Science Memes

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NASA Ping (mander.xyz)

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

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[–] [email protected] 76 points 3 months ago (2 children)

fun fact, that would make the transmission slower.

According to wikipedia cat5 cable has a propagation delay of 5.30 ns/m, which works out to about 62% of the speed of light. While radio waves propagate at the speed of light.

[–] [email protected] 24 points 3 months ago* (last edited 3 months ago) (2 children)

Yeah, the reason ethernet is generally faster compared with wifi is mainly due to interference from physical objects between the device and the transmitter. Not as much an issue when you're issuing commands into the vacuum of space from large, high-powered antennas.

[–] [email protected] 5 points 3 months ago

hehe, imagine a tcp handshake with voyager

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

Not as much an issue when you're issuing commands into the vacuum of space

[–] [email protected] 6 points 3 months ago* (last edited 3 months ago) (2 children)

Radio waves always propagate at the speed of light, it's just that the effective speed of light in copper and glass fibre is lower than that in air/vacuum.

This means that if you have long cables at some distance you'll get a lower delay by using low earth orbit satellites like Starlink. Assuming a total distance via satellite of 1000km and the effective speed of light in glass fibre to be 2/3 c, cables over 667km will have a higher delay than the satellite.

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

Some fiber-optic cables are faster than others, because they're full of air. Hollow-core fibers have a large central cutout and/or a close hexagonal packing of smaller glass tubes. The latter are technically a "photonic crystal."

[–] psud 1 points 2 months ago

Speed of light in fiberoptic cable is slower than c for a different reason. The light is in something close to vacuum, signals travel slower than c because the light doesn't follow a straight path, it zig zags bouncing off the walls.

A radio wave or laser in reasonable vacuum (in orbit for example) will be lower latency than a signal on a fiber link the same length

I'm expecting lower ping via starlink than fiber once starlink has laser links between satellites