WIMPs AWOL Again?

Eric Flesch wrote in news:mt2.0-14899-1319988383
@hydra.herts.ac.uk:

On Sun, 30 Oct 11, eric gisse wrote:
Gravitational energy itself gravitates, the idea is DOA as per lunar
ranging and the Nordtelvdt effect.

Sorry, that's nonsense. What's "gravitational energy", other than an
abuse of the term "energy"?

Binding energy. Two particles held together by gravitation have less energy
in a bound state than two particles far away.

Since my point was clearly missed, I'll expand:

Energy that would generate that depression would itself gravitate and we'd
see it through say the Integrated Sachs-Wolfe effect. Or in actuality we'd
simply have reverse dark matter: too much gravitation for what we see.

The Nordtvedt effect has not been
observed, which is consistent with gravity not gravitating. Gravity
has never been observed to gravitate.


The Nordtevdt effect is fantastic additionally for testing whether a person
understand the subject. If you have a non-null Nordtevdt effect it means
gravitational energy doesn't quite gravitate according to what GR predicts.

We have repeatedly observed the effects of binding energy on lunar ranging,
and stuff like hyperbound objects (white dawrf to neutron star, extremal
case being the black hole) would not behave as we expect were that the
case.

"Jonathan Thornburg [remove -animal to reply]"
wrote in
:


[...correct stuff...]

This is precisely what general relativity's equivalence principle
predicts. Other Gravity theories of the form "gravity is some sort of
spin-2 field on a flat background" usually predict that gravitational
binding energy *doesn't* gravitate, i.e., they predict that the
Nordtvedt effect *should* be present. The non-occurence of the
Nordtvedt effect thus refutes such theories.


Which is why I bring it up. If you predict a ton of gravitational energy
(disregarding the source of it for the moment) and don't deal with the fact
that the energy will play hell with the binding of your system, then your
theory is DOA.

This might seem trivial or irrelevant, but measuring the binding energy on
things like galactic superclusters is also a huge test of dark energy
because on that scale the binding energy of the structure is significantly
altered.

On Sun, 30 Oct 11"Jonathan Thornburg wrote:
Eric Gisse is right here, and Eric Flesch is mistaken: The thing
that's so interesting about the Nordtvedt is precisely that it's *not*
observed -- which is very strong evidence that gravitational energy
*does* itself gravitate (just like other forms of mass-energy).

Thanks for the interesting post which I will mull over for a few days
and check some things. But whilst I appear to be out-gunned here,
I'll just lay out a few simple thoughts:

(1) If "gravity gravitates", that should be translatable into a simple
adjustment on the inverse square law, which hasn't been observed.

(2) The Nordtvedt experiment is meant as a test on whether "inertia"
gravitates, using the equivalence principle. That the test turns out
negative does not, to my thinking, show that "gravity gravitates"
because the alternative explanation is that the "inertial energy"
concept, ie, "gravitational energy", is false. In other words, the
negative Nordtvedt result shows that either both paradigms of "gravity
gravitates" and "gravitational energy" are right or wrong in tandem.
My stance is that they are both wrong. Your stance is that they are
both right. Either way the Nordtvedt result is negative.

The germane saying is "things should be made as simple as possible,
but no simpler". My interpretation is simpler.

Perhaps I should simply stay out of such topics because my expertise
is not up to yours. But when I see unnecessary complexities, it is
like a red flag to an old bull; I still remember.

Eric Flesch

Eric Flesch wrote in news:mt2.0-2209-1320045114
@hydra.herts.ac.uk:

On Sun, 30 Oct 11"Jonathan Thornburg wrote:
Eric Gisse is right here, and Eric Flesch is mistaken: The thing
that's so interesting about the Nordtvedt is precisely that it's *not*
observed -- which is very strong evidence that gravitational energy
*does* itself gravitate (just like other forms of mass-energy).

Thanks for the interesting post which I will mull over for a few days
and check some things. But whilst I appear to be out-gunned here,
I'll just lay out a few simple thoughts:

(1) If "gravity gravitates", that should be translatable into a simple
adjustment on the inverse square law, which hasn't been observed.

Since binding energy will have the same distribution as the matter which
generates it, I am unclear on how you think that'd alter the inverse
square law. Besides, GR already does that - see the mathematical
description of perihelion advance which kicks in a small k/r^2 term to
the potential.


(2) The Nordtvedt experiment is meant as a test on whether "inertia"
gravitates, using the equivalence principle. That the test turns out
negative does not, to my thinking, show that "gravity gravitates"
because the alternative explanation is that the "inertial energy"
concept, ie, "gravitational energy", is false. In other words, the
negative Nordtvedt result shows that either both paradigms of "gravity
gravitates" and "gravitational energy" are right or wrong in tandem.
My stance is that they are both wrong. Your stance is that they are
both right. Either way the Nordtvedt result is negative.

You do not have a firm grasp of the subject. Inertia is irrelevant here.

Two objects at a distance have less energy than two objects stuck
together. The energy of being clumpted together itself has gravitational
influence, which makes gravitation stronger....which repeats itself
until you are tired of including additioanl contributions from self-
feedback.


