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N:dlzc D:aol T:com (dlzc)
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 Posted: Wed May 23, 2007 5:44 am Post subject: Re: Question about annihilation and gravitational waves |
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Dear valls:
<valls@icmf.inf.cu> wrote in message
news:1179872346.289995.26440@h2g2000hsg.googlegroups.com...
| Quote: |
On 22 mayo, 08:18, "N:dlzc D:aol T:com \(dlzc\)" <d...@aol.com
wrote:
Dear valls:
v...@icmf.inf.cu> wrote in message
news:1179833035.400288.133010@b40g2000prd.googlegroups.com...
...
I don't know if physicists are in agreement about the
possible gravitational field of a photon.
"Systems" (two or more) of non-parallel propagating
photons have rest mass. Only individual photons
have no mass. Light from annihilation would still
contribute to local curvature, until it propagated past
you.
It is the first time that I read about individual photons
having no mass (I suppose you refer to rest mass,
not to relativistic mass),
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Correct, rest mass for a photon is experimentally
indistinguishable from zero. Many orders of magnitude less than
E/c^2.
| Quote: |
and systems of them having non-zero rest mass.
Can you give me some references in the topic?
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"Spacetime Physics" by Taylor and Wheeler
Sections 8.3 and 8.7
http://en.wikipedia.org/wiki/Relativistic_mass#Mass_in_relativity_theory
E is a scalar
p is a vector. It is possible to have the sum of nonparallel
vectors <> 0, leaving *a system* of two or more of any kind of
particles (including photons) with non-zero rest mass (in the
center of momentum frame).
http://en.wikipedia.org/wiki/Conservation_of_mass#Serious_violations
David A. Smith |
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Bill Hobba
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| Posted: Wed May 23, 2007 6:50 am Post subject: Re: Question about annihilation and gravitational waves |
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<valls@icmf.inf.cu> wrote in message
news:1179833035.400288.133010@b40g2000prd.googlegroups.com...
| Quote: |
On 22 mayo, 05:37, Bart <bart.kowal...@gmail.com> wrote:
If I understand correctly, when two particles of *non-zero mass*
annihilate each other they are converted into pure energy and emit
*zero-mass* photons. Suppose that we had sufficiently precise
instruments to observe the gravitational effects near such an
annihilation. Would we observe the gravitational field going from non-
zero to zero in the vicinity of the event? If so, would it be possible
(theoretically) to construct a device that creates oscillations in the
gravitational field in this way?
I don't know if physicists are in agreement about the possible
gravitational field of a photon.
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Then you should learn about GR. The source of gravity is the stress energy
tensor. Photons have a stress energy tensor so have gravity. I can never
remember which is which, but an interesting consequence of this if you work
through the math is that light beams travelling in the opposite (same)
direction gravitationally attract but the other way around they don't. The
effect is so small however that is it doubtful it could ever be measured.
| Quote: |
In other words, if "pure
energy" (rest mass zero) has gravitation.
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It must - since if it has energy it has a lagrangian and so has a stress
energy tensor.
Bill
| Quote: |
If photons has gravitation
you have no reason to expect the change from non-zero to zero that you
refer.
RVHG(Rafael Valls Hidalgo-Gato)
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Bart
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| Posted: Wed May 23, 2007 11:00 am Post subject: Re: Question about annihilation and gravitational waves |
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Thanks to all who have replied. Your answers are interesting, although
I don't understand all the details. I would like to dig into this
subject into more detail. Unfortunately, all my physics textbooks only
superficially discuss GR because it is "too advanced".
So, if my understanding is correct, when annihilation occurs mass-
energy is conserved and gravity is not affected. However, I'm still
wondering about the gravitational radiation. The Wikipedia article
says that accelerating masses should radiate away energy in the form
of gravitational radiation. What properties does this radiation have?
