Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.


Math Forum
»
Discussions
»
sci.math.*
»
sci.math
Notice: We are no longer accepting new posts, but the forums will continue to be readable.
Topic:
IS ALL MOTION RELATIVE?
Replies:
6
Last Post:
Mar 31, 2013 2:59 AM




Re: IS ALL MOTION RELATIVE?
Posted:
Mar 23, 2013 10:32 AM


The following argument is valid (that is, the conclusion does follow from the hypotheses, no matter whether they are true or false):
Hypothesis 1: As the observer starts moving towards the source of the light waves with speed v, the speed of the waves relative to him shifts from c to c'=c+v. (In fact, this variation of the speed of the waves with the speed of the observer is true for all waves but here, for the sake of argument, it is advanced as a hypothesis concerning light waves only.)
Hypothesis 2: The motion of the observer cannot change the wavelength of the incoming light.
Conclusion: As the observer starts moving towards the source of the light waves with speed v, the frequency he measures shifts from f to f'=f(1+v/c).
The experimental evidence confirming the conclusion is so overwhelming as to be conclusive to all and not worth mentioning:
http://rockpile.phys.virginia.edu/mod04/mod34.pdf Paul Fendley: "Now let's see what this does to the frequency of the light. We know that even without special relativity, observers moving at different velocities measure different frequencies. (This is the reason the pitch of an ambulance changes as it passes you it doesn't change if you're on the ambulance). This is called the Doppler shift, and for small relative velocity v it is easy to show that the frequency shifts from f to f(1+v/c) (it goes up heading toward you, down away from you). There are relativistic corrections, but these are negligible here."
So we have two hypotheses which sound reasonable insofar as they are based on the analogy (often used in textbooks) between light waves and other waves. We also have a conclusion which is overwhelmingly confirmed. This is deductive science par excellence but it contradicts special relativity.
Einsteinians can try to save special relativity by proposing different hypotheses which sound reasonable again and entail (quantitatively!) the same conclusion:
Hypothesis 1: ... ?
Hypothesis 2: ... ?
Conclusion: As the observer starts moving towards the source of the light waves with speed v, the frequency he measures shifts from f to f'=f(1+v/c).
See here why Einsteinians are reluctant to offer different hypotheses:
http://fqxi.org/data/essaycontestfiles/Valev_Shift_in_Frequency_Im.pdf Shift in Frequency Implies Shift in Speed of Light
Pentcho Valev



