That has always been my understanding.
Is this to blame for the Fermi paradox?
- Thread starter RAMA
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That has always been my understanding.
If something like our normal TV broadcasts were coming from the nearest star, my understanding is we could not detect them or at least distinguish them from the background. Someone correct me if that is wrong, but I do know the distance is very limited with current tech.
With the equipment we currently have, they would have to be aiming the radio transmission our way and it would have to be pretty damn strong.
The idea that TV signals are being transmitted all over the universe from Earth has been a popular and persistent meme since it showed up in scifi movies in the 1950s.
Radio signals follow the inverse square law, though, just like anything else, and basically fall below cosmic background levels within about five light years. That before you consider that radio noise from Jupiter and the Sun are being broadcast into space at far greater intensities anyway and will drown out those signals way before then.
SETI telescopes aren't looking for accidental broadcasts from TV or radio transmissions (or the alien equivalent). They're looking for DELIBERATE attempts to communicate; that is, for their alien counterparts who are also beaming messages out into space trying to find someone to talk to. Even then, the only way to detect those signals is to be looking at exactly the right place on exactly the right frequency at exactly the right time, and even then the signal STILL might be too weak for us to detect.
Basically, aliens would have to be living on a planet within 50 to 100 light years, broadcasting extremely high intensity radio waves directly at us at the exact moment when our most powerful radiotelescopes are looking directly at them.
It's not a "fermi paradox" so much as a "fermi crapshoot."
The holodeck will be society's last invention. - Scott Adams
That is indeed the case.
Dr. Seth Shostak Answers Your Questions About SETI
NRAL - SETI questions
So with our technology, we could not pick up our TV broadcasts from any other star, including the closest ones to the Solar System.
There is a way out, however. Use much larger radio telescopes than what we have been using, but that will be rather expensive.
As to what one would see, here's a paper from nearly 40 years ago on that:
Eavesdropping: the Radio Signature of the Earth - 1979.pdf (another version: Eavesdropping Mode and Radio Leakage from Earth - ch5.4)
One would not be able to watch our TV shows without a huge antenna. That is because the full TV bandwidth is about 3 MHz and the carrier wave about 0.3 Hz or less -- a million times bigger, with a million times as much background noise. So if one can see a TV broadcast's carrier-wave signal with a 1-km telescope, one will need a 1000-km telescope to see the whole broadcast.
So ET's aren't going to be watching our TV shows over interstellar distances unless they use planet-sized antennas.
But that paper I mentioned discussed what one could learn from our TV broadcasts' carrier waves. One would watch each station rise and set, and one would watch the stations' signals get Doppler shifted from the Earth's rotation. That would give an idea of where the stations are on our planet, how big our planet is, how fast it is rotating, and the direction of one's vantage point.
The Earth's equator rotates with a linear speed of 460 m/s or 1.5*10^(-9) c
The Earth moves around the Sun at an average speed of 29.78 km/s or 10^(-4) c
The Moon's orbit velocity: 1.023 km/s
Induced on the Earth: 13 m/s or 4.2*10^(-11) c
It may be hard to detect the Earth-rotation Doppler shift, and I doubt if it will be possible to detect the Moon's pull on the Eart. But if one's patient, and our TV transmitters have enough frequency stability, then one will be able to detect the Earth's revolution around the Sun. It will be like a one-line spectroscopic binary: one can get its period and projected orbit velocity.
One should be able to see the Sun, and get a good estimate of its mass and age by finding its brightness and spectral type, and by looking for evidence of sunquakes. Sort of like what we've done for stars like Kepler-452. One can then look for planets around the Sun, but that will be rather difficult. There are four techniques that one can use:
Eavesdropping: the Radio Signature of the Earth - 1979.pdf (another version: Eavesdropping Mode and Radio Leakage from Earth - ch5.4)
One would not be able to watch our TV shows without a huge antenna. That is because the full TV bandwidth is about 3 MHz and the carrier wave about 0.3 Hz or less -- a million times bigger, with a million times as much background noise. So if one can see a TV broadcast's carrier-wave signal with a 1-km telescope, one will need a 1000-km telescope to see the whole broadcast.
So ET's aren't going to be watching our TV shows over interstellar distances unless they use planet-sized antennas.
But that paper I mentioned discussed what one could learn from our TV broadcasts' carrier waves. One would watch each station rise and set, and one would watch the stations' signals get Doppler shifted from the Earth's rotation. That would give an idea of where the stations are on our planet, how big our planet is, how fast it is rotating, and the direction of one's vantage point.
The Earth's equator rotates with a linear speed of 460 m/s or 1.5*10^(-9) c
The Earth moves around the Sun at an average speed of 29.78 km/s or 10^(-4) c
The Moon's orbit velocity: 1.023 km/s
Induced on the Earth: 13 m/s or 4.2*10^(-11) c
It may be hard to detect the Earth-rotation Doppler shift, and I doubt if it will be possible to detect the Moon's pull on the Eart. But if one's patient, and our TV transmitters have enough frequency stability, then one will be able to detect the Earth's revolution around the Sun. It will be like a one-line spectroscopic binary: one can get its period and projected orbit velocity.
