Name:______________________________________________________

In the class notes for Class #28 a description of the "Drake Equation", and its various components was provided. This equation was developed to predict how successful a radio search for extraterrestrial civilizations might be. The entire equation is reproduced here:

N = S*f_s*f_p*N_e*f_L*f_i*f_c*T

In class, we ignored the last three terms (f_i, f_c, and T), as we were interested in ANY forms of life, not just those at an advanced level of communication. These other three terms represent 1) the fraction of planets where existing life has evolved to an intelligent level (f_i), 2) the fraction of such civilizations currently able to communicate with technology as advanced, or more advanced, than that which we have (f_c), and 3) the lifetime of the communicating civilization (T). In class, ignoring the final three terms, we argued that the value of N was 500,000 for the Milky Way galaxy. For this homework assignment, I want you to estimate values for f_i, f_c, and T. Note that each of them should have values between 0 and 1 (such as 0.001, 0.33, etc.). You must also explain your reasoning. At the end, derive a new value for N. (25 points)

DO NOT BE ARBITRARY---Note that N has to be at least "1" since human civilization exists! If your answer for N is smaller than one you have used a ridiculous number somewhere. You must justify your reasoning for any numbers used!

[Note: of these three terms, only T should be confusing to you--what T represents is the fraction of a civilization's lifetime that it spends communicating by radio waves before it finds either a new means to communicate, or it annihilates itself! For example, the human race has been communicating using radio for the last 75 years. But "intelligent humans" have probably only been "civilized" for about 5,000 yrs. Will we stop using radio at some future time? You must supply an answer for this. For example, if we are still using radio communications 5,000 years from now, T would have a value of T = 0.5 (5,000 yrs without radio, 5,000 years with radio, 5,000/10,000 = 0.5). But if we kill ourselves off in some sort of nuclear war in the year 3,543, then we would have T = (3,453 - 1930)/(5,000 + 3,453) = 0.18 (where I set the year of the beginning of real radio to the year 1930).]

1) What is your value of f_i, and why (6 points)?

















2) What is your value of f_c, and why (6 points)?



















3) What is your value of T, and why (6 points)?

















4) What is N? N = 500,000 * f_i*f_c*T = ? (3 points)





5) Given your value for N, do you think it is worthwhile to spend money looking for the radio signals from other civilizations? Why/Why not? (4 points)