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What's up with gravity wave detection?



 
 
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  #71  
Old August 25th 04, 12:39 AM
Jim Greenfield
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"Androcles" wrote in message ...
"Jim Greenfield" wrote in message
m...
| "Androcles" wrote in message
...
| "Jim Greenfield" wrote in message
| om...
| | Paul Lawler wrote in message
.125.202...
| | "Androcles" wrote in
news:TmuVc.3953
| | :
| |
| |
| | Risking showing my naivitie, what is REALLY being discussed- a "one
| | of" change in gravitational field strength (pulse/wave), or a SERIES
| | of equal strength waves emanating from a static body?
| |
| | Jim G
| | c'=c+v
|
| Jim, this discussion is not about the existence or non-existence of
gravity
| waves, but about their amplitude being great enough to be detectable.
Simply
| spinning the Earth in the lunar gravity produces tides and when we
include
| solar gravity we have neap and spring tides. If the lunar orbit were
highly
| elliptical we'd have higher tides at perigee than at apogee. Thus we
would
| have a detectable gravity 'wave'; they do exist, and can be detected.
|
| Yep. As I told Old Man, I weigh less with moon above than 12 hours
| later. So the moon produces a gravity wave of frequency 1/24hour,
| right?
Relatively speaking, yes. Of course it is the spin of the Earth that
actually changes your position and produces the wave, you are simply moving
in a fixed field, the strength of which is a function of distance. 1/24hour
may be misconstrued, though. 1 cycle every 24 hours is not the same as 1
cycle in 2 minutes and 30 seconds, which is 1/24th of an hour. To be a
little more precise, the moon orbits the Earth 13 times a year (but not
exactly) and the Earth orbits the sun. 24 hours is the time from noon to noo
n (sun at zenith) but a distant star moves about 4 minutes a day from
midnight to midnight. Which star is overhead at midnight depends on your
longitude. But rougly speaking, the gravity wave has a frequency of one
cycle per day.


The change in distance between me and moon would have very small
effect, as it is only a tiny change in "r" in the gravity equation. It
is the summing of the vectors which causes the (comparitively) large
change in my weight. Dark of the moon, vector forces of gravity all
generally pulling me down; moon above, vector componenets of moon's
pull are cancelling (opposite direction to) the earth's.



|
| LIGO, however, is about detecting a gravitational field from a supernova
at
| a distance of a kiloparsec = 3260 light years, where some quantity of
matter
| is
| completely converted to energy (E= mc^2) and the resultant gravity field
is
| reduced. That would be a step pulse.
| Or it could be the field from a pulsar in orbit about a neighbour that
is
| periodically approaching and receding from us, and that would be a
| sinusoidal wave. So the answer to your question is : both. However, the
| supernova (which may produce a pulsar as a remnant) is the greater.
|
| If a star explodes, the "center of gravity" of that star remains in
| the same place afterward.

Yes. There may be a shell of matter that leaves the star, but momentum is
conserved. The same is true for a rocket. We see the rocket accelerate, but
the exhaust is flying away in the opposite direction and the centre of mass
of the combined exhaust and rocket only moves with its original velocity
before the engine was fired. The combined momentum of the entire Universe is
zero.

| As I intuitively feel that the particles
| which comprise EMR DO exert gravitational force themselves, therefore
| no pulse/wave, as the star still "acts" the same after exploding.
| However, as the EMR dissipates, opening up the angle from us (from a
| point to an expanding cloud), there should be a gradual decline in
| field strength towards/from that center of gravity. Undetectable
| change until the outer ring of the burst is over a significant arc to
| us = no wave (detectable = Ligo wont work for Sn

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.


I could never understand how it was generally accepted that the earth
was EVER flat. As a teenager, standing atop a hill by the sea, with a
straight edge, the curve was very obvious! I understand the
Phoenecians or someone worked out a pretty good earth size that way
thousands of years BC. How did that get lost? Religious persecution?


|
| If you want to express the problem mathematically: let delta be the
smallest
| amplitude detectable by the instrument used.
| Let a pulse (or wave) of amplitude A be emitted at 0 and the amplitude
at r
| where the instrument is placed be A/r^2 = delta.
| Then the amplitude at A/(r+epsilon)^2 (epsilon 0) is less than delta
and
| is not detectable.
| LIGO has a real delta, so from that estimate the greatest imaginable A
and
| calculate
| A/r^2 = delta
| r^2/A = 1/delta
| r = sqrt(A/delta)
|
| Androcles.
|
| Don't math me :-(
|
| Jim G
| c'=c+v -- don't math me. :-)
Androcles


For Eric: "Every action has an equal and opposite reaction"
Newton says so, and so do I!

