Re:Phosphine detected in the atmosphere of Venus – an indica...
by outworlder on Monday September 14, 2020 @04:08PM
(#24474522)
If you go just be what's detectable by radio emissions, there seems to be another problem.
Back when we started broadcasting radio, we needed very powerful transmitters since the receivers were pretty primitive - you could make receivers with no power source at all (Galena radios).
Then we started using them for other purposes. Powerful radars appeared. TV was invented. Later on we added digital signals and most traffic shifted to binary for computer to computer communication.
Now we have things like WIFI and 5g. The problem is that the technology has advanced so much that cellular antennas can talk to puny transmitters from miles away, while the transmitters are only outputting milliwatts. We can also electronically 'steer' transmissions so they will 'point' at the other party (beamforming).
Long range communication is shifting to satellites and fiber optic cables. Those are pretty directional and not very strong signals, by comparison (and fiber optic of course has none). We have been slowly shutting down TV stations in favor of internet streams.
Civilian radars still exist but they are relatively weak. They are also slowly being phased out in favor of technologies like ADS-B, which broadcast a fraction of the power. GPS signals are very weak.
Military radars are also more sensitive than before - and increasingly look like background noise. Given the high emphasis on stealth, they are also more directional and lower power than before. And may not even be on all the time.
Given this, it is possible that, if you are taking a SETI approach, there's only a very small window before a civilization switches to more efficient and less noisy RF comms.
> At up to 100 light year
At 100 light years you'll have very faint, possibly undetectable signals, as the strength decreases with distance squared. Unless they are pointing at us.
Back when we started broadcasting radio, we needed very powerful transmitters since the receivers were pretty primitive - you could make receivers with no power source at all (Galena radios).
Then we started using them for other purposes. Powerful radars appeared. TV was invented. Later on we added digital signals and most traffic shifted to binary for computer to computer communication.
Now we have things like WIFI and 5g. The problem is that the technology has advanced so much that cellular antennas can talk to puny transmitters from miles away, while the transmitters are only outputting milliwatts. We can also electronically 'steer' transmissions so they will 'point' at the other party (beamforming).
Long range communication is shifting to satellites and fiber optic cables. Those are pretty directional and not very strong signals, by comparison (and fiber optic of course has none). We have been slowly shutting down TV stations in favor of internet streams.
Civilian radars still exist but they are relatively weak. They are also slowly being phased out in favor of technologies like ADS-B, which broadcast a fraction of the power. GPS signals are very weak.
Military radars are also more sensitive than before - and increasingly look like background noise. Given the high emphasis on stealth, they are also more directional and lower power than before. And may not even be on all the time.
Given this, it is possible that, if you are taking a SETI approach, there's only a very small window before a civilization switches to more efficient and less noisy RF comms.
> At up to 100 light year
At 100 light years you'll have very faint, possibly undetectable signals, as the strength decreases with distance squared. Unless they are pointing at us.