Is this the one way speed of light?

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Discussion Overview

The discussion revolves around the concept of the one-way speed of light, particularly in the context of measuring distances and simultaneity between light pulses emitted by a stationary observer. Participants explore the implications of their measurements and the assumptions underlying the definitions of simultaneity and speed.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant describes a scenario where a stationary observer emits two light pulses 2 seconds apart and questions the distance between them, suggesting it could be measured as 10 meters if aligned correctly with marks.
  • Another participant challenges the notion of probability in the alignment of light pulses and marks, asserting that simultaneity is not a matter of odds.
  • A different participant points out a potential contradiction in the initial claim about the distance between light pulses, noting that 10 meters is negligible compared to the 2 light seconds separating them.
  • One participant questions the validity of establishing simultaneity, arguing that all methods of determining simultaneity rely on the assumption that the one-way speed of light equals the two-way speed.
  • A participant seeks clarification on what it means for light pulses to align with the 10-meter marks, indicating a need for further explanation of the scenario presented.

Areas of Agreement / Disagreement

Participants express differing views on the measurement of the one-way speed of light and the assumptions involved in defining simultaneity. The discussion remains unresolved, with multiple competing perspectives presented.

Contextual Notes

Participants highlight limitations in the assumptions made regarding simultaneity and the implications of measuring distances in relation to the speed of light. The discussion does not resolve these issues.

DAC
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Hello PF.
A stationary observer generates two pulses of light. The pulses are 2 seconds apart according to his watch.

What is the distance between the two pulses? Assume he marks out 10 metres and places himself half way at the 5 metre mark. If the light pulses go past and align with the 10 metre marks, the distance between the light pulses is 10 metres. Being equidistant from the 10 metre marks he records simultaneous measurements. The odds are the light and the 10 metre marks won't al;gn. But the 10 metres can be altered. ( 9,8,11,12 etc. ) until they align with the light pulses. thereby giving the distance between the pulses.
With distance and time we have speed. One way speed?
 
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The odds are the light and the 10 metre marks won't align
Odds ? There is no probability involved !
You just before this wrote he records simultaneous measurements ?
 
DAC said:
Hello PF.
A stationary observer generates two pulses of light. The pulses are 2 seconds apart according to his watch.

What is the distance between the two pulses? Assume he marks out 10 metres and places himself half way at the 5 metre mark. If the light pulses go past and align with the 10 metre marks, the distance between the light pulses is 10 metres. Being equidistant from the 10 metre marks he records simultaneous measurements. The odds are the light and the 10 metre marks won't al;gn. But the 10 metres can be altered. ( 9,8,11,12 etc. ) until they align with the light pulses. thereby giving the distance between the pulses.
With distance and time we have speed. One way speed?
I guess I'm not following what you are saying. You say "the distance between the light pulses is 10 meters", but you have stated that the distance between the light pulses is 2 light seconds. Compared to 2 light seconds, 10 meters is approximately zero.
 
DAC said:
...Being equidistant from the 10 metre marks he records simultaneous measurements...

How do you establish that the measurements are in fact simultaneous? All techniques for determining simultaneity are directly or indirectly based on the assumption that the one-way speed of light is equal to the two-way speed.

The "one-way speed of light problem" isn't that we can't "measure" the one-way speed of light. We can, just as you did: choose a definition of "simultaneous" so that we can measure the time between emission and reception and then speed=distance/time will see us home. The problem is that when our measured one-way speed comes out the same as the measured two-way speed that doesn't tell us that the speed of light is the same in both directions. It tells us that we chose a definition of "simultaneous' that assumed that the two speeds are equal.
 
DAC said:
If the light pulses go past and align with the 10 metre marks,
What does this mean?
 

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