Have you ever wondered whether we are alone in the universe?What if we are not, that is to say, if we the Earth Dwellers or the HUMANS are only a member of a large civilivation spreading through out the Universe. If you still miss my point, what I'm going to tell you is about ALIENS or EXTRATERRESTRIALS, one of the most interesting but rather controvertial topic existing in today's world.
The word 'aliens' might remind you at once of Sci-fi or stories like X-Files everybody loved to watch. But my intention is not to bring you a story about an alien abduction or a UFO crash. It'll be more intersting to see the scientific aspect of Life Beyond Earth.
Our galaxy, The MilkyWay alone has about 100000 stars, one of which is our Sun. The are about 13.7 billion galaxies found in the visible universe which runs as far as 13000 billion light years in every direction. How many planets do you expect to revolve around total of the stars found in 13 billion galaxies! To bring out my first point. isn't plausible to say that some of these planets can have conditond similar to Earth, at the very least capable of hosting some form of Life?
As Carl Segan defines Life, he says 3 fundamental requirements should be fulfilled for something to be called a Life.
1. Production of offspring
2. Ability to mutate
3. Ability to inherit such mutations to offspring.
Assuming it to be a common mechanism which operates through out the universe,scientists also expect Carbon, water, an atmosphere and a flavourable temperature fluctuation to be possessed by a certain planet to evolve and habor life just like our Earth does. But is it compulsary for an alien life to be exactly like humans in shape and functioning?
No. For an example there are millions of different forms of life on Earth as birds, replites, humans, trees, bacteria, algae etc. with different patternd of life.
Likewise, any form of life on a far distant planet can evolve in favor of the conditions it has.
So you shouldn't be suprised, if you ever would hear about an alien who dwells in air breathing carbon dioxide in and oxygen out!
A famous scientist, Frank Drak has introduced a mathematical expression which calculates the number of technological civilizations in the MilkyWay galaxy [N] .
N = R* fp ne fl fi fc fL Answers ranging from 1- 100000 are being proposed by different scientists, but can not be considered as accurate since the 'f' terms are not directly measurable.
Seaveral projects have also been intiated by researchers to detect any trace of life beyond Earth. Some of them are SETI which stands for Search for ExtraTerrestrial Intelligence and Ozma project. They use radio telescopes to capture radio signals coming from far reaches of the universe.
While people like Frank Drak merely suggest possibility of existence of extraterrestrial intelligence, some like Bob Lazors insist that such forms of alien life have somewhat control over our planet. At the sametime, another group strongly resist the very idea of possible exsistence of life in universe other than on Earth.
Who to believe is up to you. But one thing we all know for sure is that we arn't technologically fit enough to find a real answer to the question of exsistence of extarterrestrials. Just that for the time being, we can't deny everything about ALIENS. Coz' the truth with a capital T is yet to be found.