The germane saying is "things should be made as simple as possible,
but no simpler". My interpretation is simpler.

Perhaps I should simply stay out of such topics because my expertise
is not up to yours. But when I see unnecessary complexities, it is
like a red flag to an old bull; I still remember.

Eric Flesch


You are free to see red flags in a subject you do not understand,
however nobody will take you seriously when you complain about them.

http://relativity.livingreviews.org/...es/lrr-2006-3/

Go read the equivalence principle tests. It'll be useful.

On Mon, 31 Oct 11, eric gisse wrote:
Eric Flesch wrote
(2) The Nordtvedt experiment is meant as a test on whether "inertia"
gravitates, using the equivalence principle.

You do not have a firm grasp of the subject. Inertia is irrelevant here.

What was relevant at the time of my writing was my little boy waiting
for me to take him trick-or-treating, so I wrote that in a hurry.
What I meant is clear, Nordtvedt was testing the attributes of
so-called "gravitational energy",

Perhaps I should simply stay out of such topics because my expertise
is not up to yours. But when I see unnecessary complexities, it is
like a red flag to an old bull; I still remember.

You are free to see red flags in a subject you do not understand,
however nobody will take you seriously when you complain about them.

I understand it well enough to know it smells bad. As I've said, one
interpretation of the negative outcome is that the whole concept is
bunkum. Occam and me, we're pals.

http://relativity.livingreviews.org/...es/lrr-2006-3/

Go read the equivalence principle tests. It'll be useful.

Thanks, I will. Eric

Eric Flesch wrote:
(2) The Nordtvedt experiment is meant as a test on whether "inertia"
gravitates, using the equivalence principle. That the test turns out
negative does not, to my thinking, show that "gravity gravitates"
because the alternative explanation is that the "inertial energy"
concept, ie, "gravitational energy", is false. In other words, the
negative Nordtvedt result shows that either both paradigms of "gravity
gravitates" and "gravitational energy" are right or wrong in tandem.

I agree with you up to this point.


My stance is that they are both wrong.

The problem with this hypothesis [that gravitational energy doesn't
have inertia] is that it's hard to reconcile with conservation of
momentum.

[If you want to abandon conservation of momentum,
note that since momentum and energy are components
of the *same* 4-vector, that means that in other
reference frames, you have violations of conservation
of energy, i.e., you can build a (gedanken)
perpetual-motion machine. ]


That is, let's start by considering a (gedanken) apparatus (for later
use we'll call it "apparatus A") containing a pair of masses, a mechanical
linkage which lets them move with respect to each other, an electric
motor/generator hooked up to that linkage, and finally a small particle
accelerator which can make matter-antimatter particle pairs if you feed
it with electricity. And finally let's have a pair of reservoirs to
hold (respectively the matter and the antimatter, and some (gedanken)
perfectly efficient solar cells to catch any gamma rays that would
result if we let the matter & antimatter annihilate each other.

Start with the two test masses some distance apart, and the matter
and antimatter reservoirs empty. Let's call this configuration of
apparatus A "configuration #1", and let's call apparatus A's total
rest mass-energy (as operationally defined by Newton's 2nd law)
in this configuration, "M". That is, M is a measure of the inertia
of apparatus A in configuration #1.

Now let the two test masses fall towards each other, under the influence
of their (Newtonian) mutual gravitational attraction. This releases
some gravitational binding energy E which we can harvest as electricity
using the electric motor/generator. We use this electricity to run the
particle accelerator, making a mass (split 50/50 between matter and
antimatter so there's no problem with conservation of electric charge)
E/c^2, which is stored in the reservoirs. Let's call this configuration
of apparatus A (masses close together, plus some matter/antimatter),
"configuration #2". Since (following our hypothesis that gravitational
binding energy has no inertia) the two masses have the same inertia
they had before, the total rest mass-energy [again operationally
defined via Newton's 2nd law] of apparatus A in configuration #2, i.e.,
now including the newly-manufactured matter & antimatter, is M + E/c^2.

So, what we have is some apparatus which can change its inertia (i.e.,
its mass-as-defined-by-Newton's-2nd-law) between that of a mass M
(when the apparatus is in configuration #1), and that of a mass M + E/c^2
(when the apparatus is in configuration #2).

And (gedanken) it's easy to reverse this process, annihilating the
matter & antimatter to get energy, then using this via the electric
motor to pull the two masses apart from each other, returning the
apparatus to configuration #1.


To actually get a violation of conservation-of-momentum with this, we
need a bit more (gedanken) apparatus: We now place apparatus A in a
long and moderately massive tube so apparatus A can move freely back
and forth with respect to the tube. And we put (perfect, frictionless)
springs at each end of the tube, and we set apparatus A bouncing back
and forth in the tube.

Conservation of momentum implies that when apparatus A is moving to
the right, the tube is moving to the left (in a referece frame where
the center-of-mass of the whole apparatus-A-plus-tube is stationary).