One should be able to see the Sun, and get a good estimate of its mass and age by finding its brightness and spectral type, and by looking for evidence of sunquakes. Sort of like what we've done for stars like Kepler-452. One can then look for planets around the Sun, but that will be rather difficult. There are four techniques that one can use:
- Direct detection
- Transits -- a planet passing in front of the Sun
- Radial velocity -- how fast the Sun is pulled as a result of a planet's gravity
- Astrometry -- how far the Sun is pulled as a result of a planet's gravity
Re: Is this to blame for the Fermi paradox?
RAMA wrote:
This article goes in depth on one of my theories for the Fermi Paradox that I laid out in several posts. I've never seen it anywhere else.
We Can’t Find Any Alien Neighbors and Virtual Reality Might Be to Blame
http://singularityhub.com/2015/08/20...ampaign=buffer
The holodeck will be society's last invention. - Scott Adams
I don't really think it will be a case of navel gazing, in a real singularity--where the virtual may meld with the "real" to the point of being indistinguishable--it may take mankind/AI decades/centuries/millenia to stop exploring itself...before setting out to quanitify the universe...
But that time is a single grain of sand in the huge hourglass that is the existence of the universe.
The more likely explanation, is that we simply haven't advanced far enough ourselves to detect others.
Agree 100 percent. We don't even know what to look for if we are talking about life that may be 1000s or millions of years beyond us.
Plus we're looking for radio waves and I believe one program is looking for lasers. But that's just because we could make that. An alien civilization may create a communication method we can't imagine.
There may be levels of civilization beyond what we know from Earth's history. We Earthlings may be fairly primitive.
I would say that we are fairly primitive, in comparison to what we are looking for.
There has been an attemp to classify civilizations by energy content/production, the Kharashev scale. Type I civilization commands the energy of a star. Type II commands the energy of a star. Type III commands the energy of a star.
Carl Sagan had a quantitative scale for information content. The least content would be a strictly oral culture. With the invention of writing, there is a vast expansion in recorded information.
These two scales can be combined, of course. But they are generalities based on quantity. There may be qualitative differences that we can only speculate about.
I love the Threads that stretch my mind and make it hurt, just a little, in a good way. Thank you!
Maybe our Purpose, regardless of what else comes our way, is just that: to figure out our Purpose.
Sounds like a pretty flat scale.
It does, yes. I guess he meant this Kardashev scale which is nice for Sci-Fi, and sounds impressive when securing funding at the right times, but I'm not holding my breadth for any of these showing up. https://en.wikipedia.org/wiki/Kardashev_scale
Do animals born in a zoo know they are in a zoo?
Which is, honestly, a great question. We could all be nothing more than sea monkeys floating around in a jar belonging to a lifeform we can't even begin to imagine.
Re: Is this to blame for the Fermi paradox?
RAMA wrote:
This article goes in depth on one of my theories for the Fermi Paradox that I laid out in several posts. I've never seen it anywhere else.
We Can’t Find Any Alien Neighbors and Virtual Reality Might Be to Blame
http://singularityhub.com/2015/08/20...ampaign=buffer
The holodeck will be society's last invention. - Scott Adams
I don't really think it will be a case of navel gazing, in a real singularity--where the virtual may meld with the "real" to the point of being indistinguishable--it may take mankind/AI decades/centuries/millenia to stop exploring itself...before setting out to quanitify the universe...
That's a fine theory, but having observed the way the majority of people ACTUALLY USE technology, it's a lot more likely we'll spend a few decades dicking around on VR-enabled facebook while utterly failing to get any useful work done.
Or one we CAN imagine that doesn't propagate very well through space. An technologically advanced aquatic civilization, for example, would have very little use for radio waves and would probably develop fiber optics LONG before they discovered radar. Good look making interstellar contact with a species that communicates primarily through sonar...
Kardashev scale - Wikipedia:
I: Nikolai Kardashev originally defined it as using energy at the rate that humanity was using it when he published his article, about 1964, roughly 4*10^(12) watts. It's nowadays often defined as using the entire energy input that a planet gets. For the Earth, it's mostly sunlight, and it's about 1.74*10^(17) watts.
II: Using all the energy from a star. For the Sun, that is 3.846*10^(26) watts. This is for the electromagnetic spectrum only; neutrinos add about 0.023 of it.
III: Using all the energy from a galaxy. For ours, it is about 4*10^(37) watts.
I've seen it extended to IV (our Universe) and V (a multiverse).
I've also seen the Kardashev scale adjusted to nice-looking numbers, like
I: 10^(16) watts
II: 10^(26) watts
III: 10^(36) watts
By that standard, humanity is currently at about 0.72.
I: Nikolai Kardashev originally defined it as using energy at the rate that humanity was using it when he published his article, about 1964, roughly 4*10^(12) watts. It's nowadays often defined as using the entire energy input that a planet gets. For the Earth, it's mostly sunlight, and it's about 1.74*10^(17) watts.
II: Using all the energy from a star. For the Sun, that is 3.846*10^(26) watts. This is for the electromagnetic spectrum only; neutrinos add about 0.023 of it.
III: Using all the energy from a galaxy. For ours, it is about 4*10^(37) watts.
I've seen it extended to IV (our Universe) and V (a multiverse).
I've also seen the Kardashev scale adjusted to nice-looking numbers, like
I: 10^(16) watts
II: 10^(26) watts
III: 10^(36) watts
By that standard, humanity is currently at about 0.72.
