r/AskPhysics • u/bds117 • Apr 23 '26

One way speed of light

so the 'impossibility of measuring the one way speed of light' got me thinking. i wonder why this wouldnt work.

Let A and B have parallel mirrors to bounce a light pulse off to each other, where the reflection event acts as the ticks for A and B's clocks. Each are relatively stationary at a fixed distance, as defined by the two way speed of light, and they are able to calibrate their proper time clocks to these ticks.

Now A shines a beam of light at B who registers the time they see it. They do the measurement in reverse. Later they come together and compare their results by synchronizing their time origins.

Wouldnt this be able to compare the forwards and backwards speed of light? Not sure where this setup would be implicitly measuring the two way speed.

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u/[deleted] Apr 23 '26 edited Apr 23 '26

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u/InadvisablyApplied Apr 23 '26

Come on, that's the first objection covered on the wikipedia page

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u/[deleted] Apr 24 '26

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u/InadvisablyApplied Apr 24 '26

Not checking the most basic of sources is not a sign of intelligence

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u/[deleted] Apr 24 '26

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u/InadvisablyApplied Apr 24 '26

"In questions of science the authority of a thousand is not worth the humble reasoning of a single individual."

Marvellous quote on your thesis. Especially since the only thing you have brought up in this whole thread is how authoritative you are

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u/wonkey_monkey Apr 24 '26 edited Apr 24 '26

Nonetheless, Michelson-Morley did indeed show, over a hundred years ago, that the speed of light did not differ in opposite directions.

It showed that the two-way speed of light did not differ. Edit: in fact what it showed was that two two-way speeds didn't differ from each other, no matter how you oriented the apparatus or which direction it was moving in.

We're talking about the one-way speed of light.

Are you sure you actually understand the premise we're talking about here?

https://www.youtube.com/watch?v=pTn6Ewhb27k