Re: How wrong is this analogy for the curvature of Spacetime?

From: Dogger the Filmgoblin (dogger_blue_at_yahoo.ca)
Date: 11/30/04 

Date: 30 Nov 2004 12:04:52 -0800

Bill, your arguments are good, but I don't think that you have fully
appreciated the viewpoint that I expressed. I don't think the Feynman
reference you gave me is a counterargument to what I said. I'm not
claiming that the equations are something real rather than simply
something predictive. I am simply claiming that they say something
about reality (but not necessarily that 'reality is shaped like these
equations', that's the specific fallacy addressed on the Feynman
page). Something in reality (or in whatever is driving our sense
perceptions if you want to argue with the existence of reality, it
makes no difference) behaves in a way that participates in equations
with the same effects as 'curves' if the relativity equations are
predictive. Every word in that last sentence is important, not just
the fact that it is associates equations with reality. What I am
saying is that while it is true (and these days it's an undergraduate
primer lesson so you could not have taken any science course and
missed this caveat) that the equations of science are not a
*description* of reality, it is NOT true that they don't say
*anything* about reality or don't concern themselves with it at all.
This is far too blanket a statement; yes it properly denies the 'Sin
of Galileo' but it throws the baby out with the bathwater. If
equations did not say something about what we call 'reality' then they
couldn't ("a priori") exhibit any predictive power over what occurs in
it. There is a subtle difference there. But in my mind it's very
important, and I think that if this subtle difference were openly
acknowledged between you and Tom, (aside from personality clashes
which are obvious) would not be disagreeing so much as it seems. I
personally find that in reading both of your posts that I often agree
with both the argument and the criticism and I'm pretty good with
logic so when that happens it usually means people are talking at
cross-purposes. Equations are not reality. But science is very much
about 'reality' (or, again, whatever you think is driving our sense
perceptions), nevertheless. Both to me are clearly true.

DB.

"Bill Hobba" <bhobba@rubbish.net.au> wrote in message news:<Md%qd.53806$K7.19234@news-server.bigpond.net.au>...
> "Dogger the Filmgoblin" <dogger_blue@yahoo.ca> wrote in message
> news:eed9768b.0411300052.13483d77@posting.google.com...
> > TomGee and Bill Hobba, I don't have the knowledge to make my own
> > judgements about your dispute, except that Tom has done a much better
> > job of clearly pointing out logical inconsistencies in some of Bill's
> > specific arguments --
>
> You are entitled to your view. I simply suggest if you make the time and
> effort to become acquainted with the technicalities of relativity your
> opinion may change. You see Tom Gee makes false claims eg he claims GR says
> gravity is caused by the curvature of space - it makes no such claim - it
> claims gravity is space-time curvature.
>
> > but that doesn't prove anyone's viewpoint right
> > or wrong IMO. I do know that I instinctively do not trust people who
> > insist that there is only one correct viewpoint or only one useful way
> > of thinking about something. On that score I appreciate Tom's open
> > mind though I'm not sure I understand exactly what part of relativity
> > he disagrees with, if any. However, I kind of agree with Bill that as
> > long as spacetime is predictive that's all that science is concerned
> > with, because I don't think that it is even meaningful to argue
> > whether spacetime is "real" -- it strikes my as kind of the same
> > statement as to say that 'numbers are real'. You can't prove something
> > without any meaning. However, I disagree that one can conclude from
> > this that science makes no claims about reality. Science clearly makes
> > claims about reality.
>
> I am afraid it is not quite that easy. See for example
> http://www.wvinter.net/~haught/physics.html. BTW what I claim is that it is
> far too slippery a concept to be of much use. For example consider a wire
> moving between the poles of a horseshoe magnet. If we think of the magnet
> at rest then the current is caused by moving charges having a force exerted
> on them by the magnet (the Lorentz force law). Suppose we consider it from
> the point of view of the wire being stationary and the magnet moving - then
> the current results from faradays law that a changing magnetic field creates
> an electric field that causes a current to flow. Now what causes the
> current - is it the Lorentz force law or is it Faradays law - what is real?
> They can not both be real can they? Surely 'reality' should not be affected
> by how we decide to view a problem? See
> http://www.colorado.edu/philosophy/vstenger/nothing.html. BTW what you are
> discussing really belongs to philosophy not physics although philosophical
> issues related to relativity are on topic for this newsgroup.
>
> > If spacetime is confirmed by experiment to be a
> > concept with predictive power, and the relevant equations indicate
> > that this space is curved, than whatever the concept of spacetime is
> > correctly modelling must exhibit a quality that has the same effect as
> > curvature. In other words, the theory is in fact claiming that
> > something in reality is 'curved' in the sense that it behaves in
> > equations in a curve-like way.
>
> Science, a-priori, makes no claims about reality - whatever that is. All it
> has is theories that are in accord with experiment - if that tells you about
> reality is a philosophical question; not one for science to worry about. And
> you will find philosophers can not even agree what reality is let alone if
> science tells us anything about it - see
> http://www.friesian.com/feynman.htm. You see science is basically a method
> of test, hypothesize, test, hypothesize over and over.
>
> > This is a claim about the nature of
> > reality, not just a predictive tool.
>
> View it that way if you wish - but I claim that viewing it a as predictive
> tool is just as valid. Can you describe to me an experiment that will
> decide between the two views? If you can not do that then it is not science
> and people can not claim discussion of 'reality' and if 'space-time' is a
> real place and other semantic gibberish is valid. In physics theories are
> usually mathematical models ie a formalism that certain aspects of are given
> correspondence with certain physical situations. Before relativity came on
> the scene Newtonian physics was thought to be correct - did 'reality' change
> when relativity was discovered? Now I will not provide an answer to that
> question because I do not consider it a legitimate scientific question - but
> it is an issue for those that wish to claim science tells us about
> 'reality'. It is simply another example of how reality is far too slippery
> a concept to be of much use.
>
> Thanks
> Bill
>
> The fact that the idea of
> > 'curvature' itself may in the end be just as much in an analogous
> > relationship to whatever is actually going on as any rubber *** or
> > time turbulence, doesn't change the fact that the 'shape' (perhaps
> > analogous language again) of something real is being described as long
> > as people believe that the theory is true.
> >
> > DB.

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