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What's up with gravity wave detection?



 
 
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  #101  
Old August 26th 04, 02:26 PM
Androcles
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"vonroach" wrote in message
...
| On Thu, 26 Aug 2004 08:33:58 GMT, "Androcles"
| wrote:
|
|
| "vonroach" wrote in message
| .. .
| | On Wed, 25 Aug 2004 17:31:09 +0200, "Volker Hetzer"
| | wrote:
| |
| | Intuition is a dangerous tool. I don't recommend it. Better to prove
a
| | theorem mathematically and then see if intuition agrees. Thunder
| and
| | lightning arrive at different times, and a child's intuition is
| that
| | they are seperate events.
|
| It seems that vonroach is prepared to say Volker Hetzer wrote my words
AND
| Jim Greenfield wrote them also.
| Androcles
|
| No as I've already said, I don't care who wrote them. They are false.

Different people have different opinions on many subjects, and rely on
intuition to have those opinions. Since some of those opinions are
diametrically opposed (as are yours and mine), it follows that your
intuition is as reliable as you are in incorrectly attributing my words to
another. QED.


| And you impress me, speaking to Andro. ,as a pompous little sophomore
| getting a tiny sip of knowledge.

Since your 'impression' is really your intuition and is completely wrong,
once again you've proven my point.

You (speaking to roach) impress me as a totally ****ing stupid argumentative
moron without a clue of what you are arguing about, and as someone who
doesn't care who he misquotes.
*plonk*
Androcles.



  #102  
Old August 26th 04, 06:16 PM
Volker Hetzer
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"Androcles" schrieb im Newsbeitrag ...

"Volker Hetzer" wrote in message
...
|
| "Androcles" schrieb im Newsbeitrag
...
|
| "Volker Hetzer" wrote in message
| ...
| |
| | "Androcles" schrieb im Newsbeitrag
| ...
| |
| | "Volker Hetzer" wrote in message
| | ...
| | |
| | | "Jim Greenfield" schrieb im Newsbeitrag
| | om...
| | | "Dave" wrote in message
| | ...
| | |
| | | Intuition is a dangerous tool. I don't recommend it. Better
to
| prove
| | a
| | | theorem mathematically and then see if intuition agrees.
Thunder
| and
| | | lightning arrive at different times, and a child's intuition
is
| that
| | | they are seperate events. An adult sees it differently.
Until
| | | Copernicus, intuition told us the Earth is at the centre if
the
| | | universe. After all, we see the sun cross the sky daily, it
MUST
| be
| | | going around us. With greater knowledge we revise our view
that
| we
| | | are turning toward and away from the sun. Never trust
intuition,
| it
| | | is bane of science and the boon of religion.
| | |
| | | But aren't you using intuition to discard relativistic
addition of
| | | velocities in your c'=c+v (or is that c=c'+v?).
| | |
| | | Car is parked by road, another passes. At the instant both are
| | | alongside, each emits a photon (vaccum condition). I say each
emits
| | | the photon at c from source, and therefore magic is required for
| each
| | | photon to travel "with" the other. This is NOT intuition- try it
| with
| | | throwing stones off the back of a ute! c DOESN"T = c+v (car).
| | | As for relativistic addition of velocities, this totally
disregards
| | | conservation of energy/momentum, so I "intuitively" reject that
| | | nonesense to.
| | | Maybe here's a better analogy: Sound. If that depended on the
source
| | | speed, the sound wall wouldn't exist.
| | |
| | | Lots of Greetings!
| | | Volker
| | Sound DOES depend on source speed.
|
| You snipped the explanation.
| I'll return the courtesy.
| Sound DOES depend on source speed.
| Try moving through air toward a sound source such as a fire siren.
| Relatively, the source is moving toward you. All speed is relative.
| See
| http://www.place.dawsoncollege.qc.ca...ph/Chap18B.htm
| Solution to Problem 18.51
| Androcles
|
| There. I quoted you. And I don't see how 18.51 explains how a supersonic
aircraft can outfly its own
| sound under the condition that the speed of sound depends on the speed of
the aircraft.
|
| So?

In your aircraft example the speed of (engine) sound, as measured by the
plane when the plane is moving at Mach 1 through the air, is zero. Thus the
speed of sound, in this case zero, depends on the speed of the source.

In this case the result of the measurement depends on the speed of the
measurement device relative to the speed the medium carrying the sound.
That's different from the speed of sound being dependent on the speed
of the source.

