Why do all the planets orbit the sun horizontally instead of vertically, or at random angles?
In: Physics
Most of these answers are flat out wrong or answer the wrong question.
When the solar system was being formed, the was a cloud of dust, gas, and maybe rocks/ice in space much much larger than the current orbital radius of Pluto. If you calculated the center of mass of this cloud of material, every particle had some amount of angular momentum or angular motion around this point. If you did a vector sum (so things orbiting in opposite directions cancel out proportional to mass) of the angular momentum of every particle, you would find that there was some arbitrary “net” axis of rotation for the entire cloud. Normal (at 90 degrees) to this axis is the net orbital plane for the majority of objects in the solar system.
Since according to physics, angular momentum like linear momentum or energy, must be conserved in the absence of an outside force, the cloud will maintain this “net” axis of rotation as things crash into each other and stick together forming planets and larger bodies.
You can think about this, as if two objects, one moving downward across the orbital plane hits another moving upward across it, the resulting new body formed from the collision will have the “up” and “down” components canceled out, leaving only the motion in the direction around the axis along the net orbital plane.
Visual Explanation: [MinutePhysics](https://www.youtube.com/watch?v=tmNXKqeUtJM/)
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