5 ms·

I thought electric charge in conductors already moved very close to C? https://en.wikipedia.org/wiki/Speed_of_electricity https://en.wikipedia.org/wiki/Speed_of

by gibybo 6y ago

I thought electric charge in conductors already moved very close to C? https://en.wikipedia.org/wiki/Speed_of_electricity https://en.wikipedia.org/wiki/Speed_of_electricity

mcnamaratw 6y ago
Exactly. If we're pedantic about it, a charge signal moves at the speed of light. But the signals are what computers use.
whatshisface 6y ago
Only if you consider 70% or so to be close. There's some room for improvement over copper wires. Now, if there are any physicists here who want to jump in, I have a question about that. I heard waveguides are dispersive, would sending pulses of light through tiny channels slow it down as well?
- shsbsuss 6y ago
  But light in a dielectric medium also travels slower. If n=1.3 -> v = c/1.3 = 77% of c
- mcnamaratw 6y ago
  Some people working in optics say it works "at the speed of light." That's true of course ... but the speed is no different from using copper. Unfortunately something like 0.7c is about the fastest speed of EM wave propagation in an optical waveguide or along a copper waveguide. Another comment here gives a slightly faster example with n=1.3, which is maybe achievable in some kind of polymer. Or in highly purified water, for what it's worth. You can get a mild speedup, 40% or something, by moving to free space. But that is an unbelievable can of worms, taking all the signals out of the waveguides and somehow still getting 1B signals going to the right place. The 40% speedup doesn't remotely pay for giving up solid state waveguides. "Dispersive" fortunately doesn't mean a meaningful slowdown. It just means that a transmitted bit will travel at a range of slightly different speeds. If it goes very far, the shape of the pulse will get messed up. But that's a problem people are already pretty good at solving.
- LargoLasskhyfv 6y ago
  Not a physicist, but you may want to look for 'hollow core fiber / photonic crystal fiber'. Where some are said to reach up to 99.x % the speed of light in a vacuum.
  - datenwolf 6y ago
    Laser physicist here, did some work with PCF: Expensive as fuck, highly polarization dependent, almost impossible to splice.
    - LargoLasskhyfv 6y ago
      Nonetheless it feels like at least every few months or even weeks a new announcement appears in pop-science sites like eurekalert and phys.org. Feels a little bit like the always around the corner next big battery tech. Most fascinating thing i've read years ago they'd be the prime candidate for manufacturing in space, because real vacuum.
      - coralVila 6y ago
        This is a test. Sorry for the inconvenience.

by gibybo 6y ago

I thought electric charge in conductors already moved very close to C? https://en.wikipedia.org/wiki/Speed_of_electricity https://en.wikipedia.org/wiki/Speed_of_electricity

mcnamaratw 6y ago

Exactly. If we're pedantic about it, a charge signal moves at the speed of light. But the signals are what computers use.

whatshisface 6y ago

Only if you consider 70% or so to be close. There's some room for improvement over copper wires. Now, if there are any physicists here who want to jump in, I have a question about that. I heard waveguides are dispersive, would sending pulses of light through tiny channels slow it down as well?

shsbsuss 6y ago
But light in a dielectric medium also travels slower. If n=1.3 -> v = c/1.3 = 77% of c
mcnamaratw 6y ago
Some people working in optics say it works "at the speed of light." That's true of course ... but the speed is no different from using copper. Unfortunately something like 0.7c is about the fastest speed of EM wave propagation in an optical waveguide or along a copper waveguide. Another comment here gives a slightly faster example with n=1.3, which is maybe achievable in some kind of polymer. Or in highly purified water, for what it's worth. You can get a mild speedup, 40% or something, by moving to free space. But that is an unbelievable can of worms, taking all the signals out of the waveguides and somehow still getting 1B signals going to the right place. The 40% speedup doesn't remotely pay for giving up solid state waveguides. "Dispersive" fortunately doesn't mean a meaningful slowdown. It just means that a transmitted bit will travel at a range of slightly different speeds. If it goes very far, the shape of the pulse will get messed up. But that's a problem people are already pretty good at solving.
LargoLasskhyfv 6y ago
Not a physicist, but you may want to look for 'hollow core fiber / photonic crystal fiber'. Where some are said to reach up to 99.x % the speed of light in a vacuum.
- datenwolf 6y ago
  Laser physicist here, did some work with PCF: Expensive as fuck, highly polarization dependent, almost impossible to splice.
  - LargoLasskhyfv 6y ago
    Nonetheless it feels like at least every few months or even weeks a new announcement appears in pop-science sites like eurekalert and phys.org. Feels a little bit like the always around the corner next big battery tech. Most fascinating thing i've read years ago they'd be the prime candidate for manufacturing in space, because real vacuum.
    - coralVila 6y ago
      This is a test. Sorry for the inconvenience.