# Earth is rotating around the sun?

1. Jul 22, 2014

### Hardik Batra

Why the earth is rotating around the sun?

I know the centripetal force is required for the rotation of earth around the sun.

But initially there is required some force on earth to rotate around the sun.

Last edited by a moderator: Jul 23, 2014
2. Jul 22, 2014

### Chronos

Earth orbits the sun due to gravity and conservation of angular momentum. The angular momentum was provided by the accretion disc from which the earth was formed.

3. Jul 22, 2014

### A.T.

Watch this at time 1:05

4. Jul 23, 2014

### Hardik Batra

I actually don't get it what is accretion disc.

5. Jul 23, 2014

### A.T.

Have you watched the video in post #3 ?

6. Jul 23, 2014

### sophiecentaur

Did you try Google? I got a lot of hits when I tried it.

7. Jul 23, 2014

### mathman

You should try to keep your terms for the earth motion precise.

The earth rotates around its axis.
The earth revolves around the sun.

8. Jul 24, 2014

### dean barry

Balancing act

As space is void of gases, motion of the stars and planets are not inhibited, so they can keep unpowered constant speed, this is the reason satellites are put into space.

Ive attached an (unfinished) layout of a star - planet - moon system, it will give you an idea of the layout and basic principles, you can treat the earth-moon system as one mass orbiting the sun.
Also attached are the basic equations for two body stable orbit.

Hope this is a help

Dean

#### Attached Files:

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• ###### 2 body data sheet.docx
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9. Jul 25, 2014

### Hardik Batra

The earth is revolves around the sun. The centripetal force and conservation of angular momentum is used.

But the earth is also rotating around its own axis. which force the earth is gaining to rotate around its own axis?

10. Jul 25, 2014

### Staff: Mentor

angular momentum keeps it rotating, and the centripetal force is provided in part by the earth's gravity and in part by the mechanical strength of the rock that makes up the earth.

11. Jul 25, 2014

### A.T.

Centripetal force and conservation of angular momentum

12. Jul 28, 2014

### Master Sashin

If you stand on a flat surface you will stand still however if you curve the fat surface you will fall over however if you are a ball like the earth you will roll around the curvature. Massive boddies like the sun curve and warp the fabric of space and the earth is forced to roll around it.

13. Jul 28, 2014

### voko

This Pop-Sci statement is very crude and is best avoided. First, it is the spacetime, not necessarily space, that gets curved in General Relativity. The space in the vicinity of the orbit of the Earth is flat for any practical purpose.

Second, this has very little to do with the shape of the Earth. Almost anything, of any shape, as long as its mass is much less than the mass of the Sun, can revolve around the Sun exactly like the Earth does.

14. Jul 28, 2014

### A.T.

Especially if someone asks about the spin of the Earth around it's own axis. It almost sounded like the rolling on the curved surface is responsible for the Earh's spin. Very misleading.

15. Jul 28, 2014

### Master Sashin

DUde i was using it as an example. If i said he started rolling around in circles it souldve confused him and he wouldve also have been confused about spece time

16. Jul 28, 2014

### voko

The example was bad and misleading and it was physically wrong, too. There is no excuse for that. You just do not explain anything using such "examples".

17. Jul 28, 2014

### Drakkith

Staff Emeritus
I appreciate that you want to participate in discussions here at PF, and I don't intend any offense, but it was a poorly worded example. When giving explanations or examples it is important to be as clear, concise, and accurate as possible, otherwise you risk confusing others. Your explanation simply isn't accurate and is extremely vague. It's best to simply accept and learn from whatever criticism you get and to not let it get to you. Trust me, all of us here at PF have had to learn this lesson too. I don't know how many of my own posts have been corrected by others since joining.

18. Jul 28, 2014

### Student100

This isn't quite true.

19. Jul 28, 2014

### Master Sashin

OKay fine, this is my explination. Space or space time is like a trampoline. Place a few marbles on the trampoline and each of those marbles respresent a planet. If you stand in the centre of the trampoline, the marbles will move toward you because you curved the fabric of the trampolione. The marbles will not move to you in a straight line but will move in a circular motion.
SO now imagine yourself as the sun curving the fabric of space time and that curved space is pushin the earth around the sun. I am not sure but i think its getting closer.....(again, im not 100 percent sure on my last sentance)

20. Jul 28, 2014

### A.T.

Not really yours, rather a common flawed explanation of General Relativity, that you probably saw somewhere. Since the OP is already confused about classical Newtonian mechanics, I don't see the point of bringing up GR.