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Think about a chef taking a ball of pizza dough and spinning it above their head.
It doesn’t turn into a big, hollow sphere, it turns into a round, flat pizza.
Same principle, except the ball of dough is a ball of stardust in space.
It doesn’t turn into a big, hollow sphere, it turns into a round, flat pizza.
A-HAH! Checkmate, Roundearthers!
In space there is no up and down.
Except for enemy's gate, it's down.
Found Ender
Ok the planets move in a circle laying down. How come not a circle standing upright?
If you turn your head 90 degrees it would look like up and down.
If you’re asking why there seems to be a North and South for the solar system and the galaxy in general it’s because the giant clouds of matter that coalesced to make the stars began to spin around the center of mass due to gravity. As more mass was accumulated the spinning became more pronounced as everything “fell into line”
Due to conservation of angular momentum, not gravity.
Combination of several factors actually, but gravity is a primary one, otherwise more systems would be more "round", especially ones that formed earliest and had matter being pulled in from all around. Gravity, and the perceived centripetal forces it and inertia combine to create, pull matter in and "flatten" the disc despite the angular momentum of the smaller particles of matter that might come in from perpendicular angles.
Conservation of angular momentum does explain why it's likely that bodies that are at wider orbital angles likely formed outside of the formation of the system or suffered collisions with larger objects very late in or after the formation of the system since once the matter is flattened into a disc by gravitational and inertial forces, it's unlikely they would deviate from that angle of orbit without major external forces.
Ok I think i understand. So at 90 degrees the planets do not look like going around? But do they look like they are going over it?
Right.
It all depends on your reference point. Typically when orbits are depicted for human understanding, they’re given a top-down view. Think like Open Street Maps. It could be depicted on its side, like watching race cars around a race track, but it can result in more visual distortions than a simple top-down view.
Alternatively, if you’re referring to orbits with high inclinations relative to the orbital plane, that also happens. Pluto, for example, has an inclination of ~17°, which is one of the reasons there are theories it was not part of the solar system when the solar system formed.
Since, as was mentioned, there is no up and down, this depends on your own orientation. Turn yourself 90 degrees and the circle is "upright".
It does! The solar system moves through the galaxy face-first: http://rhysy.net/Art/Illustrations/Solar-System-non-Vortex/
if you mean that planets revolve around the sun roughly in the same plane, as the star itself rotates, then look in to the formation of the sun and planets from the same disk of dust.. movement is tightly coupled to the formation itself.
There is no “up” or “down” in space
It all formed from the same accretion disk. Very flat, all moving together dust and gas became the whole solar system
But why was that a disk and not a sphere?
It used to be kinda like a sphere (of mostly gas and dust) at one point, or more exactly, everything was moving in vague orbits without preference.
But with movement like that you can imagine that things bump into each other. And when they bump, part of their energy turns into heat and part of it remains as slightly slower movement (when they bounce/glance off and continue in roughly the general direction they were going before the collision). Slower movement means the orbit tightens around whatever thing it's orbiting.
That cloud of gas/dust must have had the slightest swirl in it. That means things collided slightly less when moving in the direction of the swirl, and more when against or perpendicular to it. Like moving in a crowd, it's easier to move with the crowd than against or perpendicular to it.
Over eons, the orbits got tighter and tighter because of the collisions and heating up, until the whole movement distilled itself into just the swirl - the only thing they all agreed on. Anything moving otherwise was likely to hit something and lose its movement.
There is a gif I've seen that demonstrates this using a water balloon and a drill. The knot of the balloon is in the drill chuck, and when you turn on the drill the balloon spins into a (relatively) flat disk.
I'll try to find it and add a link here. Prepare for disappointment.
Edit: best I can do is an Instagram reel (from a great creator who covers lots of physics stuff) https://www.instagram.com/reel/DKLwz5TxmIu
it does, we just usually look at it sideways
Someone fact-check me, but I'm pretty sure that there is two reasons for it. The first reason as to why all the planets are spinning in the same direction is because when the planets formed there were different planets, or basically small rocks that were going in different directions, but all the different direction ones hit each other and eventually one direction that had more planets became the only direction.
as to why the direction is not up and down, it doesn't really make sense in space as there is no up and down but there is the direction that the Sun is moving in throughout the galaxy and if that direction is up then the planets are going on the sides and not up and down and that makes sense because the Sun is pulling all of the planets in that direction, so they are dragging along, so they can't spin in front of it and then behind it.
EDIT: The reason all of the planets are spinning in the same direction is not what I wrote. It's actually about the fact that they all formed from a single gas disk. So they all formed from a disk that was spinning in a single direction. The collisions actually contributed to the growth of the planets and less so to their direction.
this post was submitted on 28 Feb 2026
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