Science Memes

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It's the law! (mander.xyz)

submitted 3 weeks ago by [email protected] to c/[email protected]

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[–] [email protected] 11 points 3 weeks ago (11 children)

I work as a software engineer and honestly, it's ridiculous how often I'm asked to or tempted to violate the laws of physics.

There's classics like measuring how long it takes to send a network packet from one device to another – you can't, because the two devices might have wildly different understandings of what time it currently is. The only way to get an accurate measurement is by measuring how long it takes to send it there + back (a.k.a. the round-trip time).
And then you divide that by 2 and pretend there's no asymmetry in transmission speed, nor delay between the other device receiving it and sending it back. 👍

In our previous project, we were recording audio chunks of one second each and then feeding it into a detector. At some point, we got asked, if we could reduce the delay until the user gets feedback from the detector. Also, we can't make the detector detect things more often, because it might make more mistakes. Alright, I guess, I'll just break up the time continuum then and give the user feedback before it has finished recording. 👍

And now in our current project, we're supposed to send network packages across the globe and also we basically can't have any latency. Yeah, so there's this thing called the speed of light/causality at about 300000 km/s. Halfway around the globe is about 20000 km. That leaves us with 66.7 ms of latency, at its theoretical minimum. Guess I'll just quickly invent a way to create worm holes, no problem. 👍

[–] [email protected] 1 points 3 weeks ago (4 children)

There’s classics like measuring how long it takes to send a network packet from one device to another

That one is on your clocks quality, not on physics. People do it all the time.

Probably on equipment that is orders of magnitude more expensive than yours, but the post isn't about costs.

[–] [email protected] 5 points 3 weeks ago (1 children)

That's just shifting the problem. There is no known way to reliably sync remote clocks except by sending packets and assuming the round-trip time is symmetrical. This is a known problem in physics: https://en.wikipedia.org/wiki/One-way_speed_of_light

[–] [email protected] 1 points 3 weeks ago (1 children)

Sure, but if we take it as true that light speed is the same in every direction – which is perfectly consistent with everything ever measured – you can measure speed between two endpoints using two atomic clocks and a synchronised experiment, with corrections for the relativistic effect of moving the clocks to the different places

[–] [email protected] 1 points 3 weeks ago

if we take it as true that light speed is the same in every direction

This is the crucial assumption, that to my knowledge hasn't been proven or disproven. Because the alternative, light goes faster in one particular direction, is also perfectly consistent with everything. And if you're moving atomic clocks, correcting for time dilations requires you to make assumptions about the one-way speed of light (which we only know from measuring roundtrip times)

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