Formation of our Solar System

Check out this quick gif of the changes to the moon over the last 4.5 billion years. When it first formed it was very hot, just like the center of our earth, but it cooled more quickly than our earth because it has no atmosphere to keep the temperature in! It was also HEAVILY bombarded during the first billion years because the solar system was still stabilizing and forming into the patterns we see today.

The solar system started as a large cloud of gas and 'dust' particles, very disorganized; because of gravity, most of the dust gathered in the middle of the cloud, enough of it to form the sun. The sun is so big, 1 million earths would fit inside of it. Check it out:

 

This is a scale model; each blue ball is the size of the Earth and the overall ball is the Sun, so the ratio of the two sizes is the same as in real life (that's the definition of a scale model) (source)

As the sun formed, the gravity in the center increased as more mass ran into it! But some of the dust was spinning around the newly-formed sun, going so fast that it could orbit around without ever getting closer (check out the link for my explanation of orbit from last year). The spinning got faster too, because of an idea called 'angular momentum' - which is the same reason an ice skater spins faster when she brings her body in close:

That's 35 spins in 12 seconds. Impressive. (source)

So the newly formed solar system started spinning faster; as I explained in the orbit post, not everything had the right speed to maintain orbit for the next 4 billion years - only 8 planet-sized objects were going the perfect speed in our solar system, and you already know what they are:

 Pluto is of course not a planet anymore - and notice that this is NOT to scale, it's only to show the rotation of each planet.

Does anybody know why Pluto is not considered a planet anymore? And how do the different tilted axes of the planets create different environments on the other planets? I'll get into that another time.