But now what happens if we have apparatus A change its inertia while
it's in flight? Let's say we have it be in the low-inertia state
(configuration #1) each time it's moving left and about to bounce off
the tube's left end-spring, and then transition to the high-inertia
state (configuration #2) when it's moving right and about to bounce
off the tube's right end-spring.

It's easy to see that after one complete left-right cycle the whole
system (tube + apparatus A) will now have acquired a net linear
momentum to the right, and with each complete cycle it will acquire
further such momentum.

That is, we've just built a "reactionless space drive", i.e., we've
violated conservation of momentum. [And as I noted above, an observer
watching this whole process from a moving reference frame would also
see violations of conservation of energy, i.e., she would say that
we've also built a perpetual-motion machine.]


In conclusion, then, while it's certainly _possible_ that gravitational
binding energy neither gravitates nor has inertia, that would imply
that neither energy nor momentum are conserved. Most physicists would
prefer to keep energy/momentum conservation, and correspondingly argue
that gravitational energy *both* gravitates *and* has inertia.

Fortunately, we should quite direct experimental evidence bearing on
this point within about 5 years: When advanced LIGO and Virgo are
operational (roughly 2015-2016), they should detect gravitational
waves from (among other sources) binary neutron star coalescences
and black hole - neutron star coalescences. If gravitational binding
energy (which is on the order of 10% to 20% of the total rest mass
for a neutron star) were "invisible" to both inertia and gravitation,
I would expect this to have significant effects on the gravitational
radiation waveforms.

ciao,

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

On Oct 30, 11:45*pm, eric gisse wrote:
Eric Flesch wrote in news:mt2.0-14899-1319988383
...
..
Since my point was clearly missed, I'll expand:

Energy that would generate that depression would itself gravitate and we'd
see it through say the Integrated Sachs-Wolfe effect. Or in actuality we'd
simply have reverse dark matter: too much gravitation for what we see.

This is confusing. If we do not see enough to explain some amount
of gravitation, wouldn't that require just dark matter? Why reverse?

The Nordtvedt effect has not been
observed, which is consistent with gravity not gravitating. Gravity
has never been observed to gravitate.


The Nordtevdt effect is fantastic additionally for testing whether a person
understand the subject. If you have a non-null Nordtevdt effect it means
gravitational energy doesn't quite gravitate according to what GR predicts.

Or maybe some dark matter distribution interferes? (Since we're at
it..)

--
Jos

Jos Bergervoet wrote in
:

On Oct 30, 11:45*pm, eric gisse wrote:
Eric Flesch wrote in news:mt2.0-14899-1319988383
...
..
Since my point was clearly missed, I'll expand:

Energy that would generate that depression would itself gravitate and
we'd see it through say the Integrated Sachs-Wolfe effect. Or in
actuality we'd simply have reverse dark matter: too much gravitation
for what we see.

This is confusing. If we do not see enough to explain some amount
of gravitation, wouldn't that require just dark matter? Why reverse?

The answer to this question requires reading what I wrote.

The energy of the depression would itself be gravitating and would be an
additional source of gravitation so if this napkin-scribble of a theory
were correct we would see an abundance of gravitation for what see see
rather than a deficit.


The Nordtvedt effect has not been
observed, which is consistent with gravity not gravitating. Gravity
has never been observed to gravitate.


The Nordtevdt effect is fantastic additionally for testing whether a
person understand the subject. If you have a non-null Nordtevdt
effect it means gravitational energy doesn't quite gravitate
according to what GR predicts.

Or maybe some dark matter distribution interferes? (Since we're at
it..)

--
Jos


Like I said, its' fantastic for sorting out those who are knowledgable and
those who think I'm just pressing buttons and making things up.

On Nov 2, 10:01*am, eric gisse wrote:
Jos Bergervoet wrote :
..
...
actuality we'd simply have reverse dark matter: too much gravitation
for what we see.

This is confusing. If we do not see enough to explain some amount
of gravitation, wouldn't that require just dark matter? Why reverse?

The answer to this question requires reading what I wrote.

That is not sufficient! You write: (first line quoted above)
"reverse dark matter: too much gravitation for what we see."
But we already have the normal definition:
Dark matter: too much gravitation for what we see.

What you wrote was in fact creating the question..

--
Jos

On Mon, 31 Oct 11 07:11:54 GMT, Eric Flesch wrote:
My stance is that they are both wrong.

I've had time now to look over JT's gedankenexpirements and EG's site.
And what I see is a house of cards. Basically if we start with the
axioms of matter-energy and a flat 3-manifold, then we end up,
fractally, with notions of gravity gravitating etc.

My point is that by adjusting the axioms, we can get a simpler
outcome. No, I don't have the solution, but I know a skunk when I
smell it.

JT's gedankens basically say that I would have a gedanken
perpetual-motion machine because other gedankens (perfect springs,
etc) could be used to make one, given my intitial stance. But if you
need X to make X, then you have not truly made X. So I think JT's
gedankens do not prove his point.

On that note, I'll bow out of this discussion, because I don't have
the breakthrough. But if you read the literature of 100 years ago,
you'll be struck by how many ladders were leaning against the wrong
walls then. Guess what, today is no different.

cheers, Eric