If you agree to go back to the speed of light, which is the
same regardless of the reference system, you might regard a simple radar
thought experiment:
Assume you have two reflectors, one (A) stationary, and one (B) moving
toward you at 0.5c.
The radar beam hits both reflectors when they are exactly 1km away
from you.
Obviously, B's echo will be blue shifted but do you really think that B's
echo arrives in about 2/3 the time of A's echo?

Lots of Greetings!
Volker
  #103  
Old August 26th 04, 11:03 PM
Androcles
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"Volker Hetzer" wrote in message
...
|
| "Androcles" schrieb im Newsbeitrag
...
|
| "Volker Hetzer" wrote in message
| ...
| |
| | "Androcles" schrieb im Newsbeitrag
| ...
| |
| | "Volker Hetzer" wrote in message
| | ...
| | |
| | | "Androcles" schrieb im
Newsbeitrag
| | ...
| | |
| | | "Volker Hetzer" wrote in message
| | | ...
| | | |
| | | | "Jim Greenfield" schrieb im
Newsbeitrag
| | | om...
| | | | "Dave" wrote in message
| | | ...
| | | |
| | | | Intuition is a dangerous tool. I don't recommend it.
Better
| to
| | prove
| | | a
| | | | theorem mathematically and then see if intuition agrees.
| Thunder
| | and
| | | | lightning arrive at different times, and a child's
intuition
| is
| | that
| | | | they are seperate events. An adult sees it differently.
| Until
| | | | Copernicus, intuition told us the Earth is at the centre
if
| the
| | | | universe. After all, we see the sun cross the sky daily,
it
| MUST
| | be
| | | | going around us. With greater knowledge we revise our
view
| that
| | we
| | | | are turning toward and away from the sun. Never trust
| intuition,
| | it
| | | | is bane of science and the boon of religion.
| | | |
| | | | But aren't you using intuition to discard relativistic
| addition of
| | | | velocities in your c'=c+v (or is that c=c'+v?).
| | | |
| | | | Car is parked by road, another passes. At the instant both
are
| | | | alongside, each emits a photon (vaccum condition). I say
each
| emits
| | | | the photon at c from source, and therefore magic is required
for
| | each
| | | | photon to travel "with" the other. This is NOT intuition-
try it
| | with
| | | | throwing stones off the back of a ute! c DOESN"T = c+v
(car).
| | | | As for relativistic addition of velocities, this totally
| disregards
| | | | conservation of energy/momentum, so I "intuitively" reject
that
| | | | nonesense to.
| | | | Maybe here's a better analogy: Sound. If that depended on the
| source
| | | | speed, the sound wall wouldn't exist.
| | | |
| | | | Lots of Greetings!
| | | | Volker
| | | Sound DOES depend on source speed.
| |
| | You snipped the explanation.
| | I'll return the courtesy.
| | Sound DOES depend on source speed.
| | Try moving through air toward a sound source such as a fire siren.
| | Relatively, the source is moving toward you. All speed is relative.
| | See
| | http://www.place.dawsoncollege.qc.ca...ph/Chap18B.htm
| | Solution to Problem 18.51
| | Androcles
| |
| | There. I quoted you. And I don't see how 18.51 explains how a
supersonic
| aircraft can outfly its own
| | sound under the condition that the speed of sound depends on the speed
of
| the aircraft.
| |
| | So?
|
| In your aircraft example the speed of (engine) sound, as measured by the
| plane when the plane is moving at Mach 1 through the air, is zero. Thus
the
| speed of sound, in this case zero, depends on the speed of the source.
| In this case the result of the measurement depends on the speed of the
| measurement device relative to the speed the medium carrying the sound.
| That's different from the speed of sound being dependent on the speed
| of the source.
|
| If you agree to go back to the speed of light, which is the
| same regardless of the reference system,

Here is why it isn't.
S1---------------------O----x---------------S2 t0
S1----------------------y----O--------------S2 t1
S1 and S2 are sources of light, and O is an observer. In the interval of
time
from t0 to t1, O has moved a distance x in time t1 with some velocity I'll
call v = x/t. Light from S1 to y will travel at c, reaching y in time t.
Hence c = y/t
Light from S2 will reach y (where the observer is) in time t also. Therefore
the observer will percieve the signal from S2 before the signal from S1, and
will calculate t2 = x/(c+v) from S2 and t1 = x/(c-v) from S1. So unless you
think he has two different times recorded that are the same, the velocity of
light in the observer O's frame of reference is not c. By way of
confirmation, Einstein wrote: "But the ray moves relatively to the initial
point of k, when measured in the stationary system, with the velocity c-v,
so that x'/(c-v) = t."


