Coulomb's law Updated 2025-07-16
Is implied by Gauss' law if Maxwell's equations: physics.stackexchange.com/questions/44418/are-the-maxwells-equations-enough-to-derive-the-law-of-coulomb
The "static" part is important: if this law were true for moving charges, we would be able to transmit information instantly at infinite distances. This is basically where the idea of field comes in.
Coulomb's Law experiment with torsion balance with a mirror on the balance to amplify rotations by uclaphysics (2010)
Source. Deriving magnetism from electricity and relativity Updated 2025-07-16
It appears that Maxwell's equations can be derived directly from Coulomb's law + special relativity:
This idea is suggested by the charged particle moving at the same speed of electrons thought experiment, which indicates that magnetism is just a consenquence of special relativity.
Why moving charges produce magnetic field? by FloatHeadPhysics (2022)
Source. Electric current Updated 2025-07-16
In the context of Maxwell's equations, it is vector field that is one of the inputs of the equation.
Section "Maxwell's equations with pointlike particles" asks if the theory would work for pointlike particles in order to predict the evolution of this field as part of the equations themselves rather than as an external element.
Measured in amperes in the International System of Units.
Electromagnetic four-potential Updated 2025-07-16
A different and more elegant way to express Maxwell's equations by using the:instead of the:
Electromagnetism Updated 2025-07-16
As of the 20th century, this can be described well as "the phenomena described by Maxwell's equations".
Back through its history however, that was not at all clear. This highlights how big of an achievement Maxwell's equations are.
Important partial differential equation Updated 2025-07-16
Maxwell's equations require special relativity Updated 2025-07-16
The following aspects of Maxwell's equations make no sense without special relativity:
- the Lorentz force would be different observers have different speeds, see e.g.: charged particle moving at the same speed of electrons thought experiment
- Maxwell's equations imply that the speed of light is the same for all inertial reference frames
When charged particle though experiment are seen from the point of view of special relativity, it becomes clear that magnetism is just a direct side effect of charges being viewed in special relativity. One is philosophically reminded of how spin is the consequence of quantum mechanics + special relativity.
Maxwell's equations with pointlike particles Updated 2025-07-16
In the standard formulation of Maxwell's equations, the electric current is a convient but magic input.
Would it be possible to use Maxwell's equations to solve a system of pointlike particles such as electrons instead?
The following suggest no, or only for certain subcases less general than Maxwell's equations:
This is the type of thing where the probability aspect of quantum mechanics seems it could "help".
Particle physics Updated 2025-07-16
Currently an informal name for the Standard Model
Chronological outline of the key theories:
- Maxwell's equations
- Schrödinger equation
- Date: 1926
- Numerical predictions:
- hydrogen spectral line, excluding finer structure such as 2p up and down split: en.wikipedia.org/wiki/Fine-structure_constant
- Dirac equation
- Date: 1928
- Numerical predictions:
- hydrogen spectral line including 2p split, but excluding even finer structure such as Lamb shift
- Qualitative predictions:
- Antimatter
- Spin as part of the equation
- quantum electrodynamics
- Date: 1947 onwards
- Numerical predictions:
- Qualitative predictions:
- Antimatter
- spin as part of the equation
Polarization of light Updated 2025-07-16
This section discusses the pre-photon understanding of the polarization of light. For the photon one see: photon polarization.
People were a bit confused when experiments started to show that light might be polarized. How could a wave that propages through a 3D homgenous material like luminiferous aether have polarization?? Light would presumably be understood to be analogous to a sound wave in 3D medium, which cannot have polarization. This was before Maxwell's equations, in the early 19th century, so there was no way to know.
Quantum mechanics experiment Updated 2025-07-16
Atoms exist and last for a long time, while in classical electromagnetic theory punctual orbiting electrons should emit radiation quickly and fall into the nucleus: physics.stackexchange.com/questions/20003/why-dont-electrons-crash-into-the-nuclei-they-orbit
In other sections:
Bibliography:
Special relativity experiment Updated 2025-07-16
- moving magnet and conductor problem: the more experiments confirm Maxwell's equations, the more special relativity has to be correct
- aberration TODO more precisely how it is evidence.
System of partial differential equations Updated 2025-07-16
In many important applications, what you have to solve is not just a single partial differential equation, but multiple partial differential equations coupled to each other. This is the case for many key PDEs including:
Wave-particle duality Updated 2025-07-16
First people thought it was a particle, as per corpuscular theory of light, notably Newton supported the corpuscular theory of light.
But then evidence of the diffraction of light start to become unbearably strong, culminating in the Arago spot.
And finally it was understood from Maxwell's equations that light is a form of electromagnetic radiation, as its speed was perfectly predicted by the theory.
But then evidence of particle nature started to surface once again with the photoelectric effect. Physicists must have been driven mad by all these changes.