single time? Quantum-network connected (entangled) sensors and computers at the two ends of the experimental facility would seem to be the obvious choice to measure a true one-way speed of light. Without discussing the quantum aspect or at least explaining to readers why such a thing cannot be done the current article remains a bit confusing. 94.21.237.197 (talk) 15:29, 10 January 2023 (UTC)
 * To 3 edit spa: Please do not use Wikipedia talk pages to discuss your own views of physics WP:NOTFORUM. Xxanthippe (talk) 23:23, 20 January 2023 (UTC).

Request for clarification
There is some seemingly contradicting information on this page. The section entitled "Experiments that can be done on the one-way speed of light" mentions that it is possible to carry out measurements that measure changes due to the motion of the source. However, further down in the "Generalizations of Lorentz transformations with anisotropic one-way speeds" subsection, we have the direct quote

> All predictions derived from such a transformation are experimentally indistinguishable from those of the standard Lorentz transformation; the difference is only that the defined clock time varies from Einstein's according to the distance in a specific direction.

Is this information contradictory? --Punyidea (talk) 22:57, 24 February 2023 (UTC)

One way speed of light experiments discussion needs to be edited
The opening paragraph states that one way speed of light experiments depend on a clock synchronization. This is stated as a a universal dogma. Not all agree. This is true only if two clocks are employed. One way speed has been observed via the femtosecond cameras at MIT and CalTech which uses only one clock. The motion picture of the light pulse is a passive observation.

Other passive sensors such as cell phones, radio telescope arrays, etc. also exhibit observables that require the correct value of a one way speed of light.

These need to be taken into consideration on how to amend this article. Theophilus71 (talk) 21:32, 12 October 2023 (UTC)


 * The one way speed of light is DEFINED as the time it takes for light to travel a fixed distance according to a pair of synchronized clocks. There is no way around the issue because it is part of the definition of the thing you are trying to measure. 2600:1017:B009:2164:7474:A4A9:90A:3FBC (talk) 22:42, 30 January 2024 (UTC)
 * The operative word in your reply is distance. The conventionality thesis alters the geometric meaning of the coordinates. The end result is that the so-called epsilon dependent speed is not distance divided by time.  It is a coordinate label divided by time.  One must consistently use the "ds" of the underlying geometry to properly interpret the equations. Theophilus71 (talk) 15:04, 16 May 2024 (UTC)
 * Another real world example that requires a one way speed of light is GPS. To solve the geolocation equations one needs to know the radii of the circles that represent the locus that the light travels in a given time.  If the actual epsilon modified "speed" of light were a physical speed then the radii could be any arbitrary radius and there would be no solution of the equations for some values of epsilon -- since the circles would not intersect at a common point = the location of the GPS receiver. The point is that the epsilon dependent speed of light is not a physical speed, i.e. it is not distance divided by time.Theophilus71 (talk) 15:08, 16 May 2024 (UTC)