Arecibo Diary: Big Dish, Big Hopes

Friday, October 20, 2000 9:35 p.m.
by Seth Shostak, Senior Astronomer

There are people who don't like this observatory. For decades, a few Puerto Rican Independentistas and members of the local communist party have railed against the Arecibo telescope, fingering it as a subtle, possibly dangerous instrument of Yankee imperialism.

The staff worried that extremists might blow up the antenna's cable moorings, with discouraging consequences for the astronomers. The communist newspaper was fond of claiming that the observatory was a repository of nuclear weapons (presumably in case of attack by Jamaica). When reporters from the paper were invited over, they intently photographed the transmitter klystrons, believing they were bombs.

The mood today is less dark. Video cameras have replaced many of the guards who once occupied small shacks set around the antenna's rim. The locals are overwhelmingly proud of this telescope - the world's most massive radio research instrument - and thousands of students and tourists visit the site every week.

There are no bombs here, but this antenna packs a heck of a punch. Its collecting area is roughly ten times that of the next largest telescope. This translates into either speed or sensitivity, depending on your personal predilictions. In the same amount of observing time, Arecibo will reach three times farther into space than its competitors. Alternatively, it can find a signal at equal distance in 1/100th the time. Bigger really is better.

The Project Phoenix staff especially appreciates the sensitivity. We can detect a narrow-band broadcast from another world if it's splashing as little as 0.0000000000000000000001 watts of power onto the observatory's 1,000-foot dish. If aliens 100 light-years distant wield an Arecibo-sized antenna, a pipsqueak 10 kilowatt transmitter will be sufficient to get in touch. That's the power consumed by a dozen hair driers.

But would they try to get in touch? After all, earthlings don't deliberately broadcast to aliens, so why should the aliens broadcast to us? Answering this question requires some insight into alien psychology. Alas, the professional literature on this subject is meager. The extraterrestrials may have large transmitters set up to search for incoming comets, or in service as a galactic GPS system. Maybe they've established space colonies and are beaming communiques back and forth. Earthlings have had radio for a century. Some aliens may have had it for tens of millennia. It's hard to guess what use they might make of this technology.

But one thing is indisputable; radio is the least expensive way to send bits of information from star to star. Whatever the aliens might be up to, it is more than reasonable to assume that they're filling the galaxy with radio signals.

So The System grinds on, stepping methodically up the dial, moving from star to star. In the last week, the most exciting source has been 4181, an F7 star 250 light-years away. The System found a signal in the direction of 4181 that was so compelling, it rang pagers back in California. The putative alien transmission turned out to be only a bit of strong, earthly radar.

That was a false alarm, but the real thing could still happen. There's a magnum of Mumm Cuvee Napa chilling in the corner refrigerator, just in case.

Some folks think we're chasing wild geese, just twiddling our electronic thumbs. Most of the world, to be candid, is probably oblivious. Project Phoenix is a small experiment, with a payroll of two dozen people. It's taking place in a part of Puerto Rico that few people care about. What happens here is far removed from the immediate tribulations of ordinary life. But if the signal comes in, this small effort will initiate a supremely profound reaction. For a million years, we have been like fish in a bowl, busy with our own lives. A SETI success would transport us to the ocean, opening us to the myriad possibilities of a vast and populated cosmos.