I wrote an article about this same general topic way back in 2007[1], wherein I conducted a thought experiment with an Arecibo observatory traveling away from Earth. I calculated that even mighty Arecibo would be unable to detect Earth's FM radio as far out as Saturn, let alone from another star.
Since that writing, we've lost Arecibo observatory, discovered gobs of exoplanets, started scrutinizing those exoplanets with JWST, and increased our radio sphere by another 19 lightyears.
I asked a friend at JPL, if there was a civilization at Alpha Centauri and they were sending out the same types of signals as Earth does today, could we detect those signals at Earth with our current tech?
Answer: No (which the article also mentions in so many words)
derbOac 18 minutes ago [-]
This was portrayed in the film Contact (1997) closely to what's described in this piece (maybe it's in the book too? I haven't read it).
throw0101a 20 minutes ago [-]
> 1936: Berlin Olympics first major TV broadcast
Bit of a plot point in Sagan's novel (and the movie adaptation):
Doppler shift would substantially change the wavelength, and frequency too.
Perhaps the number of light years a wave has traveled moving in the same direction that Earth is moving in, would be less distance than the side facing the direction that we are moving away from.
The Earth, and Solar System are always moving in motion; I would imagine doppler shift would also have a significant impact on the success of receiving such transmissions.
chasil 2 hours ago [-]
I think that an atmosphere with measurable oxygen gas is a far longer lasting, pervasive and interesting signal that by itself could prompt investigation.
The oxygen has been here for far longer than us, sometimes at much higher levels.
api 1 hours ago [-]
Earth has been screaming it has a very likely biosphere for at least 500 million to a billion years. To anyone with huge space based telescopes.
So why no visitors? If there had been, we wouldn’t know. Any probes that dropped into our planet any further back than a few tens of thousands of years (and less if they landed in a hot wet region) might be gone by now. They’d have been eaten by corrosion and mechanical erosion and eventually by plate tectonics.
They also likely would have been small, meaning even if they got fossilized we’d have to get super lucky to find one. The energy required to accelerate something to meaningful fractions of light speed and then decelerate at the other side means a probe is probably an orbiter the size of a basketball and then a little drone the size of a golf ball or something.
We might have had dozens or hundreds of little visitors over the last billion years and we’d never know unless we got real lucky.
Flyby missions are also likely due to the physics. The energy for slowing down might instead be spent just going faster to get results faster. The probe just streaks past at 7% the speed of light and takes a bunch of pictures and measurements.
DoctorOetker 1 hours ago [-]
chemistry has more reactions than just with oxygen, oxygen alone is a poor indicator of life...
jerf 33 minutes ago [-]
Oxygen is a highly reactive element that on a cosmological time frame instantly disappears by bonding with things. It is very difficult to come up with an explanation other than "life" for why an atmosphere would be full of oxygen; it may well be impossible to come up with an explanation other than "life" for why an atmosphere would be full of oxygen for 500 million years, especially on a ball of iron. Even having a transient explanation would be very difficult.
marcus_holmes 32 minutes ago [-]
Not all living organisms use oxygen (even on our planet), true.
But you don't get free oxygen on a planet without life to continually produce it.
It's a good indicator of some forms of life.
adrianN 47 minutes ago [-]
We don’t have a lot of examples of technological life forms that don’t need oxygen.
boznz 2 hours ago [-]
Nice article. I had to go down this rabbit-hole researching my first book. Actual likelihood of anyone actually being able to receive these past a few tens of LY is quite low without very sensitive receivers. Also as another commenter pointed out the window for receiving us is closing as more modern wide-band and spread-spectrum signals are more power efficient, directed, and look much closer to noise than data.
api 55 minutes ago [-]
A lot of people think the “great silence” from SETI means something, unfortunately.
A civilization using only low power radio wouldn’t be detectable in the Centauri system.
fuckinpuppers 20 minutes ago [-]
Makes me think of the intro to Contact, which was a really cool “visualization” of this… with Hitler and the 1938 Olympics being the first tv broadcast of strength, which aligns with reality
analog31 2 hours ago [-]
Something that I muse about is that this bubble may indeed be a thin shell. My rationale is that already the bulk of our communications are confined to waveguides -- optical fibers. Our wireless comms continue to be engineered to produce less power and to be almost indistinguishable from noise. Much of our AC power travels along paired wires whose fields cancel one another at the equivalent of an inverse-fourth law or worse. Soon they may all be DC.
The civilizations who are "out there" may only have a narrow time window to pick up our signals. Like we've fashioned a poor man's Dyson sphere.
marcus_holmes 26 minutes ago [-]
Agreed. Also, the audience and business model for commercial radio and television stations are declining, and it's easy to see a point where nobody listens to radio or watches television any more and they stop broadcasting.
meatmanek 2 hours ago [-]
> What they first received
Shouldn't every cell in this column be the same?
marcus_holmes 25 minutes ago [-]
I assumed that it was something to do with signal strength, but re-reading it, you're right, this doesn't make sense.
Rendered at 01:41:25 GMT+0000 (Coordinated Universal Time) with Vercel.
Since that writing, we've lost Arecibo observatory, discovered gobs of exoplanets, started scrutinizing those exoplanets with JWST, and increased our radio sphere by another 19 lightyears.
[1] https://www.damninteresting.com/space-radio-more-static-less...
Answer: No (which the article also mentions in so many words)
Bit of a plot point in Sagan's novel (and the movie adaptation):
* https://en.wikipedia.org/wiki/Contact_(novel)
Doppler shift would substantially change the wavelength, and frequency too.
Perhaps the number of light years a wave has traveled moving in the same direction that Earth is moving in, would be less distance than the side facing the direction that we are moving away from.
The Earth, and Solar System are always moving in motion; I would imagine doppler shift would also have a significant impact on the success of receiving such transmissions.
The oxygen has been here for far longer than us, sometimes at much higher levels.
So why no visitors? If there had been, we wouldn’t know. Any probes that dropped into our planet any further back than a few tens of thousands of years (and less if they landed in a hot wet region) might be gone by now. They’d have been eaten by corrosion and mechanical erosion and eventually by plate tectonics.
They also likely would have been small, meaning even if they got fossilized we’d have to get super lucky to find one. The energy required to accelerate something to meaningful fractions of light speed and then decelerate at the other side means a probe is probably an orbiter the size of a basketball and then a little drone the size of a golf ball or something.
We might have had dozens or hundreds of little visitors over the last billion years and we’d never know unless we got real lucky.
Flyby missions are also likely due to the physics. The energy for slowing down might instead be spent just going faster to get results faster. The probe just streaks past at 7% the speed of light and takes a bunch of pictures and measurements.
But you don't get free oxygen on a planet without life to continually produce it.
It's a good indicator of some forms of life.
A civilization using only low power radio wouldn’t be detectable in the Centauri system.
The civilizations who are "out there" may only have a narrow time window to pick up our signals. Like we've fashioned a poor man's Dyson sphere.
Shouldn't every cell in this column be the same?