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Making It Hard For Extraterrestrials To Hear Us
quaith writes "US astronomer Frank Drake has told scientists at a special SETI meeting in London that earthlings are making it less likely that we will be heard in space. In the past, we used huge ground stations to broadcast radio and television signals which could be picked up relatively easily — according to astronomers' calculations anyway. Now we use satellites that transmit at 75 watts and point toward Earth instead of into space. In addition, we've switched to digital which makes the transmissions even fainter. Drake has concluded that very soon, in space no one will hear us at all. I guess we'd better keep listening."
Correct me if I'm wrong (I very well may be; I'm not overly familiar with the Drake equation), but doesn't that broadcasting time apply mainly to before a civilization has the technology to broadcast? What about when they still broadcast, but in such a way that their signals don't pollute deep space? Is that taken into account?
And this is a possible answer to the Fermi paradox. Well, after you accept that interstellar travel is not economically feasible.
Broadcast is not a great communication strategy. On-demand point-to-point communication takes over most things. Advanced civilizations go silent from the outside within a blink of them transmitting their first broadcast signals. There's no reason to think that we'll ever put serious effort into sending signals into the black given all the other things on our plate. And there's no reason to think that any other civilization would have such extra resources either.
Cheers.
Any civilization advanced enough to send an invasion force would most likely have the technology to resolve the contents of the earths atmosphere from great distances. Being scared of invasion does not buy much.
[Aliens] might have the technology and desire to invade earth.
Not if they have any economic sense in their heads. Unless the aliens have some sort of magic infinite energy source or teleportation device, the cost of transporting an invasion fleet to another solar system would be orders of magnitude higher than the value of anything they could possibly gain from Earth. And if they do have an infinite energy source or teleportation device, then they could use those inventions to provide for their needs directly, without leaving their home.
So if aliens invade, it will be for solely their own entertainment, not for economic reasons.
I don't care if it's 90,000 hectares. That lake was not my doing.
Yes, but the assumption was that civilizations stopped broadcasting into space because they ceased to exist. Now we can think, maybe there are civilizations out there that are extant, but past the point of radio broadcasts. This is good news if we hope that intelligent life is still out there.
There have been several attempts at sending radio messages into space specifically for communication purposes. Whether we keep that up or not is independent of our use of radio for intraplanentary communications.
If you're an alien dude who wants to score with the alien chicks, you might just impress them by collecting humans. You could embed a human in a chunk of pure carbon-12 diamond, mount that in an iridium ring, and slip it onto her tentacle. She might have thousands of tentacles.
Maybe you collect humans to sell as an aphrodesiac. You puts the heads on top of a snack, kind of like sea urchin eggs on sushi.
Maybe you lay eggs in the humans. Ever see that movie with the pods? The aliens take over human bodies. An infected human passionately embraces an uninfected human, and then the alien penis-thing (an ovipositer maybe?) bursts out of the infected person's forehead and stabs right into the uninfected person's forehead.
Maybe you even mate with the humans. You keep them in your flying saucer and rape them with **all** your tentacles in every oriface. When the alien babies are ready to be born, the humans explode.
I've been critical of SETI efforts for this reason. Much SETI effort was focused on looking for "carriers", big constant-frequency RF sources. Broadcast AM, FM, and analog TV (which was AM video, FM audio) have strong carriers, but that was hugely inefficient. About 80% of an analog TV station's power output wasn't conveying any information other than "We're here". As receivers improved, new RF technologies used weaker carriers, then suppressed carriers, and finally, with spread spectrum, dropped the whole concept of carriers. Many modern RF signals appear to be noise unless you understand the encoding. (The same thing happened to modems decades ago; at 300 baud, you heard tones; at 9600 baud and up, it sounded like white noise.)
I once pointed out to a speaker at Stanford promoting some SETI scheme that they couldn't detect any emission that the FCC would now license for a new application. He admitted that was true. For our civilization, there was less than a century of high-powered carriers. That's a narrow window to hit for SETI purposes.
