In an Op-Ed in the New York Times, one of America’s leading astrophysicists says there’s a damn near zero percent chance that we are alone in the universe.
Adam Frank is a professor of astrophysics at the University of Rochester, with a focus on computational astrophysics (using computers to figure out space, I guess, is what that means).
He said that, given the recent discover of nearly 2,000 exoplanets by the Kepler Space Telescope, it’s a mathematical certainty that at some point in the history of the universe, somewhere, there have been aliens.
Does our newfound knowledge of planets bring us any closer to answering that question?
A little bit, actually, yes. In a paper published in the May issue of the journal Astrobiology, the astronomer Woodruff Sullivan and I show that while we do not know if any advanced extraterrestrial civilizations currently exist in our galaxy, we now have enough information to conclude that they almost certainly existed at some point in cosmic history.
The proof he uses for this is the Drake equation, which calculates the likelihood of an alien species making contact with us.
Among scientists, the probability of the existence of an alien society with which we might make contact is discussed in terms of something called the Drake equation.
The first factor was the number of stars born each year. The second was the fraction of stars that had planets. After that came the number of planets per star that traveled in orbits in the right locations for life to form (assuming life requires liquid water). The next factor was the fraction of such planets where life actually got started. Then came factors for the fraction of life-bearing planets on which intelligence and advanced civilizations (meaning radio signal-emitting) evolved. The final factor was the average lifetime of a technological civilization.
Frank Drake came up with the equation in 1961. Unfortunately, at that time, almost all his variables were unknown. Now, that’s no longer the case.
In 1961, only the first factor — the number of stars born each year — was understood. And that level of ignorance remained until very recently.
But our new planetary knowledge has removed some of the uncertainty from this debate. Three of the seven terms in Drake’s equation are now known. We know the number of stars born each year. We know that the percentage of stars hosting planets is about 100. And we also know that about 20 to 25 percent of those planets are in the right place for life to form. This puts us in a position, for the first time, to say something definitive about extraterrestrial civilizations — if we ask the right question.
And by flipping the Drake equation, Frank thinks he’s found an answer to it.
In our recent paper, Professor Sullivan and I did this by shifting the focus of Drake’s equation. Instead of asking how many civilizations currently exist, we asked what the probability is that ours is the only technological civilization that has ever appeared. By asking this question, we could bypass the factor about the average lifetime of a civilization. This left us with only three unknown factors, which we combined into one “biotechnical” probability: the likelihood of the creation of life, intelligent life and technological capacity.
You might assume this probability is low, and thus the chances remain small that another technological civilization arose. But what our calculation revealed is that even if this probability is assumed to be extremely low, the odds that we are not the first technological civilization are actually high. Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.
What does that mean?
To give some context for that figure: In previous discussions of the Drake equation, a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic. According to our finding, even if you grant that level of pessimism, a trillion civilizations still would have appeared over the course of cosmic history.
Well there you have it. Cue the Blink-182.
[Via The New York Times]