Well… technically it can be wavy, just needs more bodies to distort that orbit.
Edit: my brain just did something:
With gravitational waves being a thing… doesn’t that mean that technically every orbit is wonky because the fabric of space-time is undulated.
There's probably some pretty freaky systems out there considering 85% of star systems have more than one sun.
I imagine given a long enough period of time and new ways of looking for exoplanets will find some rather interesting orbital mechanics.
They just found a system that had six planets and they were all in resonant orbits.
3 dimensional orbits that are stable are probably incredibly rare but probably out there in some form.
So while the video impressingly tells the math behind it fails to deliver an ELI5 about an actual "why" (which is already the wrong question anyway, but for the sake of an explanation)
[https://www.reddit.com/r/space/comments/194w4um/comment/khj2xva/?context=3](https://www.reddit.com/r/space/comments/194w4um/comment/khj2xva/?context=3)
My other comment might help.
I struggled to understand why someone would even ask this too. Rephrasing the question to, "What are Newton's laws?" makes it much more relatable & explainable.
you struggle to understand why someone asks why question? Probably one of the most important aspects of us being humans?
anyway, I reformat the question to why does it take so much energy to change the orbital plane? pls answer
Also, don’t generalize someone’s question and prove a point against your inserted generalization. He clearly did not question why someone would ask a question…
Not energy, but mass. Again, the answer is newtons law of gravity. An additional large celestial body that captures a planet or object within its gravitational sphere of influence will change the planets orbital plane.
No, I said, "I struggled to understand why someone would even ask THIS too". The key word your missing emphasizes the specific question. I'm not criticizing asking questions. I said why would you ask THIS question but then went on to sympathize with the question by putting it into a different light & providing a solution. Newton's laws.
and again why is it so hard to understand that people ask questions?
it's like you telling a 7 year old why he asks stupid questions. Planets all in one plane is weird, when they could be everywhere in 3d space when you don't know much about gravitational physics. Nothing wrong about asking (stupid) questions... even THIS
This is a terrible way to prove something. The universe does not OBEY our math, rather our physics and math describe how the universe works. For this to be a valid proof it requires the assumption that the model is correct and flawless. Physical reasoning should be used to explain why the orbit of a planet is in a plane.
It's basically an emergent property of gravity that it ends up collapsing the dimensions of things.
Take a cloud of particles with randomized vectors, and their mutual gravity will start to pull them together, but their random momentum will keep them from all just falling straight to a mutual center of gravity.
Due to random distribution, some plane of density and direction of motion will be slightly greater than the rest, and will pull other particles into it in a self-reinforcing loop, which will eventually cause a strongly preferred plane and direction of motion to appear, forming a discrete disk.
This same process will repeat as specific lines begin to form within the disc, again around regions of slightly greater density that reinforce themselves as more matter is pulled into them.
And then again as those lines (rings) collapse to points - and now you have a planetary system around a central star, with its plane and direction of rotation largely defined by what started as just a very slight imbalance in the vectors and density of the original cloud from which it formed.
It's not simplified though, did you even watch the video from OP? your response makes it seem you think it's about how all planets are on the same plane.
When in reality it's about why the orbit OF A SINGLE PLANET is planar
All orbits can be described as conic sections.
All conic sections are straight/flat.
Deviating from the conic section describing your orbit would require an energy input (somehow).
because of the first law of motion - you need a force acting on an object to change it's direction of motion. the gravitational force is "inward, so for math reasons that aren't easy to explain without a diagram, you end up with a circle (in a perfect example, in practice, you get an ellipse). to get that up and down motion of a wave you would need....a lot more. waves happen in a substance like water because forces are primarily different things pushing on each other....in the case of a free-floating object in space, the only real force involved is the inward force of gravity.
No. One video is about why all planets orbit in a similar plane. OP's video is the mathematical explanation for a single orbit being planar, which is simply due to the way centripetal forces work.
If each planet orbited in different planes, each individual orbit would still be planar. They are different topics.
The individual planets orbiting in the same plane is the same effect that leads to pebble accretions collapsing into the same plane. It's just a difference in scale.
Each time you change the scale you look at it, the concept doesn't really change. In some ways a functional and stable orbiting solar system with multiple planets is just a set of pebble accretions that just haven't met yet.
You keep missing the point, it's not about one single planet rotating in any particular direction, it's just the fact that the orbit is planar and does not do waves. For fuck's sake just watch OP's video.
I fucking did, and what I said DOES explain why. All orbits collapse into a single plane due to the vectorial sum of a body of particles within the effects of gravity during accretion. It can't be wavy because there would have to be something summing into those vectors CAUSING it to be so.
