If a planet has 7x the Earth's mass, does that mean it has 7x the Earth's gravity?
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08-11-2012, 08:24 PM
Star If a planet has 7x the Earth's mass, does that mean it has 7x the Earth's gravity?
http://rt.com/news/super-earth-habitable-life-272/

A news blurb speaking about a relatively close planet that may have a habitable climate. I'd like the gravity question answered to get a better sense of the planet.
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08-11-2012, 08:34 PM
RE: If a planet has 7x the Earth's mass, ...
(08-11-2012 08:24 PM)poolboyg88 Wrote:  http://rt.com/news/super-earth-habitable-life-272/

A news blurb speaking about a relatively close planet that may have a habitable climate. I'd like the gravity question answered to get a better sense of the planet.
Yes and no. If you mean surface gravity, no - because that also depends on the diameter (or radius).

g = GM/r^2

Skepticism is not a position; it is an approach to claims.
Science is not a subject, but a method.
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08-11-2012, 10:27 PM
RE: don't make subject titles that long
Right, it depends on radius as well as mass.

E 2 = (mc 2)2 + (pc )2
614C → 714N + e + ̅νe
2 K(s) + 2 H2O(l) → 2 KOH(aq) + H2 (g) + 196 kJ/mol
It works, bitches.
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08-11-2012, 10:44 PM (This post was last modified: 08-11-2012 11:01 PM by Logisch.)
RE: If a planet has 7x the Earth's mass
Gravity has a lot to do with mass. Remember that the mass of an object can also have a lot to do with density. For instance... if you were to look up the mass and gravity on the surface of something like say... our sun. Then compare it to something with the mass of say a neutron star. You would find that even though the neutron star is only a fraction of the size of our sun, the gravity would likely be millions or perhaps billions of times stronger.

And radius does have to do with it as well. For instance, supermassive black holes at the center of the galaxy that scientists observed the effects of gravity will show stars flinging out, slowly returning into an elliptic orbit of sorts and then getting VIOLENTLY pulled and flung back out over and over.





One of my favorite talks about neutron stars by Carl Sagan. Neutrons themselves are incredibly dense.
Even more interestingly, and not discussed by the Sagan video is that neutron stars have the capability of being one of the most destructive forces in the universe. Only the possibility of that happening can be possible by extra mass the star takes in. For instance, a neighboring star where the mass is consumed or collected by the neutron star and crushes down even further on the neutron star, eventually resulting in probably one of the most spectacular things we could imagine.... but wouldn't want to be a part of.


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09-11-2012, 01:10 AM
RE: If a planet has 7x the Earth's mass, does that mean it has 7x the Earth's gravi
So what I'm gathering is that even if a planet has more mass than Earth's, if it is large enough, the mass could be diffused, and the gravity could be even less than Earth's?
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09-11-2012, 01:31 AM
RE: If a planet has 7x the Earth's mass, does that mean it has 7x the Earth's gravi
(09-11-2012 01:10 AM)poolboyg88 Wrote:  So what I'm gathering is that even if a planet has more mass than Earth's, if it is large enough, the mass could be diffused, and the gravity could be even less than Earth's?
Potentially yes. Imagine having something twice the size of earth being made out of styrofoam. Do you think it would have a large amount of gravity?
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09-11-2012, 05:52 AM
Re: If a planet has 7x the Earth's mass, does that mean it has 7x the Earth's
It's about your density... Or is it destiny. No I got it right the first time.

"Love is hot, Truth is molten!"
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09-11-2012, 06:15 AM
RE:
7 times? Not necessarily, but let's check

g=G(m/r^2)
Radius of Earth: 6371000m
Mass of Earth: 5.9722*10^24kg

Radius of planet: 1.9 to 2.5 times of Earth
Mass of planet: 7.1 times mass of Earth

For Earth:
g=9.813

For planet:
g= 19.302 (assume radius 1.9 times)
g= 3.9256 (assume radius 2.5 times)

So, we can't really tell for now Big Grin

Welcome to science. You're gonna like it here - Phil Plait

Have you ever tried taking a comfort blanket away from a small child? - DLJ
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09-11-2012, 04:22 PM
RE: If a planet has 7x the Earth's mass, does that mean it has 7x the Earth's
I was just musing over the idea that the only other "earth" like planet that humanity could ever possibly reach, would have you weigh 1000+ pounds. I'd love that situational irony. "We've found one, right on our doorstep, but can't do sh*t with it."
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10-11-2012, 11:49 PM
RE: If a planet has 7x the Earth's mass, does that mean it has 7x the Earth's
(09-11-2012 04:22 PM)poolboyg88 Wrote:  I was just musing over the idea that the only other "earth" like planet that humanity could ever possibly reach, would have you weigh 1000+ pounds. I'd love that situational irony. "We've found one, right on our doorstep, but can't do sh*t with it."


I hate to disagree with you, however if people on earth can survive actually weighing 1000 pounds. I am sure that we could figure out a way to launch them into space and slowly increase gravity until it matches what they will be dealing with on that planet. I'd love to see the kind of ship that could actually land on it though.
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