# Thread: Gravity and Planets of Different Mass

1. I am not vary educated in science so please excuse my ignorance, but I have couple of questions that I would like answered.

If gravity is a force that keeps the planets in their orbits why are the planets arranged as they are? Why are some big planet farther out and they are not pulling away from the sun and small planets are closer and they are not being sucked in?

Another question is does anyone now of any experiments are being conduct to recreate a solar system? It seems to me that if all object of mass have a pull, in space they could get objects of scale sizes to reproduce a solar system, or at least one object orbiting another.

2.

3. alwaysthinking wrote:
It seems to me that if all object of mass have a pull, in space they could get objects of scale sizes to reproduce a solar system, or at least one object orbiting another.
It seems like I heard that some human feces is orbiting the space station due to some NASA oversight....
Seriously, no joke.

cheers,
william

4. A quick reply to the original post...

It is a balance between centripetal force and gravitational force. The orbital velocity of a planet keeps it from hurling into the sun or leaving the solar system. It happens that the planet's orbital velocities are about right to prevent either of the two. If the earth's orbital velocity were to slow down for some reason, then the earth would move toward the sun.

I'll let someone else explain it better....

Cheers,
william

5. Originally Posted by william
A quick reply to the original post...

It is a balance between centripetal force and gravitational force. The orbital velocity of a planet keeps it from hurling into the sun or leaving the solar system. It happens that the planet's orbital velocities are about right to prevent either of the two. If the earth's orbital velocity were to slow down for some reason, then the earth would move toward the sun.

I'll let someone else explain it better....

Cheers,
william
It's a good explanation. For my final school exams, it was my subject in physics. Calculating the orbit of a satellite (the altitude).

6. http://www.physorg.com/news10789.html

According to this finding, a particle traveling faster than 0.57c gravitationally repels particles ahead of it.

If I had a solid consisting of many particles, shouldn"t it fly apart faster than this speed, as the gravitational repulsion "peels off" particles from the front end, so to speak?

7. Originally Posted by alwaysthinking
Another question is does anyone now of any experiments are being conduct to recreate a solar system? It seems to me that if all object of mass have a pull, in space they could get objects of scale sizes to reproduce a solar system, or at least one object orbiting another.
What you are talking about could probably only be done in a zero gravity vacuum, otherwise the major gravity source (earth) would simply pull everything down and friction would prevent the orbiting.

8. Good one, rritoch! (about recreating a solar system). Only a computer generated model could probably recreate a theoretical and potentially accurate method of how the planets formed orbits around the Sun.

OK, alwaysthinking, I'll tell you a fairly good explanation about how the solar system most likely developed.

Let's take william's idea about the Earth falling into the Sun. Forget about how the matter in our solar system originally got there. Now, the Sun was obivously the first to form, especially if it was born out of a nebula. The rocks, meteors, and other junk floating around either 1) had a high velocity, collided with each other to form planets, and eventually found their orbits around the Sun, or 2) they fell straight into the Sun because (at the time), the Sun had the largest mass = gravitational pull. The 4 small planets (Mercury, Venus, Earth, Mars) closest to the Sun had the smallest masses because the Sun "consumed" whatever was able to keep a high enough velocity and orbit to escape the Sun's grav. pull. The 4 gas giants (no more pluto!!! ) that are farther away from the Sun, (which I believe have some sort of solid mass at the center) pulled enough gases from the former nebula to become gas giants.

There you go. And Go Earth!!! I love Earth, I couldn't live without it.[/quote]

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