Presidential Candidate Gen. Wesley K. Clark: Futurist.

Eric Flesch wrote:

On Fri, 03 Oct 2003 08:14:28 -0700, Uncle Al
wrote:
Metric theories of gravitation postulate the Equivalence Principle
(all bodies fall identically in vacuum)

Well, "identical falling" presupposes a reference frame in which to
measure the identical-ness. If you use the (say) planet that the
bodies are falling toward, in separate tests, then the larger bodies
will actually fall faster because the planet falls toward them with an
acceleration proportional to the bodies' masses. Not that we're about
to be able to measure that. In fact, this might be where quantization
comes in -- if the quantum of required force is not reached, perhaps
the planet will not move.

The EP postulates that inertial and gravitational masses are
fundamentally indistinguishable. That immediately creates spacetime
curvature in metric theories of gravitation, then parallel geodesic
trajectories for local test masses. Affine theories do not posulate
the EP and can violate it with impunity until macroscopic observation
is contradicted.

http://www.mazepath.com/uncleal/eotvos.htm

Classical field theories of gravitation do not quantize. Your other
observations are absurd. Look at it from a center-of-mass origin and
see how silly you are. Gravitational acceleration of a body does not
even contain mention of a test mass.


--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

Eric Flesch wrote:

On Fri, 03 Oct 2003 08:14:28 -0700, Uncle Al
wrote:
Metric theories of gravitation postulate the Equivalence Principle
(all bodies fall identically in vacuum)

Well, "identical falling" presupposes a reference frame in which to
measure the identical-ness. If you use the (say) planet that the
bodies are falling toward, in separate tests, then the larger bodies
will actually fall faster because the planet falls toward them with an
acceleration proportional to the bodies' masses. Not that we're about
to be able to measure that. In fact, this might be where quantization
comes in -- if the quantum of required force is not reached, perhaps
the planet will not move.

The EP postulates that inertial and gravitational masses are
fundamentally indistinguishable. That immediately creates spacetime
curvature in metric theories of gravitation, then parallel geodesic
trajectories for local test masses. Affine theories do not posulate
the EP and can violate it with impunity until macroscopic observation
is contradicted.

http://www.mazepath.com/uncleal/eotvos.htm

Classical field theories of gravitation do not quantize. Your other
observations are absurd. Look at it from a center-of-mass origin and
see how silly you are. Gravitational acceleration of a body does not
even contain mention of a test mass.


--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

George William Herbert wrote:

Doesn't causality follow from relativity?

In other words, you don't have to postulate it,
it's a result of the standard model laws of physics.

No, it's an unstated postulate (which long predates relativity). We
think faster-than-light travel is a no-no _because_ it violates
causality, not because causality nonviolations fall out of relativity
theory.

--
Erik Max Francis && && http://www.alcyone.com/max/
__ San Jose, CA, USA && 37 20 N 121 53 W && &tSftDotIotE
/ \ Can I walk with you / Through your life
\__/ India Arie

"Ray Drouillard" nattered on
:


"Uncle Al" wrote in message
...

General Relativity must be incomplete because it cannot be quantized.
OK, who bells the cat? Superluminal transportation violates causality
- something the universe apparently does not tolerate. There is no
test, prediction vs. observation, in which General Relativity is not
perfect within experimental error,

What proof is there that causality must not be violated?


As any ethical physicist would tell you, causality MUST be true because
any alternative would be far too icky. The unethical ones will try to
pull an argument from necessity out of their asses.

Erik Max Francis wrote:
George William Herbert wrote:
Doesn't causality follow from relativity?
In other words, you don't have to postulate it,
it's a result of the standard model laws of physics.

No, it's an unstated postulate (which long predates relativity). We
think faster-than-light travel is a no-no _because_ it violates
causality, not because causality nonviolations fall out of relativity
theory.

Hrm. I am somewhat at a loss.
I am finding, on more research,
that this seems to be somewhat less
well clarified than I recalled.

Which seems really whacky.

It appears, to me, that causality
nonviolations fall out of standard
relatavistic spacetime. It's just the
way that it works; no FTL, no time loops,
causality happens.

