Try using the Drake equation with values that you find reasonable. How many civilizations do you estimate there are in our Galaxy?
Briefly, the Drake equation is used to arrive at a rough, probabilistic estimate of the number of intelligent, technologically advanced extraterrestrial civilizations within the Milky Way galaxy whose electromagnetic emissions are detectable.
The many variables include:
i. The average rate of star formation in our galaxy
ii. The fraction of those stars with planets
iii. The number of habitable planets per star
iv. The fraction of habitable planets on which life actually appears
v. The fraction of life-bearing planets on which intelligent life emerges
vi. The fraction of civilizations that develop a technology that releases detectable signs of their existence into space
vii. The length of time such civilizations release detectable signals into space
The estimations on these variables can range from reasonable to speculative given the lack of data sets to draw upon when it comes to the existence of life on other planets. Choosing what estimates feel right to you will depend in large part...
(The entire section contains 481 words.)
check Approved by eNotes Editorial