Extraterrestrial Life Dr. Mohammed I. Bhatti University of Texas Pan American Why do we believe that extraterrestrial might
exit? The positive answer comes from a mixture of current theories about the origin and development of stars, statistical odds, and faith. Some religious leaders have called upon scientists to search for the signs of
life in outer space. Considering the statistical odds, note that our Milky Way galaxy consists of some 300 billion stars and our sun is an ordinary star among them. The Milky Way galaxy is one of some 10 billion
galaxies in the observable universe. Now assuming an average of about 300 billion stars per galaxy time 10 billion galaxies, we get 3000 billion stars or 3x10^21 stars (close to Avagadro's number) in the observable
universe. Evidence collected over the past decade, showed that planets are formed around the stars as a part of the natural process. Presence of planets around other stars has been detected recently through Hubble
telescope and by other scientific means. Even with a very low probability of planetary system, there are plenty of planetary systems that would support life. Low, low 1 % probability means there would be 3x10^19
stars that would have planets. Thus it is a statistical observation that suitable planets for life are very likely to exit. Therefore, there should be life on other planets, life that may have achieved intelligence and
developed into a technological civilization. If extraterrestrial life exits, why have we not detected them or why have they not contacted us? The answer may be found in the unbelievable distances involved in
interstellar space. For example the diameter of our Milky Way galaxy is about 100,000 light years, which means 100,000 years will be needed to sent the radio signal across the galaxy. If some extraterrestrial on the
other side the Milky Way did receive the message and send a reply, it would take 200,000 years after the message was sent. The nearest galactic neighbor similar to our Milky Way is Andromeda, only 2 million light-years
away. In additions to problems with distance/time, there are questions about in which part of the sky you should send and look radio messages what radio frequency to use, and power of the signal sent and power of
detectors. Also what kind of signals should we expect to detect? These are very challenging limitations—we need a signal which could travel faster than speed of light. While most of the astrobiologists (hired by
NASA—hot field for research) concentrated on finding life on distant planets, some turning their attention to closer places like Mars. NASSA plans to land a half-dozen space craft to search for life on Mars. Mars's
meteorite recovered in Antarctica is believed to be tainted by Earthly bacteria, the samples from Mars may not be what they seem. Astrobiologists may have to redefine life and ask question what exactly is life? Life
does not have to have legs, wings or it does not have to be green or something like that. We find life in 250-degree thermal vents under the sea and in glacial ice. Scientists know that the criteria they use to identify
life may not apply on other planets. Life needs energy of some kind to thrive on. Any planet with a hot interior is a likely candidate to host life. Only 10% universe is visible and the other 90% are invisible
universe so called dark matter. The dark matter theory is based on the two theories called WIMPs or MACHOs—baryonic dark matter. What about life that exits in the invisible universe? God knows best who is owner of the
universe. It would be our mistake if we ran into life and did not recognize it. For more notes on Astronomy, please read my Web Page http://www.engr.panam.edu/~bhatti and click on course 1421.
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