Orbit

[morgsboi]

Okay, there probably is a simple answer, but as we know the Earth orbits around the Sun. So, why does it orbit? I know it is partly because it is in the Sun's gravitational field but what gave it the momentum to start orbiting?

When a satellite is launched, it needs some initial momentum to push the satellite around the Earth after it escapes the atmosphere.

So is this proof that anything with an orbit has had some initial momentum at some point in time, proving the big bang?

[*puffy* japanisthebest]

<--- fun face [that probably is true or alot of asteroids hit the planets and such sooooooo

[morgsboi]

<--- fun face [that probably is true or alot of asteroids hit the planets and such sooooooo

 

Yes, but where do the asteroids get there momentum?

[A Tripolation]

The Earth orbits in part because, like you guessed, it has a velocity perpendicular to the pull of the sun.

 

Now where did this initial velocity come from? It has to do with when the Solar System formed. Planetary systems form out of the same clouds that form stars. When nebulas collapse due to gravity, a protostar forms at the center, and then is surrounded by what is known as a "protoplanetary disk". Eventually through a lot of mechanisms like accretion and the removal of the disk, you get small planet-like objects. These protoplanets continue to grow in size as they accumulate more and more matter.

 

Now back to your question. These protoplanets are now spinning because the original gas/dust cloud was spinning, even if ever so slightly. Due to the law of conservation of angular momentum, these bodies spin faster and faster as they contract. And before you know it, you have spinning planets and such.

 

I think this is accurate. I welcome any corrections of my simplification of planetary system formation by the more knowledgeable members.

[Airbrush]

AT: "...Now back to your question. These protoplanets are now spinning because the original gas/dust cloud was spinning, even if ever so slightly. Due to the law of conservation of angular momentum, these bodies spin faster and faster as they contract. And before you know it, you have spinning planets and such...."

 

Your answer was almost perfect, except the question is about planets in orbit, not spinning on their axes. When a proto-planetary disk collapses, the random motion becomes uniform in one direction around the central star. That motion becomes the orbit of the planets and most of the asteroids.

Edited November 22, 2011 by Airbrush

[morgsboi]

The Earth orbits in part because, like you guessed, it has a velocity perpendicular to the pull of the sun.

 

Now where did this initial velocity come from? It has to do with when the Solar System formed. Planetary systems form out of the same clouds that form stars. When nebulas collapse due to gravity, a protostar forms at the center, and then is surrounded by what is known as a "protoplanetary disk". Eventually through a lot of mechanisms like accretion and the removal of the disk, you get small planet-like objects. These protoplanets continue to grow in size as they accumulate more and more matter.

 

Now back to your question. These protoplanets are now spinning because the original gas/dust cloud was spinning, even if ever so slightly. Due to the law of conservation of angular momentum, these bodies spin faster and faster as they contract. And before you know it, you have spinning planets and such.

 

I think this is accurate. I welcome any corrections of my simplification of planetary system formation by the more knowledgeable members.

 

Thank you. Sounds accurate to me and makes a lot of sense.