# Gravitational Waves Discovery Expected

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If they turn only gravitational mass into gravitational waves then they must be farther and farther. Do they lose kinetic energy for gravitational waves emission?

As they gain speed, I assume they would gain kinetic energy. But I have no idea if concepts like that can be applied so simply in this context.

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As they gain speed, I assume they would gain kinetic energy. But I have no idea if concepts like that can be applied so simply in this context.

Rotational Kinetic energy does not seem so simple

$KE = \frac{1}{2}m.v^2$

$RKE=I. \omega^2$

With I equalling approximating point mass I guess in this case

$RKE = m.r^2 \omega^2$

But of course

$v = \omega. r$

Which just leaves a factor of 2 which I seem to have lost

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The 'bottom' of a gravitational well is the lowest energy position.

Higher orbits are higher energy.

The fact that in our frame it seems like the infalling mass is gaining kinetic is irrelevant.

In its frame, it is in free fall and losing energy very quickly.

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The 'bottom' of a gravitational well is the lowest energy position.

Higher orbits are higher energy.

The fact that in our frame it seems like the infalling mass is gaining kinetic is irrelevant.

In its frame, it is in free fall and losing energy very quickly.

Losing potential energy very quickly and recieving kinetic energy. The kinetic energy is in a trap therefore it works like gravity is losing part of itself for gravitational waves emission.

Edited by DimaMazin
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Rotational Kinetic energy does not seem so simple

$KE = \frac{1}{2}m.v^2$

$RKE=I. \omega^2$

With I equalling approximating point mass I guess in this case

$RKE = m.r^2 \omega^2$

But of course

$v = \omega. r$

Which just leaves a factor of 2 which I seem to have lost

@Imatfaal - Try and write formulas for the following. Normally to lose orbital energy you need drag or reverse thrust. Gravitational energy is equivalent to that drag, so the orbital energy is converted to G-Rad and kinetic energy, whereas in normal orbital decay orbital energy is converted to drag (heat energy) and kinetic energy. You lose that orbital energy which has a component of gravitational potential energy in it, it is losing (reducing) that potential energy factor that is the source of the heat and kinetic and in this case G-radiation. There is the factor of 2 in those equations.

Edited by Robittybob1
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where

is the angular velocity is the moment of inertia around the axis of rotation is the kinetic energy https://en.wikipedia.org/wiki/Rotational_energy Where is factor 2 ?

Look at Wikipedia on Orbital energy. When I say factor of 2 it could even be 1/2 depending on which side of the equal sign you put it (as in the equation you highlighted). I'm not really sure what you are saying but I'll wait for Imatfaal's response.

[i might have even used the word "factor" mathematically correct for if 2 times something times some other thing = something else

2 is a factor of something else, in other words something else has a factor of 2. Please correct me if I'm wrong]

Edited by Robittybob1
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where

is the angular velocity is the moment of inertia around the axis of rotation is the kinetic energy https://en.wikipedia.org/wiki/Rotational_energy Where is factor 2 ?

You are completely correct - my initial equation was just wrong by a factor of 1/2 and that carried all the way through dunno how I missed that. Thanks

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Yees I read about it! I guess first time I saw some info on kingdom of universe fanpage, and thanks to that i'm here. Thanks for all explanation!

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Article suggests the LIGO black hole pair may have been produced by a single collapsing star. It says "if the star were spinning very rapidly, its core might stretch into a dumbbell shape and fragment into two clumps, each forming its own black hole."

So cool!

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Now it has been proven Gravity Waves exist , could we not do a much smaller experiment , a lot nearer home ? Say with 10 meter arms?

We could allow two steel balls to collide , one falling under gravity toward a much larger steel ball. And with a device not dissimilar to two pencils ( tubes ) at right angles , with some form of fibre optic detectors at the far ends , hand held detecting the ' Gravitational waves ' on an oscilloscope . After all ' c' the speed of light is quite slow , as demonstrated by reporters trying to discuss on T.V. , where the signal goes 40,000 miles return journey to the communication satellites. I think it would be orders of nanoseconds for the pencil type detector .

Last time I was through Pisa Airport , there was a steel ball a meter across swinging from the roof 50 feet above , celebrating Galileo . You could let a steel ball from a ball race , fall from above , and detect the 'Gravity Waves' with your hand held " Gravitometer " ?

Then we would not have to detect something super massive , coming from a massive distance , traveling for 1.3 billion years , so faint a signal as to require the large detector . ( now we know the Gravity Waves are there ) ?

Mike

Edited by Mike Smith Cosmos
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The gravity wave sensors were very sensitive to motion eg trucks going past etc. The sort of experiment you describe would tend to produce quite considerable ground shaking. It might be difficult to separate the two.

