Re: "Deep Impact" predictions

In article <C5adnSFJEIUSKnbfRVn-pg@xxxxxxx>,
Tom Van Flandern <tomvf@xxxxxxxxxxxxxxxx> wrote:
> "Paul Schlyter" <pausch@xxxxxxx> writes:
>
>>> [tvf]: GR has two physical interpretations: field GR and geometric
>>> GR. In the former (as favored by Einstein, Dirac, and Feynman, among
>>> others), gravitation is a classical force, period. In the latter (the
>>> version more commonly taught these days), gravity is just 4-space
>>> geometry.
>
>> [Schlyter]: The geometric GR has one big advantage: it nicely explains
>> why the inertial mass and the gravitational mass are the same.
>
> Geometric GR has two giant disadvantages because it violates
> two principles of physics (causality and "no creation ex nihilo") as I
> explained in my last post, which falsifies it for many practical
> purposes.

Who defined those principles? Yourself?

I think you'll find it hard to merge your request for causality with
some quantum mechanical effects. Such as Heisenberg's uncertainty
principle, the "tunnel effect", etc. So we can conclude that your
request for causality in each and every situation is contradicted by
observation at the quantum mechanical level. Yes, it's counterintuitive.
Yes, Einstein disliked it too, but eventually he accepted it, since
what counts is observations and experiments, not human ideas.


> Moreover, the field interpretation of GR has an even bigger
> advantage than the one you mention as favoring geometric GR: it explains
> why inertial and gravitational mass are *not* always the same, as
> demonstrated by D. M. Greenberger and A. W. Overhauser writing about the
> COW [Colella-Overhauser-Werner, 1975] neutron interferometer experiment
> in Rev.Mod.Phys. 51:43 (1979). This was also written up by the same
> authors in easier-to-read language in "The role of gravity in quantum
> theory", Sci.Amer. 242 (May):66-76 (1980).

Now you've entered the realm of quantum mechanics. GR is a classical
physical theory which is no longer valid in the quantum mechanical
realm.

Perhaps you can find some other example, in the macroscopic realm
where GR remains valid, where gravitational and inertial matter of
some body is different from one another? No?

Perhaps the initial attempts of merging QM and GR is easier with your
field interpretation of GR, but that's because "field GR" appears
somewhat more similar to NP (Newtonian Physical) than "geometric GR".


> Yet surprisingly, it turns out that the result of the COW experiment is
> incompatible with the geometrical weak equivalence principle because
> interference effects in quantum mechanics depend on the mass. It is only
> in taking the average values of the trajectory parameters that the mass
> drops out.

Why is that surprising? Didn't we already know that GR is valid only
outside the reaml of QM ???

> Since quantum mechanics contradicts the geometrical weak equivalence
> principle,

(yawn....)

>> [Schlyter]: Btw do you know about any experimental situation we are
>> able to realize, or any natural situation we are able to observe,
>> where the field GR and the geometric GR produce different predictions?
>> Do they ever produce different predictions?
>
> The COW experiment seems to be an example of just such a difference.

The COW experiment is in the realm of QM, which we already know is
outside the realm of GR. Unfortunately we have no QMGR avaialble.....

> Experiments aside, a model or physical interpretation that
> does not require magic or miracles (such as causality violations or
> creation ex nihilo) is to be preferred over one that does require them.
> So that is a logic-based difference between field GR and geometric GR.

I don't see why there's more "magic" in geometry than in "action over
a distance" which the "force of gravity" really is.....

But this means we both agree on this:
-----------------------------------------------------------------------
A collection of macroscopic bodies (i.e. bodies large enough such
that QM effects become negligible) in an otherwise empty universe,
which initially are at rest in space relative to one another, will
start to move due to their mutual gravitation. And this is predicted
both by geometric GR and by field GR, and they both predict precisely
the same trajectory for each body.
-----------------------------------------------------------------------
Can we agree on this ? Or do you claim that in this scenario geometric
GR will yield a different prediction compared to field GR ?


>>> [tvf]: In fact, Vigier and I explained why the geometric
>>> interpretation of GR may now be considered falsified: 1) Geometric GR
>>> has no cause to initiate the motion of bodies at rest in a
>>> gravitational field. (Curvature alone cannot initiate motion unless a
>>> force acts. There is no "downhill" in space.)
>
>> [Schlyter]: Nothing _can_ be "at rest" in 4-dimensional space-time. In
>> the "t" (time) dimension, everything moves at the speed of light.
>
> Of course. But why change the subject?

I didn't "change the subject" - I merely steered back the subject so
that it included a very important property of GR which you had
neglected.