you might regard a simple radar
| thought experiment:

Thought experiments are something Einstein came up with. His contain errors.
Real experiments are much better. However, I'll take a look.


| Assume you have two reflectors, one (A) stationary, and one (B) moving
| toward you at 0.5c.
| The radar beam hits both reflectors when they are exactly 1km away
| from you.
| Obviously, B's echo will be blue shifted but do you really think that B's
| echo arrives in about 2/3 the time of A's echo?

In air, no. In the vacuum of space, yes.
Androcles.

|
| Lots of Greetings!
| Volker


  #104  
Old August 27th 04, 01:02 AM
Jim Greenfield
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Sam Wormley wrote in message ...
How Do You Add Velocities in Special Relativity?
http://www.edu-observatory.org/physi.../velocity.html

Read it Greenfield... it's right and you're wrong.


Clearly explained to me by George D privately.
If you, EG and George wish to immunise SR against the rules/laws of
vector addition (or don't you think velocity IS a vector), go ahead!
But it won't work in THE REAL WORLD

Jim G
c'=c+v
  #105  
Old August 27th 04, 01:42 AM
vonroach
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On Thu, 26 Aug 2004 13:26:22 GMT, "Androcles"
wrote:

You (speaking to roach) impress me as a totally ****ing stupid argumentative
moron without a clue of what you are arguing about, and as someone who
doesn't care who he misquotes.
*plonk*
Androcles.


As I thought a pompous sophomore with little learning. Profanity
doesn't add any weight to your adolescent note.
  #106  
Old August 27th 04, 01:47 AM
vonroach
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On Thu, 26 Aug 2004 15:01:17 +0200, "Dirk Van de moortel"
wrote:

There. I quoted you. And I don't see how 18.51 explains how
a supersonic aircraft can outfly its own
sound under the condition that the speed of sound depends
on the speed of the aircraft.

So?


So, well done, Androcles!


You are in over your head, Andy. Speed of sound `depends' on speed of
aircraft? ROFLMAO Dirk, you must be an idiot.
  #107  
Old August 27th 04, 01:51 AM
vonroach
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On Thu, 26 Aug 2004 13:54:12 +0200, "Volker Hetzer"
wrote:

yes, but according to androcles the speed of sound is supposed to depend on
the speed of the aircraft, right?


wrong
  #108  
Old August 27th 04, 11:17 AM
Dirk Van de moortel
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"vonroach" wrote in message ...
On Thu, 26 Aug 2004 15:01:17 +0200, "Dirk Van de moortel"
wrote:

There. I quoted you. And I don't see how 18.51 explains how
a supersonic aircraft can outfly its own
sound under the condition that the speed of sound depends
on the speed of the aircraft.

So?


So, well done, Androcles!


You are in over your head, Andy. Speed of sound `depends' on speed of
aircraft? ROFLMAO Dirk, you must be an idiot.


Perhaps you don't know the meaning of the word 'fumble'?
http://users.pandora.be/vdmoortel/di...undSource.html
It is Androcles who claims that speed of sound `depends' on speed of
aircraft.
It is me who claims that Androcles is an idiot.

Dirk Vdm


  #109  
Old August 30th 04, 07:48 PM
Bilge
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Eric Flesch:
On Fri, 20 Aug 2004 17:34:31 +0000 (UTC),
wrote:
In sci.astro Eric Flesch wrote:
You're missing the point. The stress-energy tensor is a classical
description which assumes continuous motion. But QED shows that the
photon path is the summation of all possible paths (diffraction
gratings are an application of this) and the delayed-choice experiment
shows explicitly that the travelling photon cannot be pinpointed to
any particular location in its presumed path(s). The point is that
the "travelling photon" can be modelled only by a quantum description,
and the classical stress-energy tensor does not apply.


Everything you say here is just as true of neutrons, or protons, or
any other elementary particle. Are you saying that we should therefore
not use GR at all?


Of course not. Bosons classically manifest routinely and so their
gravitational vectors can be described. But photons have *no*
classical manifestation between emission and absorption. There is a
real difference here in their behavior "in the wild".


Say what? Neutrons and protons are fermions, i.e., spinors, not vectors.
On the other hand, the photon _is_ a four-vector.

