Gravity waves detected for the first time ever

Discussion in 'Physics & Math' started by Plazma Inferno!, Jan 12, 2016.

  1. Beer w/Straw Transcendental Ignorance! Valued Senior Member

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    Off topic:

    You were bribing your professor?
     
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  3. danshawen Valued Senior Member

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    I paid tuition to the University of Maryland College Park in Fall 1970, part of it as a general state tuition scholarship awarded me by congressman Steny Hoyer.
     
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  5. danshawen Valued Senior Member

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    I would be interested in your opinion about whether gravity waves will be detected, but you don't need to if you don't want to. You see some of the responses a strong opinion can fetch. Should have probably stuck with my first response.
     
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  7. Beer w/Straw Transcendental Ignorance! Valued Senior Member

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  8. paddoboy Valued Senior Member

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    While that's true beery, re the original claim [they certainly over enthusiastically jumped the gun], it was also mainstream science that showed it to be in error with another experiment, Planck: I mean it wasn't some outstanding revelation from a science forum haunter, if you know what I mean. Although some may say that "I told you so"

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    sort of 2 bob each way bet.
    The bloke here who tweeted his tweet claiming that possibility is a reasonably credited and reputable cosmologist, but he could also be wrong.
    We just need to wait and see.

    BTW, what we are talking about is "direct detection" of gravity waves, which so far not withstanding this rumour, we do not have, but we do have evidence for GW with the Hulse-Taylor Pulsar system and data.
    http://www.astro.cardiff.ac.uk/research/gravity/tutorial/?page=3thehulsetaylor
     
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  9. danshawen Valued Senior Member

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    And for the record, I do not dispute or doubt the existence of gravity waves.
     
  10. danshawen Valued Senior Member

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  11. Q-reeus Valued Senior Member

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    Ignoring what I wrote earlier (and in previous threads on this topic), you again fall back to a fantasy scenario. No-one in the 'GW astronomy' community would ever consider searching for GW's in the light-years wavelength ballpark. Far too feeble and far too subject to noise in that band. Even for SMBH binaries. eLISA will look for those and other sources in the 0.1-100 mHz band. ALIGO/VIRGO etc. search in the ~ 1-10 kHz frequency band. Which is the expected region of interest for compact stellar mass binary mergers. How can you not be aware of that?
    Triangulation. More than one detector in use - as long planned to be the case.
    The actual practical utility of 'GW astronomy' is imo very limited even allowing for eventuality of actual GW detection. There are too many complicated unknowns re NS or WD internal structure, so only 'pure BH-BH' mergers would likely give 'clean' results, and only then if spin of both partners is accurately known ahead of merger event. Non-detection (my expectation based on very different reasoning to yours) otoh would force a drastic rethink.
    Someone already managed. My prediction is eLISA will be scrapped. Unless ALIGO et al deliver that is.
     
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  12. Schmelzer Valued Senior Member

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    So, fine, and now let's read what http://motls.blogspot.com/2016/01/ligo-rumor-merger-of-2-black-holes-has.html writes about what would be the expected origin of these gravitational waves:

    0.01 second of the orbit gives a wavelength of 0.01 light seconds, which are 3000 km. Which is already down to Earth. Now, the size of the devices is nonetheless much smaller, it is about 3 km. But they work with extremal accuracies:
     
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  13. danshawen Valued Senior Member

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    For the Hulse-Taylor (PSR B1913+16) binary, the orbital period is 7.75 (Earth) hours, so I will admit, you've got a solid argument against one of the reasons I gave as a justification that GWs will be hard to detect.

    https://en.wikipedia.org/wiki/PSR_B1913+16

    And since we have no information about whether the pulsar is tidally locked (a likely scenario) to whatever else is going on inside of the binary pair, detecting a faster oscillation would not necessarily rule out the idea that you have detected a GW originating from there. One or both masses could be rotating in other complex ways to produce GWs. Possibly this one of the best reasons for doing the current experiment, although no one here has yet mentioned it. It might tell us something about what is going on INSIDE of the EH of a black hole, something that is not supposed to be possible.

