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Universe
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Ana Offline
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Post: #1
Universe
Considering the fact that between the Moon and Earth there is a gravitational force, then why doesn't the Moon fall on Earth?Huh

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(This post was last modified: 10-01-2013 10:42 PM by Ana.)
10-01-2013 10:40 PM
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Said Offline
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Post: #2
RE: Universe
Its because the two gravitational forces attract AND repel each other. Gravitational forces are weird. Tongue

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(This post was last modified: 10-02-2013 08:22 PM by Said.)
10-02-2013 08:19 PM
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Ana Offline
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Post: #3
RE: Universe
(10-02-2013 08:19 PM)Said Wrote:  Its because the two gravitational forces attract AND repel each other. Gravitational forces are weird. Tongue
Not exactly...
The gravitational forces only attract, not repel.
Therefore, if between the Moon and Earth there is only the gravitational force, then the Moon should fall on Earth. The same situation is between the Sun and Earth, 'cause neither Earth doesn't fall on the Sun.
So, the gravitational force between 2 celestial bodies is only of attraction, not repulsion, isn't it? Rolleyes

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10-02-2013 10:18 PM
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Ibrahim Offline
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Post: #4
RE: Universe
The god created this
10-08-2013 11:47 PM
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Said Offline
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RE: Universe
Well, ok then its because the moon orbits around it, and the earth around the sun. But they are getting closer every year.

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10-10-2013 07:33 PM
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Ana Offline
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Post: #6
RE: Universe
(10-10-2013 07:33 PM)Said Wrote:  Well, ok then its because the moon orbits around it, and the earth around the sun. But they are getting closer every year.

The Moon is kept in its orbit around Earth due to the force of attraction between Earth and the Moon. Nevertheless, actually, the Moon is getting away from Earth with approx. 4 cm every year (what, apparently, seems little, but, in time, the effects could be major).
So, the question is still: "Considering the fact that between the Moon and Earth there is a gravitational force, then why doesn't the Moon fall on Earth?"
Rolleyes

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10-10-2013 10:33 PM
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Mr. Marius Offline
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Post: #7
RE: Universe
Let me try.. Because there is no friction in space, planets keep their inertia (kind of like a billiard ball moving on an ice pool table, but even less slippery). Since they keep their inertia, the moment gravity acts on a planet (from the Sun let's say), the planet will move tangentially to the curve that describes the orbit (think what happens if you let go of the wheel on a car that just entered a curve, it will straighten out).
Anyway, when all this "magic" happens, the planet starts moving on a circular path and that's when centrifugal force comes into play (again with the car example, when it turns right, you are pushed to the left). When gravity and centrifugal force are equal, the planet stays in the same orbit.
11-06-2013 12:41 AM
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Ana Offline
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Post: #8
RE: Universe
Mr. Marius, you are right, of course. There are 2 major forces that keep the planet or a satellite in its orbit. These forces, the gravitational and the centrifugal force, act in opposite directions and are usually equal in their absolute value, as you said. Otherwise, the planet or the satellite would get out of the orbit in the direction of the bigger force (the centrifugal force or the gravity force, which in this case it is the centripetal force).

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11-06-2013 08:21 PM
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