“Getting a Ph.D. in astrophysics is already like jumping off a fucking bridge,” Siemion tells me. “The likelihood of getting a tenure-track faculty job is so small—it’s difficult to hitch your wagon to anything that’s not guaranteed. Graduate students are really smart and savvy, especially about their career. They know who is getting tenure-track jobs. It’s easier to recruit graduate students when you have $100 million, but to make it sustainable over time, you need government funding, or you need an endowment.”

I tell Siemion he should be pitching Elon Musk. In recent years, Musk has been vocal about how badly he wants to know whether intelligent life exists elsewhere in the universe. Siemion says he has yet to reach out to Musk, but he hints that other help might be on the way. He tells me that Milner prefers a “collaborative” investing style. In his private-sector investments, Milner doesn’t like to fund more than 20 percent of a venture. “It’s not me who is going to be talking to Musk,” Siemion says. “It’s Milner.”

I ask Siemion if he’s nervous about testifying at a congressional hearing for the first time. “In the past, there has been a ‘giggle factor’ around SETI,” Siemion tells me. “There have been a couple of times when some person in Congress will use SETI as an example of wasteful government spending.” Most recently, in 1991, the former Senator Richard Bryan, a Democrat from Nevada, successfully lobbied for the termination of NASA’s SETI program.

SETI has more swagger now, and more scientific credibility, thanks to the recent discovery of planets orbiting other stars. The profusion of new planet discoveries also motivated Milner’s pledge, which is going to buy some sweet science: An international consortium of SETI institutions will use the money to fix sensitive radio telescopes on thousands of local stars, to listen for radio beacons directed at Earth. The program, called Breakthrough Listen, will search each star more thoroughly than any single star has ever been searched. There is also talk of using the Square Kilometer Array to check nearby stars for unintentional radio leakage, the sort that comes from ordinary technological activity, like television broadcasts.

I tell Siemion that radio searches have always felt parochial to me, because they’re fixated on technologies we use now, or those we can imagine using. But our technological imagination is likely to be quite limited. After all, we’re only a few centuries removed from the industrial revolution, and that’s a mere microsecond on cosmic time scales. If there are technological civilizations littered throughout the galaxy, ours is almost certainly among the youngest, meaning our technology is most likely primitive, in the extreme. For all we know, searching for radio signals is like searching for Olduvai hand axes.

Siemion answers by quoting Jill Tarter, the former Director of the SETI Institute and Carl Sagan’s inspiration for the heroine of Contact. “We reserve the right to get smarter,” he says. “But for now, we have to do the best searches we know how to do, with our current understanding of physics.”