Speed Limits on Light and Mass
There are various claims of a speed limit for light and for mass
This video clearly explains the velocity limit for light but makes a drastic mistake when mentioning Einstein. Einstein is mentioned separately below
From Wikipedia's topic: Maxwell's equations
Maxwell's equations explain how these [light] waves can physically propagate through space. The changing magnetic field creates a changing electric field through Faraday's law. In turn, that electric field creates a changing magnetic field through Maxwell's addition to Ampère's law. This perpetual cycle allows these waves, now known as electromagnetic radiation, to move through space at velocity c.
Relative permittivity is the factor by which the electric field between the charges is decreased relative to vacuum.
There are also factors for relative permeability and magnetic susceptibility.
The propagation of light is a self-propagating series of electric and magnetic fields, Its velocity is determined ONLY by the medium. An instantaneous change in medium causes an instantaneous change in propagation velocity. This transition is observed at the surface of glass or water.
This propagation begins and continues at the same velocity regardless of any velocity of the source of its propagation.
All of the above is correct, regardless of anything Einstein did.
He had nothing to do with the velocity of light.
Some question whether a moving light source affects the velocity of its light. Einstein had thought experiments about it.
The velocity of light propagation is always defined by the medium.
The velocity and direction of a light source affects the energy in the light but not its rate of propagation.
If the light source is moving then it has kinetic energy.
In thermodynamics, energy cannot be lost or gained but only exchanged or transformed.
Around the sphere of radiated energy, wave lengths are reduced in the direction of travel or increased in the opposite direction. Each wave length change is determined by the velocity and direction at that point relative to c, the constant velocity of light in a vacuum. If the light source is in a medium, the z is the same because the medium affects the propagation not the initiation. Energy is maintained around the radiated sphere at the instant of emission and the propagation velocity of the light emission is not affected.
The velocity and direction of a moving light source has no effect on the velocity of its light.
Einstein did have something to do with the velocity of mass, a mistake.
He worked only with the context of a moving observer, the "special" observer in both "general" and "special" relativity..
Einstein's belief, of a velocity limit on mass, shared by others in the 1800's, has no justification in physics.
For many years, Einstein's unjustified belief has been refuted.
excerpt from Wikipedia:
In 1993, Thomson et al. suggested that the (outer) jet of the quasar 3C 273 is nearly collinear to our line-of-sight. Superluminal motion of up to ~9.6c has been observed along the (inner) jet of this quasar.
Superluminal motion of up to 6c has been observed in the inner parts of the jet of M87. To explain this in terms of the "narrow-angle" model, the jet must be no more than 19° from our line-of-sight.
A plasmoid, like in 3C 273 or M87, holds substantial electromagnetic energy. The sustained force of a magnetic field on charged particles can result in velocities far faster than c and this has been measured many times.
The motion of mass is not a process dependent on the medium.
Motion is affected by the medium only with its friction on the surface of the mass in motion. Friction is an exchange of kinetic energy to thermal energy. Friction does not define a velocity limit.
Applying a force to a mass results in its acceleration. The force can be maintained for a specific time to achieve the desired velocity. This is a continuous transfer of energy from the source to kinetic energy.
This process of energy transfer is observed during every launch of a space probe.
Once a mass is in motion it has kinetic energy. It must maintain that energy, so it remains in motion, until this energy is transferred like with friction. Friction is a transfer of kinetic energy into thermal energy.
As long as a force continues to transfer more energy into more kinetic energy, the velocity must increase. There is no velocity limit during this energy transfer.
Einstein wrote equations causing changes to the moving observer when near the velocity of light, including relativistic mass, so their possible velocity limit was set in math not physics. At c = v, the relativistic mass is m divided by zero which is either infinite or not allowed!
"Oxford lecturer John Roche states that relativistic mass is not referenced in nuclear and particle physics, and that about 60% of authors writing about special relativity do not introduce it."
Proposing mass has a velocity limit at c means when applying more force to a mass when nearing or at the velocity of c, energy is being lost rather than transferred to kinetic energy.
This loss is a violation of thermodynamics.
The practical velocity limit for a specific mass is set by the force required to reach that velocity.
The velocity limit on light is set by the medium.
Light always propagates at a velocity set by the medium.
There is no defined velocity limit on mass.
Someone asked: If white light enters, why does a rainbow leave?
The medium affects wave lengths differently where shorter slow more than longer.
This causes the bluer side to lag behind the redder side.
Note the beam really diverges at the transition out of the medium which is the instant of return to the top velcity.