Have you ever wondered if aliens exist or how many there are? I sure have and so have many scientists. In 1961, Frank Drake created an equation to estimate the number of intelligent alien civilizations that may exist in our galaxy. This equation is called the Drake Equation.
The terms of this formula are the following:
N = # of civilizations in Milky Way with detectable emissions
R* = stars made in Milky Way per year
Fp = fraction of stars with planets
Ne = fraction of those planets with environment suitable for life
Fl = fraction of planets that actually have life
Fi = fraction of planets with intelligent life
Fc = fraction of planets that have developed technology that produces detectable signals
L = # of years communicating intelligent civilization lasts
One of the reasons why the Drake Equation is so famous and popular is because it is very straight forward and easy to follow. It is so straight forward that it can be compared to more mundane estimates such as the number of students at a school. However, the downside to this equation is that their are many uncertainties. The only variable which scientists are confident about is R*. Scientists have many different predictions for the other six variables, leading to a wide range of values for N. Overall, the equation is a great tool to consider, but until all variables are know for sure, the number of intelligent alien civilizations in the Milky Way Galaxy will still remain a mystery.
Sabrina Alperin 
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