Biology Lecture No. 3: The Drake Equation
Monday January 16 , 2012
The Known Universe & Our Galaxy:
-Our galaxy is known as the Milky Way galaxy and is composed of an estimated 100 billion stars.
-It is unimaginably profound in that it takes light (at 299,792 km/s) 100,000 years to travel its diameter.
Our Place In Distance And Time:
-The nearest known star to the current sun in our solar system is Proxima Centauri near the constellation Centaurus. It is
4.22 light years away from our visible sun.
- Due to lack of technological sophistication, distances in our galaxy are currently too great to travel and explore. Space
travel is not the way that Earth humans will currently contact other intelligent life successfully.
-This may be a more suitable method of contacting extra-terrestrials with today’s technology as other civilizations
should be able to detect radio waves from Earth.
-One of the groups involved in this process is SETI or the “Search for Extraterrestrial Intelligence.”
-The signal sent would be in a distinct ordered frequency pattern that would imply it was an artificial message and prove
existence of Earth’s intelligent life.
The Drake Equation:
-N = N ×sf × np× f ×ef l i × fc× L
- N = Number of advanced civilizations in our galaxy
N s Number of stars
fp= the fraction of those stars that have planets
n = number of planets that can potentially support life
fl= the fraction of those planets that develop life
fi= the fraction of planets that develop intelligent life
fc= the fraction of planets willing and able to communicate
L = average lifetime of a civilization N (Number Of Stars):
-There are an estimated 100 billion stars in the Milky Way galaxy.
Fs(Fraction Of Stars With Planetary Systems):
-The Kepler Mission is a project organized to investigate the number of stars with planetary systems using the Kepler
Space Probe. Kepler is responsible for charting a specific part of the sky which encompasses 150,000 stars.
-Planet formation is a natural consequence of star formation. If the fraction of stars with planetary systems is estimated
to be half; that would be equivalent to 50 billion stars that have planets around them.
The Transit Method:
-A method utilized by the Kepler Space Probe where it picks up the decrease in brightness when a planet revolves in
between the star and Kepler. The probe looks for a very regular, predictable pattern in the motion of planets.
-The photodetector on Earth picks up these minute changes in brightness with great sensitivity. There are 2,326 planets
and counting. Some planets even inhabit binary star systems.
N eNumber Of Planets That Can Potentially Support Life):
-The number of habitable planets depends on the mass of the planet and its distance from the parent star.
-Its mass is described as its ability to hold on to an atmosphere. The habitable zone of the planet is known to be where
the temperature is optimal relative to its star.
-If the number of pla