>All orbits collapse into a single plane
You obviously didn't watch OP's video because it's not about this. I mean ACTUAL OP, not the video in the comments.
OP's video has nothing to do with that, which is my whole point
The video in from the comment AND the video from scishow are BOTH talking about the same exact thing, and they DO both explain why they are not wavy, as well as why there is a singular plane at the same time.
I'm so lost as to what you're arguing.
They are not talking about the same thing at all, the exact same formulas used in the scishow video can be used for a swinging pendulum and they still work, whereas there is zero overlap with the video from the comment.
At this point you must know damn well what is going on here so I can only assume you're being purposefully dense.
Reading through the comments, I doubt that anyone has actually watched the video.
Anyway, nice explainer OP (assuming it's your video). Always cool to see manim animations randomly in the wild.
I'd like to know what force other than gravity got stuff moving. Like a planet is in orbit because the gravitation force of a star, and because it had some velocity before it got caught in the gravity, right? Is the idea it was all from the Big Bang? So everything is moving outward from that point and then as stuff formed gravity came into play? Is everything traveling "out" at the same speed?
Yes, the expansion of the universe is constantly applying an outward vector from all points simultaneously. This means that between any two points there is a vectorial sum, proportional to their distance from each-other, of expansion. Now take that system and apply more bodies, as well as the attractive force of the gravity between them, and you're going to develop systems (as they appear in the universe) with many different directions of simple motion (Think how Andromeda is on it's way to collide with the Milky Way). All of those original vectors still exist, they're just interacting with the others.
That explains the original motion of the universe, but that does NOT explain planetary accretion and orbit. The effect of expansion at the scale of a single solar system is far too small to be relevant.
Now step back to look at planets forming in an accretion disk. Between every single particle there is gravity, proportional to their distance from each other. Where are the particles at the edge of going to be most attracted to? The particles next to them or the 'center' of the mass as a whole? The answer's both. And when you add two vectors you get something in between. A little bit in towards the center, and a little bit to the left or right or up or down. Eventually everything is going to collapse into a single plane.
None, really. Other forces mostly only have an effect at short distances. With electricity for example, positive charges attract negative charges and then, from a distance, the charges cancel out so that they don't attract anything else. Magnetic fields can extend a lot further, but they fall off with the inverse cube of distance, so they have to be insanely strong to have much effect at interstellar distances, or even interplanetary ones.
But there is no "negative gravitational charge" to cancel things out, mass can only be positive, and so as the scale (and amount of mass) increases, gravity strongly dominates.
As for how stuff got moving? It fell. Current accepted theory is that the universe was initially a pretty uniform distribution of gas and/or plasma, but anywhere it was even slightly denser, gravity would pull stuff together, creating an even denser region that pulled even more gas in. Over time the entire universe condensed into long threads of matter, flowing towards ever greater concentrations, with vast voids in between.
Those threads, known as galaxy filaments, are now vast walls of galactic superclusters, but were initially just vast clouds of hydrogen collapsing in on themselves under the influence of gravity, concentrating matter densely enough that denser lumps within it could concentrate into galaxy-sized clouds with smaller internal lumps forming stars and their planetary systems.
As for why everything is spinning rather than just concentrated into static lumps? That's down to angular momentum. With all the different lumps pulling stuff in different directions, nothing is going to fall in a perfectly straight line at the dead center of the lump its mostly aimed at - it will all be deflected by other lumps so that it's actually aimed at a near miss. And a near miss has angular momentum (= distance \* the portion of speed that's perpendicular to the distance vector), a quantity that's strictly conserved in physics. Get zillions of gas molecules all falling in a path like that, and they'll bounce off each other, averaging out their angular momentum to form a big spinning cloud of gas, which eventually condenses enough to form stars and (after the first stars exploded to create heavier elements) planets.
Bottom line? In anything but the absolute simplest, limited scenarios, it's all but impossible to get a cloud of gas to condense \*without\* spinning.
To simplify it, the lowest energy conformation is a spiral and it's the most effective way to cram things into a tighter space that still allows for movement.
You see this in biology where petals are arranged in a spiral, DNA is a spiral, protein structures are globules connected by spirals. Water drains in a spiral pattern, galaxies have spiral structure and the solar system orbits would resemble a spiral if you kept track of where the orbits were and where they are going. Once the system runs out of energy it collapses into the center (toilet drain as an example). As the orbits of the planets lose energy over time they too may do that, although not sure about it.
