Re: Is spacetime curvature the source of inertia?
- From: "Sue..." <suzysewnshow@xxxxxxxxxxxx>
- Date: 30 May 2007 14:35:07 -0700
On May 30, 4:48 pm, "Todd" <T...@xxxxxxx> wrote:
In the May issue of The American Journal of Physics there is an article by
Ronald Newburgh with the title _Inertial forces, absolute space and Mach's
principle: The genesis of relativity_. I'm intrigued by the last sentence
of the abstract which reads:
'Einstein later abandoned Mach's principle and found the
source of inertia in the nonzero curvature of the space-time
metric, a fact that does not diminish the importance of Mach
in Einstein's early thinking.'
Both the Levi-Civita connection and Mach's priniciple are discussed
without conflict in the ~1923 lecture. I would want to see some
later references where he abandons Mach's principle because
his argument favoring it is quite persuasive.
<< Already Newton recognized that the
law of inertia is unsatisfactory
in a context so far unmentioned in this
exposition, namely that it gives no
real cause for the special physical
position of the states of motion of the
inertial frames relative to all other
states of motion. It makes the observable
material bodies responsible for the
gravitational behaviour of a material
point, yet indicates no material cause
for the inertial behaviour of the material
point but devises the cause for it
(absolute space or inertial ether). This
is not logically inadmissible although
it is unsatisfactory. For this reason
E. Mach demanded a modification of the
law of inertia in the sense that the
inertia should be interpreted as an
acceleration resistance of the bodies
against one another and not against "space".
This interpretation governs the expectation
that accelerated bodies have concordant
accelerating action in the same
sense on other bodies (acceleration induction).
This interpretation is even more
plausible according to general relativity
which eliminates the distinction between
inertial and gravitational effects.
It amounts to stipulating that, apart
from the arbitrariness governed by the
free choice of coordinates, the
gm v -field shall be completely determined
by the matter. Mach's stipulation is favoured
in general relativity by the circumstance
that acceleration induction in accordance
with the gravitational field equations really
exists, although of such slight intensity
that direct detection by mechanical experiments
is out of the question. >>
http://nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-lecture.html
Does GR really show that the source of inertia is the nonzero curvature of
spacetime? Unfortunately, the author of the paper does not provide support
for this statement nor does he give a reference. Does anyone here agree
with the author's statement? If so, can you elaborate or give a reference?
Minkowski space time is man-made abstraction. I know of no references
where gravity or inertia is attirbuted to students rolling up papers
with
green lines on them. GR is a formalism not a mechanism so its
inner workings can be absurd so long as it has quantitative utility.
As I understand it, GR shows that the distribution of matter in the universe
determines the spacetime metric. But no matter what the metric, at any
spacetime point you can always find a family of local inertial reference
frames in which the inertia of a marble, say, could be measured.
No... the functional coupling doesn't allow that.
<<A Lorentz transformation or any other coordinate
transformation will convert electric or magnetic
fields into mixtures of electric and magnetic fields,
but no transformation mixes them with the
gravitational field. >>
http://www.aip.org/pt/vol-58/iss-11/p31.html
So the formalism constructs a psurdo-space where
mass/energy equivalence is related to a volume
of space-time. Newton's ether is mathmatically
simulated but absent the details of a causal
mechanism.
A plausible mechanism is explored here:
http://www.mypage.bluewin.ch/Bizarre/GRAV.htm
(That is,
you could measure the force required to accelerate the marble from rest to 1
m/s over a time interval of 1 s.) The amount of inertia of the marble would
be the same no matter which local inertial frame you choose. Changing the
distribution of matter in the universe would not affect the inertia of the
marble as measured in any local inertial frame. So, it seems to me that the
amount of inertia of the marble is an intrinsic property of the marble that
is not accounted for by GR nor is the amount of inertia connected in any way
to the nonzero curvature of spacetime. Am I missing something here?
An experiment that relates expansion and the cosmogical constant
to inerta is a bit difficult to get through the laboratory door so
the
only thing you might be missing is several hundred points of view
on the subject. ;-)
Sue...
Thanks,
Todd
.
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