UFO's and extraterrestrial intelligent life
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John G. Fuller in the book UFO's? Yes! says "I would point out that we have always been bombarded by certain wavelengths of radio as universal background noise from the edge of the universe. Until we discovered a way to generate and use radio for our own purposes, we had no way to know of it's existence "out there"...Now that technology exists to "listen", we can use that information to add to the description of the universe." Who knows how many other means of describing the universe have yet to be discovered? Infinity is a very big place... and we see only a very narrow spectrum of such a small piece of it.
The prospect of discovering extraterrestrial life has fascinated humans for centuries. When we think of this possibility, we usually have in mind much more exciting then just finding life. We are looking for extraterrestrials with whom we can share ideas and stories. In other words what fascinates us the most is the opportunity to communicate with "intelligent civilizations", which we may define as groups of beings with self-consciousness and with complex interactions between them, beings who can share their music, poetry, traditions and learning.
Donald Goldsmith and Tobias Owen in the book The Search For Life in the Universe, state "The number of currently active civilizations in our galaxy approximately equals the lifetime of an average civilization with communications ability and desire, measured in years" . We can try to estimate the probability of life evolving on another planet, which should have the right conditions for the formation of life. We need to estimate the number of galaxies, the number of stars in an average galaxy, the number of stars that have planetary systems and the number of Earth like planets that are suitable for the formation of life.
Some 100 billion galaxies are visible to modern telescopes and the total number in the universe must be even bigger, but lets stick to that. There are as many as hundreds of billions stars in an average galaxy, but once again let's be conservative and call it 100 billion. So the total number of stars in the universe is roughly going to be 100 billion x 100 billion. At this point there are only 50 stars have been discovered that have planetary systems, but we have very little data to work with. « mai multe referate din Astronomie