5 ms·

No; not without heating up (since the inside of the sphere can't radiate it back to the star at the center). As the sphere heats up it radiates outwards in inc

No; not without heating up (since the inside of the sphere can't radiate it back to the star at the center). As the sphere heats up it radiates outwards in increasingly energetic spectra. Since entropy (in this case in the form of unusable heat) always goes up, the sphere couldn't stay dark forever.

yellowapple 7y ago
What about radiating it in a specific direction (one that just happens to be away from us)?
- contravariant 7y ago
  Heat radiates in all directions by definition. It is theoretically possible to direct it to some extent (at the cost of raising entropy elsewhere) but it would require massive effort for no good reason.
- haolez 7y ago
  That was one of the alternatives that I was thinking as well :)
- ClumsyPilot 7y ago
  You could never direct 100% of it, since any matter not at absolute zero has to radiate longer wavelengths. Once you do direct it, someone will still see you if they are in the path of the beam. It appears to be an exercise in futility.
  - pixl97 7y ago
    Beam it at a black hole
    - phinnaeus 7y ago
      Hopefully it's a special kind of black hole like the one mentioned in the article. Wait...
  - yellowapple 7y ago
    > You could never direct 100% of it No, but you could direct enough of it that anything left is too dim to see unless you've got really good eyes ("eyes" in this case being whatever sensors we're using to detect black-body radiation). > someone will still see you if they are in the path of the beam. Space is big. What's the chance that we'd actually cross paths with that beam? On the other hand, space is big. That beam would probably hit something eventually, and I suspect in that case we might pick up a reflection. > It appears to be an exercise in futility. Assuming the point is actually to hide. Maybe instead it's an attempt to recapture some of that energy otherwise lost as heat?

yellowapple 7y ago

What about radiating it in a specific direction (one that just happens to be away from us)?

contravariant 7y ago
Heat radiates in all directions by definition. It is theoretically possible to direct it to some extent (at the cost of raising entropy elsewhere) but it would require massive effort for no good reason.
haolez 7y ago
That was one of the alternatives that I was thinking as well :)
ClumsyPilot 7y ago
You could never direct 100% of it, since any matter not at absolute zero has to radiate longer wavelengths. Once you do direct it, someone will still see you if they are in the path of the beam. It appears to be an exercise in futility.
- pixl97 7y ago
  Beam it at a black hole
  - phinnaeus 7y ago
    Hopefully it's a special kind of black hole like the one mentioned in the article. Wait...
- yellowapple 7y ago
  > You could never direct 100% of it No, but you could direct enough of it that anything left is too dim to see unless you've got really good eyes ("eyes" in this case being whatever sensors we're using to detect black-body radiation). > someone will still see you if they are in the path of the beam. Space is big. What's the chance that we'd actually cross paths with that beam? On the other hand, space is big. That beam would probably hit something eventually, and I suspect in that case we might pick up a reflection. > It appears to be an exercise in futility. Assuming the point is actually to hide. Maybe instead it's an attempt to recapture some of that energy otherwise lost as heat?