why aliens did not directly contact us
Dr. Seth Shostak more upbeat on alien life
The truth about aliens
NASA Kepler mission updates its project findings constantly. In our milky way galaxy itself, there is enough "real estate" as around 300 earthlike planets were discovered in a small area of 4% scouted by Kepler mission. Kepler mission discovered astonishing facts within a time span of 2 years that could pioneer many more such missions. Gravitational miicrolensing and planetary transit observations by independent studies discovered the probability of almost 160 billion stars in our own milky way galaxy having an earthlike planet around them. SETI equation that quantifies the probability of alien civilizations in the cosmos is getting augmented with these findings.
is there intelligent alien life in our galactic neighborhood
Astronomy lovers the world over ponder over the fact that there are no direct contacts from alien life or rather alien civilisations with the governments, people, space missions, etc .After revelation of probability of incredible no of billions of earthlike planets in milky way galaxy, the mystery deepens. A large no of citizens however believe based on information through the media, internet, etc., that aliens have already established contacts with governments. But governments also deny such beliefs. Whitehouse had gone further and issued a flat denial. Based on assumption that there are no such direct contacts, there could be some reasons at the local galactic level.
1. The diameter of our galaxy is 100 K light years. The center of galaxy has dense congregation of stars upto 15000 light years radius. Our Sun is located in inner rim of Orion arm and at a distance of 27000 light years from the Galactic center.This is the galactic habitable zone beyond which the spiral arms start separating out from each other and stretch out into the cosmos thousands of light years away. The next arm, Perseus, is located @ 6500 light years away from Sun.
On one side of galactic plane of our Solar system, galactic core with dense clusters and with a x ray emitting black hole at the center renders difficult for the life to form and survive. The other side, galactic arms stretching far away may have similar solar systems impossible to discover due to the incredible distances.
In our neighborhood, there are more no of stars that are less bright with an absolute magnitude less than 8.5. That could be due to reason that these stars are in red dwarf stage. This indicates the hope to find similar solar system in our neighborhood are rather low. This also indicates the lesser probability of similar civilisation like ours.
2. Our Sun had so far made about 18 orbits around the galaxy and hardly a 1/1250 fraction of an orbit ever since humans evolved. Even if other advanced aliens noticed earth during one of Sun's revolutions, it is quite impossible that we as dwellings of earth could have been noticed because humans would have not originated. Only a primitive earth with little or no life could have been found by advanced aliens in our galactic neighborhood. Hence they would not have deemed it fit to establish communications.
3. The arms of our galaxy could be definitely hosting planets with advanced life. But the structure of our galactic arms is even now unknown. The galactic arms stretch themselves farther from each other in an ever advancing universe causing huge galactic movements.
4. Milky way galaxy already went through 2 galactic mergers quite early in its age of 13.2 billion years. Probably some of the stars that hosted planets with intelligent life could have been destroyed in the process. There were no major mergers for the last 7 to 8 billion light years. Based on human civilization's origin and development into intelligent beings, it is reasonable to conclude that a star requires 2 to 4 billion years to evolve planets with intelligent life. Hence, we can assume other non local sections of galaxy should be bristling with life intelligent enough to communicate with others. Probably we are either unable to decipher their signals or they are not directly communicating with us, as they do not have more than a passing interest with a distant solar system and its planets.
unclear galactic structure
what ails contacts with alien life
1. Our galaxy formed within early stages of universe. Much of the evolved intelligent life within our galaxy could have perished due to merger effects that lasted till 6 to 7 billion years ago. The advanced life from other galaxies might have had no inclination for communications.
2. Life in earthlike planets around Sun like stars are more probable in galactic arms in safe distances from galactic center's radiation. But that also makes communications with other civilizations rather remote.
3. We are in a twilight zone of our galaxy placed with hot core on one side and with incredibly far arms on the other whose structure is yet unknown.
4. Simple absence of galactic coordination within its own structures might have been preventing one alien civilization from contacting others.
5. Those advanced intelligent forms could have found earth in a primitive way with a primitive human life unable to communicate with aliens from outer space. That definitely doesn't enthuse a wanderer!
6. Some of the advanced civilizations in our galactic neighborhood could have perished in conversion of stars to red dwarf stage. Most of the stars are in our galaxy are red dwarfs which emit harmful radiation.
7. Incredibly long distances of milky way galaxy within its own arms (100 K light years) might be preventing advanced life forms to really initiate communications with us.
8. Probably our earth itself would have been inhabited by various plants and animals from a neighborhood stars' life forms carried by various interstellar objects! We are probably aliens ourselves!
7. Our technology has developed only for the last 100 years to receive and understand a signal. We may have yet to develop suitable technologies that can receive and understand alien signals.
Finesse mission of NASA is set to launch in 2015 and can directly collect infinite details about extrasolar / earthlike planets. Upon detection of first signal about an intelligent alien life, our perceptions about intelligent alien life are bound to transform.
The galactic details have been collected from Wikipedia and on my interpretation of the data. Comments are most welcome.