Newtonian Relativity

ReferenceA Logical Approach to Theoretical Physics

Newtonian relativity is an expansion upon Galilean relativity, which states that the laws of motion are the same in all inertial frames. Galileo Galilei first described this principle in 1632 using the example of a ship traveling at constant velocity, without rocking, on a smooth sea; any observer doing experiments below the deck would not be able to tell whether the ship was moving or stationary.


Inertial Frame of Reference

Newton considered the background of stars, which was at absolute rest, as the basis of all motion. According to Newton, all frames of reference, that are neither rotating nor accelerating, are in a state of constant, rectilinear motion with respect to one another. In other words, the first law of motion applies equally to these frames. Such a frame is called inertial frame of reference. Measurements in one inertial frame can be converted to measurements in another by a simple Galilean transformation.

In an inertial frame of reference, a body does not accelerate unless force is applied to it. In the absence of force, the body either stays at rest or moves at a constant speed in a straight line. Conceptually, the physics of a system in an inertial frame have no causes external to the system.

The inertial frame of reference operates from the perspective of MATERIAL-VOID duality. There is only matter that is homogeneous and isotropic throughout. The matter moves in the void with its space. The is no free space (see Matter, Void and Space).


Newton’s Assumptions

Newton assumes that matter can move at different uniform velocities independent of density. This assumption is valid for the material region since the velocities are so small that their variation has negligible effect on density.

Newton also assumes that the Laws of Motion (and the Galilean transformation) apply to objects on Earth for motions relative to the Earth. This assumption is valid because Earth adds the same motion to these objects relative to the fixed stars.

Newton also assumes that the Laws of Motion (and the Galilean transformation) apply to the motion of planets of the solar system, when Earth, or the Sun, is used as the basis of motion (instead of the fixed stars). This assumption is generally valid as long as the variations in densities are negligible (see The Universal Frame of Reference).


Mercury’s Orbit

Error occurs in calculating the precession of the perihelion of Mercury’s orbit because the variation in the densities involved is considerable. Mercury is 12 times as dense as the Sun, and 4 times as dense as the Earth. Therefore, neither Earth nor the Sun can be used as the basis of motion in lieu of the fixed stars.

Einstein resolved this problem through his theory of special relativity (SR), by using the speed of light as the basis of motion. This basis is just as workable as the basis of fixed stars because the speed of light is an intrinsic motion relative to fixed stars (see The Universal Frame of Reference).

Einstein says in The Evolution of Physics:

We really have no choice. We tried to save the Galilean relativity principle by assuming that systems carry the ether along in their motion, but this led to a contradiction with experiment. The only way out is to abandon the Galilean relativity principle and try out the assumption that all bodies move through the calm ether-sea.

The phrase “systems carry the ether along in their motion” seems to refer to the inertial frame operating from the perspective of MATERIAL-VOID duality (see above). Einstein seems to think that the problem is with the Galilean relativity principle.

The truth is that the problem arises because Earth and Sun are being used as the basis of motion instead of the fixed stars.


Local and Universal Motion

Newton’s Laws of Motion, and the Galilean transformation, apply to motion relative to fixed stars. The fixed stars are assumed to have an intrinsic motion of zero. The intrinsic motion is a characteristic that is inherent to the substance and it does not depend on anything outside of the moving body. We refer to intrinsic motion as universal motion because it is the same throughout the universe like other intrinsic properties, such as, mass.

Therefore, the fixed stars provide the zero of a scale, relative to which we can measure intrinsic or universal motion.

In contrast to universal motion we have local motion, which is measured relative to a local body, such as, the Earth or the Sun. Working with local motion is like working with unlike quantities that require conversion to like quantities before adding and subtracting. Therefore, local motion must be converted to universal motion before Galilean transformation can be applied, especially if the densities of the moving bodies are different.

Current physics uses the terms relative and absolute motion. This is confusing because relative motion exists on the absolute scale also. By absolute motion we really mean intrinsic, or universal motion.

Therefore, the terms local and universal motion are more useful than the terms relative and absolute motion.


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  • vinaire  On September 30, 2019 at 5:44 AM

    Instead of relative and absolute motion, the vocabulary should emphasize local and universal motion.

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