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 omnidirectional 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 radius 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)
the article seems way too generous, we'd barely be able to detect things like 1980s tv broadcasts, they fall below galactic noise before alpha centauri, let alone 50 light years out.
WBCQ in Monticello, ME (USA) says it broadcasts to outer space via a modulated laser.
From <http://www.wbcq.com/>:
WBCQ’s laser broadcasting service is available to beam your program into outer space via our high-powered, modulated, laser system. So in addition to broadcasting worldwide over shortwave radio, you can transmit into space over our high-powered lasers. It’s a lot of fun. The cost for this service is $50 an hour.
I’d love for this chart to also capture the loudest signals we’ve sent. Surely somebody must have accidentally broadcasted a non-directional megawatt radio signal at some point right?
Actually humm maybe nukes are our brightest non directional transmission?
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.
In the book Diaspora, ancient aliens replaced the elements with the unusual form - I forget the details, but say N15 instead of the common N14, O15 instead of O16. Gives a big bright signal that something unusual is happening on this planet.
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.
I consider this a disproof of the "dark forest" hypothesis. That doesn't affect the Three Body Problem as a work of science fiction at all; science fiction gets to make a few assumptions and then ride from there. But if it were advantageous to pre-emptively nuke anything that looks like a threat Earth should have been toasted hundreds of millions of years ago.
(And no, the dinosaur asteroid was not it. If an alien species is going to destroy Earth, they will destroy it, not slightly inconvenience the biosphere.)
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.
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.
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.
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.
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.
There was a Star Trek book (The Abode of Life?) that had a planet that where the communication was mostly confined to the planet. I think Uhura detected the planet from the background noise.
Given that we don't receive signals like this from at least some direction in the universe, I feel like we can be relatively certain that once this signal reaches some specific area humanity will be toast.
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
Since that writing, we've lost Arecibo observatory, discovered gobs of exoplanets, started scrutinizing those exoplanets with JWST, and increased our radio sphere radius by another 19 lightyears.
[1] https://www.damninteresting.com/space-radio-more-static-less...
Bit of a plot point in Sagan's novel (and the movie adaptation):
* https://en.wikipedia.org/wiki/Contact_(novel)
Answer: No (which the article also mentions in so many words)
From <http://www.wbcq.com/>: WBCQ’s laser broadcasting service is available to beam your program into outer space via our high-powered, modulated, laser system. So in addition to broadcasting worldwide over shortwave radio, you can transmit into space over our high-powered lasers. It’s a lot of fun. The cost for this service is $50 an hour.
Actually humm maybe nukes are our brightest non directional transmission?
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.
(And no, the dinosaur asteroid was not it. If an alien species is going to destroy Earth, they will destroy it, not slightly inconvenience the biosphere.)
I think we can rule that out.
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.
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 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.
Well except for that one special time of year, but honestly Eurovision ought to be streaming online instead of broadcasting on TV already!
Shouldn't every cell in this column be the same?