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Re: [Phys-L] Sun going around the Earth?



Hi,

John C. asked: "But I would like to know, in short, what the philosopher was arguing."

It is a bit complicated but I'll try to provide a short explanation. Based on phenomenology (Husserl etc.), the philosopher stated that as you cannot
feel the Earth move, it does not move in your direct experience. His PhD thesis discussed this quite thoroughly and I suppose it makes sense from the point
of the given philosophical framework. However, he then continued to saying that also from the point of view of *the relative theory* it makes no sense to talk about moving Earth as all frames are equivalent. He referred to Mach to support this view. It is not hard to see why the latter argument fails: Mach's total relativity is not compatible with the GR. Let me quote Frank Wilczek here (<http://ctpweb.lns.mit.edu/physics_today/phystoday/(356)Total%20Relativity.pdf>):

"Total relativity can also be stated as a symmetry principle. It instructs us that in the primary equations (in other words, before their solution reveals the
crucial influence of distant bodies!) we should put motions on an equal footing, not just those that correspond to constant relative. velocity...[snip] On that basis any choice of
coordinates should be on equal footing, since the labels implementing the coordinates could be undergoing arbitrary motions. But in general relativity, spacetime is not without structure, and it is not true that all coordinate systems are equally good (notwithstanding contrary statements that pervade the literature--starting, as we've seen, with Einstein's original paper)."

The debate between the philosopher and the physicist went further and further. Eventually the physicist wrote a piece - with another relativity physicist - on relativity deniers! (BTW, before studying and researching physics, the physicist majored in theoretical philosophy, almost completing the studies.)

I hope that I did not bore Phys-L people too much with this story :-):

Antti


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