By that, I mean, why do planets always orbit… horizontally(?) around the sun. Why not vertically? Space is a 3D space, I’d course. So why would the planets not end up going up as well as sideways?
Edit: Space science is a lot more complicated than I thought, and I am here for this rabbit hole. Ty everyone for your answers so far!
In: 2352
It’s actually quite interesting and a little tricky to ELI5.
But it has to do with things spinning around in circles and laaaarge timescales. Imagine, if you will, a random star in a vacuum without anything around it.
You, as the omnipotent imaginer, throw a little rock/piece of dust in it’s general direction. Maybe you hit it, but more likely you’ll miss the star. And when you miss the star the little rock/pice of dust starts circling around the star (thats not quite how orbital mechanics works but works for this illustration).
The way your little rock/dust orbits the star is determined by how you missed it. If you threw it “over” the star it’ll start swinging around in a vertical orbit. If you missed it to the right it will start whizzing around in a horizontal orbit. you could imagine it like a string being connected between the star and the rock/dust you threw.
Now you throw another piece. And another piece, and another, and another. You start throwing maaaaaaaaany many little rockts and pieces of dust and ice at the star. with some you almost hit the star and they end up in a very close circle around it. Others end up in a very large circle around the star. Others again end up doing ellipses around the star, being close at some point and far away at another point. And the planes all the pieces orbit in are also all different, because some flew past the star on the left when you first threw them, some on the right, some above, some below, others, somewhere in between.
And you keep throwing little rocks and dust at your star and suddenly the first two little pieces collide. And they most likely don’t collide head on and rather at an angle, where they just combine or create a little debris and the pieces fly of in a different direction.
As you wait and throw more and more little rocks at your star (now surrounded by a cloud of a uncountably many rocks and dust specs) more collisions happen, and some rocks combine into larger groups as they collide.
The larger pieces have a little bit of a stronger gravity and attract more pieces. And slowly the cloud of pieces coalesces into larger clumps which gather up even more dust.
With every collision the pieces involved change the direction a little bit, according to their masses and velocities. So a collection of tiny rocks has the mass of all the pieces and the average direction of and velocity of the pieces (not super accurate phrasing, but it works i guess).
these clumps turn into planets over a looong time as they gather more and more pieces. Since they all collect pieces from the same cloud of dust and rocks they have a very similar direction of travel because it is very close to the average direction of travel of the original cloud. This is the first part of the explanation because eventually all planets can be seen as the averaged remnants of your cloud.
The second part is, because of the planets attracting each other. conceivably you could have all planets orbiting in close to the same plane with one planet being an outlier, orbiting perpendicular to that plane. When that anomalous planet is on its point furthest away from the plane of the other planets the other planets will attract him and try to pull the “rogue” one into the same plane of rotation. This tugging is veeery small, but over eons of years it will eventually pull the odd one out into the same plane as all the others.
Thats how you end up with them all rotating in the same plane. If you want to get into the weeds of it there is a lot of interesting effects with orbital mechanics, angular momentum and gravitational interaction involved.
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