This website describes an alternative approach to the Theory of Relativity using the Newtonian mechanics with variable mass1.
The constancy of the speed of light is not postulated, and the Lorentz transformation is not used to derive the relativistic equations.
Before proceeding, we recommend that you read the “Notice to the reader”.
Two important findings
The start of this alternative approach is based on two important findings.
Max Born reports on the first finding. In his book “Einstein’s Theory of Relativity” – page 244-247 he shows that there is a “simple proof of Einstein” for the equation E=mc², which “does not make use of the mathematical formalism of the theory of relativity”.
Richard Feynman mentions the second result in his work “Lectures on Physics“. He points out that the Second Law of Motion is applicable with the relativistic mass formula.
Since the Second Law of Motion with constant mass describes classical mechanics, the question arises:
What can the same law do with variable mass?
Newton’s law combined with E=mc² leads to the theory of relativity
Well, it turns out that Newton’s law, combined with the energy-mass equivalence E=mc² derived from classical physics, can introduce the theory of relativity in a simple and intuitive way.
This path was consistently followed in the book “Newton and Relativity” with astonishing results:
Starting from the Second Law of Motion with variable mass, the equations of the special theory of relativity up to the constancy of the speed of light can be proved by a sequence of comprehensible derivations.
Newton’s law is generally valid
It is shown that the Second Law of Motion remains generally valid even under relativistic conditions. This allows a direct transition from Newtonian to relativistic mechanics.
It follows that classical mechanics should no longer be regarded as a special case of relativistic mechanics:
Rather, it is the theory of relativity that can be interpreted as a logical extension of Newtonian mechanics.
Ultimately, it is a question of reunifying classical and relativistic mechanics in a single scientific discipline.
This is essentially the approach taken here.
The aim is to provide simple introduction to the Theory of Relativity, avoiding the paradoxical assumptions on which the traditional interpretation of the theory is based.
Concepts such as “length contraction“, “time dilation“, “Lorentz transformation” and finally the “constancy of the speed of light” are not the prerequisites but the results of this alternative approach to the theory of relativity.
We recommend that you click on the “Sequence of Relativistic Proofs” to continue reading.
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The aim of this website is to introduce the theory of relativity using a new, simple and accessible demonstration method.
To support this project, please order the book “Newton and Relativity“.
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- On this website, we consistently use Newton’s second law of motion in its original form, according to which the force is equal to the time derivative of the momentum:
\[\vec{F}=\frac{d(m\vec{v})}{dt}=m\frac{d\vec{v}}{dt}+\vec{v}\frac{dm}{dt}\]
In this form, Newton’s law is also compatible with variable mass as it occurs at relativistic speeds. ↩︎
“The constancy of the speed of light is not postulated”.
Indeed, it doesn’t have to be postulated. It is derived from Maxwell’s equations. If you write c, you are using a universal constant, a constant that depends only on the choice of the units.
“It is shown that the Second Law of Motion remains generally valid even under relativistic conditions”.
No! It is not valid in a strong gravitational field. You have to use General Relativity. Furthermore, it has only a limited significance in Special Relativity. You can use it when a charged particle enters a magnetic field: case of a circular uniform motion.
In Einstein’s original formulation of special relativity, the constancy of the speed of light in a vacuum is taken as one of the two fundamental postulates of the theory.
While Maxwell’s equations imply that electromagnetic waves propagate at a constant speed c in a medium (the aether), they do not imply that this speed is the same in all inertial frames. It was only through the Michelson–Morley experiment that it was shown that the expected ‘aether wind’ does not exist, and that the speed of light in a vacuum is the same for all inertial observers.
The second law of mechanics is not used in general relativity because gravity is not conceived as a force in the usual Newtonian sense; rather, it is the manifestation of curved spacetime geometry.