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rfmcdonald80 Beats has the happy news.
The post ends by reporting Drake's suggestion that SETI researchers will have to look harder, but radio engineer Scott Bidstrup argues in a very detailed essay that even outside the questions of digital transmissions making the identification of coherent signals unlikely and the exceptional sensitivity that would be required, simpler factors like the movements of the Earth and the width of narrow-beam transmissions make it unlikely that anything but the loudest beacon would be detected. There's only a narrow period of time between the advents of analog and digital radio transmissions, judging by our experience, and there's little enough that makes our planetary system a likely target.
The telescopic observation of worlds in other planetary systems might be more likely to produce signs of extraterrestrial civilization, he concludes. That doesn't give us quite the amount of safety we might like--we might have gone dark to worrisome extraterrestrial civilizations, but with sufficiently large telescopic arrays they'd be able to see some of our more impressive works--but I'm pleased with this all the same. In order to avoid being caught by far more capable predators with many sharp teeth, small prey need to make as quiet a ::meep:: as possible.
If you’ve been expecting to hear from a far-off alien civilization, don’t hold your breath, suggests Frank Drake, the founder of Search for Extraterrestrial Intelligence (SETI)–the odds of ET phoning Earth may be diminishing. And your digital TV might well be to blame.
Speaking at a meeting of the Royal Society in London, Drake said that digital transmissions are effectively “gagging” the planet. In the fast-fading analog age, TV and radio signals transmitted around the world escaped into space. At present, the Earth is surrounded by a 50 light year-wide ‘’shell” of radiation from analogue TV, radio and radar transmissions, he said [The Telegraph]. Those signals reach distant stars, which means that if someone is home at any of those stars, they could heard us.
But Drake says that phasing out analog transmissions from TV, radio and radar is making our planet electronically invisible from outer space. While an old-style TV transmitter might generate one million watts, Drake says the power of a digital satellite signal is around 20 watts. He added that present-day satellites tend to point towards the earth rather than old-school transmitters which beam their signals all over the place [The Guardian], and notes that digital cable is even more impossible to detect from space. He also said that if Earth is making itself “invisible,” albeit unintentionally, then other civilizations are probably doing the same. And he further hypothesizes that in some cases it might even be deliberate; a proverbial drawing of the kitchen blinds, so to speak [Wired].
The post ends by reporting Drake's suggestion that SETI researchers will have to look harder, but radio engineer Scott Bidstrup argues in a very detailed essay that even outside the questions of digital transmissions making the identification of coherent signals unlikely and the exceptional sensitivity that would be required, simpler factors like the movements of the Earth and the width of narrow-beam transmissions make it unlikely that anything but the loudest beacon would be detected. There's only a narrow period of time between the advents of analog and digital radio transmissions, judging by our experience, and there's little enough that makes our planetary system a likely target.
If our experience is typical, for any given alien civilization out there, we've got only about a hundred year window from the time they discover radio and are using modulation techniques that generate signals of a type we can detect, to the time they start using digital signals that to us are indistinguishable from noise. During that brief time, they have to use high-powered microwave transmitters and huge parabolic antennas that are sufficient to generate signals concentrated enough for us to detect them, and that means the chances of their transmitting in the right direction are one in tens of millions; we have to be listening at just the right time (during a window of a few seconds per day), a chance of one in thousands, and on the right frequency out of an infinity of frequencies, and our listening in just the right direction for just the right type of emission.
But are they transmitting in our direction deliberately? The possibility exists that another civilization may be attempting to attract our attention, and doing so with a beacon signal aimed our direction.
Why would they suppose that this very ordinary star of ours, with its very ordinary solar system is any different than most, in that it harbors a supposedly intelligent civilization? Our solar system does not really stand out in any way that would presuppose they would think it a likely candidate. A far more likely candidate would be a solar system with a Jupiter-like planet orbiting about the same distance from the sun as us, a planet with a large family of moons, one or more of which is likely to be the right size to be earthlike. That lets us out. Our solar system is more unlikely than most - an earth-sized body too close to its star to be habitable (Venus), and another body at just the right distance, but too small to retain an atmosphere that is thick enough to make it hospitable or even habitable (Mars). The planet in the middle between them has a large moon, meaning it has been the object of a collision with a sizeable planet in the distant past, and that reduces the likelihood of its habitability. Likely to be a desert planet, with a thin atmosphere, bombarded by lots of meteorites, enough to make a civilization unlikely. Guess we'd best pass that solar system up and aim our beacon beam elsewhere towards a more likely candidate solar system.
The telescopic observation of worlds in other planetary systems might be more likely to produce signs of extraterrestrial civilization, he concludes. That doesn't give us quite the amount of safety we might like--we might have gone dark to worrisome extraterrestrial civilizations, but with sufficiently large telescopic arrays they'd be able to see some of our more impressive works--but I'm pleased with this all the same. In order to avoid being caught by far more capable predators with many sharp teeth, small prey need to make as quiet a ::meep:: as possible.
