## Michael Crichton and SETI

Michael Crichton, as you will have heard by now, is dead. Unfortunately.

The *Wall Street Journal* today reprinted an excerpt of a speech Crichton gave called “Aliens Cause Global Warming.” Regular readers of this blog will know Crichton’s opinion on the certainty of man-made catastrophic climate change. Just a reminder (from his speech):

No longer are [climate] models judged by how well they reproduce data from the real world — increasingly, models provide the data. As if they were themselves a reality. And indeed they are, when we are projecting forward. There can be no observational data about the year 2100. There are only model runs.

This fascination with computer models is something I understand very well. Richard Feynman called it a disease. I fear he is right. Because only if you spend a lot of time looking at a computer screen can you arrive at the complex point where the global warming debate now stands.

Nobody believes a weather prediction twelve hours ahead. Now we’re asked to believe a prediction that goes out 100 years into the future? And make financial investments based on that prediction? Has everybody lost their minds?

To explain why he was flummoxed, Crichton first made a point about SETI, the Search for Extraterrestrial Intelligence. A lot of people in that field make reference to the Drake Equation, originated by SETI big cheese Frank Drake. That equation is

- N = R
^{*}x f_{p}x n_{e}x f_{l}x f_{i}x f_{}X L

.

We want to solve for N, which is the number of civilizations in our galaxy with which intelligent communication is possible. N depends on the rate of star formation R ^{*}, the fraction f_{p} of those stars that have planets, and all those other things you can look up.

Crichton says:

This serious-looking equation gave SETI a serious footing as a legitimate intellectual inquiry. The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. And guesses — just so we’re clear — are merely expressions of prejudice. Nor can there be “informed guesses.” If you need to state how many planets with life choose to communicate, there is simply no way to make an informed guess. It’s simply prejudice.

The Drake equation can have any value from “billions and billions” to zero. An expression that can mean anything means nothing. Speaking precisely, the Drake equation is literally meaningless, and has nothing to do with science. I take the hard view that science involves the creation of testable hypotheses. The Drake equation cannot be tested and therefore SETI is not science. SETI is unquestionably a religion.

The fact that the Drake equation was not greeted with screams of outrage — similar to the screams of outrage that greet each Creationist new claim, for example — meant that now there was a crack in the door, a loosening of the definition of what constituted legitimate scientific procedure. And soon enough, pernicious garbage began to squeeze through the cracks.

I agree with him that none of these terms can be known exactly, or even sufficiently precisely to calculate a quantitative answer for N. I also agree that the pursuit of N can take on religious qualities.

But I can’t agree that SETI itself is worthless, nor can I agree that interest in it loosens the definition of “legitimate scientific procedure.” SETI is not just the Drake equation.

Now, I will not attempt to defend even one procedure that SETI workers use, nor will I comment on any statement made by any of its proponents. I cannot say, for example, that searching nearby stars for signals in the hydrogen line makes any sense. But I will say SETI is not the same as religion

I am interested in saying something about the probability of this proposition:

S = “Intelligent/sentient life besides that on planet Earth exists”

Because we must calculate the probability of S is conditional on some evidence, I offer this blog. Yes, because this blog—because you and I—exist, it means that the universe is set up to allow at least one species of sentient life. Therefore, it is rational to believe that the probability of S given this evidence is greater than 0. I have no idea how much larger than 0 it is. If you are a fan of the reasoning behind the Fermi Paradox, you might say that the probability, while non-zero, is trivially small.

The Fermi Paradox basically says that, since the universe is about 10-13 billion years old, and the one sentient-life example we know of only took about 4-5 billion years to evolve, and since there are plenty of stars and galaxies, there should be sentient life all over the place. That is, SETI should be easy, and since it isn’t, since we haven’t made contact yet, this implies that we are the first or only sentient species. There are obvious subtleties to each stage of that argument that I glossed over, but that’s the gist.

The Fermi Paradox is also conditional on information not articulated. One obvious item is the proposition that all sufficiently advanced civilizations would want to make contact with us. Not just with other species, but with us. That’s a mighty big supposiion. Another hidden assumption is that we ourselves are sufficiently advanced enough to detect messages aimed at us, or have the ability to intercept messages meant for other beings. Pretty big guess, especially with the knowledge that the more efficient a message gets, the more it looks to an outside like noise (basic information theory; deep ties with probability and statistics there), and so civilizations more advanced than us might have communications which are impenetrable to us.

That argument cuts both ways, of course. If the messages are too complex, any search for them is fruitless. And, well, you get the idea. It’s complicated, so much so that it is not an open and shut judgment that SETI is valueless.

Though we have to be careful. Wishcasting is always a danger here, as everywhere. A lot of people—me included—want S to be true and this naturally clouds our judgment.