Can these waves be reflected and amplified like EM waves? Given
enormous amounts of energy, could a "gravitational oscillator" be
constructed? |
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Edward Green
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| Posted: Wed May 23, 2007 4:02 pm Post subject: Re: Question about annihilation and gravitational waves |
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On May 22, 2:48 pm, ca314159 <ca314...@bestweb.net> wrote:
| Quote: |
Igor wrote:
On May 22, 6:37 am, Bart <bart.kowal...@gmail.com> wrote:
If I understand correctly, when two particles of *non-zero mass*
annihilate each other they are converted into pure energy and emit
*zero-mass* photons. Suppose that we had sufficiently precise
instruments to observe the gravitational effects near such an
annihilation. Would we observe the gravitational field going from non-
zero to zero in the vicinity of the event?
No, since in GR, all external sources of energy contribute to
gravitational fields.
Gravity model of trade
http://en.wikipedia.org/wiki/Gravity_model_of_trade
The net is being carved up into information plantations:
http://technology.guardian.co.uk/weekly/story/0,,2080775,00.html
"The more popular a site becomes, the more it comes
to dominate search results, which ends up funnelling ever
more links and traffic to it. On the internet, the big get bigger.
It wasn't supposed to be like that."
|
Probably conforming to some inevitable progression of society: all
utopian schemes, after a start-up period, begin to resemble the bad
old societies they were supposed to supercede. |
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Edward Green
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| Posted: Wed May 23, 2007 4:10 pm Post subject: Re: Question about annihilation and gravitational waves |
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On May 23, 6:07 am, Bart <bart.kowal...@gmail.com> wrote:
| Quote: |
Thanks to all who have replied. Your answers are interesting, although
I don't understand all the details. I would like to dig into this
subject into more detail. Unfortunately, all my physics textbooks only
superficially discuss GR because it is "too advanced".
So, if my understanding is correct, when annihilation occurs mass-
energy is conserved and gravity is not affected. However, I'm still
wondering about the gravitational radiation. The Wikipedia article
says that accelerating masses should radiate away energy in the form
of gravitational radiation. What properties does this radiation have?
Can these waves be reflected and amplified like EM waves? Given
enormous amounts of energy, could a "gravitational oscillator" be
constructed?
|
Good questions. The rule in GR is apparently that an oscillating
quadrapole moment of the mass distribution is necessary to produce
radiation -- unlike EM, where an oscillating dipole is sufficient.
Another difference is that GR is a fundamentally non-linear theory,
whereas EM is linear: but there is probably some linearized version of
gravitational radiation, in the weak field limit.
An oscillating quadrapole implies a limited spatial distribution of
mass, undergoing some internal rearrangements. An accelerating mass
is more open-ended: in fact, in EM, the radiation properties of a
constantly accelerating charge are still a source of some debate and
confusion among experts! I imagine there are similar subtleties in
GR.
I'm no expert, but I hope at least I've said nothing misleading. |
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Edward Green
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| Posted: Wed May 23, 2007 4:11 pm Post subject: Re: Question about annihilation and gravitational waves |
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On May 23, 6:07 am, Bart <bart.kowal...@gmail.com> wrote:
| Quote: |
Thanks to all who have replied. Your answers are interesting, although
I don't understand all the details. I would like to dig into this
subject into more detail. Unfortunately, all my physics textbooks only
superficially discuss GR because it is "too advanced".
So, if my understanding is correct, when annihilation occurs mass-
energy is conserved and gravity is not affected. However, I'm still
wondering about the gravitational radiation. The Wikipedia article
says that accelerating masses should radiate away energy in the form
of gravitational radiation. What properties does this radiation have?
Can these waves be reflected and amplified like EM waves? Given
enormous amounts of energy, could a "gravitational oscillator" be
constructed?
|
Good questions. The rule in GR is apparently that an oscillating
quadrapole moment of the mass distribution is necessary to produce
radiation -- unlike EM, where an oscillating dipole is sufficient.
Another difference is that GR is a fundamentally non-linear theory,
whereas EM is linear: but there is probably some linearized version of
gravitational radiation, in the weak field limit.
An oscillating quadrapole implies a limited spatial distribution of
mass, undergoing some internal rearrangements. An accelerating mass
is more open-ended: in fact, in EM, the radiation properties of a
constantly accelerating charge are still a source of some debate and
confusion among experts! I imagine there are similar subtleties in
GR.
