this post was submitted on 05 Apr 2025
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Science Memes

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410
It's the law! (mander.xyz)
submitted 1 week ago by [email protected] to c/[email protected]
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[–] [email protected] 11 points 1 week ago (4 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. πŸ‘

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. πŸ‘

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. πŸ‘

[–] [email protected] 9 points 6 days ago* (last edited 6 days ago) (3 children)

Send it through the earth, you can reduce it theoretically to 42.5ms (using mean radius and speed of light in vacuum).

[–] [email protected] 5 points 6 days ago

Oh, good point, I recently learned that the speed of light in fiber optics is around 200000 km/s. I always thought physicists were saying "in vacuum" to be technically correct, but that's actually a huge difference...

https://en.wikipedia.org/wiki/Optical_fiber#Refractive_index

[–] [email protected] 3 points 6 days ago* (last edited 6 days ago)

Send it through the earth, you can reduce it theoretically to 42.5ms

This isn't as ridiculous as it sounds and you just need a neutrino-beam... which has a horrible bandwidth (of 0.1 bits/s) plus the ridiculous upfront cost of running two particle-accelerators for a full-duplex link. (Google it up, this exists.)

[–] [email protected] 1 points 6 days ago

Unfortunately you then get the low bandwidth of the frequencies that can penetrate that much ground

[–] [email protected] 2 points 6 days ago

Alright, I guess, I'll just break up the time continuum then and give the user feedback before it has finished recording. πŸ‘

Quantum physics might work too. No, seriously.

[–] [email protected] 1 points 6 days ago* (last edited 6 days ago)

That speed of causality is usually at least 3 times better than you can get in real life

You get 300 million metres per second in light (including radio in free space) so wifi to your laptop is at that speed

A wave in wire (eg ethernet over cat6 cable) is seldom better than 0.9c

Laser light in an optic fibre (how almost all data moves long distance) is about 200 million metres per second as it follows a zig zag path in the fibre reflecting off the walls of the fibre

The future promise of starlink – where your connection goes to a satellite then to another and another satellite until being down linked to the server farm hosting the content – should provide much lower latency

[–] [email protected] 1 points 1 week ago (2 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 1 week 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 6 days 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 6 days 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)

[–] [email protected] 10 points 1 week ago (1 children)

My mom sucks, though

[–] [email protected] 17 points 1 week ago* (last edited 1 week ago)

She does it well, so there's that.

[–] [email protected] 6 points 1 week ago

Nevar!

. . .to the second part. My mom is cool.

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

Thanks Peter Griffin

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

That’s a ballchinian.

[–] [email protected] 2 points 1 week ago

Is this a logical statement? And does the runtime support short-circuiting? It would mean you don't have to obey physics if you don't love your mom, which is neat.