Classical gravity: drop an object down the side of a vertical
building, and observe the curved path. Pass photons by the sun, and
observe the curved path.

Jim G
c'=c+v
  #72  
Old August 25th 04, 02:08 AM
Androcles
external usenet poster
 
Posts: n/a
Default


"Jim Greenfield" wrote in message
om...
| "Androcles" wrote in message
...
| "Jim Greenfield" wrote in message
| m...
| | "Androcles" wrote in message
| ...
| | "Jim Greenfield" wrote in message
| | om...
| | | Paul Lawler wrote in message
| .125.202...
| | | "Androcles" wrote in
| news:TmuVc.3953
| | | :
| | |
| | |
| | | Risking showing my naivitie, what is REALLY being discussed- a
"one
| | | of" change in gravitational field strength (pulse/wave), or a
SERIES
| | | of equal strength waves emanating from a static body?
| | |
| | | Jim G
| | | c'=c+v
| |
| | Jim, this discussion is not about the existence or non-existence of
| gravity
| | waves, but about their amplitude being great enough to be
detectable.
| Simply
| | spinning the Earth in the lunar gravity produces tides and when we
| include
| | solar gravity we have neap and spring tides. If the lunar orbit were
| highly
| | elliptical we'd have higher tides at perigee than at apogee. Thus we
| would
| | have a detectable gravity 'wave'; they do exist, and can be
detected.
| |
| | Yep. As I told Old Man, I weigh less with moon above than 12 hours
| | later. So the moon produces a gravity wave of frequency 1/24hour,
| | right?
| Relatively speaking, yes. Of course it is the spin of the Earth that
| actually changes your position and produces the wave, you are simply
moving
| in a fixed field, the strength of which is a function of distance.
1/24hour
| may be misconstrued, though. 1 cycle every 24 hours is not the same as 1
| cycle in 2 minutes and 30 seconds, which is 1/24th of an hour. To be a
| little more precise, the moon orbits the Earth 13 times a year (but not
| exactly) and the Earth orbits the sun. 24 hours is the time from noon to
noo
| n (sun at zenith) but a distant star moves about 4 minutes a day from
| midnight to midnight. Which star is overhead at midnight depends on your
| longitude. But rougly speaking, the gravity wave has a frequency of one
| cycle per day.
|
| The change in distance between me and moon would have very small
| effect, as it is only a tiny change in "r" in the gravity equation.

Tidal height of sea water is only a few feet. I'd call that a very small
effect when compared to the Earth's diameter, and an enormous effect when
it washes away my sandcastle. (shrug)

| It
| is the summing of the vectors which causes the (comparitively) large
| change in my weight. Dark of the moon, vector forces of gravity all
| generally pulling me down; moon above, vector componenets of moon's
| pull are cancelling (opposite direction to) the earth's.
|
|
|
| |
| | LIGO, however, is about detecting a gravitational field from a
supernova
| at
| | a distance of a kiloparsec = 3260 light years, where some quantity
of
| matter
| | is
| | completely converted to energy (E= mc^2) and the resultant gravity
field
| is
| | reduced. That would be a step pulse.
| | Or it could be the field from a pulsar in orbit about a neighbour
that
| is
| | periodically approaching and receding from us, and that would be a
| | sinusoidal wave. So the answer to your question is : both. However,
the
| | supernova (which may produce a pulsar as a remnant) is the greater.
| |
| | If a star explodes, the "center of gravity" of that star remains in
| | the same place afterward.
|
| Yes. There may be a shell of matter that leaves the star, but momentum
is
| conserved. The same is true for a rocket. We see the rocket accelerate,
but
| the exhaust is flying away in the opposite direction and the centre of
mass
| of the combined exhaust and rocket only moves with its original velocity
| before the engine was fired. The combined momentum of the entire
Universe is
| zero.
|
| | As I intuitively feel that the particles
| | which comprise EMR DO exert gravitational force themselves, therefore
| | no pulse/wave, as the star still "acts" the same after exploding.
| | However, as the EMR dissipates, opening up the angle from us (from a
| | point to an expanding cloud), there should be a gradual decline in
| | field strength towards/from that center of gravity. Undetectable
| | change until the outer ring of the burst is over a significant arc to
| | us = no wave (detectable = Ligo wont work for Sn
|
| 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.
|
| I could never understand how it was generally accepted that the earth
| was EVER flat. As a teenager, standing atop a hill by the sea, with a
| straight edge, the curve was very obvious! I understand the
| Phoenecians or someone worked out a pretty good earth size that way
| thousands of years BC. How did that get lost? Religious persecution?

