The planets of our solar system orbit the sun in a flat disc shape and when we see distant galaxies, we see disc shapes with a spiral form.
The standard explanation for why solar systems and galaxies have a disc-like shape rather than being more three-dimensional is somewhat convoluted and unsatsifying. It is a story of inhomogeneous matter in expanding space spontaneously forming an ordered pattern in one plane.
In the story taught in many classrooms, it is assumed that space is flat or uniform prior to the introduction of matter. The alternative is to assume that there might be pre-existing, large-scale inhomogeneities. Galaxies and solar systems might form with an orientation following boundaries between the inhomogeneities. For example, with matter collecting in discs along the surfaces of bubbles, some of the surfaces would be mostly flat, such that a clean, spiral shape would form. Other surfaces would have a saddle shape, creating an S-shaped galaxy. In the language of non-linear dynamics these are different types of ‘fixed attractors’.
When I saw a video of a boat powered by soap, I started thinking about how matter might form on the surfaces of bubbles of space.
In such a video, the boat invariably traces out a spiral shape like that of a galaxy. This is caused by the interaction of the boat with its own, soapy wake.
I imagine this happening on the surface of a bubble, as when frost branches out from a stationary imperfection or when a boat-like imperfection traces out a spiral shape.
Many times, when young scientists encounter an idea which is not in line with the consensus they were taught in school, they will reflexively label it as crackpottery. This is the natural response of an intellectual immune system, but real thinking requires breaking past this natural response and evaluating ideas based on first principles.
Some people think that there is power in repeating what the group believes, but grown-ups understand that real power comes from being able to look past what the group believes and look at an issue from several perspectives.
I think that galaxy shape might be explained by the Marangoni effect within inhomogeneous, bubble-like space that looks like strands of a cosmic web when viewed from a distance.
But the idea that space is composed of bubbles with a distribution of discrete length scales tells only an incomplete story for the discrete masses of the solar system. To finish that story, I’ll start where an astronomer left off in How does a planet start to rotate? He concluded: “There is no unanimously accepted theory but there certainly are other factors besides protoplanetary disk at work.”
After the protoplanetary disk forms, you have globs of matter swirling around a central point, like dirt swirling around on the surface of water. Why would these globs start to spin and stick together? Gravity and conservation of momentum, of course, but how does it happen?
If we use what we know about moving charges and how they interact with their own electromagnetic fields, we can make an analogy with how a moving mass would interact with its own gravitiational field.
These sorts of problems are typically described with Lienard Weichert potentials.
In this framework, a glob of matter orbiting a sun emits gravitational waves propagating at the speed of light. These waves travel in a straight line, forming a chord with the glob’s curved trajectory.
The glob’s longer, slower, curved path causes it to trail the gravitational wave and experience its wake.
You can think of the glob as a boat for which the wake is faster than the boat. The boat is turning into the wake, causing the front of the boat to go up and the back to go down.
This would cause the head of the glob to gain energy relative to the tail, imparting relative motion of the head and tail. For a glob that is not stuck together by gravity, this would break it into smaller pieces, but for a rigid body, like a planet, this would impart a spin about an axis perpendicular to the direction of motion
If the spinning matter carries a charge and creates a current loop, like a dynamo, this will create a magnetic field with the north pole of the planet pointed directly towards the sun.
If, due to similar motions about the solar system’s center of mass, the sun also has a magnetic field, this will interact with the planet’s magnetic field.
I like to imagine a bunch of balls rolling on a spinning disc. As they turn into dynamos, the magnetic field of the sun rotates them so that they are spinning like tops on the disc.
From a quantum perspective, the mass travelling around the sun is emitting and absorbing gravitons which are analogous to photons in the Lienard-Weichert treatment of a relativistic electron travelling on a curved trajectory. This self-similar picture gives a sense of the fractal nature of our universe.
“Collective effects” or how order emerges from disorder also plays a role in how planets form. Systems often have resonances which define how objects will organize themselves. For example, if you oscillate electrons of a given energy up and down, over and over, they will organize themselves in a regular, ordered pattern. There must be something similar going on in solar systems.
To turn this mental animation into scientific knowledge, we would need a good simulation and some measurements.
Some people get the impression that I am a contrarian about all of physics, but this isn’t really the case. I am merely a contrarian about the fragmentation and compartmentalization of physics. I like forming coherent narratives about how things came to be the way they are and I find that the stories physics tells today are lacking in consistency and dimension.
I first posted some of this content on quora.com
The artwork in the header is by Mark Garlik