Sciences and their founders
wpc at cs.strath.ac.uk
wpc at cs.strath.ac.uk
Wed Mar 22 02:51:23 MST 1995
Philip
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I don't think that Einstein's relativity theory extended
Newton's laws to new conditions. The quote from Hawkins does not say that
a science simply extends its founders to new conditions. Einstein's
theory provided new terms and formulations for science
Paul replies
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This argument is not significant on its own account
but is from the standpoint of the conclusions that
are being drawn from it. It seems to be part of
a rather cavalier attitude towards the sciences that
allows one to say things like : post Einstein
Newton and Galileo are out the window, post
Althusser Marx goes out the window etc.
Since the specific example given to justify this
is the apparent 'refutation' of Galileo and
Newton by Einstein, I will try again to show
that this is wrong.
Galilean relativity states that the laws of
motion of bodies are unaffected by an arbitrary
choice of uniformly moving reference frame.
This is accepted by modern physics which, however,
is able using general relativity to extend this
invariance to accelerating frames of reference.
The result of Galileo that the acceleration
of falling bodies is independent of the compostion
is also unaffected.
The Newtonian laws of motion, and in particular
the inverse square law of gravitation are also
retained.
In particular the equivalence of gravitational
and inertial mass has exhaustively tested
and confirmed.
' In fact, it is fair to say that, not only does
Einstein's theory not supplant Newtons theory,
it explains Newton's theory. ( I think this
is a point that is not often appreciated.)
In Newton's work, the inverse square law
appears as a means of accounting for the
observations of the solar system, in particular
Keplers interpretation of Brahes observations
in terms of a relationship between periods
and radii. ... There is no explanation in
Newton's theory of why it had to be an inverse
square law. This explanation was finally provided
in 1915 and 1916 by Einsteins theory. If
you adopt Einsteins theory that the force of
gravity is due to a curvature in space time,
and follow that where it leads you, you
find out that you can not, without standing
on your head make a theory of gravity in which
the force at large distances is anything other
than an inverse square law.'
Stephen Weinberg in 300 Years of Gravitation CUP
Beyond this it must be said that Newtonian
formulations are much more usefull. It is
only under the most extreme conditions that
one has to introduce relativistic corrections.
In practice, calculations of satellite orbits
etc continue to use Newtonian methods.
If Marx's theories
had been so formulated that they could be
subject to equivalent testing and with the
same result, then this is the sort of 'refutation'
that any theory could rest content with.
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