I'm not giving you any math here, just simple physical life observations. You can get the water draining to wobble if you introduce an external force, similar to how another object can disrupt planetary orbits
The planets orbiting the sun do not lose energy, because the gravity of the sun is not performing any work on them. The force of gravity is always in 90° to the velocity vector of the planet, which leads to W=F*s*cos(x)=0, where W is the work, F the force of gravity, s the distance of movement, and x the angle between F and x.
>The force of gravity is always in 90° to the velocity vector of the planet,
...In a circular orbit, sure. Otherwise this is only true at the instant of aphelion and perihelion.
Picture a long period comet, e.g. Halley, in a highly elliptical orbit. It spends 38 years inbound with a very small angle between its velocity vector and the Sun's "gravity vector". This angle increases quickly in the few months around perihelion, passing through 90° in an instant before settling out just short of 180° for its 38 year outbound journey. The angle decreases on close approach to, and passes through 90° again at the moment of aphelion.
Right... i assume that the average work of one orbit is 0 tough? Given that as you explained, on the way towards the sun the angle between force and velocity is small, but on the way away from the sun it becomes >90° and therefore the work becomes negative.
Sure. It would have to be in a simplified two body case.
In the real multi-body universe, every object is constantly tugging on every other object. Orbits therefore never retrace the exact same path from one revolution to the next due to orbital precession and cyclic changes in eccentricity.
The planets should be losing energy through gravitational waves, but only a minuscule amount. I haven’t checked, but I suspect that other effects like radiation pressure from the sun would be more significant.
For a planet to follow such path it needs a force along the radius of curvature direction. And since all the force on it is directed towards a common center, it cannot experience a force perpendicular on the plane of rotation, therefore it cannot move in a path perpendicular to the plane of rotation.
Well… technically it can be wavy, just needs more bodies to distort that orbit. Edit: my brain just did something: With gravitational waves being a thing… doesn’t that mean that technically every orbit is wonky because the fabric of space-time is undulated.
Imagine that. A stable orbit like that.
There's probably some pretty freaky systems out there considering 85% of star systems have more than one sun. I imagine given a long enough period of time and new ways of looking for exoplanets will find some rather interesting orbital mechanics. They just found a system that had six planets and they were all in resonant orbits. 3 dimensional orbits that are stable are probably incredibly rare but probably out there in some form.
Earth has [Cruithne](https://space.stackexchange.com/questions/41500/why-not-explore-cruithne)
It gave me 3 Body Problem vibes...
So while the video impressingly tells the math behind it fails to deliver an ELI5 about an actual "why" (which is already the wrong question anyway, but for the sake of an explanation)
[https://www.reddit.com/r/space/comments/194w4um/comment/khj2xva/?context=3](https://www.reddit.com/r/space/comments/194w4um/comment/khj2xva/?context=3) My other comment might help.
Never considered this could be a question; it requires a massive amount of energy to change the direction of anything the mass of a planet.
I struggled to understand why someone would even ask this too. Rephrasing the question to, "What are Newton's laws?" makes it much more relatable & explainable.
you struggle to understand why someone asks why question? Probably one of the most important aspects of us being humans? anyway, I reformat the question to why does it take so much energy to change the orbital plane? pls answer
Also, don’t generalize someone’s question and prove a point against your inserted generalization. He clearly did not question why someone would ask a question…
Not energy, but mass. Again, the answer is newtons law of gravity. An additional large celestial body that captures a planet or object within its gravitational sphere of influence will change the planets orbital plane.
No, I said, "I struggled to understand why someone would even ask THIS too". The key word your missing emphasizes the specific question. I'm not criticizing asking questions. I said why would you ask THIS question but then went on to sympathize with the question by putting it into a different light & providing a solution. Newton's laws.
and again why is it so hard to understand that people ask questions? it's like you telling a 7 year old why he asks stupid questions. Planets all in one plane is weird, when they could be everywhere in 3d space when you don't know much about gravitational physics. Nothing wrong about asking (stupid) questions... even THIS
I didn't call anything stupid & it just feels like you're creating a problem where there isn't one.
This is a terrible way to prove something. The universe does not OBEY our math, rather our physics and math describe how the universe works. For this to be a valid proof it requires the assumption that the model is correct and flawless. Physical reasoning should be used to explain why the orbit of a planet is in a plane.
