CPL.Luke said:you can derive the lorentz transformation by just assuming that the speed of light is constant, so why is the first postulate of special relativity necessary?
CPL.Luke said:well every textbook on special relativity I've ever seen (I've seen quite a few at this point) derives the transformation based off of the constancy of the speed of light without reference to the first postulate.
Then this one must be one of the ones you missed. From Classical Electrodynamics - Second Edition, Hans C. Ohanian, page 172CPL.Luke said:well every textbook on special relativity I've ever seen (I've seen quite a few at this point) derives the transformation based off of the constancy of the speed of light without reference to the first postulate. however you do make a point that another frame could see things happen differently without the first postulate put into the theory.
The principle of the universality of the speed of light is sometimes regarded as a corollary of the Principle of Relativity, because the validity of Maxwell's equation's in all inertial frames implies that light waves propagate in the same way in all such reference frames. However, such a deduction hinges on the assumption that Maxwell's equations are valid laws of physics. Althought it is true that Einstein was led to relativity by thinking about
Maxwell's equations, the theory of relativity is more fundamental than Maxwell's theory. It is therefore undesireable to make relativity logically dependant on Maxwell's equations, and it is preferable to adopt a second postulate for the universality of the speed of light.
That is the way that Einstein first stated that postulate, sure. However the speed of light being independant of the source is identical to saying that the speed of light is invariant. That's why Einstein reffered to the second postulte as the "constancy of light" in his book The Meaning of Life.yogi said:Einstein's second postulate does not say the speed of light is constant - it says it is independent of the velocity of the source - it is simply a repudiation of the ballistic theory of light, which was really nothing new. The constancy of the speed of light is consequent to Einstein's method of synchonization of two clocks - this forces the one way speed to be constant in all inertial frames.
I think you took what I said in a vacuum, i.e. you didn't consider what else Einstein said in that second posulate. That's most likely my fault. Sorry.yogi said:Pete - this is an academic thing but I do not see how you arrive at your conclusion. The speed of all known waves depend upon the properties of the medium and not the velocity of the source; the measured speed of waves in all cases other than em depend upon the motion of the receiver relative to the medium
I think he could have left that last part out since it is implied in the first part, i.e. in "light is always propagated in empty space with a definite velocity c"...and also introduce another postulate, which only apparently irreconcilable with the former, namely, that light is always propagated in empty space with a definite velocity c which is independant of the velocity of the source.
You're welcome Sir. Anytime.yogi said:Obviously my interpretation is not the majority view - thanks for the clarification
Yogi
Yes, the first postulate is necessary for scientific experiments. It states that the laws of nature are constant and universal, providing a basis for reliable and repeatable experiments. Without this postulate, the results of experiments would not be predictable or generalizable.
The first postulate is significant because it establishes a fundamental principle of science - that the laws of nature are consistent and applicable to all phenomena. This enables scientists to make predictions and draw conclusions based on evidence and observations.
No, the first postulate cannot be proven. It is a fundamental assumption that is accepted based on the success of scientific experiments and the lack of evidence contradicting it. However, if new evidence were to arise that contradicts the first postulate, it would need to be reevaluated.
The first postulate is a crucial part of the scientific method. It provides the foundation for hypotheses, experimental design, and the interpretation of results. Without the first postulate, the scientific method would not be able to function as it relies on the assumption that natural laws are consistent and universal.
There are some alternative theories to the first postulate, such as the idea that there may be multiple sets of laws of nature operating in different parts of the universe. However, these theories have not been widely accepted and the first postulate remains the dominant principle in scientific research.