Proving gravity waves

trevor borocz johnson

trevor borocz johnson

Registered Senior Member
could gravity waves be proven by letting a large steel mass bounce on a spring above a weight measuring device and looking for the pattern of the mass's movement in the decimal range of the measuring instrument?
 
Then is their an instrument precise enough to measure the movement of a reasonably sized weight in the described experiment? I ve heard they have some really precise instruments.
 
trevor borocz johnson said:
Then is their an instrument precise enough to measure the movement of a reasonably sized weight in the described experiment? I ve heard they have some really precise instruments.
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To detect Gravitational Radiation one would certainly need very precise instruments...LIGO and LISA are two possibilities and there are probably others that may detect GR.
Still those GR to be detected from or near Earth, would need to be produced by planetary or stellar sized objects and remnants. eg: Colliding BH's, Neutron stars, White Dwarfs etc etc.
 
trevor borocz johnson said:
Well I wouldn't be looking for gravity waves from enormous events or masses at huge distances, I'm looking for local waves at a much smaller scale.
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That's what I'm getting at. I believe they would be impossible to detect at those scales.
Much like detecting time dilation and length contraction at 100kms/hr.
But I'm only an amateur, so someone may be able to enlighten more.
 
I guess the question is are seismic waves of what ever surface you put the scale on to loud to hear the gravity waves, if they were you could cause momentary free fall of the scale by attaching it to a slinky that is held up from a ladder and then let the slinky go causing the scale to sort of float for a moment
 
Gravity waves created anything less than binary colliding neutron stars and black holes are far too small too detect with our current technology. They get lost in the noise.

"This knowledge gap is primarily due to the massive presence of noise in the low frequencies where antennas currently operate. Gravitational waves are expected to have frequencies 10−16 Hz < f < 104."
https://en.wikipedia.org/wiki/Gravitational_wave#Difficulties_in_detection
 
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huh, well maybe its like trying to hear one guy whispering in a crowd of yelling drunk fans at a football game. The only way you could hear him is if you stuck your ear right in his face. Maybe if the measuring device was placed millimeters from the source of the gravity waves. The source doesn't have to be a bouncing spring mass either it could be any number of things: an explosion, a circulating loop system, machines, the IC engine, etc.. You could eliminate any disturbances from the atmosphere or seismic by enclosing the whole system in a vacuum and using the free fall slinky method or other free fall methods.
 
trevor borocz johnson said:
huh, well maybe its like trying to hear one guy whispering in a crowd of yelling drunk fans at a football game. The only way you could hear him is if you stuck your ear right in his face. Maybe if the measuring device was placed millimeters from the source of the gravity waves. The source doesn't have to be a bouncing spring mass either it could be any number of things: an explosion, a circulating loop system, machines, the IC engine, etc.. You could eliminate any disturbances from the atmosphere or seismic by enclosing the whole system in a vacuum and using the free fall slinky method or other free fall methods.
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We're talking about neutron stars here.

There may be ... logistical difficulties in getting to within a few millimetres of it, or by mounting it on springs.
 
DaveC426913 said:
Gravity waves created anything less than binary colliding neutron stars and black holes are far too small too detect with our current technology. They get lost in the noise.

"This knowledge gap is primarily due to the massive presence of noise in the low frequencies where antennas currently operate. Gravitational waves are expected to have frequencies 10−16 Hz < f < 104."
https://en.wikipedia.org/wiki/Gravitational_wave#Difficulties_in_detection
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what is the current technology for detecting gravity waves its not small changes in a capacitor is it?
 
When a gravitational wave passes through the interferometer, the space-time in the local area is altered. Depending on the source of the wave and its polarization, this results in an effective change in length of one or both of the cavities. The effective length change between the beams will cause the light currently in the cavity to become very slightly out of phase with the incoming light. The cavity will therefore periodically get very slightly out of resonance and the beams which are tuned to destructively interfere at the detector, will have a very slight periodically varying detuning. This results in a measurable signal. Note that the effective length change and the resulting phase change are a subtle tidal effect that must be carefully computed because the light waves are affected by the gravitational wave just as much as the beams themselves
https://en.wikipedia.org/wiki/LIGO

I have a basic understanding of lasers, that they use lenses to focus energy, it sounds like they're saying the space/time the beam is in is altered by the gravity wave and they detect the signal by vibrations in the light beam?
 
trevor borocz johnson said:
When a gravitational wave passes through the interferometer, the space-time in the local area is altered. Depending on the source of the wave and its polarization, this results in an effective change in length of one or both of the cavities. The effective length change between the beams will cause the light currently in the cavity to become very slightly out of phase with the incoming light. The cavity will therefore periodically get very slightly out of resonance and the beams which are tuned to destructively interfere at the detector, will have a very slight periodically varying detuning. This results in a measurable signal. Note that the effective length change and the resulting phase change are a subtle tidal effect that must be carefully computed because the light waves are affected by the gravitational wave just as much as the beams themselves
https://en.wikipedia.org/wiki/LIGO

I have a basic understanding of lasers, that they use lenses to focus energy, it sounds like they're saying the space/time the beam is in is altered by the gravity wave and they detect the signal by vibrations in the light beam?
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No experiment performed locally (only) can measure anything with respect to absolute space, nor absolute time, nor "curvature" of spacetime, any more than Michaelson-Morley could measure an aether wind using an interferometer. If you wish to measure a passing gravity wave anywhere, you would need to compare the passage of time locally with the passage of time somewhere sufficiently distant from the gravity wave that is passing so that a difference can be measured.