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The gravity wave sensors were very sensitive to motion eg trucks going past etc. The sort of experiment you describe would tend to produce quite considerable ground shaking. It might be difficult to separate the two.

My illustration of the large steel ball at Pisa, is slightly ' Tongue in cheek ' .

I am really asking , now that it has been established that there are Gravity Waves from some collision say of 'black holes or supernova collapse ' yet very far away in time and distance . . By the time , now it has reached us , it is very weak .

Surely now we know they are there , we could surely get the same if not better gravity waves , by looking NOW , more closer ( like a meter away ) and by a mass collision far less substantial say two (2) heavy metal spheres. And that the measuring device could ? Surely be at a much smaller scale ? Say a meter or two ?

Maybe I am wrong in my assumptions ?

Mike

Edited by Mike Smith Cosmos
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The problem is gravity is so weak, it's extremely difficult to distinguish a gravity wave from background interference. A mere vibration from any source can I interfere. (Vibration etc)

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The problem is gravity is so weak, it's extremely difficult to distinguish a gravity wave from background interference. A mere vibration from any source can I interfere. (Vibration etc)

I think I read the the movement on the 'arms' was some fraction of the size of a proton.

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The problem is gravity is so weak, it's extremely difficult to distinguish a gravity wave from background interference. A mere vibration from any source can I interfere. (Vibration etc)

What was the system doing in principle ,to distinguish their gravity wave from ( the two collapsing black holes ) from general interference ? Presumably their signal was very very small ?

And why could that not be used on the handheld version , I was describing above ?

Mike

Edited by Mike Smith Cosmos
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What was the system doing in principle ,to distinguish their gravity wave from ( the two collapsing black holes ) from general interference ? Presumably their signal was very very small ?

And why could that not be used on the handheld version , I was describing above ?

Mike

They spent oodles of cash and brainpower on isolating the measuring devices from their environment - none of this would be possible with handheld. The measurement was minuscule even with a huge set of arms - with a handheld it would be vanishingly small; the length of the arms allowed the effect to be measured over a larger area (length? volume?) and thus magnified.

Gravity is very weak compared to the other forces and even the nearby sources of decent gravity do not produce gravitational waves as they are not moving in a way which would do so. We can measure the gravity between two masses in a lab - but it is not something we are yet as good as we are for measuring other stuff; I think we still use a posh version of the torsion balance (ie an up to date Cavendish Experiment) which was first used in the 18th century. To get gravitational waves we need to be wither able to use the distortion of space over large distances or measure local gravity to a much much higher level than we can at present. There is a thread on communication by gravitational waves in speculations in which Janus gives an idea of the power required.

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Now it has been proven Gravity Waves exist , could we not do a much smaller experiment , a lot nearer home ? Say with 10 meter arms?

We could allow two steel balls to collide , one falling under gravity toward a much larger steel ball. And with a device not dissimilar to two pencils ( tubes ) at right angles , with some form of fibre optic detectors at the far ends , hand held detecting the ' Gravitational waves ' on an oscilloscope . After all ' c' the speed of light is quite slow , as demonstrated by reporters trying to discuss on T.V. , where the signal goes 40,000 miles return journey to the communication satellites. I think it would be orders of nanoseconds for the pencil type detector .

Last time I was through Pisa Airport , there was a steel ball a meter across swinging from the roof 50 feet above , celebrating Galileo . You could let a steel ball from a ball race , fall from above , and detect the 'Gravity Waves' with your hand held " Gravitometer " ?

Then we would not have to detect something super massive , coming from a massive distance , traveling for 1.3 billion years , so faint a signal as to require the large detector . ( now we know the Gravity Waves are there ) ?

Mike

"Whereas initial LIGO uses 25-cm, 11-kg, fused-silica test masses, the fused silica test mass optics for Advanced LIGO are larger in diameter (~34 cm) to reduce thermal noise contributions and more massive (~40 kg) to keep the radiation pressure noise to a level comparable to the suspension thermal noise. Compensation of the thermal lensing in the test mass optics (due to absorption in the substrate and coatings) is added to handle the much-increased power - of the order of 1 MW in the arm cavities."

There are 4 test masses in the system. So regular LIGO has 44 kg of just test masses. Advanced LIGO, 160 kg. Not really conducive to a handheld device. For most non-giants or titans.