> My remarks obviously referred to 3-space plus time, where "rest" relative
> to a source mass is well-defined. The causality principle applies to real
> space and time.

Your causality principle is flawed. It works well in Newtonian Physics
but fails in QM (the uncertainty principle, the tunnel effect, etc) as
well as in GR (your flawed conclusion that geometric GR says that those
bodies initially at rest in space will remain in rest just because
gravity is a pseudo-force. Yor flaw is corrected by integrating space
and time to space-time, instead of keeping them separate as you insist on
doing, like in Newtonian Physics).

> Mathematical abstractions such as GR's "spacetime" (actually a variant
> of proper time for most applications) are of little use when one is
> discussing physical interpretations or experimental evidence because
> observations must be made in 3-space plus time, not in Minkowski
> 4-space.

Observations made in 3-space plus time, in a known reference frame,
can be integrated into 4-spacetime and be used to validate or refute
the theory. But perhaps your real objection here is that the math
involved is complex? That's true, but it's merely about how practical
the method is - it doesn't invalidate the principle itself. The
argument "That theory must be wrong because I don't understand it" is
NOT valid !!!!

>> [Schlyter]: Even if everything is initially at rest in the "space
>> coordinates" (x,y,z), due to the curvature of space-time things will
>> start moving in the x,y,z coordinates as well
>
> But that was my point: Mathematically, one can just say "it moves" and
> ignore the physics. But in physics, transition from rest in 3-space to
> accelerated motion requires a cause (called a "force" by definition)
> and a source of new momentum.

You seem to have hardwired your causality principle into your brain.. :-)

> No exceptions are allowed in "deep reality physics"

What's this "deep reality physics" ?? A new buzzword you just invented?

There is only one reality: the observations we make. Behind them we
build our physical model, using mathematics as the language. And it
doesn't really matter whether we use "forces" or "geometry" --
they're both just different viewpoints, each having some "magic".
Every model is btw based on some "magic": the fundamental assumptions
which aren't proved but which are used to build the model. For some
of these fundamental assumptions we can make the "magic" vanish by
pointing to some other model - a model which may have its own set of
"magic". But for the remaining assumptions we have no other model to
point to, but merely choose our fundamental assumptions so they appear
"reasonable". Forces vs geometry can be viewed as such a choice.
Your brain find it impossible to accept geometry as the fundamental
cause in GR - my brain find it more acceptable. So it's perhaps just
a matter of personal preferences?

> So think of geometric GR as a computational device that must be set
> aside when one's interest is in understanding the physics of gravitation.

Interestingly, Copernicus used the same argument for his heliocentric
model of the solar system, which the church considered unacceptable:
he said it was just a computational device .....

By setting aside geometric GR we also set aside our understanding why
gravitational and inertial masses are the same (at the macroscopic
level, outside the realm of QM - so don't bring up that COW experiment
again, please).


>> [Schlyter]: You seem to want to consider space dimensions (x,y,z)
>> separately from the time dimension (t) in GR. You cannot do that.
>
> On the contrary. That is what field GR is all about. Moreover, the
> entire field of celestial mechanics, which provides the interface
> between GR and observations made in the real world, is based on 3-space
> plus time. Without these considerations, GR would be an untested theory.

Classical celestial mechanics use Newtonian mechanics, with only small
relativitist corrections in a few cases. This works well in the solar
system and visual double stars, but fail in situations like a binary
pulsar.


>>> [tvf]: Geometric GR requires creation -ex nihilo- for the new 3-space
>>> momentum of target bodies in a gravitational field.
>
>> [Schlyter]: well GR is certainly not a TOE (Theory Of Everything) -
>> but we already knew that, didn't we? So leave the creation out of the
>> discussion here and consider GR as a model of something which already
>> exists. OK?
>
> The point of my remark was to show that geometric GR is falsified in physics.
> Gravity cannot be simply geometry because that provides no source for new
> momentum.

Does this mean you claim that geometric GR predict that a collection of
bodies initially at rest in space relative to one another and subjected
to no other forces than their mutual gravity, that these bodies will
remain at rest? As predicted by geometric GR of course. If not, and
if geometric GR predicts the motions which actually are observed, in what
way are geometric GR "falsified" ?


>> [Schlyter]: Of course GR must mimic NP at is low-speed and low-gravity
>> limit! And this includes the instantaneous potential gradients,
>> creating an illusion of gravity propagating instantly.
>
> In what sense is this "an illusion"? When a source mass accelerates,
> the target body responds almost instantly, as binary pulsars prove.

