And when things “move” it’s just that they’re making changes in the grid next to them, and some patterns just so happen to do so in a way where, after a certain period, it’s the same pattern translated… is that what we think happens in our universe? Are electrons moving “just causal propagations”? Somehow this feels more natural for the Game of Life and less natural for physics.
This is what we think happens in our universe!
Both general relativity and quantum field theory are field theories: they have degrees of freedom at each point in space (and time), and objects that “move” are just an approximate description of propagating patterns of field excitations that reproduce themselves exactly in another location after some time.
The most accessible example of this is that light is an electromagnetic wave (a pattern of mutually-reinforcing electric and magnetic waves); photons aren’t an additional part of the ontology, they’re just a description of how electromagnetic waves work in a quantum universe.
(Quantum field theory can bedescribed using particles to a very good degree of approximation, but the field formalism includes some observable phenomena that the particle formalism doesn’t, so it has a strictly better claim to being fundamental.)
Beware, though; string theory may be what underlies QFT and GR, and it describes a world of stringy objects that actually do move through space… But at the very least, the cellular-automata perspective on “objects” and “motion” is not at all strange from a modern physics perspective.
EDIT: I might go so far as to claim that the reason all electrons are identical is the same as the reason all gliders are identical.
Beware, though; string theory may be what underlies QFT and GR, and it describes a world of stringy objects that actually do move through space
I think this contrast is wrong.[1] IIRC, strings have the same status in string theory that particles do in QFT. In QM, a wavefunction assigns a complex number to each point in configuration space, where state space has an axis for each property of each particle.[2] So, for instance, a system with 4 particles with only position and momentum will have a 12-dimensional configuration space.[3] IIRC, string theory is basically a QFT over configurations of strings (and also branes?), instead of particles. So the “strings” are just as non-classical as the “fundamental particles” in QFT are.
QFT doesn’t actually work like that—the “classical degrees of freedom” underlying its configuration space are classical fields over space, not properties of particles.
Note that Quantum Field Theory is not the same as the theory taught in “Quantum Mechanics” courses, which is as you describe.
“Quantum Mechanics” (in common parlance): quantum theory of (a fixed number of) particles, as you describe.
“Quantum Field Theory”: quantum theory of fields, which are ontologically similar to cellular automata.
“String Theory”: quantum theory of strings, and maybe branes, as you describe.*
“Quantum Mechanics” (strictly speaking): any of the above; quantum theory of anything.
You can do a change of basis in QFT and get something that looks like properties of particles (Fock space), and people do this very often, but the actual laws of physics in a QFT (the Lagrangian) can’t be expressed nicely in the particle ontology because of nonperturbative effects. This doesn’t come up often in practice—I spent most of grad school thinking QFT was agnostic about whether fields or particles are fundamental—but it’s an important thing to recognize in a discussion about whether modern physics privileges one ontology over the other.
(Note that even in the imperfect particle ontology / Fock space picture, you don’t have a finite-dimensional classical configuration space. 12 dimensions for 4 particles works great until you end up with a superposition of states with different particle numbers!)
String theory is as you describe, AFAIK, which is why I contrasted it to QFT. But maybe a real string theorist would tell me that nobody believes those strings are the fundamental degrees of freedom, just like particles aren’t the fundamental degrees of freedom in QFT.
*Note: People sometimes use “string theory” to refer to weirder things like M-theory, where nobody knows which degrees of freedom to use...
This is what we think happens in our universe!
Both general relativity and quantum field theory are field theories: they have degrees of freedom at each point in space (and time), and objects that “move” are just an approximate description of propagating patterns of field excitations that reproduce themselves exactly in another location after some time.
The most accessible example of this is that light is an electromagnetic wave (a pattern of mutually-reinforcing electric and magnetic waves); photons aren’t an additional part of the ontology, they’re just a description of how electromagnetic waves work in a quantum universe.
(Quantum field theory can be described using particles to a very good degree of approximation, but the field formalism includes some observable phenomena that the particle formalism doesn’t, so it has a strictly better claim to being fundamental.)
Beware, though; string theory may be what underlies QFT and GR, and it describes a world of stringy objects that actually do move through space… But at the very least, the cellular-automata perspective on “objects” and “motion” is not at all strange from a modern physics perspective.
EDIT: I might go so far as to claim that the reason all electrons are identical is the same as the reason all gliders are identical.
I think this contrast is wrong.[1] IIRC, strings have the same status in string theory that particles do in QFT. In QM, a wavefunction assigns a complex number to each point in configuration space, where state space has an axis for each property of each particle.[2] So, for instance, a system with 4 particles with only position and momentum will have a 12-dimensional configuration space.[3] IIRC, string theory is basically a QFT over configurations of strings (and also branes?), instead of particles. So the “strings” are just as non-classical as the “fundamental particles” in QFT are.
I don’t know much about string theory though, I could be wrong.
Oversimplifying a bit
4 particles * 3 dimensions. The reason it isn’t 24-dimensional is that position and momentum are canonical conjugates.
QFT doesn’t actually work like that—the “classical degrees of freedom” underlying its configuration space are classical fields over space, not properties of particles.
Note that Quantum Field Theory is not the same as the theory taught in “Quantum Mechanics” courses, which is as you describe.
“Quantum Mechanics” (in common parlance): quantum theory of (a fixed number of) particles, as you describe.
“Quantum Field Theory”: quantum theory of fields, which are ontologically similar to cellular automata.
“String Theory”: quantum theory of strings, and maybe branes, as you describe.*
“Quantum Mechanics” (strictly speaking): any of the above; quantum theory of anything.
You can do a change of basis in QFT and get something that looks like properties of particles (Fock space), and people do this very often, but the actual laws of physics in a QFT (the Lagrangian) can’t be expressed nicely in the particle ontology because of nonperturbative effects. This doesn’t come up often in practice—I spent most of grad school thinking QFT was agnostic about whether fields or particles are fundamental—but it’s an important thing to recognize in a discussion about whether modern physics privileges one ontology over the other.
(Note that even in the imperfect particle ontology / Fock space picture, you don’t have a finite-dimensional classical configuration space. 12 dimensions for 4 particles works great until you end up with a superposition of states with different particle numbers!)
String theory is as you describe, AFAIK, which is why I contrasted it to QFT. But maybe a real string theorist would tell me that nobody believes those strings are the fundamental degrees of freedom, just like particles aren’t the fundamental degrees of freedom in QFT.
*Note: People sometimes use “string theory” to refer to weirder things like M-theory, where nobody knows which degrees of freedom to use...