# What makes the world go 'round

#### Dagenais

Hmmm...

Some people say money, some say love.

I just want to double check. In short, what makes the world go around is basically the sun's gravitational pull which rotates the Earth and other planets around it right?

Or is love really the answer?

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#### Ivan Seeking

Staff Emeritus
Gold Member
Originally posted by kenikov
I just want to double check. In short, what makes the world go around is basically the sun's gravitational pull which rotates the Earth and other planets around it right?

Or is love really the answer?

Conservation of angular momentum. When a mass is trapped in the gravitational field of another body, a set of equations from Johann Kepler tell us that cirtain stable orbits can result. When this happens, as is the case with our planet, the momentum that the planet had continues until something steels it away.

Of course, I am not aware of any proofs that show that conservation of angular momentum is not love.

#### Dagenais

Okay, so my Sun theory was somewhat right, right?

Last edited:

#### Ivan Seeking

Staff Emeritus
Gold Member
Originally posted by kenikov
Okay, so my Sun theory was somewhat right, right?
The sun only tries to pull us towards its center. We go around the sun because just as much as it pulls on us, we try to run away in a straight line. An elliptical orbit results. The earth spins on its axis because as the earth formed, the material was caught in the earth’s gravitational field; which made it orbit the earth. As this material crashed into the forming planet, the momentum of this motion is conserved as the rotation of the planet.

So, right. You were wrong on this one. That's OK though. Most of science is about being wrong many times, but then getting it right just once in a great while.

#### Dagenais

Hrm, thanks.

Hanging around here will make me look so much more knowledgable in school.

#### Mr. Robin Parsons

IMO Truth, makes everything go!!.

#### HallsofIvy

Homework Helper
Actually, the original question was very ambiguous.

"What makes the world go round?" Is that referring to earth's rotation on it's axis or it's orbit around the world?

The later question "whether sun's gravitational pull which rotates the Earth and other planets around it right?" doesn't make it any clearer!

#### LURCH

I suppose it could be looked at as a two-part question. Momentum makes the Earth go (it was in motion when it formed, and nothing has happened to stop it), and the Sun's gravity makes that "going" round (rather than straight).

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