# Apparent Violations of Principle of Relativity?

• I
• BruceAW
In summary, the conversation discusses the concept of absolute velocity and proper motion with respect to the center of mass of the universe and the cosmic microwave background radiation. The principle of relativity is also mentioned, stating that any inertial frame of reference is equally valid for observing and understanding motion and forces. The conversation then delves into the topic of relativistic mass and its relation to gravity. The idea of a preferred frame of reference is also brought up, along with examples such as the calculation of proper motion and the violation of relativity in cases such as the Critical Ionization Velocity. The conversation also touches upon the use of Lorentz transformations in calculating velocity and the transformation of electrical and magnetic fields.
BruceAW
TL;DR Summary
I consider the concept of ' 'Proper motion', in response to apparent violations of the principle of relativity.
Relativistic mass. Parallel currents., violate inertial frames of reference. Cavendish balance, can measure relativistic mass..
I am aware of Lorentz transformations
I have for a long time been pondering the concept of 'Absolute velocity'. Or, 'Proper motion'.
The velocity of an object, with respect to the center of mass of the universe, and the cosmic microwave background radiation.
Ways, it seems to make more sense, than merely relative velocities, with no preferred frame of reference.

The principle of relativity ,Which can be paraphrased as.
'Any inertial frame of reference (at zero or constant velocity), is as valid as any other, for observing and understanding motions and forces.'
Or. If two observers have a constant relative velocity. Then either may be considered 'at rest', and the other to have the whole of the relative velocity.

The first time I questioned 'relativity' was in relation to relativistic mass (Mrl)
(I will assume 'we' know relativistic mass is gravitational)
Relativistic mass, Mrl = M/sqrt[1-(v^2 /c^2)
{Relativistic mass, Mrl . rest mass, M. Velocity v. light speed,c.}
If we imagine that an observer,moving at velocity V (With respect to what??)
Has a Cavendish balance, that can measure the gravitational attraction between two sample test masses, the effect of various velocities, on their relativistic mass, Mrl, could be measured.
If they could be accelerated, in various ways until the minimum value of relativistic mass, was measured. they could be considered to be 'at rest', in that situation. And, their rest mass, M, could be determined.
To measure the magnitude of their velocity, they then only measure relativistic mass,Mrl, and calculate V, with the equation for Mr as a function of M and v, (above)
{v = c* sqrt[1 - M^2/Mrl^2 ], I velieve. But the point is, a value for v ccould be calculated from measurements of rest mass M , and relativistic mass M.}

This implies to me, a 'prefered frame of reference', where the measure of the gravitational force between the test masses is least.
And a 'proper motion', calculated from comparison of the rest mass and relativistic mass.

Also, there is the case of two charges moving 'side by side'. each other, at equal velocities V in the x direction. Maintaining equal x coordinates. A short distance from each other in the y direction.
I have read that this conundrum, is sorted out by application of Lorents transformations.
Two electrons, with a relative velocity V, with respect to, and moving away from, observer A , along the x axis.
Observer A, sees the electrons converging, due to the attractive magnetic force, of 'parallel currents'.
Observer B, moving with the electrons, Must also, see them converge!
But, observer B, sees the electrons 'at rest', in the x direction. And, expects, them to move away from each other, due to elevtrostatic repulsion.
Observer B, must conclude that the electrons are moving at a significant velocity V. Which he could calculate from the motion of the electrons. With respect to the 'prefered frame of reference', in which we can calculate the magnetic forces of parallel currents.)
He might have to use Lorentz transformations to calculate the correct velocity.
But, No Lorentz transformation, involving the 'Gamma function' (1 / sqrt[1-(v^2/c^2)], will change the sign of a measurement of an attractive force, to some relativistic repulsive force.
{ {I think}}

Another example of a violation to 'relativity', might be, 'Critical Ionization Velocity'.
https://en.wikipedia.org/wiki/Critical_ionization_velocity
Hydrogen ionizes, at 0.5 m/s. With Respect to what?
Could this be due to repulsive magnetic forces of the anti-parallel currents?

BruceAW said:
I will assume 'we' know relativistic mass is gravitational
You assume wrongly. The source of gravity in relativity is the stress-energy tensor.
BruceAW said:
a Cavendish balance, that can measure the gravitational attraction between two sample test masses
This will measure the rest mass of the sample masses, since it is at rest with respect to them, so the only relevant part of the stress-energy tensor is the rest energy density of the samples.
BruceAW said:
Why? You already stated the obvious result - the charges repel. The Lorentz transforms applied to the Faraday tensor will let you work out the details in the frame where the charges are moving if you want.

BruceAW said:
Another example of a violation to 'relativity', might be, 'Critical Ionization Velocity'.
That depends on the velocity difference between two media. That is not a violation of relativity.

You keep asking: velocity relative to what. In each case you have mentioned except the last, it is relative to an arbitrarily chosen standard of rest. Usually, you and your lab, although not always.

Last edited:
sysprog and berkeman
BruceAW said:
(I will assume 'we' know relativistic mass is gravitational)
But we already know that relativistic mass is unrelated to gravitational mass
Observer A, sees the electrons converging, due to the attractive magnetic force, of 'parallel currents'.
Observer B, moving with the electrons, Must also, see them converge!
But, observer B, sees the electrons 'at rest', in the x direction. And, expects, them to move away from each other, due to elevtrostatic repulsion.
You have to correctly transform both the electrical and magnetic fields according to Maxwell's equations. When you do the apparent paradox disappears.

This thread is closed. We can host a discussion of some of the complicated and easily misunderstood corner cases of special relativity, and we can help you understand the parts of the the theory that appear contradictory at first glance , but that's not this thread.

vanhees71 and berkeman

## 1. What is the Principle of Relativity?

The Principle of Relativity is a fundamental concept in physics that states that the laws of physics should be the same for all observers in uniform motion. This means that the laws of physics should not depend on the observer's frame of reference or their relative motion.

## 2. What are apparent violations of the Principle of Relativity?

Apparent violations of the Principle of Relativity occur when an observation or experiment seems to contradict the principle. This can happen when the laws of physics appear to be different for different observers or when an object seems to be moving at a speed faster than the speed of light.

## 3. How have scientists addressed apparent violations of the Principle of Relativity?

Scientists have proposed various theories and experiments to address apparent violations of the Principle of Relativity. These include the theory of special relativity, which explains the behavior of objects moving at high speeds, and the theory of general relativity, which describes the effects of gravity on space and time.

## 4. Can the Principle of Relativity be proven?

The Principle of Relativity is a fundamental principle in physics and cannot be proven in the traditional sense. However, it has been extensively tested and has been confirmed by numerous experiments and observations.

## 5. Are there any exceptions to the Principle of Relativity?

There are no known exceptions to the Principle of Relativity. However, some scientists have proposed theories that suggest the principle may not apply at very small scales or in extreme conditions, such as near black holes. These theories are still being studied and have not been confirmed.

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