3 ms·

> Fun fact: light travels a bit faster in space than in an optic cable. Doesn't it have to travel farther, tho? Does that cancel it out?

• cronin101 3y ago
  Starlink is only an extra ~10% of the Earth radius at orbit height, but optic cables slow light by ~30%. So it's actually counterintuitive but "could" be just as fast. (Depending on how far you need to send data, it will regress for intra nation but will theoretically improve long distance communication).
  • jagrsw 3y ago
    What's the theoretical max bandwidth in LEO's near-vacuum? Could we use a wide 1GHz-1THz channel for directional beams to hit 1Tbps, given a decent SNR? Cosmic dust and H atoms seem like non-issues for 1000km links? Would power or thermal reqs be an issue here? I understand it's only about satellite-to-satellite, but still it's interesting.
  • sidewndr46 3y ago
    You're missing the fact that Starlink doesn't take your traffic to the destination. It takes to a nearby downlink station. Then it goes on those same optic cables to the destination.
    • dotnet00 3y ago
      It can take your data to the destination via inter-satellite laser links. That's how they offer service over water and near/at the poles, where downlink stations are not in line of sight for the satellites.
      • sidewndr46 3y ago
        "can take your data" is not the same as thing as "takes the shortest path". There is no way that Starlink is using precious inter-satellite capacity when your data can go direct to a downlink station and transit on dirt cheap fiber
        • dotnet00 3y ago
          No one's saying they are, the point was that they're capable of it.
  • gbil 3y ago
    Seems that they operate in various altitudes but taking your approximation of 10% of the earth radius, that is 10% + 10% as the signal needs to travel to and from the satellite to the ground, that increases the total distance travelled
• dotnet00 3y ago
  In certain cases low orbit constellations with inter-satellite links (like Starlink) can beat underwater cable for latency: https://news.satnews.com/2020/10/14/leo-speed-when-milliseconds-are-worth-millions-an-nsr-insight/ https://news.satnews.com/2020/10/14/leo-speed-when-milliseco...
• crote 3y ago
  Fiberoptic cables aren't perfectly straight either, and light in space is about 30% faster than light in fiber. Considering the link up&down to space adds about 1100km, the break-even point is at around cross-continental distances. The speed difference is big enough that high-frequency traders have been using microwave relay networks for years now. Turns out that a relay chain of point-to-point radio links (which also operate at light-in-space speeds) has enough of an advantage over regular fiber links to be worth the hassle.