... You can write down a low-energy effective action for
the gravitational field without knowing details of quantum gravity.


"Details"? Quantum gravity is vaporware. You can't quote it as
though it were a reference.


``Aspects of Quantum Field Theory in Curved Spacetime'', Fulling, S.A.,
``Quantum Fields and Strings: A course for Mathematicians'', Witten, E.,
and others, ed., 2 volume set.


You can't have it both ways here. If you want to talk about what ``QED
shows,'' you have to allow standard techniques from QED.


You mystify me. What have I said to limit the application of QED?
I'm saying that where QED's description differs from GR, QED rules.


I hate to break this news to you, but the spacetime of special relativity
from which qed derives is no less ``continuous'' than the spacetime of
general relativity. It is possible to formulate qed (and quantum field
theories, in general) in curved spacetime, e.g., see the references above.

GR is not, and was never meant to be, a description of the nature of
light.


But general relativity is a theory of the spacetime in which light
propagates. Are you suggesting that there is something special about flat
spacetime other than the particular value for the curvature, (i.e., zero)
or that spacetime is relevant to the light which propagates in spacetime?

No it won't be. The mass might have some miniscule effect on the
local geometry, that is all.


Are you serious? You claim that a mirrored box filled with radiation does
not weight more than an empty box?


Would you like to describe how a mirror works? How efficient mirrors
are?


What difference does that make?

Every mirror that we've ever built, if we build the box that you
describe, toss in some photons and close the box, the photons would be
absorbed (and converted to heat) in an infinitesimal fraction of a
second.


The point being what? Then, the heat contributes to the mass. If you
want to debate the point of how well insulated from heat leaks one can
make the box, be my guest. All you need do is note that a decent 5 litre
dewer of liquid nitrogen will still contain liquid after a week, to see
that one can insulate the box pretty darn well - certainly long enough
to weigh the box.

[...]

Here's a simple exercise. I assume you accept that electromagnetic
radiation is red-shifted in a gravitational field, right?


It depends on the vector. Photons departing the gravitational field
are red-shifted, certainly.

So consider a box with a
mirror at the top and one at the bottom, containing radiation in a coherent
state (you accept QED, right?) with an expectation value of momentum that's
in the purely vertical direction and an expectation value of wave packet
width (z^2-z^2) that's small compared to the size of the box. Compute
the momentum transfer to the mirrors, using however much QED you like. You
will find that the momentum transfer to the bottom, where the energy is
blue-shifted, is greater than the momentum transfer to the top. That means
``the radiation will be attracted toward the mass.''


In that sense you are right. But I am reminded of one of Bohr's
refutations of Einstein's gedankenexperimenten where Einstein's
premise of increased mass was countered by the different rates of time
flow in a differential gravitational field.


Which was what, precisely?

I suspect the same applies here. In any event, this does not show that
the "in-flight" photon exerts gravitation.


So, if I place a radioactive source which decays by positron emission
in a thermally insulated box, then what do you predict the mass of the
box to be,

(1) before any of the nuclei decay,

(2) after all of the nuclei have decayed and the positrons have
anihilated with electrons in the walls of the box,
via e+ e- - \gamma\gamma (In the interest of simplicity, I'll
skip the bremsstrahlung prior to any anihilation which is only
relevent if you have a very convoluted answer to this question),

(3) times in between (1) and (2)?

Also, in the interst of simplicity, you may ignore the neutrinos
unless you really want to punish yourself estimating the fraction of
the energy which is carried off by neutrinos which escape the box.
If you are into self-abuse, then make sure you do it correctly by
calculating the cross-section of the neutrinos with the box, and
assume some material and thickness for the walls. If you're going
to be pedantic, you might as well go all the way. You've already
turned a simple, straightforward question into a something much
more complicted than was necessary.


  #110  
Old August 30th 04, 09:19 PM
Eric Flesch
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On Mon, 30 Aug 2004 18:48:29 -0000,
(Bilge) wrote:
Eric Flesch:
Of course not. Bosons classically manifest routinely and so their
gravitational vectors can be described. But photons have *no*
classical manifestation between emission and absorption. There is a
real difference here in their behavior "in the wild".


Say what? Neutrons and protons are fermions, i.e., spinors, not vectors.
On the other hand, the photon _is_ a four-vector.


Sorry, frightful slip, I meant baryons.

"Details"? Quantum gravity is vaporware. You can't quote it as
though it were a reference.


