Slate: What's your plan to find aliens?Read the rest of the interview.
Marcy: If Gene Roddenberry is right and the Klingons and the Romulans are really out there, they have to communicate with each other. They aren't going to do this by stringing fiber optic cables between the stars, they are going to do it with lasers. Lasers are a logical way to go, because you can maintain a level of privacy by confining your laser to a beam narrow enough that it just hits a spacecraft or the civilization that's around another star three light years away. Not to mention, you save energy. Why spread energy everywhere like a radio transmitter does?
If our galaxy is teeming with advanced technological life, it has lasers crisscrossing it—tens of thousands, millions of them—and we should be able to pick up some spillover. Also, some aliens are going to try to communicate with us. Maybe they are literally pointing their lasers at us and we just aren't looking.
Slate: You think aliens may have identified Earth as a habitable planet?
Marcy: In the next century or two, we humans will have planet-finder telescopes that span our solar system with mirrors strewn from here to Jupiter, giving us enormous angular resolution so we can do the kind of science that a self-respecting advanced civilization ought to be doing. We should someday be imaging the continents on other planets. We can't do that yet, but aliens can do that already, so they know we are here.
Slate: What makes you sure aliens can do this already?
Marcy: Oh, because our galaxy is 10 billion years old. The Earth is only 4.5 billion years old. We are a firefly flicker in the great astrobiology of the galaxy. They presumably have had their light bulbs on for much longer.