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Gravity Waves

gravity waves

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15 replies to this topic

#1 A941

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Posted 11 February 2016 - 06:32 PM


Just read it in the News: Gravity Waves have been proven to exist.



#2 Lazarus Long

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Posted 11 February 2016 - 08:17 PM

https://au.news.yaho...t-100-years-on/

 

http://www.space.com...-raw-video.html



#3 Antonio2014

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Posted 11 February 2016 - 09:57 PM

Congratulations to the whole LIGO collaboration! This is a historical discovery!



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#4 shifter

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Posted 12 February 2016 - 03:27 AM

How can we apply this knowledge to the real world? ie Can we advance any technology from it? Could we make our own waves and ride them like a surf board throughout space or something? I'm hearing how we proved a theory correct but want to know what we can now do knowing this knowledge. :)

Do these waves created extend outwards like a ripple in a pond? (but in space it would be spherical).

#5 Antonio2014

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Posted 12 February 2016 - 08:31 AM

Why should every knowledge have immediate applications? It's not enough to have opened a new window to the universe?

 

http://www.nature.co...NEWS_1508_RHBox


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#6 A941

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Posted 14 February 2016 - 09:55 PM

What does this say about Quantumphysics?



#7 Rocket

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Posted 26 February 2016 - 03:05 AM

The thing that gets me,is the number of physicists that buy into the whole premise of quantum gravity, gravitons, and the belief that gravity is just another force like the nuclear weak force that is mediated by particles. These physicists.... To them Einstein's GR and the idea that the force of gravity is caused by the geometry of space (and time) is as wrong as is the idea that the sun revolves around the earth. Yeah string theory is a neat idea, but it seems to be just a set of mathematics that gives a really good approximatation of the world, but it offers no proof, cannot be tested, and makes dumb predictions like with the gravitons and like spacetime is 26 dimensions... It gets really hoaky! Its really sad to see so many physicists and even the whole branch of science itself going down this dead end rabbit hole.
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#8 Antonio2014

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Posted 26 February 2016 - 07:41 AM

Unlike the force carriers of the other forces, gravitation plays a special role in general relativity in defining the spacetime in which events take place. In some descriptions, matter modifies the 'shape' of spacetime itself, and gravity is a result of this shape, an idea which at first glance may appear hard to match with the idea of a force acting between particles.[9] Because the diffeomorphism invariance of the theory does not allow any particular space-time background to be singled out as the "true" space-time background, general relativity is said to be background independent. In contrast, the Standard Model is not background independent, with Minkowski space enjoying a special status as the fixed background space-time.[10] A theory of quantum gravity is needed in order to reconcile these differences.[11] Whether this theory should be background independent is an open question. The answer to this question will determine our understanding of what specific role gravitation plays in the fate of the universe.[12]

 

[...]

 

In physics, the graviton is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory. If it exists, the graviton is expected to be massless (because the gravitational force appears to have unlimited range) and must be a spin-2 boson. The spin follows from the fact that the source of gravitation is the stress–energy tensor, a second-rank tensor (compared to electromagnetism's spin-1 photon, the source of which is the four-current, a first-rank tensor). Additionally, it can be shown that any massless spin-2 field would give rise to a force indistinguishable from gravitation, because a massless spin-2 field must couple to (interact with) the stress–energy tensor in the same way that the gravitational field does. Seeing as the graviton is hypothetical, its discovery would unite quantum theory with gravity.[4] This result suggests that, if a massless spin-2 particle is discovered, it must be the graviton, so that the only experimental verification needed for the graviton may simply be the discovery of a massless spin-2 particle.[5]

 

https://en.wikipedia.org/wiki/Graviton


Edited by Antonio2014, 26 February 2016 - 07:42 AM.


#9 albedo

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Posted 28 February 2016 - 12:48 PM

What does this say about Quantumphysics?

 

Congratulations LIGO/VIRGO!

 

I stand with the quote from Antonio from wikipedia. IMHO, the huge range of distances GR is now proved right reinforces me believing diffeomorphic invariance and background independence, both of which GR underlies at fundamental level, need to be taken very seriously in any theory of quantum gravity, e.g. see Rovelli's et al. Loop Quantum Gravity approach. Eventually even String Theory, which comes rather from the particle physics camp (vs. GR) where quantum fields evolve in a predefined space-time background (be it flat or curved) will get to somehow merge with LQG. At the end, gravity looks "predicted" by ST (together with a grand unification of forces which is not the ambition of LQG) and the two approaches need to converge in something more general describing Nature. Lot of very smart people are working in that direction.
 