    There is no guarantee that this object will necessarily be the brightest object in the GW sky however. It's a very big sky, and we have no clue from visual observation what sorts of processes may be going on up there. So if the period of whatever GWs are detected are different from 7.75 hours, then what? It could take longer to identify the source of the GWs through optical or other means than it has already taken us to construct and test a more sensitive detector.

    And as for "How can I not be aware of that?":

    Orbiting bodies are only one process that might produce GWs. We know next to nothing about whether other processes like stellar convection:

    http://www.astro.utu.fi/~cflynn/Stars/l9.html

    could produce GWs as well. The masses which move interior to our own Sun account for the equivalent of thousands of Earth masses moving in small orbits in the interior of a massive body much closer to us than the Hulse-Taylor binary. And as far as I am aware, even GR models of gravity don't tell us anything about gravitational-thermal processes moving masses interior to a star. But if they did, we could predict things like solar mass ejections, couldn't we? That sounds like a more than marginally useful thing to investigate.

    For that matter, is LIGO as it has been configured now or during the last 10 years even been capable of detecting the GWs of the Earth-Moon system responsible for Earth's tides? That information can't (or shouldn't) be a deep, dark secret, should it? Unless it actually can't. The LHC can detect Earth's tides, and it wasn't even designed to do that.

    How can YOU not be aware of THAT? Don't you KNOW anything about the inverse square law? Or is that another law that applies to all other kinds of waves except for GWs? I kind of expect that if a local interferometer based GW detector would work for detecting much closer sources, we would already have seen lots of GWs using a less sensitive detector a very long time ago.

    So, now as far as I am concerned, there are several more reasons to expect this experiment will come up with another null, or at most a perplexing set of results.

    And THAT (not knowing) is the principle reason we do ANYTHING in science in the first place.
     
    Last edited: Jan 19, 2016
  14. Q-reeus Valued Senior Member

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    Too many non-requiters in that lot for me to go through one-at-a-time. So... The inferred GW emissions from Hulse-Taylor binary are of course detected as orbital decay and again no-one expects to ever directly detect GW emission from there. Even with a period of 7-8 hrs, predicted GW amplitudes way below detection threshold. Overwhelmingly it's just the dying moments of stellar mass binary merger events that LIGO & Co expect to detect emissions. That's when the bulk of the orbital energy is violently shed - presumed to appear as chirped GW's: http://www.ligo.org/science/GW-Inspiral.php
    Schmelzer comment re ~ 100Hz reminded me I was somewhat out (relying on hazy memory) as to ALIGO frequency band that probably goes down to around 30Hz or so:
    https://www.advancedligo.mit.edu/summary.html (fig.3)
    Which then almost nicely dovetails with the proposed eLISA bandwidth window. Between them eventually covering all told most of around eight orders of magnitude ~ 10^-4 to 10^4 Hz.
    As for other detectors of the resonant mass kind, some seem to think they are still viable but hard to see how given the inherent narrow bandwidths.

    You think convective turbulence in the sun acts like you say and could generate detectable GW's?! Then, assuming you have done some meaningful quantitative calculations to back up that notion - I suggest try contacting e.g. GWIC: https://gwic.ligo.org/index.shtml
    Please DO inform me of any feedback! Steel yourself Dan.
     
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  15. danshawen Valued Senior Member

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    Best post of the thread, Q-reeus Thanks.
     
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  16. PhysBang Valued Senior Member

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    Sure, but now they are not working in the manner you suggested. And what about a couple of machines that simply record the time when something was aligned with a certain point on a meter stick? How are we to use them to make a measurement? Can't we go back in their records and compare the times?