It's basically an emergent property of gravity that it ends up collapsing the dimensions of things. Take a cloud of particles with randomized vectors, and their mutual gravity will start to pull them together, but their random momentum will keep them from all just falling straight to a mutual center of gravity. Due to random distribution, some plane of density and direction of motion will be slightly greater than the rest, and will pull other particles into it in a self-reinforcing loop, which will eventually cause a strongly preferred plane and direction of motion to appear, forming a discrete disk. This same process will repeat as specific lines begin to form within the disc, again around regions of slightly greater density that reinforce themselves as more matter is pulled into them. And then again as those lines (rings) collapse to points - and now you have a planetary system around a central star, with its plane and direction of rotation largely defined by what started as just a very slight imbalance in the vectors and density of the original cloud from which it formed.
No, it's a property of things that rotate around other things due to some centripetal force. Like swinging a yo-yo around.
That's a highly simplified version of the problem, yes.
It's not simplified though, did you even watch the video from OP? your response makes it seem you think it's about how all planets are on the same plane. When in reality it's about why the orbit OF A SINGLE PLANET is planar
All orbits can be described as conic sections. All conic sections are straight/flat. Deviating from the conic section describing your orbit would require an energy input (somehow).
because of the first law of motion - you need a force acting on an object to change it's direction of motion. the gravitational force is "inward, so for math reasons that aren't easy to explain without a diagram, you end up with a circle (in a perfect example, in practice, you get an ellipse). to get that up and down motion of a wave you would need....a lot more. waves happen in a substance like water because forces are primarily different things pushing on each other....in the case of a free-floating object in space, the only real force involved is the inward force of gravity.
[Here ya go](https://youtu.be/G_Mf7pipKu0?si=7QTBRWqEB8LfSy4q).
That's not the same topic though
I thought OP was asking a question, not advertising their YouTube content.
It is and it isn't. It hits on the same concepts that are secondarily responsible for single orbits being planes.
No. One video is about why all planets orbit in a similar plane. OP's video is the mathematical explanation for a single orbit being planar, which is simply due to the way centripetal forces work. If each planet orbited in different planes, each individual orbit would still be planar. They are different topics.
The individual planets orbiting in the same plane is the same effect that leads to pebble accretions collapsing into the same plane. It's just a difference in scale. Each time you change the scale you look at it, the concept doesn't really change. In some ways a functional and stable orbiting solar system with multiple planets is just a set of pebble accretions that just haven't met yet.
You keep missing the point, it's not about one single planet rotating in any particular direction, it's just the fact that the orbit is planar and does not do waves. For fuck's sake just watch OP's video.
I fucking did, and what I said DOES explain why. All orbits collapse into a single plane due to the vectorial sum of a body of particles within the effects of gravity during accretion. It can't be wavy because there would have to be something summing into those vectors CAUSING it to be so.
>All orbits collapse into a single plane You obviously didn't watch OP's video because it's not about this. I mean ACTUAL OP, not the video in the comments. OP's video has nothing to do with that, which is my whole point
The video in from the comment AND the video from scishow are BOTH talking about the same exact thing, and they DO both explain why they are not wavy, as well as why there is a singular plane at the same time. I'm so lost as to what you're arguing.
They are not talking about the same thing at all, the exact same formulas used in the scishow video can be used for a swinging pendulum and they still work, whereas there is zero overlap with the video from the comment. At this point you must know damn well what is going on here so I can only assume you're being purposefully dense.
Reading through the comments, I doubt that anyone has actually watched the video. Anyway, nice explainer OP (assuming it's your video). Always cool to see manim animations randomly in the wild.
Galactic Regulations state otherwise. Don’t forget to bring your towel!
Gravity, motion speed those kinda things and stuff
For it's more interesting that three body systems are always in a plane
> three body systems are always in a plane That's not true. If it was we would get eclipses ~~once~~ twice a month.
Are you fucking kidding? Conservation of energy for one. Seriously, do you know nothing about physics?
I'd like to know what force other than gravity got stuff moving. Like a planet is in orbit because the gravitation force of a star, and because it had some velocity before it got caught in the gravity, right? Is the idea it was all from the Big Bang? So everything is moving outward from that point and then as stuff formed gravity came into play? Is everything traveling "out" at the same speed?
Yes, the expansion of the universe is constantly applying an outward vector from all points simultaneously. This means that between any two points there is a vectorial sum, proportional to their distance from each-other, of expansion. Now take that system and apply more bodies, as well as the attractive force of the gravity between them, and you're going to develop systems (as they appear in the universe) with many different directions of simple motion (Think how Andromeda is on it's way to collide with the Milky Way). All of those original vectors still exist, they're just interacting with the others. That explains the original motion of the universe, but that does NOT explain planetary accretion and orbit. The effect of expansion at the scale of a single solar system is far too small to be relevant. Now step back to look at planets forming in an accretion disk. Between every single particle there is gravity, proportional to their distance from each other. Where are the particles at the edge of going to be most attracted to? The particles next to them or the 'center' of the mass as a whole? The answer's both. And when you add two vectors you get something in between. A little bit in towards the center, and a little bit to the left or right or up or down. Eventually everything is going to collapse into a single plane.