``Aspects of Quantum Field Theory in Curved Spacetime'', Fulling, S.A.,
``Quantum Fields and Strings: A course for Mathematicians'', Witten, E.,
and others, ed., 2 volume set.


These are speculative works. What has quantum gravity ever predicted
which has been observationally confirmed? (which is the topic of this
thread)

You can't have it both ways here. If you want to talk about what ``QED
shows,'' you have to allow standard techniques from QED.


You mystify me. What have I said to limit the application of QED?
I'm saying that where QED's description differs from GR, QED rules.


I hate to break this news to you, but the spacetime of special relativity
from which qed derives is no less ``continuous'' than the spacetime of
general relativity. It is possible to formulate qed (and quantum field
theories, in general) in curved spacetime, e.g., see the references above.


A pity fhen that photons don't travel in continuous paths, shown by
the delayed-choice experiment. If your speculative references are
modelling photon behavior to be different than observed behavior, then
they are a waste of paper.

GR is not, and was never meant to be, a description of the nature of
light.


But general relativity is a theory of the spacetime in which light
propagates. Are you suggesting that there is something special about flat
spacetime other than the particular value for the curvature, (i.e., zero)
or that spacetime is relevant to the light which propagates in spacetime?


No, I would say rather that GR is incomplete when it comes to the way
that light interacts with spacetime.

Every mirror that we've ever built, if we build the box that you
describe, toss in some photons and close the box, the photons would be
absorbed (and converted to heat) in an infinitesimal fraction of a
second.


The point being what? Then, the heat contributes to the mass.


Sure, but the mass is missing whilst "in-flight" as a photon -- the
quantum description shows the photon has no mass in the classical
sense. Why then the insistence that the in-flight photon should exert
gravitation just as though the mass was present?

In that sense you are right. But I am reminded of one of Bohr's
refutations of Einstein's gedankenexperimenten where Einstein's
premise of increased mass was countered by the different rates of time
flow in a differential gravitational field.


Which was what, precisely?


It was the last one, after which Einstein no longer tried to pick
holes in Bohr's model. Here is an accounting from Pagels' "The Cosmic
Code": Einstein imagined one had a clock in a box present so that it
would open and close a shutter very quickly on the light-tight box.
Inside the box was also a gas of photons. When the shutter opened, a
single photon would escape. By weighing the box before and after the
shutter opened, one could determine the mass and hence energy of the
escaped photon. Consequently it was possible to determine both the
energy and the time of escape of the photon with arbitrary precision.
This violated the Heisenberg energy-time uncertainty relation delE x
delt GE h, and hence, Einstein concluded, quantum theory must be
wrong.

Bohr spent a sleepless night thinking about the problem. If
Einstein's reasoning was correct, quantum mechanics must fail. By
morning he discovered the flaw in Einstein's reasoning. The photon,
when it escapes from the box, imparts an unknown momentum to the box,
causing it to move in the gravitational field which is being used to
weigh it. However, according to Einstein's own theory of general
relativity, the rate of a clock depends on its position in the gravity
field. Since the position of the box is uncertain by a small amount
because of the 'kick' it gets when the photon escapes, so is the time
it measures. Bohr showed that the thought experiment devised by
Einstein did not in fact violate the uncertainty relation but rather
confirmed it. After this, Einstein never disputed the consistency of
the new quantum theory.

I suspect the same applies here. In any event, this does not show that
the "in-flight" photon exerts gravitation.


So, if I place a radioactive source which decays by positron emission
in a thermally insulated box, then what do you predict the mass of the
box to be,

(1) before any of the nuclei decay,

(2) after all of the nuclei have decayed and the positrons have
anihilated with electrons in the walls of the box,
via e+ e- - \gamma\gamma (In the interest of simplicity, I'll
skip the bremsstrahlung prior to any anihilation which is only
relevent if you have a very convoluted answer to this question),

(3) times in between (1) and (2)?


I expect (ignoring neutrinos) that the box will weigh less the more
"in-flight" radiation there is inside the contained box, so W(1)=W(3)
and W(2) is less. Do tell me about any such experiment which has been
done -- citation please.

You've already
turned a simple, straightforward question into a something much
more complicted than was necessary.


Actually, my objection is that it all is simpler than currently
modelled. If one accepts that the "in-flight" photon has no classical
existence and so does not exert gravitation, then a great many
physical processes can be described more simply.

Eric

 




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