Arguably, though, any sufficiently advanced civilization will monitor all RF passing through their solar system and will be able to detect anything which has a pattern which can be synched up. Although carriers are going away, all signals between distant points need some form of synchronization information. The synch information may be a tiny fraction of the transmitted data, but there has to be something upon which the receiver can lock.
We have large synchronized power grids. They'll get a signal that's 2x the line frequency. As the Earth turns, you get modulation of various sorts: frequency, phase, amplitude.
Amplitude goes down for oceans, and up for land. You get more 100 Hz for the Old World, and more 120 Hz for the New World. As different country-sized areas with the same line frequency pass into view, you get phase change.
It all has a nicely repetitive 24-hour period.
The smart aliens will use full encryption anyways so no way to tell any transmission apart from background radiation noise anyways. Think TrueCrypt plausible deniability ;)
I'm presuming the extraterrestrials have developed technology to travel between galaxies in a few months or less.
I wouldn't expect a space ship to be usable as a comfortable living environment for extended periods of time.
There's a lot the Drake Equation fails to account for. As a mathematical estimate, it's fairly useless. Its chief contribution to science (although some might question whether this is a contribution) is that it gets people talking about extraterrestrial life.
maybe they wouldn't need a big fleet.
just one virus
or nanobots - grey goo us all...
to stop the pink goo*
*: Pink Goo is mankind. It replicates relatively slowly, but some people think it will nevertheless fill any amount of space given enough time. In the pink goo worldview the spread of humanity is a catastrophe and space exploration opens up the possibility of the entire galaxy or the universe getting filled up with Pink Goo - the ultimate crime, something to be stopped at any cost.
Exception Duck - may or may not contain chicken.
His guess was that the broadcasts would last for 10,000 years. So yeah, he was thinking the radio emissions would last as long as the civilization was capable of producing them.
We hope your rules and wisdom choke you / Now we are one in everlasting peace
Imagine a sphere of radio transmissions expanding at the speed of light from every civilized planet - sooner or later these are going to permeate space, so if you can't detect anything it starts to look a bit odd.
Now imagine that civilizations typically switch to non-broadcast and/or digital signals (the latter, if efficiently compressed, will "sound" like random noise) within a century of inventing radio. Instead of spheres, space will be full of 100 light year thick "shells" of easily detectable signals. So its far more likely that we find ourselves in one of the gaps between shells.
Of course, the Drake equation/Fermi paradox ideas are only plausibility arguments, make all sorts of assumptions about how civilizations develop based on extrapolation from one data point (us).
In a survey of 100 programmers, 111111 thought that duck-typing was a good idea.
Radio waves spread in accordance with the inverse square law. For every doubling in distance traveled, they become 1/4 as strong. It may well be that the *practical* limit for detecting our own tv/radio signals is somewhere near Alpha Centauri, but that's a limit imposed by our own equipment. The signal propogates forever, or at least until it's stopped by another planet/star/comet/dust/whatever. And space is mighty vast and mighty empty.
I have no problem with your religion until you decide it's reason to deprive others of the truth.
No, more advanced.
Violence doesn't matter, since it makes no difference whom initiates, so if the less advanced civilization is more violent the end result is the same as if the more advanced civilization is more violent.
Alpha Cenrauri is about 4-1/2 light years away. Electromagnetic energy would get there in 4-1/2 years. As a result, they've long since lost interest in I Love Lucy (if anyone is there and listening). There are about 50 stars within 15 light years. We can't uncap that bottle, so we'll have a stream of broadcast television and radio signals continuing on the journey, lasting for decades. The fact we stop doesn't mean we're suddenly invisible. We've left some tracks in the sand on a calm beach. I'm pretty confident we don't have an invasion fleet coming at this point in the game, but if they are, I bet they think we taste like chicken.
A great book on the early discovery of sentient species by a superior species:
The Killing Star
Relativistic weapons impacting earth from outer space with Michael Jackson's "We are the world" warbling in over all the radio frequencies.
Great book.
I tried every decent and legal way I could think of to resolve the issue w/the business before I rented the chicken suit