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

From: Bill Hobba (bhobba_at_rubbish.net.au)
Date: 12/01/04 

Date: Wed, 01 Dec 2004 01:17:41 GMT

"Dogger the Filmgoblin" <dogger_blue@yahoo.ca> wrote in message
news:eed9768b.0411301204.70ca2baa@posting.google.com...

I was going to give you one last post on the matter but just as I was about
to send it we had a power surge and I lost all my work. So I will simply
make a few brief comments and leave it at that.

I have read Tims reply and agree with him. Study the theory yourself and
make up your own mind - post any difficulties you have - we have plenty of
knowledgeable people here that can help you. Basically what you have been
engaging in is pointless philosophical banter.

> 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.

With all due respect I studied science at both undergraduate and graduate
level and discussions about 'reality', correctly, was not part of the
course. Such is properly left to philosophy courses; which I also have
taken. Indeed if you read the classic Feynman Lectures on physics you will
find what a master physicists thought should be taught to undergraduate
students. From the Feynman Lectures in Physics Volume 1 12-2:

'Any simple idea is approximate; as an illustration consider an object ....
what is an object. Philosophers are always saying 'Well just take a chair
for example' The moment they say that you know they do not know what they
are talking about any more. What is a chair? Well a chair is a certian
thing over there ...... certain? how certain? The atoms are evaporating
from it from time to time - not many atoms, but a few - dirt falls in it and
gets dissolved in the paint so to define a chair precisely to say exactly
which atoms are chair, and which atoms are air or which atoms are dirt or
which atoms are paint that belongs to the chair is impossible. So the mass
of the hair can be defined only approximately. In the same way to define
the mass f a single object is impossible because their are not any single
left alone
object in the world - every object is a mixture of lots of things, so we an
deal only with a series of approximations and idealizations'

The point being, as I have said time and time again, reality is far too
slippery a concept to be of any real value to physics. For the record I
agree with the following editorial
http://physicsweb.org/articles/world/10/6/1. I agree with what Weinberg
says. But I claim that semantic bantering about the meaning of reality is
pointless and not necessary to do science. Tom Gee and their ilk's constant
ranting about space-time is not a real place and other such nonsense is
simply camouflage for their lack of understanding.. They introduce it
because it is all they have - they need to introduce issues that science is
not concerned about to attempt to justify their rubbish - sticking to the
facts leaves then high and dry. But do not take my word for it - study the
real deal (eg Sean Carrolls lectures Tim gave the link to -
http://nedwww.ipac.caltech.edu/level5/March01/Carroll3/frames.html) and make
up your own mind. You will find nothing in there about 'realty' and other
such issues - but that is not a problem because science is really not
worried about it.

Thanks
Bill

> 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.

Quantcast