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sirwan
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Which of them larger? The gravity of the Earth to the moon or the gravity of the sun to the moon?
sirwan said:of course I mean the gravitational force ,why the moon does not orbit the sun? Is it relate to the difference of amount of gravitational force of each the sun and Earth to the moon or related to the different distance of the moon from sun and Earth ?
That's a trickier issue than you think. Do the calculation. The gravitational force on the Moon toward the Sun is about twice that toward the Earth.HallsofIvy said:You could, of course, actually calculate both forces but it seems to me that the fact that the moon orbits the earth, not the sun, says it all.
There are two problems here. One is that you are thinking along the lines of "A orbits B" and "A orbits C" are mutually exclusive. It's not an either-or proposition. The Moon orbits the Earth and it also orbits the Sun.sirwan said:of course I mean the gravitational force ,why the moon does not orbit the sun? Is it relate to the difference of amount of gravitational force of each the sun and Earth to the moon or related to the different distance of the moon from sun and Earth ?
That final statement is wrong. Consider an object orbiting the Earth at a fiftieth of an AU. That obviously qualifies as "closer to the Earth". Yet the Sun's gravitational influence is going to dominate over that of the Earth by any reasonable definition of "gravitational influence". This orbit is not stable.manojr said:See this wikipedia article on Hill Sphere.
Moon is closer to Earth therefore its gravitational influence on Moon is more than that of Sun.
D H said:What do you mean by "gravitational influence"?
D H said:The question at hand is "why can we say that the Moon is orbiting the Earth?" The Hill sphere doesn't address this question. What answers the question of "why can we say that the Moon is orbiting the Earth?" is mechanical energy. The Moon's mechanical energy with respect to the Earth is negative: The Moon is gravitationally bound to the Earth.
You didn't answer my question. What effect? Don't worry, it's a rhetorical question.manojr said:I mean resultant/dominant effect. I agree that this may not be appropriate term in physics.
That is exactly how I interpreted the question. The answer is not the Hill sphere. The answer is in terms total mechanical energy, or perhaps even better, escape velocity. Energy is a concept that can be grasped at the high school physics level. If the total mechanical energy is negative the object is "orbiting". At least now it is. Escape velocity is similarly within the grasp of a high school student. An object is currently orbiting some other object if the magnitude of the velocity with respect to that other body is less than escape velocity.As you already answered OP's actual question i.e. The gravitational force on the Moon toward the Sun is about twice that toward the Earth, I read the question as "why does moon orbit the Earth instead of Sun (that attracts with twice the force)?"
That's wikipedia for ya. Sometimes it's very good, sometimes it's rather lousy. This is one of wikipedia's many articles of lesser quality. That's my opinion, of course.The article I pointed to begins as "Hill sphere is the region in which it dominates the attraction of satellites. To be retained by a planet, a moon must have an orbit that lies within the planet's Hill sphere." So I thought it is good article to read.
D H said:Energy is a concept that can be grasped at the high school physics level.
Alright, I did not pay attention in physics class long back :)D H said:Escape velocity is similarly within the grasp of a high school student.
The Earth has a diameter of approximately 12,742 kilometers, while the Sun has a diameter of approximately 1.4 million kilometers, making the Sun about 109 times larger than the Earth.
The gravitational force of the Earth is much weaker than that of the Sun. The Sun's mass is approximately 333,000 times greater than the Earth's mass, resulting in a much stronger gravitational pull.
Yes, the Moon is affected by both the Earth's and the Sun's gravitational forces. However, the Earth's gravity is stronger than the Sun's, so the Moon primarily orbits around the Earth.
The gravitational force between two objects is inversely proportional to the square of the distance between them. This means that as the distance between the Earth and the Sun increases, the gravitational force between them decreases.
The Moon is kept in orbit around the Earth by the Earth's gravitational force. This is because the Earth's gravitational pull is stronger than the Moon's own gravitational pull. However, the Sun's gravitational force also plays a role in the Moon's orbit around the Earth.