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STS 497I: Space Colonization
Spring 2001

1/26/01

Instructor: Dr. Chris Churchill
Today's Guest: Dr. Frank Drake


Review class website and schedule page.

Next week (Feb. 2): 11:15AM movie "For all mankind" by National Geographic.
Followed by discussion of book "The Discoverers", Book 2

Change in due date of paper: Due in class Feb. 9th, the following week.
(Refer back to email dated 1/19/01).

Presentation: Life in the Universe: the Drake Equation


	      N = R* x f_p x n_e x f_l x f_i x f_c * L

	          |---------------|--------------| * |
   	                          |                  |
				 rate               time


N = Rate x Time = number of detectable civilizations in our galaxy
  = the number of civilizations in our Galaxy that can communicate
    across stellar distances today.


R* = rate at which suitable new stars are forming each year in the
     Galaxy ("suitable" = long star lifetime, sufficient energy)

   The Galaxy has ~400,000,000,000 stars, which are forming, living
     and dying in billion year cycles
   Star forming regions are distributed throughout the Galaxy
   R* pretty well known from observations
=> R*  ~10 stars per year


f_p = fraction of suitable new stars around which planets form

   f_p ranges from 0 to 1
   planet detections via Doppler velocity method (detect the wobble
     of a star caused by gravitational tug of orbiting planets)
   this technique selectively detects massive planets with short
     periods (close to star)
   plans for space-based infrared interferometry (Darwin, TPF)
     which could detect Venus and Earth from 30 ly
   f_p is becoming better known as we speak... long term Doppler
     programs and future space missions like TPF and Darwin will
     increase our knowledge
=> f_p ~ 0.5


n_e = number of planets residing in an ecosphere, the shell of life
      two things to consider: energy and climactic evolution

   direct energy: light from star
                  proximity to star
                  atmosphere of planet (climatic evolution)

   indirect energy

   Venus (too close to Sun) vs Mars (too far)
         is our Earth rare?

   Serious unknowns:
     What are conditions under which life can arise?
      i.e., what is a "primordial" ecosphere?
     How does early life modity "primordial" ecosphere?
     How do planetary atmospheres and oceans evolve and how do
      they respond to astrophysical pressures (eg. supernovae)
      
=>  n_e is probably zero in some planetary systems and a few in others


f_l = fraction of ecosphere planets on which life arises

    ?
=>  f_l = 0.1-1?


f_i = fraction of life-bearing planets upon which intelligence arises

    Note: dinosaurs existed on the Earth much longer than humans
    defining intelligence: encephalization quotient, measures how
      "intelligent" a species is relative to other comparable life
       forms

                   EQ = E(actual)/E(average)

        eg. human EQ=8, dogs EQ=1, Troodon dinosaur EQ = 6

=> f_i = 0.1-1?


f_c = ?


L = ?

Lbar = sum of (p_i x L_i) 


Credits:
Minutes courtesy Dr. Lisa Brown (Pennsylvania Space Grant Consortium) 
Kindly typed in by Dr. Jane Charlton (Penn State Astronomy)
Minutes to be completed by Cwc (these are as of Feb 2 and are not
quite complete!)


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