This does not mean that gravity waves cannot be detected and/or measured. I'm saying it cannot be measured locally using distance, time, velocity, or the speed of light local to a passing gravity wave as a metric. This used to be part of relativity 101. I have no idea where the idea somehow got lost.
 
For a time in my telecommunications career, I was involved in configuring tests with ground penetrating radar. The smallest object that is resolvable with radio or microwaves using ground penetrating radar is about 1/3 of a wavelength. I know this because during an early study, we constructed a corner reflector to test a 50 MHz GPR system.

If the same 1/3 wavelength rule applies to gravitational waves, a minimum separation of three times the diameter of the orbit of Jupiter with respect to the Sun would be required in order to measure any gravity waves which were the result of Jupiter's orbit about the Sun, because that is as far away as you would need to be to reliably measure one cycle of that gravity wave, AND it would require observations recorded over a span of time in excess of 400 YEARS to determine the magnitude of that particular gravity wave. Gravity waves may be there, but if they exist at all, the rate of change of a single cycle of any event or orbit producing them will fall somewhere between the limits of "at rest" and lethargic with respect to the time scale of any scientific measure on our scale of the passage of time.
 
danshawen said:
For a time in my telecommunications career, I was involved in configuring tests with ground penetrating radar. The smallest object that is resolvable with radio or microwaves using ground penetrating radar is about 1/3 of a wavelength. I know this because during an early study, we constructed a corner reflector to test a 50 MHz GPR system.

If the same 1/3 wavelength rule applies to gravitational waves, a minimum separation of three times the diameter of the orbit of Jupiter with respect to the Sun would be required in order to measure any gravity waves which were the result of Jupiter's orbit about the Sun, because that is as far away as you would need to be to reliably measure one cycle of that gravity wave, AND it would require observations recorded over a span of time in excess of 400 YEARS to determine the magnitude of that particular gravity wave. Gravity waves may be there, but if they exist at all, the rate of change of a single cycle of any event or orbit producing them will fall somewhere between the limits of "at rest" and lethargic with respect to the time scale of any scientific measure on our scale of the passage of time.
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The misinfo expressed above and in #16 was dealt with successively in two previous threads, the latter one: http://www.sciforums.com/threads/gravity-waves.152710/ p4 post #77 and on, also referred back to: http://www.sciforums.com/threads/ligos-new-ear-for-the-universe.152662/ - p1 post #9 and on. Groundhog Day till death then, Dan?
 
Q-reeus said:
The misinfo expressed above and in #16 was dealt with successively in two previous threads, the latter one: http://www.sciforums.com/threads/gravity-waves.152710/ p4 post #77 and on, also referred back to: http://www.sciforums.com/threads/ligos-new-ear-for-the-universe.152662/ - p1 post #9 and on. Groundhog Day till death then, Dan?
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To recap: paddoboy redirected my attention to the Hulse-Taylor experiment, still in progress, which demonstrates the existence and intensity of gravity waves alright, BUT THIS USES GENERAL RELATIVITY AND IS NOT BASED ON LOCAL INTERFEROMETRY TO REACH ITS CONCLUSIONS.

No one actually reads and understands my posts, and that has not changed. And I don't make this stuff up.
 
danshawen said:
To recap: paddoboy redirected my attention to the Hulse-Taylor experiment, still in progress, which demonstrates the existence and intensity of gravity waves alright, BUT THIS USES GENERAL RELATIVITY AND IS NOT BASED ON LOCAL INTERFEROMETYRY TO REACH ITS CONCLUSIONS.
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Translation: BNS orbital decay data can and has been numerically equated to standard linearized GR quadrupole GW emission formula, but there is to date no direct evidence via LIGO etc. We all know that. The extent to which such interferometry-based setups can be considered 'local' was discussed in those earlier threads. There have to actually be GW's there for the differential techniques to reveal any such - as discussed in those threads. Point is though your comments above are skew of the main misinfo appearing in #16 ('local' restriction), #17 (equating a hoped-for GW wavelength with some small multiple of the relevant planetary orbital size). Wrong, and wrong - as discussed in those earlier threads.
No one actually reads and understands my posts, and that has not changed. And I don't make this stuff up.
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Many I think actually read them, but agreed the understanding bit is often lacking. There are various possible reasons for the latter.:rolleyes:
 
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