As far as I understand, even if c is different in some circumstances or changes over time it would be hard to measure because everything else is expressed with c

It's like trying to measure if your fingers have grown longer, but doing it with only those fingers as a measure

[–] HubertManne@kbin.social 2 points 6 months ago (1 children)

so you believe c was never directly measured?

[–] bitfucker@programming.dev 1 points 6 months ago (1 children)

Well, how would you measure C directly? You can only always get 2C.

[–] HubertManne@kbin.social 2 points 6 months ago (1 children)

I wouldn't but it has been historically. Unsurprisingly with mirrors but always under the not insignificant influence of the suns gravity. Our most recent measurements I believe use cosmic bodies I believe which is what makes me wonder if our measurement is accurate. https://www.speed-of-light.com/historical_measurements.html

[–] bitfucker@programming.dev 1 points 6 months ago (1 children)

Oh sorry, I was talking about measuring C rather than 2C (since that is the only way we can get C, IIRC, you cannot measure C directly since SOME information must be conveyed when measurement begins AND ends, hence 2C). For C in a gravitational field, I have no idea but I suspect it will have something to do with relativity and time dilation if it has any effect at all.

[–] HubertManne@kbin.social 2 points 6 months ago

well we measure it assuming it has no effect and that is why going way back in this chain I said I would like a measurement outside the influence of a gravity well.