Extraterrestrial Life: The Drake Equation

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By Prisha Goyal

In 1960, Frank Drake conceived the Drake Equation: N = R∗ × fp × ne × fl × fi × fc × L. In this equation:

R* represents the number of stars in the Milky Way

fp represents the stars that have solar systems

ne represents the planets in a system that are ideal for life

fl represents the fraction of those planets that have developed life

fi represents how often intelligent life arises

fc represents the share of those civilizations that emit signals we can detect

L represents the time that those civilizations will be active for

Scientists have estimated that there are 100-400 billion stars in the Milky Way, and the Kepler Space Telescope confirmed that almost every star has a solar system. It is hard to answer the question of what planets are ideal for life, but we can look at planets in the Goldilocks Zone. This is the area where conditions are just right, neither too hot nor cold for liquid water. Stars that are alike to our Sun number at around 4 billion, and anywhere from 0.3-2 billion planets are similar to Earth. We can’t know the fraction of planets that have developed life, because Earth has been our only observation. The consensus for intelligent life arising on those planets is that it is likely to be very rare, but again, Earth is our only observation. The civilizations that emit signals could have reached out, but maybe the distance was too long, or the signals were garbled. Or it could be that our detectors can’t pick them up. Finally, there are many reasons why a civilization might not last for very long. Their own technology could have done them in. Or maybe more advanced and stronger civilizations have taken over weaker ones, which is why we don’t hear from them.

In the end, there are many possible reasons for why there may or may not be extraterrestrial life. Maybe we are being watched over by an ancient civilization. Maybe aliens have already visited us. Or maybe, we really are the only civilization in the entire galaxy.