Posted: December 2nd, 2015

Section C. Finish your personal Drake Equation

Section C. Finish your personal Drake Equation

Your estimate from the previous homework should be that ~39 million habitable, Earth-like planets might exist around solar-type stars in our galaxy. Do not worry if you got a different answer! You will have opportunity to discuss, and correct, your calculations in the Reaction Paper for the next homework. For the rest of this assignment, assume that this estimate of habitable planets represents the first three factors [R^* n_e f_p] in the Drake Equation. Admittedly, this result is an estimate, but it is based on recent, astronomical evidence that has only become available in our generation.

The remaining four factors are much more uncertain. Nevertheless, you should follow the instructions below to estimate your own values and conclude by calculating your own value of “N,” the number of intelligent civilizations in our galaxy who might wish to communicate with us.

First, in separate paragraphs discuss, and justify, your personal estimate for the next four factors in the Drake Equation: “f_l, f_i, f_c, L.”  The numbers are not as important as your justifications. Note that Drake’s final factor “L,” has a different meaning in our approach. Instead of using a lifetime in years, use “L” to indicate the fraction of intelligent civilizations that are still alive even though their planets and stars may have been born toward the beginning of our galaxy (~10 Gyrs ago).

You do not need to agree with Drake, Fermi, or anyone else.  Remember the idea behind Fermi-like thinking: “… one can proceed on the basis of different assumptions and still arrive at estimates that fall within range of the answer. The reason is that, in any string of calculations, errors tend to cancel out one another.”

Second, multiply all these numbers together to produce your own estimate (“N”) of the number of intelligent civilizations that might wish to communicate with us in our galaxy. Your value for “N” should be calculated as follows: N = [R^* n_e f_p] f_l f_i f_c L = [39 million] * f_l f_i f_c L.