Why are planetary orbits elliptical and not circular?
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I think something a lot of comments are failing to address is the fact that elliptical orbits don’t turn into circular orbits. For example, even though there’s infinitely more ways for a bubble to be elliptical, bubbles look pretty much like perfect spheres, and if something messes with them, they stretch a bit into an elliptical shape but then return to a sphere.
So, the reason that planetary orbits are elliptical and not circular is because elliptical orbits are *stable*, meaning that an elliptical gravitational orbit, if not effected by external forces, will stay the exact same shape. The reason for this is math that I don’t understand well enough to ELI5. What that means is that if an orbit starts out as circular, any little external force, like gravity from other planets or impacts, will change the orbit from a circle to an ellipse, and it will remain in that new elliptical orbit until another change, which will probably not return it to a circle.
Actually they can be circular. It is a “all squares are rectangles but not all rectangles are square” situation
For a given orbit length, only one very specific configuration is circular while the rest (an infinite amount) are elliptical. As there is no general force that acts to make an orbit more circular, it’s simply statistically much more likely to find orbits that are elliptical rather than ones that are circular.
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