If a large mass is moved with a non-gravitational force, how long
time would it take for the surroundings to sense the changed gravity
force? According to you it would happen instantly. According to GR
it would happen with light-speed delay. And in reality? We don't
know, and we won't know until we've been able to perform the
experiment.

If the gravitation potential changes instantly also over large
distances, no matter whether the body is moved by gravitational or
non-gravitational forces, then gravity does indeed propagate FTL as
you claim. But if the graviation changes instantly only when the
body is moved by gravitational forces, but changes with a light-time
delay when the body is moved by non-gravitational forces, then the
"gravity propagates faster-than-light" is an illusion - it can not be
used for e.g. sending messages faster than light.

You believe that the gravitation potential should change with the
same speed no matter if the body is moved with a gravitational or a
non-gravitational force. That's your belief - we are currently not
able to test it experimentally. "But it's not logical to believe
that the potential should propagate at different speeds depending on
whether the body is moved with a gravitational or a non-gravitational
force!" I hear you object. Perhaps -- OTOH Nature is not limited by
what we humans consider "logical" .....



> Moreover, the Sun also emits light, which obviously travels
> at the speed of light. Yet the gradients of the light field are
> retarded, not instantaneous. What logic exists for instantaneous
> relativistic potential gradients in gravitational fields when a source
> mass accelerates, while gradients for light fields remain retarded?

In geometric GR, gravity bends spacetime while light does not. Of
course the full answer is in the field equations of gemoetric GR, which
neither you nor I understand.....

>> [Schlyter]: The best I can do here is to point to the sci.physics FAQ,
>> where Steve Carlip writes about how fast the force of gravity
>> propagates.
>
> We have argued in print that Carlip's argument is not viable. Our reasoning
> is simple to understand, and there has been no counter-argument from anyone,
> including the three referees of the paper (who questioned many things, but
> not that).

That's your view. What's Carlip's view? Does he explicitly agree
with you that he's wrong and you're right? <g>

>> [Schlyter]: Perhaps Carlip thinks he can do better things with his
>> time than discuss with someone who e.g. thinks that space coordinates
>> can be dealt with separately from time in geometric GR... :-) And
>> perhaps you feel you've won this discussion. But winning a discussion
>> is one thing - actually being right is something different.
>
> When one argument shows the fallacy in another, that is usually a step
> toward getting the physics right. No one in science should be counting
> progress in understanding as "winning". This isn't about personalities
> of contests. Our logical arguments stand or fall on their merits alone.

If so, why do you talk so much about "interpretations"? Why do you
consider geometry "magic" but not forces ("action at a distance")?

If it really was as simple as you suggest in your latest paragraph
above, wouldn't the facts themselves be enough, without any need of
interpretations?

>> [Schlyter]: if you want me to change my opinion about your ideas, you
>> must stop talking about the instantaneous potential of the force of
>> gravity as if it was a "proof" for gravity propagating much faster
>> than light in GR.
>
> I do not understand. If I show that a race car was at point x1 at time
> t1 and reached point x2 at time t2, can't I conclude that the
> minimum speed at which it traveled was (x2 - x1) / (t2 - t1)?

I thought we were discussing GR, not NP..... rewrite those formulae
using the field equations of gemoetric GR please..... <evil grin>

>> [Schlyter]: ...an interesting collection of ad hoc hypotheses....
>
> That is what your question asked for: a "feasible mechanism".
> I provided three.

Yep, three ad hoc hypotheses .... when others patch on ad hoc
hypotheses you complain.....

>> [Schlyter]: Phase changes: they occur naturally of course. The most
>> well-known example is of course water freezing, melting, evaporating,
>> condensing. But did you ever see any explosions during such a phase
>> change?
>
> A correspondent following this discussion who prefers not to
> join in directly wrote: "In the early and middle years of the steam age,
> boiler explosions were common. Some were large scale disasters, killing
> dozens of people and destroying lots of property. They still happen in
> parts of the world where steam powered trains are used. This may not be
> close enough to what Paul is talking about to satisfy him, but it is a
> real world example of explosion resulting from phase change. And under
> the right conditions. . Mountains crumbling into sand piles (as water
> gets into the cracks, freezes, and expands) could be described as an
> extended series of tiny explosions. Each one is just a little "pop", but
> size seems to be a secondary consideration here."

True, phase changes can cause local explosions, even killing humans
and destroying property. But was any of these explosions able to
eject stones, or very big rocks, at Earth escape velocity (11 km/s)
or larger? That what's required to make your EPH hypothesis produce
asteroids.

