I read that only a narrow band of radio waves are reserved for astronomical observation, and humans emit all sorts of electromagnetic waves, which leads to my question:

Could there be signals of advanced life lost in the chaos of all the other EM bands we emit on? We haven't been listening for aliens as long as we've been blasting out waves, and any far off source would be very quiet, so are we potentially drowning signals out?

Aren't the bands we specifically use the ones most likely for other civilizations to be emitting on?

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    $\begingroup$ I imagine this has been debated and discussed, just as someone interested in SETI I haven't seen this question asked or answered. Thanks! $\endgroup$
    – joeyfb
    Commented May 7, 2022 at 19:05
  • $\begingroup$ "The Allen Telescope Array sorts out these confusing signals by comparing the cosmic static received from one part of the sky with that from another." -- seti.org/faq#obs9 $\endgroup$ Commented May 8, 2022 at 2:25
  • $\begingroup$ Aren't the bands we specifically use the ones most likely for other civilizations to be emitting on? How could we possibly know this? $\endgroup$ Commented May 8, 2022 at 13:59
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    $\begingroup$ Have you read here? en.wikipedia.org/wiki/… $\endgroup$ Commented May 8, 2022 at 13:59
  • $\begingroup$ Wouldn't our own EM emissions come from the Earth, while the EM emissions from intelligent life elsewhere come from elsewhere? In other words, if we point our telescopes towards the sky, the EM radiation we detect would overwhelmingly be from extraterrestrial sources? $\endgroup$
    – Allure
    Commented May 11, 2022 at 3:47

1 Answer 1



Did you know that the Asian region doesn't have the same frequency allocations as the United States? Even their cell phone networks operate on different bands. Since humans on Earth don't agree on frequency allocations, why would we expect extra-terrestrials to allocate theirs similar to ours?

Also, our choices in frequency allocations are influenced by our atmospheric composition. Atmospheric water, oxygen, and carbon dioxide attenuate certain bands, which precludes some kinds of uses. Health and human safety precludes using high powered microwaves in populated areas. Differences in atmosphere or alien morphology could then cause their frequency allocations to look different from ours.

However, it is true that we could have a miss-match between where in the RF spectrum we are looking, and where aliens might be broadcasting. In the future, it might be nice to have a SETI station on the far side of the Moon, free from human generated RF interference.


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