Is the solar system flat? Do planetary orbits more or less align like they do on our models of the solar system? Or do orbits spin in full 3 dimensions? If the solar is flat, why is that? How does that work?
All the planets in the solar system do roughly go around the Sun in one plane (called the ecliptic). The reason for this lies in how the solar system formed. The Sun and its planets formed out of a cloud of gas that was very large and spun very slowly at first. As this cloud collapsed due to gravity it started to spin faster and faster. This is just the same thing that happens when you spin yourself slowly with your arms outstretched and then pull them in - you start spinning much faster (the physical principle behind this is conservation of angular momentum).
Why is this important? Well, once the cloud spins rapidly, particles won't fall towards the centre in the plane they are spinning in - they become stabilized in orbits. The particles that lie above and below the plane of the spin keep falling in though. So essentially as the cloud collapses most of the material above and below the ecliptic kept falling in, but the material in the ecliptic stayed in its orbit around the centre. With gravity doing its work, larger objects soon started forming in this disk of gas and dust and eventually we were left with our planets and asteroids.
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