Astronomers are working on more expensive strategies as well: One idea that's been around for quite a while calls for putting a radio observatory on the far side of the moon, virtually the only place in the solar system that is perpetually shielded from terrestrial transmissions.
Another way-out strategy would be to set up a monitoring station far from the sun - maybe 500 to 1,000 times as far away as Earth. At that distance, the sun could focus light waves (and radio waves) from cosmic frontiers like a giant lens.
"We could well have an Internet for the galaxy, based on gravitational lenses," Drake said. Berkeley astronomer Dan Wertheimer, one of the scientists behind the SETI @ home alien-hunting screensaver program, said observers at such a gravitational-lens observatory could "read the license plates on an extrasolar planet."
And if things get too quiet on Earth, as Drake suspects, that might be just a temporary situation. The deployment of space solar-power satellites would involve sending gigawatts' worth of power down to Earth, and some of that energy would be reflected back into space. "If we go this route, the earth will become visible again," Drake said.