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 × LWhere,
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.
JOIN THE SEARCH:Posted by Stephen Gordon at July 26, 2004 10:44 AM | TrackBack