system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - Why is there an inner (Rocky planets) and outer (Gas planets) ring system? Why are they different and how were they created?
gpt
\*Roughly\* speaking the general model is that our solar system formed out of a cloud of gas and dust, which collapsed under the influence of its own gravity (possibly after receiving a nudge from, say, an exploding star).  It was spinning, and because spinning things spin faster as they contract (like an ice skater pulling in their arms), it ended up flattening out like a ball of pizza dough turning into a flat pizza.

Friction made the ball of gas and dust get hot as it collapsed.  The middle got the hottest and became the S while the outside stayed fairly cold.  

Little bits of the gas and dust started sticking together and growing into planets.  In the parts where it was still hot, only things that can be solid when its hot (like rock and metal) could do this.  In the parts where it was cold, the rock and metal could still grow, but so could things like ice--and there was a \*lot\* more ice than there was rock and metal, so these planets grew to be much bigger.  So big in fact that their gravity could pull in lots of stuff that was just gas, too.

Once the Sun got properly going, it started blowing a wind away from it, which got rid of most of the gas that was just lying around, so the inner planets lost anything that wasn't already solid and were left with just the rock and metal.  The outer planets were big enough and cold enough and far enough out that their gases didn't get blown away.

Now that we're finding planets around other stars, we've found some with big gassy planets that are very close in to their stars, which is confusing when you look at how we think they were made, so now we think that some of the time these big planets can get slowed down and move closer in to their star, but that didn't happen in our solar system.