Drake Equation Estimates
In 1961, astronomer Frank Drake developed an equation that can be used to estimate the number of alien civilizations in our galaxy with whom we might come into contact. This chart explains how to use that equation, which is:
N = R* x fp x ne x fe x fi x fc x L
Variable |
Explanation |
Estimates |
|
 |
R* |
The average number of new stars that appear in our galaxy every year (or you can use the number of stars in our galaxy divided by the age of our galaxy) | 7 |
 |
fp |
The fraction of the above stars that have planetary systems | Optimistic: 0.6 Pessimistic: 0.2 Compromise: 0.4 |
 |
ne |
The number of planets in the above systems that could support life | Optimistic: 2 Pessimistic: almost zero Compromise: 1 |
 |
fe |
The fraction of the above planets that actually do develop life | Optimistic: 1.0 Pessimistic: almost zero Compromise: 0.5 |
 |
fi |
The fraction of the above planets that develop intelligent life | Optimistic: 1.0 Pessimistic: almost zero Compromise: 0.5 |
 |
fc |
The fraction of the above planets that develop civilizations with the technology to send detectable signals into space | Optimistic: 1.0 Pessimistic: almost zero Compromise: 0.5 |
 |
L |
The number of years that the above civilizations exist before being destroyed or destroying themselves | Optimistic: 1 billion+ Pessimistic: 100 Compromise: 10,000 |
Number of alien cilizations = |
Optimistic: billions Pessimistic: none Compromise: 3,500* *this would put the nearest civilization about 100 light years away and make it very unlikely that we will ever hear from them |
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