Ask Columbus. I'm sure some of his deck hands were concerned about falling
off the edge if they went far enough west.
But seriously, The curvature of the Earth and its spherical nature was know
to the ancient Greeks from seeing recognizable stars from the bottom of a
well and the shadow of the Earth eclipsing the Moon, and from Navigators who
used Polaris to find latitude. Longitude is far more difficult, you need an
accurate time piece set to London (Greenwich) time to know how far East or
West you are from London. GPS still uses that convention.

|
|
| |
| | If you want to express the problem mathematically: let delta be the
| smallest
| | amplitude detectable by the instrument used.
| | Let a pulse (or wave) of amplitude A be emitted at 0 and the
amplitude
| at r
| | where the instrument is placed be A/r^2 = delta.
| | Then the amplitude at A/(r+epsilon)^2 (epsilon 0) is less than
delta
| and
| | is not detectable.
| | LIGO has a real delta, so from that estimate the greatest imaginable
A
| and
| | calculate
| | A/r^2 = delta
| | r^2/A = 1/delta
| | r = sqrt(A/delta)
| |
| | Androcles.
| |
| | Don't math me :-(
| |
| | Jim G
| | c'=c+v -- don't math me. :-)
| Androcles
|
| For Eric: "Every action has an equal and opposite reaction"
| Newton says so, and so do I!
|
| Classical gravity: drop an object down the side of a vertical
| building, and observe the curved path. Pass photons by the sun, and
| observe the curved path.
|
| Jim G
| c'=c+v


  #73  
Old August 25th 04, 02:08 AM
Eric Gisse
external usenet poster
 
Posts: n/a
Default

On Tue, 24 Aug 2004 20:07:17 GMT, "Androcles"
wrote:


"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?).
|
|
| daveL

You'd really need to ask Jim that. You have my response to him (above)
confused with his statement x' = c+v.

However, I will state that the vector addition of velocities, c+v, is used
by Einstein in his equation
½[tau(0,0,0,t)+tau(0,0,0,t+x'/(c-v)+x'/(c+v))] = tau(x',0,0,t+x'/(c-v))


[snip]

Why do you insist on keeping the difficult notation? Trim out the
zeros and simplify the damn thing. You might learn something.
  #74  
Old August 25th 04, 02:23 AM
Eric Gisse
external usenet poster
 
Posts: n/a
Default

On 24 Aug 2004 16:55:37 -0700, (Jim
Greenfield) wrote:

"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.


Momentum is still conserved in relativity, but not if you use
classical mechanics...

Why are you mixing classical mechanics and relativity?


Jim G
c'=c+v


daveL



  #75  
Old August 25th 04, 04:31 PM
Volker Hetzer
external usenet poster
 
Posts: n/a
Default


"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
  #76  
Old August 25th 04, 05:45 PM
Androcles
external usenet poster
 
Posts: n/a
Default


"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.
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





Androcles



  #77  
Old August 25th 04, 06:09 PM
Dave
external usenet poster
 
Posts: n/a
Default

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.
Try moving through air toward a sound source such as a fire siren.
Relatively, the source is moving toward you. All speed is relative.


The speed of sound through air doesn't depend on the speed of the source or
the detector, but the detected frequency depends on the speed of both the
source and the detector.


DaveL


  #78  
Old August 25th 04, 06:16 PM
Volker Hetzer
external usenet poster
 
Posts: n/a
Default


"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.

So, how does a supersonic aircraft manage to outfly its own engine noise?

Lots of Greetings!
Volker
  #79  
Old August 25th 04, 06:39 PM
Androcles
external usenet poster
 
Posts: n/a
Default


"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.
Androcles



  #80  
Old August 26th 04, 12:59 AM
Jim Greenfield
external usenet poster
 
Posts: n/a
Default

Eric Gisse wrote in message . ..
On 24 Aug 2004 16:55:37 -0700, (Jim
Greenfield) wrote:

"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.


Momentum is still conserved in relativity, but not if you use
classical mechanics...

Why are you mixing classical mechanics and relativity?


"Adding velocities" using slopes (graphs with d/t), ignores the fact
that placing one slope on the other (x axis onto hypotenuse), is
CHANGING the DIRECTION; the added body's velocity is NO LONGER in the
same direction.
Therefore, unless you are only considering massless objects
velocities, a force has been ignored which would have been required to
bring about that change of direction.
So whether SR or any other system uses this method of adding
velocities, it is wrong= false results .

Jim G
c'=c+v
 




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