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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."
This issue was already known to Drake when he formulated his famous equation -- a key parameter is the time window during which a civilisation is broadcasting radio signals.
It reduces the probability that earth could be quickly located.
We gotta consider the possibility, that any extraterrestrials close enough to hear our signals in any reasonable amount of time, and with the sophistication to pinpoint us....
Might have the technology and desire to invade earth.
E.g. Consider earth itself... fast forward a few dozen generations...... massive overpopulation, lack of resources, land, severe overcrowding.
Extreme desire for another habitable place to live.
And then you detect an alien signal.. a foreign world. You step foot there, and you're greeted by basically an aboriginal species (compared to your civilization).
Habitable world, massive resources, very primitive 21st-century level technology, nothing compared to your 23rd century tech.
Oh.... so some colonists start travelling from earth to 'the new world' for a better life.
Settlers VS the Natives all over again.
It's happened before, it could happen again. Except us earth inhabitants could be the primitive natives / "Indians" / etc.
Scary, huh? :)
Has anyone considered the historical evidence of what happens when superior civilizations encounter lesser ones? The Native Americans, the Mayans, the Incas, the Australian Aborigines, the tribes of South America, the natives of Pacific Islands, to name a few, all cry out to humanity to avoid at all costs encounters of the first, second, and third kinds. We have no reason to expect anything but annihilation from advanced alien races- either they are truculent and violent like we are, or they will destroy us as a service to the rest of the galaxy. We do not wants aliens to find us!
I keep asking this question: Why can't we detect ET's transmissions?
DRM'ed, no doubt.
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.
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.