Who made up aliens and how did they get made up?

Answer 1

No one made up aliens. They either exist or they don't. Dr. Frank Drake of the SETI Institute designed a formula that can be used to predict the potential for the existence of life elsewhere (anywhere other than Earth) in the universe. Essentially, the Drake Equation is a probability predictor, and presents the high probability that life does exist somewhere.

The equation is: N = R* • fp • ne • fl • fi • fc • L

What that means is:

N = Is the number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable.

R* =Is the rate of formation of stars suitable for the development of intelligent life.

fp = Is the fraction of those stars with planetary systems.

ne = Is the number of planets, per solar system, with an environment suitable for life.

fl = Is the fraction of suitable planets on which life actually appears.

fi = Is the fraction of life bearing planets on which intelligent life emerges.

fc = Is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.

L = Is the length of time such civilizations release detectable signals into space.

The idea that there could be other life in the universe was a groundbreaking concept in 1961 when Drake first presented his idea. At that time, we did not know of any other planetary bodies around other stars. As of the writing of this answer (October 2013) 990 planetary bodies have been discovered in 754 planetary systems. The Kepler mission has detected thousands of potential candidate stars with potential planets orbiting them, and 252 potentially habitable planets.

It has been estimated that there may be 17 billion Earth-sized planets in the Milkyway Galaxy (our galaxy) alone. Considering the numbers and what we have discovered so far, it would the the height of arrogance to presume we are alone in the universe.

990 planets in 754 planetary systems