#10 Rocket

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Posted 29 February 2016 - 02:43 AM

Some people are very good at cut and paste, but have never done the roll up your sleeves work. Polly want a cracker. Polly want a cracker.
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#11 A941

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Posted 01 March 2016 - 05:12 AM

Another interessting question I have about gravity waves:

Since gravity can not be blocked out do you think it is possible that some advanced civilization has decided to use this sort of waves to communicate with others?

 

What would be necessary to do so?

Many celestial bodies which can be manipulated to create "unnatural" patterns while moving in a way which should not be possibel?



#12 Antonio2014

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Posted 01 March 2016 - 08:10 AM

What would be necessary to do so?

 

Huge amounts of energy. Better use neutrinos or some similar particle. Also, neutrinos can be beamed.



#13 Rocket

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Posted 02 March 2016 - 03:03 PM

Another interessting question I have about gravity waves:

Since gravity can not be blocked out do you think it is possible that some advanced civilization has decided to use this sort of waves to communicate with others?

 

What would be necessary to do so?

Many celestial bodies which can be manipulated to create "unnatural" patterns while moving in a way which should not be possibel?

 

No.

 

The question of communication across LY distances has the same answer as FTL travel: active manipulation of wave function collapse. 


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#14 Lazarus Long

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Posted 13 August 2016 - 12:48 PM

Here is a video that models the principle behind gravity waves quite well and perhaps will help visualize gravity better for some.  One aspect I differ on is that I think the assumption that gravity is a form of energy is suspect.  If Einstein is correct the wave phenomenon is an effect of distorted space/time, not the cause of the distortion.

 

Gravity waves


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#15 albedo

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Posted 13 August 2016 - 02:39 PM

Here is a video that models the principle behind gravity waves quite well and perhaps will help visualize gravity better for some.  One aspect I differ on is that I think the assumption that gravity is a form of energy is suspect.  If Einstein is correct the wave phenomenon is an effect of distorted space/time, not the cause of the distortion.

 

Gravity waves

 

I did not watch the video but feel you are both correct and here is probably the beauty and difficulty to understand Einstein’s General Relativity (GR) and use it.

 

It depends how you look at the GR’s field equation, which is mathematically equaling, in appropriate units, the Einstein’s G tensor (usually on the left side), built from the space-time curvature (which, in the Einstein's vision, is gravity) to the stress-energy tensor T (usually on the right side). The energy (density) is the 00 component of T.  So in that sense I think you can say gravity (on the left side) is a form of energy (on the right side)

 

In practice what you do is to measure what is in your space (which gives the components of T) and find the curvature, i.e. the metrics, or G, satisfying the equation. But exactly because of the equality, you can also try, as cosmologist do, to measure the curvature and infer the content of the universe, so distinguishing between different cosmological models.

 

I feel that is for the beauty. For the difficulty, that means that the field equations are intrinsically non-linear in that the “source” T determines G but G contributes also to the "source" T! That is difficult. You have different approaches one being, when studying how the gravitational waves propagate and which energy they carry, to linearize the equation and in first approach decompose the metric g in two parts, one being a non-curved (flat) tensor plus a term (usually called h) in which you solve the equations and which gives the physical properties of the waves such as their energy, momentum, polarization etc … which you can then measure experimentally.

 

The two Wikipedia articles might give a good starting point:

 

https://en.wikipedia...s–energy_tensor

https://en.wikipedia...vitational_wave



#16 albedo

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Posted 28 September 2017 - 12:14 PM

New detection of gravitational waves, this time from both the European and the US teams (3 detectors in all). This allowed a significant reduction of the location of the volume in space where the black holes merges occurred and also reportedly for the first time to probe the polarization of waves with important theoretical implications. Wonderful!

http://www.nature.co...SDAILY-20170927

The technical paper of the announcement is here:

https://dcc.ligo.org...814/public/main

 

(edit: spelling)


Edited by albedo, 28 September 2017 - 12:25 PM.





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