July 26, 2004

Moore Meets Drake

Seth Shostak of the SETI Institute is predicting "First Contact" with an alien civilization within a generation. To be specific the prediction is:

If intelligent life exists elsewhere in our galaxy, advances in computer processing power and radio telescope technology will ensure we detect their transmissions within two decades.

Shostak came to his conclusion by taking assumptions about alien civilizations already adopted by SETI to determine how long it will take us to find the first civilization with accelerating technology.

This brings together two ideas near and dear to the Speculist heart: Drake's Equation, and Moore's Law.

Drake's Equation was developed by Dr. Frank Drake to estimate the number of communicating civilizations in the galaxy. It is:

N = R* fp ne fl fi fc L

N = The number of communicative civilizations

The number of civilizations in the Milky Way Galaxy whose radio emissions are detectable.

R* = The rate of formation of suitable stars

The rate of formation of stars with a large enough "habitable zone" and long enough lifetime to be suitable for the development of intelligent life.

Fp = The fraction of those stars with planets

The fraction of sun-like stars with planets is currently unknown, but evidence indicates that planetary systems may be common for stars like the sun.

ne = The number of "Earths" per planetary system

All stars have a habitable zone where a planet would be able to maintain a temperature that would allow liquid water. A planet in the habitable zone could have the basic conditions for life as we know it.

fl = The fraction of those planets where life develops

Although a planet orbits in the habitable zone of a suitable star, other factors are necessary for life to arise. Thus, only a fraction of suitable planets will actually develop life.

fi = The fraction life sites where intelligence develops

Life on Earth began over 3.5 billion years ago. Intelligence took a long time to develop. On other life-bearing planets it may happen faster, it may take longer, or it may not develop at all. For more information, please visit Dr. William Calvin's "The Drake Equation's fi".

fc = The fraction of planets where technology develops

The fraction of planets with intelligent life that develop technological civilizations, i.e., technology that releases detectable signs of their existence into space.

L = The "Lifetime" of communicating civilizations

The length of time such civilizations release detectable signals into space.

The problem with Drake's equation (which Drake would certainly acknowledge) is that all variables are unknown. We can make educated guesses, but we can't know with any degree of certainty as long as our sample size for known civilizations is one.

Nevertheless, in attempting to maximize the chances of finding an extra terrestrial civilization, SETI has made some assumptions. Shostak took those assumptions and found that between 10,000 and one million radio transmitting civilizations should exist in this galaxy.

We have a lot of territory to search - there are about 100 billion stars in our galaxy. Fortunately, for purposes of the search, many stars can be excluded from the survey as being outside of the Galactic Habitable Zone.

Shostak also took into account existing and planned radio telescopes and our improving ability to analyze these signals with computers.

Shostak assumed that computer processing power will continue to double every 18 months until 2015 as it has done for the past 40 years. From then on, he assumes a more conservative doubling time of 36 months as transistors get too small to scale down as easily as they have till now.

Within a generation, radio emissions from enough stars will be observed and analysed to find the first alien civilisation, Shostak estimates.

There are naysayers:

Paul Shuch, executive director of the SETI League, a separate organisation in New Jersey, says Shostak's prediction ignores one important factor. "It is altogether reasonable to project the development of human technology, based upon past trends and planned investments," he says.

"But predicting the date, the decade or even the century of contact is another matter because the 'other end' of the communications link is completely out of our hands. It would be nice to think we know something about the existence, distribution, technology and motivation of our potential communications partners in space, but in fact, we don't."

Shuch is right that we don't have any knowledge about alien civilizations. Drake's equation has always been better for providing a framework for speculation than for proving anything. But Shostak has expanded Drakes' framework and has given SETI a goal.


Richer All the Time

Fisking Sci Am


Posted by Stephen Gordon at July 26, 2004 10:44 AM | TrackBack

That's odd. I see on the Foresight Exchange that it's 24-26% by 2050. Didn't even budge when the news came out.

Posted by: Karl Hallowell at July 27, 2004 12:14 AM

Stephen -

What's the estimated radio footprint of a civilization expected to be? Ours would be about 100 light years and counting. It's been suggested that eventually computer technology leads technological civilizations to pursue inner, rather than outer space. In Greg Egan's fiction, this is called the problem of "solopsism." So maybe there are lots of civilizations out there, but they've gone quiet because they've moved out of the "real" universe into syberspace.

If so, the universe is still frustratingly quiet, but at least it's not because there is no one there, or because civilizations always nuke themselves out of existence.

Karl -

How long does news such as this typically take to filter into the Foresight Exchange? Also, does the market typically overreact to new developments the way financial markets do?

Posted by: Phil at July 27, 2004 10:02 AM

How long does news such as this typically take to filter into the Foresight Exchange? Also, does the market typically overreact to new developments the way financial markets do?

First, I'd have to say that my original quip was somewhat tongue in cheek. There are some problems with the market for this particular claim.

How well news filters depends on the FX (Foresight Exchange) claim. The claim mentioned above, "XLif2" is relatively illiquid. Those tend to respond poorly to news stories unless the news is widely reported. This story was relatively well reported and XLif2 did trade in the near past so I think the current market price reflects it to an extent, but it may take a while for the market to adjust.

Claims that have a lot of investment and a fair number of investors respond well to news stories. So FX may be inaccurate when predicting the future, but it's generally much better at reacting to news. There have been many times when I find out about a news story by observing the trading on FX.

The Foresight Exchange seems to be a typical market. Sometimes it overreacts to new information (there's one funny example involving sun spot counts and an almost completely ignorant market) and sometimes it doesn't react enough.

I think a more crucial moment will occur when the corresponding paper detailing the arguments for this probability is published (hmmm, no evidence of a preprint out there, too bad).

My feeling is that this paper won't measurably change the odds of the contract because no new information is really present. Drake's equation doesn't really give us a framework for calculating the odds past a crude point. We can estimate the number of potentially livable worlds and that's as far as we can get now without venturing into the real of fantasy.

OTOH, one crucial piece of information I personally lack is a good estimate of the growth in sensitivity, frequency bandwidth, and other parameters of the search space of future SETI programs. This author may be able to provide that. That sort of information could change the estimate of XLif2 (even if it influences just one trader). Another possibility is that this news story could entice new investors which is significant for an illiquid claim. In such a claim, a single dedicated investor could substantially change the price of the claim over time.

Posted by: Karl Hallowell at July 27, 2004 05:21 PM
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