The silence of the void
I've been fascinated by the search for extraterrestial life since I was a little kid, so I wasted no time clicking on the Drudge Report's headline about NASA saying that the discover of intelligent life on other worlds was less than 20 years away. Alas, it turns out to be just a CBS News report about NASA holding a press conference to tout its plans to search for E.T.s, and playing the numbers game to confidently assert that success must be right around the corner:
“Just imagine the moment, when we find potential signatures of life. Imagine the moment when the world wakes up and the human race realizes that its long loneliness in time and space may be over — the possibility we’re no longer alone in the universe,” said Matt Mountain, director and Webb telescope scientist at the Space Telescope Science Institute in Baltimore, which plans to launch the James Webb Space Telescope in 2018.
“What we didn’t know five years ago is that perhaps 10 to 20 per cent of stars around us have Earth-size planets in the habitable zone,” added Mountain. “It’s within our grasp to pull off a discovery that will change the world forever.”
Describing their own estimates as “conservative,” the NASA planet hunters calculate that 100 million worlds within the Milky Way galaxy are able to sustain complex alien life forms. The estimate accounts for the 17 billion Earth-sized worlds scientists believe to be orbiting the galaxy’s 100 billion stars.
The NASA panel says that ground-based and space-based technology – including the Hubble Space Telescope, the Kepler Space Telescope and the Spitzer Space Telescope – will be able to determine the presence of liquid water, an essential sign of potential alien life.
“I think in the next 20 years we will find out we are not alone in the universe,” said NASA astronomer Kevin Hand, who suggested that alien life may exist on Jupiter’s Europa moon.
Look, I hope they're right, and I hope I live long enough to see them proven right. I'm all in favor of using the best technology at our disposal to conduct the search for life in the universe. And I'm as bummed as anyone that it hasn't produced any results so far.
But just for starters, this whole P.R. opportunity is deliberately conflating intelligent life with non-terrestrial organisms that might be as simple as bacteria. Not that finding extra-terrestrial bacteria on, say, Europa wouldn't be a fantastic discovery, but (a) that ain't happening in 20 years, and (b) it would still be life from within this Solar System, created by the same forces that shaped life on Earth, "extra-terrestrial" in only the most stringently literal sense of the term.
Likewise, all this talk of how many planets must be orbiting various stars in habitable zones, or even the actual verified discovery of such worlds with potentially Earth-like water and atmosphere, is purely hypothetical, and unless those planets are pumping out electromagnetic signals like we are, it's not going to make any practical difference to the search for alien life for the next 20 centuries, never mind 20 years. Maybe we'll soon solve the riddle of faster-than-light travel and start exploring those other worlds, but unless something paradigm-changing like that happens, we aren't going to be opening any petting zoos on planets hundreds of light-years away.
As for the search for intelligent life, many astronomers find it somewhat perplexing we haven't picked up any bona-fide alien transmissions yet. But there are issues of range and signal degradation to consider, and above all, there is the almost incomprehensible scale of cosmic time. The human race has only been producing signals that could be detected from other worlds for less than a century. That's nothing, less than a grain of sand on the vast shores of time. For all we know, entire civilizations have risen and fallen in our region of the galaxy over the past few million years. Maybe there's one currently lumbering through its Stone Age around a nearby star. But contrary to all the talk about how the galaxy must be teeming with habitable worlds, it would actually be a stroke of incredible luck to achieve our current level of technology at the same time someone in the same galactic neighborhood is doing it.
And if there's a civilization reaching human levels of technology in the further reaches of the Milky Way, we ought to be picking up their early radio and TV programs in another millennium or so, assuming the signals aren't devoured by the background music of the stars. It seems like a reasonable assumption that most intelligent life would eventually begin emitting coherent electromagnetic signals, and perhaps the odds favor a great deal of such life existing in the universe, but the challenge of finding each other through the vast physical and temporal void separating us is formidable.