I'm no expert, but I hope at least I've said nothing misleading. |
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ca314159
Guest
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| Posted: Wed May 23, 2007 7:46 pm Post subject: Re: Question about annihilation and gravitational waves |
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Edward Green wrote:
| Quote: |
On May 22, 2:48 pm, ca314159 <ca314...@bestweb.net> wrote:
Igor wrote:
On May 22, 6:37 am, Bart <bart.kowal...@gmail.com> wrote:
If I understand correctly, when two particles of *non-zero mass*
annihilate each other they are converted into pure energy and emit
*zero-mass* photons. Suppose that we had sufficiently precise
instruments to observe the gravitational effects near such an
annihilation. Would we observe the gravitational field going from non-
zero to zero in the vicinity of the event?
No, since in GR, all external sources of energy contribute to
gravitational fields.
Gravity model of trade
http://en.wikipedia.org/wiki/Gravity_model_of_trade
The net is being carved up into information plantations:
http://technology.guardian.co.uk/weekly/story/0,,2080775,00.html
"The more popular a site becomes, the more it comes
to dominate search results, which ends up funnelling ever
more links and traffic to it. On the internet, the big get bigger.
It wasn't supposed to be like that."
Probably conforming to some inevitable progression of society: all
utopian schemes, after a start-up period, begin to resemble the bad
old societies they were supposed to supercede.
|
A big beer goes flat:
http://en.wikipedia.org/wiki/The_World_is_Flat#Overview
"One bottle of beer on the wall, one bottle of beer.
Take one down and pass it around,
no more bottles of beer on the wall."
Last call:
http://en.wikipedia.org/wiki/Greenhouse_effect#Anthropogenic_greenhouse_effect
"Plop plop fizz fizz, oh what a relief it is."
http://en.wikipedia.org/wiki/Clathrate_gun_hypothesis
Gravity's eminent domain:
http://en.wikipedia.org/wiki/Buoyancy
http://www.fourmilab.ch/gravitation/foobar/
--
"Drink up. Muscle relaxant, you'll need it."
- HHGTTG |
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Bilge
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| Posted: Thu May 24, 2007 11:39 pm Post subject: Re: Question about annihilation and gravitational waves |
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On 2007-05-23, Bart <bart.kowalski@gmail.com> wrote:
| Quote: |
Thanks to all who have replied. Your answers are interesting, although
I don't understand all the details. I would like to dig into this
subject into more detail. Unfortunately, all my physics textbooks only
superficially discuss GR because it is "too advanced".
So, if my understanding is correct, when annihilation occurs mass-
energy is conserved and gravity is not affected. However, I'm still
wondering about the gravitational radiation. The Wikipedia article
says that accelerating masses should radiate away energy in the form
of gravitational radiation. What properties does this radiation have?
Can these waves be reflected and amplified like EM waves? Given
enormous amounts of energy, could a "gravitational oscillator" be
constructed?
|
Hulse and Taylor received the nobel prize for calculating the
gravitational radiation which explained the orbital decay of a
binary pulser system. Note the scale corresponding to ``enormous
anounts of energy.'' |
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Tomoko Kanazawa
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| Posted: Mon May 28, 2007 6:02 am Post subject: Re: Question about annihilation and gravitational waves |
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| Quote: |
If I understand correctly, when two particles of *non-zero mass*
annihilate each other they are converted into pure energy and emit
*zero-mass* photons. Suppose that we had sufficiently precise
instruments to observe the gravitational effects near such an
annihilation. Would we observe the gravitational field going from
non-
zero to zero in the vicinity of the event?
|
What.
I just love that reference to "pure energy". What is that, the 5th force ?
What.
Strong, weak, gravity, EM, and "pure" ?
What. What.
6th state of matter ? Are we bored with plasma now ?
What. |
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Autymn D. C.
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| Posted: Mon May 28, 2007 10:50 am Post subject: Re: Question about annihilation and gravitational waves |
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On May 22, 6:26 am, malibu <vega...@accesscomm.ca> wrote:
| Quote: |
Everything is energy.
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You don't even know what is means. |
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