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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."
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.
We appear to be waiting for a crisis, wherein the surface of Earth is sterilized by a marauding enemy. We'll then live underground long enough to retrofit the Yamato as a space battleship, and send her and her brave crew out as the last hope of mankind.
-- Two men say they're Jesus. One of them must be wrong. - Dire Straits
The guy is right that having Jupiter as a shield definitely has made a difference in Earth's ability to support life over the long term; however, he doesn't touch on what might the more significant fact: our solarsystem is located in the boondocks of our galaxy. What this means is there is a whole lot less debris floating around to smash into earth. The closer you move towards the galactic core, the more crap there is and the less effective a Jupiter shield would be.
That's all part of "L". The lifetime of the civilization. It doesn't matter how we die, if all of humanity dies, or falls below the level of technology able to communicate, then we drop out the Drake equation.
Multiply by 2 and add 30.
Chelloveck
I give up on debugging. From now on, SIGSEGV is a feature.
Gravity.
There are a number of problems with space colonization, but one of the killers is gravity.
But what about oxygen, food, etc you may ask?
Gravity takes care of the containment for you. Your gravity isn't going to spring a leak and start venting air away (assuming it is great enough to hold it in place at a proper pressure).
Further, without physical stress (ie: weight) bones/muscles deteriorate requiring more maintanence to keep the human colonists functional.
Food: A planet provides a MASSIVE surface area with which to grow crops (even if the soil is unarable, large hydroponics systems could deal with it). A self sustaining station would require massive amounts of materials to make a farm large enough to feed its inhabitants. Let alone if a small asteroid came along and broke the ceiling out of your greenhouse...
Assuming you aren't eating nutritional pills by then.
http://xxx.lanl.gov/abs/astro-ph/0201003
No, you dont. You must build a spacecraft that can _accelerate to 66.9 Million Miles per hour, and deccellerate a few decades later.
Once you have picked up speed in space there is no additional effort to keep it, since there is very little friction in the near-emptyness of space.
You are right about one thing though.
Interplanetarry travel is a lot harder than most people think...
"First lesson," Jon said. "Stick them with the pointy end."
Asimov has many life-capable planets out there in this Foundation universe (and several other stories). However, none have developed intelligent life. 90% of earths history was like
that. You'd just see deserts and a little bit of scum in the water. Worms and such developed in the last 12% of the earth's age. Fishes and plants in the final 6%.
it's an equation where you plug three variables in to get the number of inhabited (not just habitable, I believe) planets in the universe; of course you pull the three values out of your ass and end up with anything between 0 and one hundred billion kadgillion (or whatever) quite easily.
One small correction: Venus isn't terraformable. Why? because Venus is almost tidelocked to the sun. Even if you could alter the atmosphere the 'day' and 'night' would last months, resulting in temperatures of hundreds of degrees F to minus hundreds of degrees F. While the right size and (possibly) the right composition, a planet that's tidelocked or nearly tidelocked isn't in any way, shape, or form terraformable.
Max
My god carries a hammer. Your god died nailed to a tree. Any questions?