Re: Why
- From: John Kennaugh <JKNG@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 30 Mar 2005 09:33:03 +0100
Bilge writes
John Kennaugh:
>In message <slrnd4bsc3.n0h.dubious@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, Bilge
><dubious@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> writes
>> John Kennaugh:
>> >Bilge writes
>> >> John Kennaugh:
>> >>
>> >> >
>> >> >The real answer is that to make SR work conceptually each observer has
>> >> >to inhabit his own parallel universe.
>> >>
>> >> By your same argument, the coordinate transformation,
>> >>
>> >> x' = x cos(A) - y sin(A)
>> >> y' = y cos(A) + x sin(A)
>> >>
>> >>requires changing universes to pick a different coordinate system.
>> >>So, if I turn a map upside down, are all of the cities in a different
>> >>universe?
>>
>> I see you decided to try and sidestep the hole you dug.
>>
>> >>
>> >>[...]
>> >>
>> >> >The twin paradox is explained in that one twin has travelled through
>> >> >several different universes before ending back in the same universe as
>> >> >his brother so it is not surprising he is of a different age. This is
>> >> >described in space time geometry as travelling different world >> >> >lines (or
>> >> >something).
>> >>
>> >> ... or something. If you can't draw two sets of axes and understand
>> >>how to transform between the two coordinate systems, you should simply
>> >>get used to the idea that you'll never understand newtonian mechanics,
>> >>let alone relativity.
>> >
>> >As usual I talk about concepts you can only talk about the maths.
>>
>> Your so-called concepts are nothing more than an attempt to
>>take a pefectly simple concept, i.e., a coordinate transformation,
>
>A purely mathematical manipulation. A perfectly simple mathematical
>concept. I am talking about what it means in the physical sense.
Apparently the concept is not simple enough for you to grasp, since you keep insisting that transforming coordinates changes physics.
>You know 'physics' not ' mathematics'.
Actually, I know a good bit about both, although I know more about physics than mathematics.
You do not seem to understand the difference.
I have a computer program which predicts the height of the tide. It is an accurate mathematical model. It accurately predicts physical things but being able to use it does not mean I understand the physics. For that one has to understand the causality. The water does not go up and down because the maths says so. As the program works one might assume that whoever wrote it had a proper understanding of the physics although there is a remote possibility that he had a misunderstanding and still ended up with something which works.
To take a classically familiar example, in times past the motion of the planets across the night sky could be described to any desired degree of accuracy on the basis of the Earth being the dynamic centre of the universe. A better understanding came by questioning the underlying assumptions and simplification achieved by means of a Sun-centred theory. This surely demonstrated the importance of being able to recognising and being able to question the underlying assumptions of any theory.
Relativity is a principle theory - a mathematical model. If you look at the underlying assumptions, from a causality stand point then it was assumed that light propagated in the ether which caused light speed to be independent of that of the source. No other causality has been suggested. You try and claim that the maths which has evolved from that assumed causality is actually the cause and you expect me to take you seriously.
The original ether theory failed to predict the result of MMX. Lorentz came up with a fix - interaction between matter and the ether - The Lorentz transforms - which you still use and swear by. Lorentz's theory said that light travelled in the ether (so was source independent) at c but because of the transforms it appeared to every observer that he is stationary w.r.t the ether.
Einstein's starting point was unashamedly Lorentz's theory. That is why he assumed source independence. His aim was not to get rid of the ether but to achieve symmetry. He in effect assumed that every observer's relationship with the ether is the same. That it not only appeared to every observer that he is stationary w.r.t the ether but that he IS stationary w.r.t the ether. That is what is implied by the second postulate. That works mathematically but cannot be interpreted in terms of physical causality. Mathematically you assume each observer has his own ether which he is stationary w.r.t - which you call his FoR. Light propagates everywhere in his ether/FoR at c because he is stationary w.r.t it. It is independent of the speed of the source because it is propagating in his ether/FoR.
All your answers may be summed up as "the maths say.......". Where is the physical causality? I am not talking about predicting physical results. My computer program will predict physical tides. The causality for my tide program is the motion of the earth, the moon and the sun and a mysterious, but demonstrable force we call gravity acting upon the ocean which in turn acts upon the land mass.
A FoR is a mathematical abstraction the only physical thing defining it is the observer who's FoR it is. The physical space it defines is according to you devoid of ether. i.e. has no physical substance which can have a causal effect on the light so you are left with the absurdity that the only physical thing which can cause light speed to be constant w.r.t the observer is the observer himself.
It is important to be able to recognise and to be able to question the underlying assumptions of any theory. Einstein's assumptions were that light propagated IN something so its speed is source independent and that the universe is naturally symmetrical i.e. the PoR. Your underlying assumption is that universe complies with the maths which evolved from Einstein's assumptions while rejecting his key assumption.
--
John Kennaugh
"The nature of the physicists' default was their failure to insist sufficiently
strongly on the physical reality of the physical world." Dr Scott Murray
.
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