Dr. Drake started it all in 1960 when he pointed a radio telescope at a pair of sunlike stars hoping to hear a “hello.” He heard nothing, which has pretty much characterized the effort ever since.

No amount of cosmic silence, however, has been able to discourage astronomers who theorize that radio signals can bridge the gulfs between stars more cheaply than spacecraft, allowing distant species to communicate by a sort of cosmic ham radio or galactic Internet. And, they note, only a few thousand of the Milky Way’s 200 billion stars have been sampled, on only a few of the billions of possible radio channels — a minuscule piece of what they call the “cosmic haystack.”

A simple squeal or squawk, or an incomprehensible stream of numbers by a radio antenna pointed at one of those stars, would change history.

“We have a responsibility to not stop searching,” Mr. Milner said in an interview. “It should always be happening in the background. This is the biggest question. We should be listening.”

Mr. Milner has recruited a small coterie of scientists to run the project. Among them are Martin Rees of Cambridge University, Britain’s astronomer royal, who will lead an advisory group; Peter Worden, former director of the NASA Ames Research Laboratory, home of the Kepler effort; Geoffrey Marcy of the University of California, Berkeley, a renowned exoplanet hunter; Dr. Werthimer; Andrew Siemion, also of Berkeley; and Ann Druyan, a co-author of both “Cosmos” television series and widow of the astronomer Carl Sagan.

According to Dr. Werthimer, about a third of Mr. Milner’s money will go toward building new receiving equipment, and about a third will go toward hiring students and other astronomers.

The rest will be used to secure observing time. For now, that effort will include two of the largest radio telescopes in the world: the Robert C. Byrd Green Bank Telescope in West Virginia and the Csiro Parkes Telescope in New South Wales, Australia.