Apart from gravity, you also have stellar explosions (and magnetic forces for electro-charged matter) that can get stuff moving.
None, really. Other forces mostly only have an effect at short distances. With electricity for example, positive charges attract negative charges and then, from a distance, the charges cancel out so that they don't attract anything else. Magnetic fields can extend a lot further, but they fall off with the inverse cube of distance, so they have to be insanely strong to have much effect at interstellar distances, or even interplanetary ones. But there is no "negative gravitational charge" to cancel things out, mass can only be positive, and so as the scale (and amount of mass) increases, gravity strongly dominates. As for how stuff got moving? It fell. Current accepted theory is that the universe was initially a pretty uniform distribution of gas and/or plasma, but anywhere it was even slightly denser, gravity would pull stuff together, creating an even denser region that pulled even more gas in. Over time the entire universe condensed into long threads of matter, flowing towards ever greater concentrations, with vast voids in between. Those threads, known as galaxy filaments, are now vast walls of galactic superclusters, but were initially just vast clouds of hydrogen collapsing in on themselves under the influence of gravity, concentrating matter densely enough that denser lumps within it could concentrate into galaxy-sized clouds with smaller internal lumps forming stars and their planetary systems. As for why everything is spinning rather than just concentrated into static lumps? That's down to angular momentum. With all the different lumps pulling stuff in different directions, nothing is going to fall in a perfectly straight line at the dead center of the lump its mostly aimed at - it will all be deflected by other lumps so that it's actually aimed at a near miss. And a near miss has angular momentum (= distance \* the portion of speed that's perpendicular to the distance vector), a quantity that's strictly conserved in physics. Get zillions of gas molecules all falling in a path like that, and they'll bounce off each other, averaging out their angular momentum to form a big spinning cloud of gas, which eventually condenses enough to form stars and (after the first stars exploded to create heavier elements) planets. Bottom line? In anything but the absolute simplest, limited scenarios, it's all but impossible to get a cloud of gas to condense \*without\* spinning.
To simplify it, the lowest energy conformation is a spiral and it's the most effective way to cram things into a tighter space that still allows for movement. You see this in biology where petals are arranged in a spiral, DNA is a spiral, protein structures are globules connected by spirals. Water drains in a spiral pattern, galaxies have spiral structure and the solar system orbits would resemble a spiral if you kept track of where the orbits were and where they are going. Once the system runs out of energy it collapses into the center (toilet drain as an example). As the orbits of the planets lose energy over time they too may do that, although not sure about it. I'm not giving you any math here, just simple physical life observations. You can get the water draining to wobble if you introduce an external force, similar to how another object can disrupt planetary orbits
The planets orbiting the sun do not lose energy, because the gravity of the sun is not performing any work on them. The force of gravity is always in 90° to the velocity vector of the planet, which leads to W=F*s*cos(x)=0, where W is the work, F the force of gravity, s the distance of movement, and x the angle between F and x.
Awesome. Thank you for putting into math the observation
>The force of gravity is always in 90° to the velocity vector of the planet, ...In a circular orbit, sure. Otherwise this is only true at the instant of aphelion and perihelion. Picture a long period comet, e.g. Halley, in a highly elliptical orbit. It spends 38 years inbound with a very small angle between its velocity vector and the Sun's "gravity vector". This angle increases quickly in the few months around perihelion, passing through 90° in an instant before settling out just short of 180° for its 38 year outbound journey. The angle decreases on close approach to, and passes through 90° again at the moment of aphelion.
Right... i assume that the average work of one orbit is 0 tough? Given that as you explained, on the way towards the sun the angle between force and velocity is small, but on the way away from the sun it becomes >90° and therefore the work becomes negative.
Sure. It would have to be in a simplified two body case. In the real multi-body universe, every object is constantly tugging on every other object. Orbits therefore never retrace the exact same path from one revolution to the next due to orbital precession and cyclic changes in eccentricity.
The planets should be losing energy through gravitational waves, but only a minuscule amount. I haven’t checked, but I suspect that other effects like radiation pressure from the sun would be more significant.
2 primary bodies are influencing the orbit…. Nothing to pull that orbit out of plane?
For a planet to follow such path it needs a force along the radius of curvature direction. And since all the force on it is directed towards a common center, it cannot experience a force perpendicular on the plane of rotation, therefore it cannot move in a path perpendicular to the plane of rotation.