E-Letter responses to:

special/news: Richard A. Kerr Are We Alone in the Universe? Science 2005; 309: 88 [Summary] [Full text] [PDF]

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Published E-Letter responses:

weak answer

John Macauley   (5 August 2005)

Flaw in Logic

Roberto Gonzalez-Plaza   (22 July 2005)

endless permutations

Paul G Mathieu   (22 July 2005)

We Must Put Time In the Equation

Bernard Raab   (6 July 2005)

Show Me the Numbers

Clinton P. Mah   (6 July 2005)

SETI : Is it looking in the right direction?

Harish Radhakrishnan   (1 July 2005)

weak answer 5 August 2005
John Macauley, tech executive Respond to this E-Letter: Re: weak answer	"The universe is big, so there's got to be life out there." That's the best you can do? I love this issue of Science, but that's a weak answer to this question. I admit I am stunned and surprised by the silence we've experienced. But we've listened to enough of the "audible" universe that we should have heard something if there were something to hear (I presume that other intelligent life would ask the same question -- and have been looking for us a lot longer than we've been looking for them!). And yet after years of listening -- nothing. It suggests to me that you're just hoping for a jingle from the stars before we conclude we're alone. And the implications of that conclusion are profound. I'll keep reading. You keep watching. Maybe we'll get lucky. Or not.
Flaw in Logic 22 July 2005
Roberto Gonzalez-Plaza, Faculty Northwest Indian College Respond to this E-Letter: Re: Flaw in Logic	Kerr's enthusiastic report on SETI and the search for "life" elsewhere in the Universe is logically flawed. Why does he assume that the probability of finding conditions leading to life-as-on-Earth has anything to do with terrestrial statistics?
endless permutations 22 July 2005
Paul G Mathieu, retired none Respond to this E-Letter: Re: endless permutations	I had long assumed that with some 10 to the 23 or 24 star systems in the universe, it was likely that intelligent life forms should also exist elsewhere. On reflection, I now doubt it: Over the last four plus billion years, we have gone through endless random permutations before the first living organism appeared, then we went through endless mutations, not to mention inumerable species extinctions, to arrive at our current stage. And out of these four billion years, only the last couple of hundred years can be thought of as significantly intelligent. That the same process should be repeated elsewhere in the universe might well be less than one in 10 to the 24th.
We Must Put Time In the Equation 6 July 2005
Bernard Raab, retired physicist Respond to this E-Letter: Re: We Must Put Time In the Equation	In his exposition of the probability of finding other intelligent life in the universe, Richard Kerr points to the enormous numbers of potential planets, which he concludes makes it only a matter of time before the evidence of such life is uncovered. But he ignores the very parameter, time, which may severely limit the number of candidate planets inhabited by such life. In round numbers, it has taken some 15 billion years, measured from time zero, for sentient life to develop on Earth. Such life has existed in the state capable of long-range communication for only the last 100 years. The next step requires considerable guesstimation: How much longer can we continue to inhabit Earth before we either run out of resources (e.g., food, energy) or destroy each other. Let's be generous and say 10,000 years. If we assume that we have a typical planet, then anyone looking directly at our planet at any point in history would have to be looking during this 10,000-year period over the 15-billion-year history of the universe, or roughly one chance in a million of looking at just the right time. In our search of stars, we do in fact look at stars of all ages and stages of development without discrimination. In other words, a SETI search team would have to probe some one million planets that actually have developed or will develop intelligent life at some point in their history to have a reasonable chance of detecting one with active communicating life forms. If only one star in a million has ever or will ever develop a planet with advanced life forms, then the actual probability of finding one such becomes one in 10(12), which exceeds the number of stars in our galaxy. Rather than the slam-dunk implied by Richard Kerr, the success of the search would seem to be far from assured.
Show Me the Numbers 6 July 2005
Clinton P. Mah, information engineer ACM Respond to this E-Letter: Re: Show Me the Numbers	To justify the OZMA project, Frank Drake proposed a simple formula for computing the probability of intelligent life elsewhere in the Milky Way. How should that formula be recast today in light of new knowledge in biology and astronomy? Has the probability gone up or gone down? From the latest data about the proclivity of gas giant planets to migrate inward toward their stars, one would wonder if many terrestrial planets can actually survive for long.
SETI : Is it looking in the right direction? 1 July 2005
Harish Radhakrishnan, Graduate Student Washington State University Respond to this E-Letter: Re: SETI : Is it looking in the right direction?	The project SETI makes a rather restrictive assumption that intelligent life-forms if any, will develop over time to invent means of communication using radio waves. A glance at the biosphere should indicate all life-forms other than man have never made an attempt to do so. The same might hold true in the future also. The vastness of the universe suggests a strong possibility of the presence of other places hospitable to the development of life-forms. The key would be to analyze the events that led to development of man, who is capable of much higher level when compared with the coexisting creatures.