Life off Earth, not on Gliese 581c
Earlier this year, news surfaced about a planet or three that orbit the star Gliese. Three planets were found to be orbiting that star which lie within the 'Goldilocks Zone' of the star. The Goldilocks Zone is the area around a star which is the correct distance to maintain liquid water. The liquid water is thought to be an important indicator for potential extra-terrestrial life. One of the planets most cited was Gliese 581c, it was thought that greenhouse effects on that planet plus it's proximity to the star Gliese would have formed a temperature range and atmospheric conditions similar to those on Earth. According to a recent report, however, that information seems incorrect. New calculations show that Gliese 581c is probably similar to Venus - which a runaway greenhouse effect that keeps the planets temperatures about 100 ° C.
No worries, though. The sister planet Gliese 581d is standing in the shadows ready to take the title of most likely planet to be inhabited. Gliese 581d is a little farther from that systems sun, and as such should be a little cooler. The bad news is that Gliese 581d is about 15 times more massive than earth...ie it has about 15 times the gravity. If there is life on that planet - it's probably some sort of roach. I think we should strongly aim not to bring any of those roaches to earth.
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technoratiPretty sure I'm right
On July 9th, 2007 G Kontos says:
Perhaps my knowledge of the nature of gravity is a little shaky, but I'm pretty sure that the gravitational pull of a planet is directly related to the planet's mass. This is in contrast to the size of the planet, and also to the planet's density. If I'm wrong, please point me to a reliable source of information. Until then I'm going to continue saying that a planet with a mass 15 times that of earth with have a gravitational pull that is 15 times stronger that of Earth.
And actually, I went ahead and looked this up on wikipedia...
"According to the law of universal gravitation, the attractive force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them."
ie. gravity has nothing to do with density or size. Gravity has to do with mass.
Gravitational Constants
Found this browsing for a
On October 17th, 2007 Anonymous (not verified) says:
Found this browsing for a paper on Gliese 581 star system. Just have to comment that your knowledge of the nature of gravity is indeed shaky, even though it's about three months late. Formula for gravity is as follows:
F = (G*m1*m2)/r^2
F is the force exerted by gravity, G is the gravitational constant of the universe, m1 is the mass of the planet, m2 is the mass of the body on which the force is being exerted, and r is the distance between the two objects. Gravity of a planet is calculated as if the entire force were centered at an infinitesimal point in the center of the planet, i.e. r here should be the radius of the planet.
Therefore a planet with a mass 15 times that of Earth would only have a gravity 15 times that of Earth if the radius of the planet were equal to the radius of Earth.
If 581d's radius is 3.9 times the radius of Earth, the gravity would be equal to that of Earth.
No, it will be NOT 15 times
No, it will be NOT 15 times stronger. It would be possible only if Gilese 581 d was same size like Earth. And this is for various physical reasons impossible. So it will be somewhat less gravity on surface.