What factors effect the gravity of a planet?

Question

Also, say for instance there was a terrestrial planet that had a diameter 8 times that of Earth. Would it be possible for a planet of that size to have a gravity similar to Earth’s?

I know that the planet's core has something to do with the world's gravity and after doing some research, I found estimations of the size of Earth's inner and outer core. [http://news.nationalgeographic.com/news/2005/08/0825_050825_earthcore.html]

From the estimations I figured that the inner core’s radius is about 19% of the Earth’s total radius and the radius of the outer core is about 55% of the Earth’s total radius, I think my math could be off, it’s not my best subject.

I’m not sure how to word this, but if these percentages were used in determining the core size of the imaginary planet with the diameter 8x the size of Earth’s would that mean that the gravity could be similar on both worlds?

Answer 1

Mass, density and radius. The higher the mass and higher the density (which generally would be inverse to radius) and the smaller the radius, the higher the gravitational pull on the planet's surface. Density and radius will not be so important to gravitational pull on objects further away such as a moon or other object traveling through space, but are direct factors in surface gravity.

A planet 8 times the size of earth (in terms of radius) could have the same gravity, as long as the mass and density were adjusted accordingly. See the equation at the link below.

Answer 2

The gravity at the surface is determined by the mass and the volume. If its too dense you get a black hole. If its not dense enough - a gas giant.

Its plausible to have a planet much larger than earth, but filled with less dense stuff, that has an equivalent surface gravity.

I dont know what the magnetic field would be like. The liquid Iron in the center of the eart is thought to make the earths magnetic field. The liquid thorium there is thought to keep it liquid through fission.

Might be interesting if the core was a superconductor.. made the magnetosphere totally different than earth. Things like lasant pumping might do to keep it cool. You should read sentencet to prism.
http://www.amazon.com/Sentenced-Prism-Alan-Dean-Foster/dp/034531980X

Answer 3

pondering the quantity of mass in even a tiny planet, the belief is ridiculous, no remember how cleverly George Lucas levels it. yet impossibility aside, you need to ask HOW the planet replaced into "destroyed". oftentimes, planets in solid orbits merely influence each others' orbits particularly as they bypass one yet another. in the adventure that your planet replaced into merely broken up, the mass, and the gravity, would nevertheless be there, slowly smearing around its orbit in a hoop of asteroids. it somewhat is container would be extra effective and doughnut-shaped yet weaker and extra even. the different planets would sense a weaker yet extra even pull. If it have been by some skill converted to power, that should create an mind-blowing shockwave (probable destroying your planet killer) that should influence different planets with radiation and regardless of have been given pushed in front of the flexibility, however the gravity container would crumple, so its impact would leave. the different planets' orbits would substitute merely insofar by way of fact the perturbation of the passing former planet does no longer happen. And in the adventure that your planet killer replaced into able to drop the planet into some form of wormhole or different length, it would remember on what form of result the effect had on the encompassing area. would the effect proceed particularly than the planet, and would it not distort area like gravity does? Or would this be a real disappearance with no longer something left? you need to think of slightly extra stable approximately your impossible situations.

Answer 4

See the reference for details and derivation. If the planet is spherically symmetric, all you need to know is the total mass and the distance to the center. Given that simplification, you can do the math to figure out what the mass would need to be, and how the average density would differ from earth. It's certainly possible.

Answer 5

Mass and Weight
Before we get into the subject of gravity and how it acts, it's important to understand the difference between weight and mass.
We often use the terms "mass" and "weight" interchangeably in our daily speech, but to an astronomer or a physicist they are completely different things. The mass of a body is a measure of how much matter it contains. An object with mass has a quality called inertia. If you shake an object like a stone in your hand, you would notice that it takes a push to get it moving, and another push to stop it again. If the stone is at rest, it wants to remain at rest. Once you've got it moving, it wants to stay moving. This quality or "sluggishness" of matter is its inertia. Mass is a measure of how much inertia an object displays.

Weight is an entirely different thing. Every object in the universe with mass attracts every other object with mass. The amount of attraction depends on the size of the masses and how far apart they are. For everyday-sized objects, this gravitational pull is vanishingly small, but the pull between a very large object, like the Earth, and another object, like you, can be easily measured. How? All you have to do is stand on a scale! Scales measure the force of attraction between you and the Earth. This force of attraction between you and the Earth (or any other planet) is called your weight.

If you are in a spaceship far between the stars and you put a scale underneath you, the scale would read zero. Your weight is zero. You are weightless. There is an anvil floating next to you. It's also weightless. Are you or the anvil mass-less? Absolutely not. If you grabbed the anvil and tried to shake it, you would have to push it to get it going and pull it to get it to stop. It still has inertia, and hence mass, yet it has no weight. See the difference?

The Relationship between Gravity and Mass and Distance
As stated above, your weight is a measure of the pull of gravity between you and the body you are standing on. This force of gravity depends on a few things. First, it depends on your mass and the mass of the planet you are standing on. If you double your mass, gravity pulls on you twice as hard. If the planet you are standing on is twice as massive, gravity also pulls on you twice as hard. On the other hand, the farther you are from the center of the planet, the weaker the pull between the planet and your body. The force gets weaker quite rapidly. If you double your distance from the planet, the force is one-fourth. If you triple your separation, the force drops by one-ninth. Ten times the distance, one-hundredth the force. See the pattern? The force drops off with the square of the distance. If we put this into an equation it would look like this:

F=Mm/r2

The two "M's" on top are your mass and the planet's mass. The "r" below is the distance from the center of the planet. The masses are in the numerator because the force gets bigger if they get bigger. The distance is in the denominator because the force gets smaller when the distance gets bigger. Note that the force never becomes zero no matter how far you travel.

This equation, first derived by Sir Isaac Newton, tells us a lot. For instance, you may suspect that because Jupiter is 318 times as massive as the Earth, you should weigh 318 times what you weigh at home. This would be true if Jupiter was the same size as the Earth. But, Jupiter is 11 times the radius of the Earth, so you are 11 times further from the center. This reduces the pull by a factor of 112 resulting in about 2.53 times the pull of Earth on you. Standing on a neutron star makes you unimaginably weighty. Not only is the star very massive to start with (about the same as the Sun), but it is also incredibly small (about the size of San Francisco), so you are very close to the center and r is a very small number. Small numbers in the denominator of a fraction lead to very large results!

So as to your question of a terrestrial planet that had a diameter 8 times that of Earth. Would it be possible for a planet of that size to have a gravity similar to Earth’s the answer would be YES

Answer 6

The gravitational force of attraction between one object and another object is directly proportional to the product of the objects' mass, and inversely proportional to the square of the distance of their separation. This is Newton's law of gravitation.

The diameter of the planet is irrelevant in this situation, it's the planet mass and it's distance from the sun that's of relevance.

Answer 7

The gravity of the planet is effected but many things grave.
Loss of humour
Loss of love
Not living consciously
Lack of peace in the world
Too much mindedness.
Silly questions

Answer 8

Simple answer, its Mass, rotational speed

Answer 9

its size NO unless it was gas planet!