Further, c is not slow. The signal from LIGO had oscillations that had a period of around ten milliseconds. If your separation is too small, I think you run into a problem of sampling too small a fraction of a full fringe in the time it takes the light to traverse the system. The LIGO test masses were separated by 4 km, so that has a round trip time of a few microseconds. That means vibrations at higher frequencies tend to get averaged out before the photons are detected, but for a smaller device you would be measuring that noise.

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"Whereas initial LIGO uses 25-cm, 11-kg, fused-silica test masses, the fused silica test mass optics for Advanced LIGO are larger in diameter (~34 cm) to reduce thermal noise contributions and more massive (~40 kg) to keep the radiation pressure noise to a level comparable to the suspension thermal noise. Compensation of the thermal lensing in the test mass optics (due to absorption in the substrate and coatings) is added to handle the much-increased power - of the order of 1 MW in the arm cavities."

There are 4 test masses in the system. So regular LIGO has 44 kg of just test masses. Advanced LIGO, 160 kg. Not really conducive to a handheld device. For most non-giants or titans.

Further, c is not slow. The signal from LIGO had oscillations that had a period of around ten milliseconds. If your separation is too small, I think you run into a problem of sampling too small a fraction of a full fringe in the time it takes the light to traverse the system. The LIGO test masses were separated by 4 km, so that has a round trip time of a few microseconds. That means vibrations at higher frequencies tend to get averaged out before the photons are detected, but for a smaller device you would be measuring that noise.

They spent oodles of cash and brainpower on isolating the measuring devices from their environment - none of this would be possible with handheld. The measurement was minuscule even with a huge set of arms - with a handheld it would be vanishingly small; the length of the arms allowed the effect to be measured over a larger area (length? volume?) and thus magnified.

Gravity is very weak compared to the other forces and even the nearby sources of decent gravity do not produce gravitational waves as they are not moving in a way which would do so. We can measure the gravity between two masses in a lab - but it is not something we are yet as good as we are for measuring other stuff; I think we still use a posh version of the torsion balance (ie an up to date Cavendish Experiment) which was first used in the 18th century. To get gravitational waves we need to be wither able to use the distortion of space over large distances or measure local gravity to a much much higher level than we can at present. There is a thread on communication by gravitational waves in speculations in which Janus gives an idea of the power required.

Very informative quotations , thank you.

I was of the mind that , it was not the gravitational mass , that was being picked up by LIGO , but rather the sudden change , say by collision or explosion , or disappearance of mass ( say by annihilation , black holes self distruction , sun supernova, etc ) , not the mere presence of mass and gravity . Is that not so?

I am not even sure what the gravity waves travel in? Is it in the matter side of free space or what ?

Ps.

I thought there was possibly some form of Fermion grid that pervaded space , and only responding to fermion style matter ( particles ) , and so propagating ' gravity waves ' ?

Leaving electromagnetism happy to do its business in nothingness as Boson style matter ( particles ) , propagating as light or Electromagnetic waves / photons ?

If there is some mechanical vibration present here somehow ( I cannot see that ) , or perhaps only here on earth with all our surrounding matter . Then my hand held detector ( being in my soft flesh body and hand will be well insulated from vibration .

I have been thinking in terms of the experiment , sometimes undertaken with plates at very small distances with atomic particles where minute forces are detected , with plates being pushed apart.

These I know are electrostatic ( I think ? ) . However I was thinking more in terms of the ' Gravitational Waves ' being measured at similarly very short distances , perhaps . Now we know they are there ?

But I am still not sure what the waves are in ?

I will go and study up ' Janus' discussion

Mike

Pps . I am still of the opinion the speed of light is reasonably slow ( time - astronomic - wise ) .

We do see reporters nearly tripping over themselves when conducting tv interviews with people abroad . The em waves move slowly enough to put a 2 second delay , by merely going some 22,000 miles up into space and back . I think I did the sums one day to see if I could set a pulse of Electro Magnetic wave off at one side of the lab and pick it up the other side . The delay was in nano seconds , which most oscilloscopes can cope with nanoseconds .

Also the image of the Pharos erecting the pyramids will barely be a quarter way in toward the centre of our Galaxy ( Milky Way ) . Let alone toward another Galaxy . By these measures ' c' is comparatively measurable ( slowish ) .

Edited by Mike Smith Cosmos
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Very informative quotations , thank you.

I was of the mind that , it was not the gravitational mass , that was being picked up by LIGO , but rather the sudden change , say by collision or explosion , or disappearance of mass ( say by annihilation , black holes self distruction , sun supernova, etc ) , not the mere presence of mass and gravity . Is that not so?

The system is shedding energy, so its mass ultimately decreases. That's the only way you are getting rid of the mass. The released energy is in the form of gravitational waves. The mere presence of mass and gravity doesn't require energy to be released anywhere close to that scale.

