Earth off the radar

The ever-reliable Reg. ET won't find us because we're increasingly invisible, according to a Reg story, Earth to disappear from alien radar. Remember that scene in Contact where they finally decode part of the alien signal, and it's an image of a Nazi swastika? "Oh, great," moans one despairing Federal meddler, wearily. Talk about putting your best foot forward. Well, that foot is getting retracted.

According to New Scientist our transition from radio tranmissions to cable TV could mean that our window of detectability is no more than 100 years.

Maybe that's good - there's some real room for doubt about the existence of terrestrial intelligence in what's coming out on cable these days. The Drake Equation may have to be revised to include the length of time that a civilization maintains a minimum level of intelligence.

The New Scientist article is pretty interesting

Chances of aliens finding Earth disappearing

15:59 09 August 04

NewScientist.com news service

A pioneer of the search for extraterrestrial intelligence (SETI) has warned that for any intelligent aliens trying to search for us, "the Earth is going to disappear" very soon.

What?! No more Star Trek reruns? OK, they've got those archived several times over already, but what about upcoming seasons of CSI?

Frank Drake's point, made at a SETI workshop at Harvard University on Friday, is that television services are increasingly being delivered by technologies that do not leak radio frequencies into space.

But he added that in some ways the observation is good news for SETI, as it means that the failure of Earth-based observers to detect aliens so far may be less worrisome than it would otherwise seem.

Somehow I don't think the Cold Silence from Space really gnaws at most people's sense of self-worth.

Most SETI efforts have focused on detecting radio signals that might be emitted by intelligent beings on planets around nearby stars. For humans, such signals "are the strongest signs of our existence", Drake said, thanks to television.

Traditional television broadcast antennas put out one megawatt each, and this radio-wave bubble now extends about 50 light years out from the solar system.

And the worst part of that is: there's no calling those photons back. ET will curse us forever for those horrible Neil Diamond songs that stick in your head in freeway traffic. And think of all those movies that Cuba Gooding Jr. has been in - worse, starred in - since Jerry MacGuire. They won't be used only to break ex-Taliban at Guantanamo. They can become part of the torture arsenal of any alien civilization.But don't worry - a paradigm shift is coming

Laser beacon

Drake's insight has important implications for search strategies. It means that eavesdropping on unintended alien transmissions is unlikely to succeed and "argues for an emphasis on detecting beacons", i.e. signals intentionally sent our way.

That's probably a good emphasis anyway - who wants to develop massive instruments for picking up every alien civilization's oversweetened breakfast cereal radio jingles, or the ET equivalent of Howard Stern? And we might decode these transgalactic cultural treasures only shortly before the originating civilizations snuff themselves out in their own global nuclear holocausts. It could give you some serious teen angst. Too much of it and we could turn into Planet of the SETI Goths.

Some SETI strategies have already begun shifting toward that approach, including efforts to find optical beacons based on high-powered lasers deliberately aimed at nearby stars.

Now this is actually pretty interesting stuff - try a Google on 'OSETI'. I was following this for a while, because of a slight interest in robotically-positionable amateur astronomer telescopes.

While optical communications across interstellar distances was initially thought impractical, military research has led to lasers sufficiently powerful to make such signalling much more efficient than any radio beacon.

And that kind of encouraging too, isn't it? Imagine approaching some general about using his Spy Satellite Killer Ray Gun to beam episodes of Mister Ed to a nearby star. They might make an exception for I Dream of Jeanie, but it's sort of a built-in crap filter to have the signal controlled by people with a reputation to uphold.

Nuclear-powered lasers on the drawing boards could produce pulses that would outshine the sun by a factor of 10,000, said Harvard University physicist Paul Horowitz, who has already been searching for such pulses. He has designed a new telescope that will soon be dedicated full-time to that search.

And other innovative ideas keep coming along. Planet hunter Geoffrey Marcy of the University of California, Berkeley, said someday we may learn to use the sun itself as a gravitational-lens telescope, with a detector parked at its focal length of 500 astronomical units.

Now that's truly visionary, you must admit. Of course, 500 AU is over 10 times the distance between here and Pluto's apogee, raising some questions about how you'd power any such unit to relay the signals from its orbit back down to Earth. Also, unless it had some maneuverability, it would be scanning the sky very slowly indeed. You'd need to launch a lot of these, I think.

But having done that, how likely is it that anybody out there would ever have to listen to - much less try to figure out - Rush Limbaugh?