(42) Thu 24 Apr 97 19:59 By: Sheppard Gordon To: All Re: Alone in the galaxy St: ------------------------------------------------------------------------------ @EID:d4ea 22989f60 @MSGID: 1:278/15 00187f47 Is anybody out there? (extraterrestrials) New Scientist 11/23/96 Before last August, it would have been easy to believe that life beyond the Earth was rare or even nonexistent. Everything changed, however, with the sensational claim that a meteorite from Mars contains fossil evidence of microorganisms. Whether or not the claim withers under intense scientific scrutiny, few doubt that primitive organisms could have evolved on ancient Mars, where titanic rivers once gushed beneath a thick, gaseous atmosphere. But add to this the recent discovery that many nearby stars are accompanied by planets, and there is the possibility that our galaxy is teeming with life. But if life is widespread, why has the search for extraterrestrial intelligence, or SETI, drawn a blank? Where is everybody? One person who is convinced he has the answer is Frank Tipler of Tulane University in New Orleans. "If the Martian evidence holds up," he says, we may have to face the fact that primitive life is common in the universe but that the development of intelligence is vastly improbable. I believe we are the very first intelligence to arise in our galaxy," he says. This claim is based on a comparison between the age of our galaxy and the time it would take a civilization capable of interstellar travel to explore and colonize it. According to Tipler, such a colonization would be achieved most efficiently by dispatching self-reproducing probes to the stars. On arrival at a star, the probes would use the available resources to build and launch copies of themselves. "One probe would become two, two would become four, and so on," says Tipler. "They would proliferate exponentially." The probes would need to be highly intelligent; in a sense, they would be life forms in their own right, and the space-faring successors of planet-based life. Traveling at 90 percent of the speed of light, a probe would take about five years to reach a star 4.3 light-years away--the distance between the sun and its nearest neighbor, Alpha Centauri. If the probe takes' say, 100 years to make a copy of itself, then the average speed at which all probes would spread throughout the galaxy would be about 1/25th the speed of light. At such a speed, the exploration of the galaxy, which is roughly 100,000 light- years across, would take about 3 million years. Even at the speed of current rockets, it would take only 300 million years to explore the galaxy and maintain a base around each star. "The time needed to explore the galaxy is hugely less than the age of the galaxy, which is around 10 billion years," says Tipler. "So, if extraterrestrials exist, they should be here in the solar system today. Since they're obviously not, they don't exist." Understandably, other scientist are reluctant to accept that we are alone in the universe. Some say Tipler is premature in claiming there are no extraterrestrials in our back yard. "It's impossible to tell," says Edward Harrison of the University of Massachusetts at Amherst. "The evidence of life may be written across the sky, and we may simply not recognize it." Tipler counters that he assumes only that intelligent life forms behave like all known life forms on Earth, all of which go through a dispersal phase. He says it is time astronomers admitted that intelligent life is subject to the same evolutionary laws as other life. Other possible explanations for the absence of extraterrestrials in our neighborhood include the "self-destruction hypothesis" and the "contemplation hypothesis." According to the self-destruction hypothesis, civilizations blow themselves up or otherwise commit suicide before they can travel to other stars. The contemplation hypothesis holds that mature civilizations grow out of the adolescent urge to colonize, preferring to stay home and explore the frontiers of art or contemplate the meaning of life. All these possibilities suffer from the same flaw. "Technological civilizations are likely to be diverse just like living organisms," says Tipler. "So, even if most self-destruct or stay at home to gaze at their navels, there will always be the exceptions. And the exceptions, by the logic of Darwinian evolution, are bound to come our way." In the long term, says Tipler, even extraterrestrials with a tendency to be couch potatoes would have to move on. "Just as the sun will turn into a red giant and force us to leave the Earth, the stars of alien races would eventually force them to go forth and colonize," he says. Nothing, it appears, can deflect Tipler from his almost messianic conviction that we are alone in the galaxy. And he goes further: By the same logic, "we are the first intelligence to evolve in the whole universe," says Tipler. "We are totally alone." If Tipler is right, it will mean an end to the human race's centuries-long slide into cosmic obscurity. First, Copernicus taught us that the Earth went around the sun and not vice versa. Then we learned that the sun was a very ordinary star in the Milky Way. Finally, we learned that the Milky Way was a run-of-the-mill galaxy in a universe containing billions of others. Now Tipler wants to put the human race firmly at the center of creation. "We're special," he says. "If we extinguish ourselves, the universe will remain lifeless." And we may also be a master race: "Our descendants will colonize the entire universe." -> Alice4Mac 2.4.4 E QWK Hiya:05Nov94 Origin: ----------> Jack Sargeant, you look fabulist! --- PCBoard (R) v15.4/M 10 Beta * Origin: MoonDog BBS þ RIME NetHub Brooklyn,NY (1:278/15) SEEN-BY: 12/12 24/888 102/2 106/2000 109/7 124/1 130/1 1008 133/2 140/23 SEEN-BY: 143/1 147/34 2021 154/222 167/166 170/400 202/777 1207 1919 SEEN-BY: 213/213 218/2 801 890 900 901 907 244/1500 267/200 270/101 275/429 SEEN-BY: 280/1 169 282/1 62 310/666 323/107 343/600 346/250 356/18 371/42 SEEN-BY: 377/86 380/64 382/92 396/1 2 45 690/660 730/2 732/10 2401/0 SEEN-BY: 2442/0 3603/420 3606/10 3612/41 3615/50 3619/25 3632/21 3651/9 SEEN-BY: 3652/1 3667/1 3674/1 5100/8 @PATH: 278/230 3615/50 396/1 218/907 801