living standards. Simultaneously, extinction rates of natural species had soared due to environmental disruption and habitat destruction. The land was laced with superhighways, power transmission lines, and fiber-optic communications networks; the sky was crisscrossed with transcontinental jet contrails and the starlike gleams of orbital satellites; the air itself was filled with electromagnetic chatter from radios, televisions, and mobile phones, as well as with rising amounts of carbon dioxide from the frenzied combustion of the planet’s reservoirs of fossil fuel. Rapid, successive revolutions in information technology had made powerful computers networked, ubiquitous, and personal, creating vast virtual realms often only tenuously linked to the world of atoms.
What those changes meant for the future of our culture and our world remained to be seen, though it seemed possible that, given a few centuries’ time, we might not even recognize whatever our descendants had become. I mentioned to Drake that many of the same Silicon Valley tycoons who helped fund the SETI Institute often chattered about a dawning era of even more radical and rapid change, a coming “technological singularity” in which exponential growth in computingpower and sophistication would profoundly transform, at minimum, the entire planet. Some techno-prophets spoke worshipfully or fearfully of computers becoming sentient and gaining godlike powers. Others speculated that someday humans would break free of their carbon-based chains by uploading their minds into silicon substrates, where they could, in some manner, live forever. All seemed to agree that if humans themselves weren’t destined to inherit the Earth, they would certainly author whatever ultimately would. A few even conjured up the bygone Space Age dreams of Drake’s youth, envisioning a new golden era of prosperity and exploration in which humans would travel with their intelligent machines throughout the solar system, and perhaps someday to other stars.
“Yeah, I’ve heard all that stuff,” Drake replied. “It would be nice if we made it to Mars. But I don’t hold with the hypothesis that we’ll all slowly become or be replaced by computers. And of all the things we might someday do, I don’t think we’ll ever colonize other stars.”
I asked why not.
“I don’t think computers can have fun,” he said. “I think joy is a quality not available to computers. But what do I know?” He laughed. “Interstellar travel, on the other hand, I’ve worked on that quite a bit. Putting a hundred humans around a nearby star costs about a million times as much as putting them in orbit in your own system. You’d have to be pretty rich to pull that off.
“Let’s say you have two colonies ten light-years apart—that’s probably the typical distance between habitable planets, I’d guess. The fact is, you can’t really go faster than about a tenth of light-speed. At speeds higher than that, if you hit anything of any substance whatsoever, the amount of energy released approaches that of a nuclear bomb. So you’re limited to about ten percent, a speed we currently can’t come anywhere close to, and that means you’re looking at journey times of at least a hundred years. The distances, times, and speeds are daunting, but the most daunting thing of all is the cost. Take something the size of a Boeing 737 plane, which is about the smallest that might make areasonable crewed expedition, and send it at a tenth the speed of light to a nearby star, okay? Now just work out the kinetic energy that’s in it. It turns out to be about equal to two hundred years of the total electric power production in today’s United States. And that’s assuming a one-way trip, where you don’t even slow down and enter orbit on the other end. The inherent difficulty of interstellar travel is one of the big reasons why looking for things like radio signals is so appealing.”
“So you think we’re
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