The universe is unbelievably big – trillions of stars and even more planets. Soo… there just has to be life out there, right? But where is it? Why don’t we see any aliens? Where are they? And more importantly, what does this tell us about our own fate in this gigantic and scary universe?
The basic points of the argument, made by physicists Enrico Fermi and Michael H. Hart, are:
- There are billions of stars in the galaxy that are similar to the Sun, many of which are billions of years older than Earth.
- With high probability, some of these stars will have Earth-like planets, and if the Earth is typical, some might develop intelligent life.
- Some of these civilizations might develop interstellar travel, a step the Earth is investigating now.
- Even at the slow pace of currently envisioned interstellar travel, the Milky Way galaxy could be completely traversed in about a million years.
According to this line of thinking, the Earth should have already been visited by extraterrestrial aliens. In an informal conversation, Fermi noted no convincing evidence of this, leading him to ask, “Where is everybody?” There have been many attempts to explain the Fermi paradox, primarily suggesting either that intelligent extraterrestrial life is extremely rare, or proposing reasons that such civilizations have not contacted or visited Earth. [Via: Wikipedia]