Billions of Habitable Planets?

cbv writes: "MSNBC has an interesting article about new calculations by Charly Lineweaver and Daniel Grether, both of the University of New South Wales in Australia, which provides an interesting answer to the question on how many potentially habitable planets exist in our galaxy."

Comments

you mean...

[youngerpants]

N = R* × fp × ne × fl × fi × fc × L

Where,

N = The number of communicative civilizations
The number of civilizations in the Milky Way Galaxy whose radio emissions are detectable.

R* = The rate of formation of suitable stars
The rate of formation of stars with a large enough "habitable zone" and long enough lifetime to be suitable for the development of intelligent life.

fp = The fraction of those stars with planets
The fraction of Sun-like stars with planets is currently unknown, but evidence indicates that planetary systems may be common for stars like the Sun. more info

ne = The number of "earths" per planetary system
All stars have a habitable zone where a planet would be able to maintain a temperature that would allow liquid water. A planet in the habitable zone could have the basic conditions for life as we know it. more info

fl = The fraction of those planets where life develops
Although a planet orbits in the habitable zone of a suitable star, other factors are necessary for life to arise. Thus, only a fraction of suitable planets will actually develop life.

fi = The fraction life sites where intelligence develops
Life on Earth began over 3.5 billion years ago. Intelligence took a long time to develop. On other life-bearing planets it may happen faster, it may take longer, or it may not develop at all. For more information, please visit Dr. William Calvin's "The Drake Equation's fi"

fc = The fraction of planets where technology develops
The fraction of planets with intelligent life that develop technological civilizations, i.e., technology that releases detectable signs of their existence into space.

L = The "Lifetime" of communicating civilizations
The length of time such civilizations release detectable signals into space.

Re:you mean...

[LordNimon]

For those who don't know, the above equation is known as the Drake Equation. What a lot of people don't realize is that the equation itself is more interesting than the answer, because no one can truly know what values to use for the seven unknowns. To quote the above link:

The real value of the Drake Equation is not in the answer itself, but the questions that are prompted when attempting to come up with an answer. Obviously there is a tremendous amount of guess work involved when filling in the variables. As we learn more from astronomy, biology, and other sciences, we'll be able to better estimate the answers to the above questions.

the technical article

[awhoward]

here's the technical article (on the preprint servers):

http://xxx.lanl.gov/abs/astro-ph/0201003