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Comment by griffzhowl | Hacker News Reader

> it just happens to be a frequency near one we expect to be used as a signal.

What's the reasoning for this? I've seen noted that the Wow signal of 1420 MHz is near the hydrogen line frequency, and is commonly detected astrophysically.

So is the reasoning just that, if you want to send a signal, then you might choose this frequency because other civilizations will probably have detectors tuned to it?

But then the flip-side of that is that if you detect this frequency, then it's almost certainly natural origin, from the excitation of hydrogen.

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In Carl Sagan’s novel Contact, the aliens chose to transmit their signal at «hydrogen times pi» — which is around 4462 MHz.

yes that other 'people' will be listening, no, because you can pulse it with the fibbonaci sequence or prime numbers, which are not easily produced by astrophysical processes.

Of course if there's a pattern like that it would change things. This signal seems to have been a single pulse though

We have no idea whether the signal had a pattern because the only recording we have of it consists of averages over 10-second samples, so any modulation <10s (or patterns larger than the 72s recording) would have been lost. It could have been an AM broadcast of a herd of circus elephants playing the William Tell Overture for all we know.

True. That's why I hedged with "seems to". Our only measurement of it is consistent with it being a single pulse

On our timescale, sure. But then we wouldn't want to communicate with intelligences that experience time so differently that a pulsed signal from their perspective would be a single pulse from our perspective.

Random aside, but relevant to the discussion. If you haven’t read The Dragon’s Egg, you’re in for a treat.

https://en.m.wikipedia.org/wiki/Dragon%27s_Egg

Yep. It's wildly unlikely that this was any kind of deliberate signal. Whatever caused it, it only happened once -- which isn't what you'd expect from aliens hoping to make contact.

We only recorded the fact of the signal's existence, without enough resolution to make out any pattern within it. If the aliens were hoping we'd decode it, they were banking on us happening to catch their signal at a very specific instant in time, never to be repeated.

> it only happened once -- which isn't what you'd expect from aliens hoping to make contact.

Actually it’s exactly what we did with the Arecibo message, our only attempt to make contact.

https://en.wikipedia.org/wiki/Arecibo_message

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