If causality nonviolations fall out
of standard relatavistic spacetime,
then what breaks if we redefine all
the occurrances of the causality postulate
with the causality nonviolation that
falls out of standard relatavistic
spacetime? What I'm saying, is that
just because it was a postulated precondition,
doesn't mean that it's necessarily a
true postulate. If identical behaviour
is an effect of standard spacetimes,
then maybe that is *all* that it is.
We don't need to worry about it being
violated because it isn't, and we can
show that it isn't in the spacetime.

How can you tell the difference between
it being a postulate and being an effect
of the spacetime we're embedded in?

And if other conditions than the standard
spacetime don't result in it always being
enforced, then so what?


-george william herbert

There is no test, prediction vs. observation, in which General Relativity is not perfect within experimental error,

Try buying a telescope.

JS

George William Herbert wrote:

It appears, to me, that causality
nonviolations fall out of standard
relatavistic spacetime. It's just the
way that it works; no FTL, no time loops,
causality happens.

It's been said before, and it'll be said again: relativity, causality,
and FTL. Pick exactly two.

How can you tell the difference between
it being a postulate and being an effect
of the spacetime we're embedded in?

How do you know you've reached the final theory of everything? You
don't, and you can't. You have to proceed on what your current
knowledge is and what experiments are telling you.

This issue is not new, and not even really surprising. Considering this
principle: The results of experiments are independently repeatable.
There is no way to prove this is correct, even through science; it's a
supposition. It turns out that it's probably a really good one because
1. it appears to work very well and 2. science would be pretty pointless
if it weren't true. But it's an assumption of science, part of the
philosophy that goes into conducting science.

Causality is a very similar situation. It seems like a completely
sensible assumption, but we have no way to demonstrate conclusively that
it's right. Certainly we don't see causality violations going on all
around us, so if causality _isn't_ preserved, then it must be broken
only in very exceptional circumstances, ones we've never experienced
before.

It's special relativity, with the assumption of causality, that leads
you to conclude that faster-than-light travel (within special relativity
anyway) is impossible. If you relax the causality constraint, then you
can get faster-than-light travel no problem, you just have causality
violations.

--
Erik Max Francis && && http://www.alcyone.com/max/
__ San Jose, CA, USA && 37 20 N 121 53 W && &tSftDotIotE
/ \ Human love is often but the encounter of two weaknesses.
\__/ Francois Mauriac

On Fri, 03 Oct 2003 15:12:40 -0700, Uncle Al wrote:
Eric Flesch wrote:
On Fri, 03 Oct 2003 08:14:28 -0700, Uncle Al wrote:
Metric theories of gravitation postulate the Equivalence Principle
(all bodies fall identically in vacuum)

Well, "identical falling" presupposes a reference frame in which to
measure the identical-ness. If you use the (say) planet that the
bodies are falling toward, in separate tests, then the larger bodies
will actually fall faster because the planet falls toward them with an
acceleration proportional to the bodies' masses.

Look at it from a center-of-mass origin and
see how silly you are.

Well, let's drop a rock towards the Earth in one case, and drop
Jupiter towards the Earth in the other case. See if the acceleration
is the same, from the center-of-mass origin if you want. Size does
matter. The equivalence principle is that the effect of gravity is
indistinguishable from inertial acceleration. But in the real
universe, the differential forces from the attracting body can, in
principle, be measured to distinguish gravitationally-caused
acceleration from pure inertial acceleration. Similarly, "all bodies
falling identically in vacuum" is an idealization which in practice is
only approached. That was my point.

Eric

"George William Herbert" wrote in message
...
Erik Max Francis wrote:

Hrm. I am somewhat at a loss.
I am finding, on more research,
that this seems to be somewhat less
well clarified than I recalled.

Yep.

For some illustration of the complexity of the problem, a google turns up a
website that talks about "50 years of the cauchy problem in general
relativity".

http://fanfreluche.math.univ-tours.fr/

You don't need 50 years of discussion for a simple well clarified problem
:-)

"John Schoenfeld" wrote in message
om...
There is no test, prediction vs. observation, in which General
Relativity is not perfect within experimental error,

Try buying a telescope.

Telescopes and GPS receivers are consistent with general relativity. No -
really, they are! Seriously.

We now return you to your regularly crossposted flame-war.