>> [Schlyter]: Can we expect to see a piece of melting (or freezing) ice
>> spontaneously explode, scattering itself around? No. So is it
>> reasonable to expect a whole planet to explode just because the lava
>> inside "freezes"?
>
> "The Krakatoa volcano explosion in the 1883 is another
> example of a phase-change-caused explosion. Much larger in scale and
> natural rather than man made."

....and all that huge explosion managed to do was to destroy a small
island and put some tons of dust in the atmosphere.... again not
sufficient to produce asteroids. Sorry....

> I might add that ice volcanoes are one of the newer fads in planetary
> astronomy. And the idea of phase changes as a planet explosion
> mechanism has been in the peer-reviewed literature since Ramsey's work
> in 1950.

Perhaps you should try to build your EPH on something mode solid
than fad theories..... :-)


>> [Schlyter]: Natural fission reactors: requires a lot - a lot ! - of
>> uranium to be able to explode a whole planet.
>
> Geophysicists have come to accept natural fission reactors
> as a reality of planets because of the discovery of some operating on
> Earth's surface in the distant past (e.g., at Oklo, Gabon, Africa). The
> geophysical literature now contains many corollary speculations, such as
> that the excess heat flow from the gas giant planets (twice or more what
> they receive from the Sun) is caused by natural fission reactors in
> these planets operating today. (See bibliography in the web paper I
> cited.)

....and how much did these earthly natural fission reactors eject into
our atmosphere? More or less than Chernobyl? Krakatoa?

>> [Schlyter]: Gravitational heat energy: occurs mainly in the
>> contraction phase so this mechanism would mean that the contracting
>> body would "bounce back" and disintegrate. But would a planet really
>> have formed in such a case?
>
> The Le Sage model (see the subject of the latest book on the
> nature and origin of gravitation: "Pushing Gravity") requires
> gravitation to be a continuous source of heat, even when a planet is in
> equilibrium and no longer contracting. But if something like a core
> collapse traps that heat, sooner or later one cannot avoid an explosive
> release of all the continually increasing, stored energy.

How old is this Le Sage model?

>> [Schlyter]: it's not enough that you yourself consider the
>> explanations feasible. You must also convince the scientific community
>> that they are feasible to have your model accepted as a mainstream
>> model.
>
> The history of science shows that the "mainstream" rarely accepts an
> alternative model unless some traumatic event forces a revolution.

Yep - science is radically open to marginal change and marginally open
to radical change.

> For example, it took the great Leonid meteor storm of 1833 over
> well-populated areas of the Eastern U.S.,

Eastern US? I though it happened in France.....

> which many took to be a sign that the world would soon end, to finally
> convince astronomers and everyone else that rocks did fall from the sky.
> Yet compelling evidence for that had already been published a generation
> earlier.

It's always easy to, after the fact, find "compelling evidence" for
something. But before the event it's not that easy. There are
"compelling evidence" for a lot of things, a lot of which will turn
out to be false when investigated more thoroughly. Science has to
find a balance here. What would you favor yourself:

1. Accepting a theory which later turns out to be false, because
that theory had "compelling evidence" ??

2. Rejecting a theory which has "compelling evidence", a theory
which later turns out to be true, but at this point there's no
hard evidence for that theory.


> The only alternative, according to Thomas Kuhn's work, is that the
> mainstream model receives patch after patch until it becomes
> indistinguishable from the alternative model.

That can only happen if the alternative model is a big patchwork
to begin with. I mean, you didn't get GR and QM by patching NP .....

> We can already see that continuing to happen with the competition
> between the Dirty Snowball and the Satellite Model for comets, perhaps
> accelerated to several patches at once called for by the Deep Impact
> experiment.

....and why was the Deep Impact experiment even performed, if the mainstream
is uninterested in new theories and merely want to live comfortable lives
as you claim in the next paragraph.

> So those looking for comfortable lives will remain with the conservative
> majority for a generation or so until the majority becomes a minority.
> Meanwhile, those looking for answers affording a deeper understanding and
> for models that make genuine predictions of new phenomena, it appears that
> carefully selected alternative models (supported by many thoughtful people
> over a period of time) are usually better than mainstream models because
> the alternatives came into existence to solve puzzles and anomalies where
> the mainstream model failed and had to be patched ad hoc.

Perhaps you should be a bit more specific when talking about
"alternative models". An "alternative model" is anything which
contradicts the "mainstream models" (yes there are competing models
also within the mainstream). And you'll find a very wide spectrum
among the "alternative models" - almost everything from future
mainstream models to outright New Age-inspired lunacy.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
.

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