3 ms·

I always thought it would be a cool investigation to look at the distribution of entropy signals coming from celestial bodies and group them. I'd bet there is a

I always thought it would be a cool investigation to look at the distribution of entropy signals coming from celestial bodies and group them. I'd bet there is a non-'natural' entropic signal coming from planets with biological processes on them.

breezeTrowel 3y ago
How would you measure entropy signals at astronomical distances?
- deleted 3y ago
  [deleted]
PeterisP 3y ago
It's interesting that both compression and encryption turn otherwise clearly "engineered" signals into something that's literally indistinguishable from noise, removing any redundancy or regularity.
- giantrobot 3y ago
  The inverse square law means we're not going to pick up stray radio signals from an alien civilization. If you build an Arecibo-equivalent telescope (AET) in space and flew it out of the solar system our radio noise (uncompressed and unencrypted) would fade into the cosmic background at about half a light year out. Even powerful radars wouldn't be detectable much past Alpha Centauri assuming their beam even happens to sweep the portion of the sky where the receiver will be taking into account proper motion between the systems. The only way alien civilizations will pick up each others' signals is if they're intentionally directed at those systems with highly focused emitters. If you're intentionally sending a signal in hopes another civilization will see it you're definitely not going to encrypt it. Compression also serves little purpose as there's no shared context to decompress the message.
  - m4rtink 3y ago
    It should be possible to build much larger (and lighter!) radiotelescopes in the microgravity of space & whole arrays of them.
- nonameiguess 3y ago
  Encryption can't hide the fact that there is a signal. Sufficiently secure encryption makes it so that any ciphertext you receive is equally likely to have been produced by any plaintext. But if you're able to observe that some ground station on Earth transmits radio to the same point in orbit, at the same time, every day, and receives a response, the fact that that is happening can defininitely be distinguished from any natural process. By the same token, if humanity disappeared but left a bunch of encrypted hard drives around and aliens came and found them, they may have no hope of distinguishing the bits from random bits, but they'd be able to tell that no natural process encodes any kind of bits at all onto magnetic discs or flash drives or whatever else we manage to come up with. The actual issue is what the other commenter said about the impossibility of detecting such low power radio at all.
  - kragen 3y ago
    you can observe that there is a radiation source, but if what it's emitting is nearly isotropic white noise, the most likely explanation is that it's just hot historical forms of signal modulation like ook and fm don't look very much like white noise, because they're designed to be demodulated by circuits with 1-10 vacuum tubes, but more modern modulations can look pretty white. they'd look a lot whiter if they weren't constrained by regulation to strongly attenuate bands used by obsolete forms of signal modulation

breezeTrowel 3y ago

How would you measure entropy signals at astronomical distances?

deleted 3y ago
[deleted]

PeterisP 3y ago

It's interesting that both compression and encryption turn otherwise clearly "engineered" signals into something that's literally indistinguishable from noise, removing any redundancy or regularity.

giantrobot 3y ago
The inverse square law means we're not going to pick up stray radio signals from an alien civilization. If you build an Arecibo-equivalent telescope (AET) in space and flew it out of the solar system our radio noise (uncompressed and unencrypted) would fade into the cosmic background at about half a light year out. Even powerful radars wouldn't be detectable much past Alpha Centauri assuming their beam even happens to sweep the portion of the sky where the receiver will be taking into account proper motion between the systems. The only way alien civilizations will pick up each others' signals is if they're intentionally directed at those systems with highly focused emitters. If you're intentionally sending a signal in hopes another civilization will see it you're definitely not going to encrypt it. Compression also serves little purpose as there's no shared context to decompress the message.
- m4rtink 3y ago
  It should be possible to build much larger (and lighter!) radiotelescopes in the microgravity of space & whole arrays of them.
nonameiguess 3y ago
Encryption can't hide the fact that there is a signal. Sufficiently secure encryption makes it so that any ciphertext you receive is equally likely to have been produced by any plaintext. But if you're able to observe that some ground station on Earth transmits radio to the same point in orbit, at the same time, every day, and receives a response, the fact that that is happening can defininitely be distinguished from any natural process. By the same token, if humanity disappeared but left a bunch of encrypted hard drives around and aliens came and found them, they may have no hope of distinguishing the bits from random bits, but they'd be able to tell that no natural process encodes any kind of bits at all onto magnetic discs or flash drives or whatever else we manage to come up with. The actual issue is what the other commenter said about the impossibility of detecting such low power radio at all.
- kragen 3y ago
  you can observe that there is a radiation source, but if what it's emitting is nearly isotropic white noise, the most likely explanation is that it's just hot historical forms of signal modulation like ook and fm don't look very much like white noise, because they're designed to be demodulated by circuits with 1-10 vacuum tubes, but more modern modulations can look pretty white. they'd look a lot whiter if they weren't constrained by regulation to strongly attenuate bands used by obsolete forms of signal modulation