I am not even sure what the gravity waves travel in? Is it in the matter side of free space or what ?

Why do they have to travel "in" anything? EM radiation doesn't.

Ps.

I thought there was possibly some form of Fermion grid that pervaded space , and only responding to fermion style matter ( particles ) , and so propagating ' gravity waves ' ?

Gravity waves and gravitational waves are actually two distinct phenomena.

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...The em waves move slowly enough to put a 2 second delay , by merely going some 22,000 miles up into space and back . I think I did the sums one day to see if I could set a pulse of Electro Magnetic wave off at one side of the lab and pick it up the other side .

You aren't thinking of the extra distance the light signal travels through cables, time delays via switching and data processing etc as electrons. They travel at some fraction of the the speed of light. Add all those together and there's the reason for it being "slow".

Edited by StringJunky
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Gravity waves and gravitational waves are actually two distinct phenomena.

..

A) what is a Gravity wave

B) what is a gravitational wave

I thought Electro- Magnetic waves were able to exist and travel in nothing , because they were sort of self supporting .

Namely as electric field collapses to a minimum it induces a magnetic field to increase to a maximum. Then as the magnetic field collapses to a minimum it induces an electric field to increase to a maximum. Then all over again , and again and again . Like a skipping rope being flipped , except this is ' self flicking ' the wave moves off at ' c '.

Gravity does not have two states like E-M waves does it ? Or does it ?

So how can ' Gravity waves ' , travel in nothing , unless space is not nothing ?

Are we back to ' the rubber sheet' . Somehow by the presence of mass , the fabric of space time is disturbed into a new shape , which has the effect of other masses falling towards the mass causing the disturbance. Thus all of space time must be some form of field matrix . This is General Relativity is it not ?

Then as something by way of a large disturbance in a mass , waves move out across this field at ' c' . Is that what is supposed to be happening here , in this LIGO phenomenon.

If that is the case we should be able to probe that rubber sheet of fields right here 18 inches away from my face . If I poke it with some means . Then look at a position of a few millimetres away . If I am able to poke it , I should be able to detect the poke a few millimetres away .

What am I looking for to poke ?

Mike

You aren't thinking of the extra distance the light signal travels through cables, time delays via switching and data processing etc as electrons. They travel at some fraction of the the speed of light. Add all those together and there's the reason for it being "slow".

Yes you are probably right ! Sorry .

But even so the signal has to go , up and down , 44,000 miles . So at 186,000 miles per second . That makes a quarter of a second . So you are right the other delay must be in the system and cables.

Even so the signal will take a second to reach the moon , and from the Egyptian Pharos building the pyramids to today to reach barely a quarter of the distance to the centre of our Galaxy .

Mike

The following two POSTs by. STRANGE and STRING JUNKIE are very good . I do not want to meddle with these points right now , as I need to retire for the night . Take up tomorrow .

Edited by Mike Smith Cosmos
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A) what is a Gravity wave

An effect in fluid dynamics: https://en.wikipedia.org/wiki/Gravity_wave

B) what is a gravitational wave

The transmission of regular changes or ripples in the curvature of space-time: https://simple.wikipedia.org/wiki/Gravitational_wave

So how can ' Gravity waves ' , travel in nothing , unless space is not nothing ?

They travel through space-time. Whether you consider that to be "nothing" or not is a matter of semantics and not terribly relevant or helpful.

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..So how can ' Gravity waves ' , travel in nothing , unless space is not nothing ?

What things 'are' is of no consequence in science. All that matters is that those things have measurable parameters. What they were looking for WRT gravitational waves is changes in distance-with-time between the two arms at each of the two LIGO observatories.

LIGO's observatories are technically known as interferometers. Used in many scientific fields, interferometers merge two or more sources of light in order to create an interference pattern. Such patterns result from overlapping waves of light. When the peaks of two waves of light overlap, they combine to form a larger peak (constructive interference). In contrast, when the valley of one light wave overlaps with the peak of another light wave, the two waves cancel each other out (destructive interference). Interference patterns provide scientists with clues about the properties of the sources that emitted the light.

Within LIGO, the lasers beamed down its arms bounce back and are set to cancel each other out completely. As a result, no light reaches another LIGO component called a photodetector. If, however, a gravitational wave were to pass through the LIGO facility, it would stretch one detector arm and compress the other, throwing off this perfect destructive interference. Some light would then reach the photodetector. The pattern of this light would provide information about the changes the arms underwent, and thus reveal properties about the incident gravitational waves and their source.

http://www.kavlifoundation.org/how-ligo-works

Edited by StringJunky

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