4 ms·

If we could compute faster we'd be able to do digital visible light interferometry, but for now we're stuck with lenses and mirrors bolted to heavy tables, and

by Vecr 2y ago

If we could compute faster we'd be able to do digital visible light interferometry, but for now we're stuck with lenses and mirrors bolted to heavy tables, and our telescopes have to be very close together.

fanf2 2y ago
We would also need an optical atomic clock at each receiver in order to have enough time resolution to correlate the signals correctly. A few optical clocks exist but they are still highly experimental.
- kragen 2y ago
  maybe you could just send a reference light beam between the receivers over an optical fiber to provide a phase reference?
  - Vecr 2y ago
    The dream would be a planet-sized optical telescope, but even a European country sized 'scope would have trouble with your idea.
    - kragen 2y ago
      people already send light beams over ocean-length optical fibers (that's how we're talking). this is achieved by the use of erbium-doped fiber amplifiers, which preserve wavelength and phase information, but even without amplification you can reach 500 km: https://phys.org/news/2023-06-scientists-km-quantum-key.html https://phys.org/news/2023-06-scientists-km-quantum-key.html and of course we're only talking about these rube goldberg setups because we're perversely trying to build a telescope with a giant rock in the middle of it. if we build the telescope in solar orbit, we can just shine a light through space for the phase reference
kragen 2y ago
well, i can see best around 540 terahertz, so i think you'd need digital state transition rates around a couple petahertz for digital visible light interferometry, about six orders of magnitude faster than this cellphone. that's clearly physically possible, but one or another technology might be able to compute much faster than this cellphone while topping out in the low terahertz such speeds would likely require that most bit operations be reversible to avoid vaporizing due to landauer's limit (perhaps coincidentally also first proposed by von neumann)

by Vecr 2y ago

fanf2 2y ago

We would also need an optical atomic clock at each receiver in order to have enough time resolution to correlate the signals correctly. A few optical clocks exist but they are still highly experimental.

kragen 2y ago
maybe you could just send a reference light beam between the receivers over an optical fiber to provide a phase reference?
- Vecr 2y ago
  The dream would be a planet-sized optical telescope, but even a European country sized 'scope would have trouble with your idea.
  - kragen 2y ago
    people already send light beams over ocean-length optical fibers (that's how we're talking). this is achieved by the use of erbium-doped fiber amplifiers, which preserve wavelength and phase information, but even without amplification you can reach 500 km: https://phys.org/news/2023-06-scientists-km-quantum-key.html https://phys.org/news/2023-06-scientists-km-quantum-key.html and of course we're only talking about these rube goldberg setups because we're perversely trying to build a telescope with a giant rock in the middle of it. if we build the telescope in solar orbit, we can just shine a light through space for the phase reference

kragen 2y ago

well, i can see best around 540 terahertz, so i think you'd need digital state transition rates around a couple petahertz for digital visible light interferometry, about six orders of magnitude faster than this cellphone. that's clearly physically possible, but one or another technology might be able to compute much faster than this cellphone while topping out in the low terahertz such speeds would likely require that most bit operations be reversible to avoid vaporizing due to landauer's limit (perhaps coincidentally also first proposed by von neumann)