    I do not deny that we can use light to synchronize clocks; but if we are speaking purely of SR, then there must be some other means used to fix a distance before we can do this, even if it is an arbitrary assignation of coordinates. If you have a means of fixing distance before clock synchronization, or of synchronizing clocks before fixing distance, then please show us.

    If we are talking about the way a length contracts when we are merely considering a change of coordinate system, then it is clear that the contraction happens everywhere, since all points are subject to translation, and nowhere, since we are not changing any object, just the coordinate system used.

    If we are considering a body already in motion in a system of coordinates and looking at the electromagnetic (or other) relationships between its parts, then, we would see the effect of motion everywhere throughout that body.

    If we are talking about the contraction of a body as it is accelerated, then there are a number of factors that come into play, depending on what part of the body is accelerated first. But then we are speaking of a different problem than the translation of coordinates.

    There seems to be no problem here.
     
  17. The God Valued Senior Member

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    Nope, QM is not consistent with SR ? Where did you learn this ? Try Schrodinger equation. and of course do not come up with the obvious that it has a relativistic version. Only dirac, maxwell and gordon equations are within spacetime ambit.

    Moreover your first line is also bad, it conveys that people have problem reconciling with GR even though GR is consistent.
     
  18. PhysBang Valued Senior Member

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    I take the successful construction of quantum field theory to be the evidence that one can successfully use SR and QM.
    The real conflict between QM and relativity is, if one takes accepts the conflict, with GR. I did not introduce talk of the Standard Model, I merely responded to it; I assumed that danshawen was mentioning the problem of where to include a gravity particle within an expanded Standard Model.
     
  19. Schmelzer Valued Senior Member

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    This position is, of course, not unreasonable. It works, so to say, for all practical purposes.

    But it fails if one looks at the fundamental issues. To work, it needs renormalization. Renormalization works quite fine practically, but not conceptually. It needs regularization, but this regularization cannot be done in a completely Lorentz-covariant way. Then, after the renormalization procedure, one can take the limit to infinity, and the non-invariant cut is no longer visible. But this cut is necessary to obtain a reasonable theory. Then, it essentially computes only infinite limits - the scattering matrix. This is essentially all what one can measure - the human devices which measure the results of what happens in particle colliders are so large, in comparison with the particles themself, that the infinite limit is fine. But outside the infinite limit, the theory is not even well-defined (in particular, not gauge-invariant). Last but not least, there is Haag's theorem that there are no nontrivial quantum field theories. There have been found some quite artificial exceptions, ways to circumvent this theorem, but nonetheless none of these ways have been really relevant for the real world.

    And, of course, there is the violation of Bell's inequality in the background, which means you have to reject realism and causality - or to accept a preferred frame. So, QFT, which does not change a bit for this problem, is faced by the same dilemma: Or to be nor realistic (rejecting the EPR criterion of reality) nor causal (rejecting Reichenbach's common cause principle), or to live with a preferred frame.

    So, QFT is sufficient for everybody who follows the "shut up and calculate" ideology: Do not care about any fundamental problems. Else, it is not sufficient.
     
  20. danshawen Valued Senior Member

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    At the time the article was released, everyone seemed to be dissing this:

    http://www.extremetech.com/extreme/...stance-at-least-10000-times-faster-than-light

    But here is a more recent account of quantum entanglement experiments of the same type done by Dutch researchers:

    http://www.dailymail.co.uk/sciencet...oky-quantum-entanglement-phenomenon-real.html

    "Now, writing in the journal Nature, scientists say two of the most important loopholes have been closed by a new version of the test.
    The Dutch team entangled electrons held in tiny diamond traps 0.8 miles (1.3km) apart on opposite sides of the campus at Delft University."

    "Nature" is one of the gold standards of peer-reviewed scientific literature, if I understand the rough hierarchy of authority status of scientific publication. And the most recent experiment description bears a striking similarity to the first one.

    No part of the theory of relativity even hints of the possibility of information being transferred faster than light, and you can take that to the bank. Entanglement isn't going FASTER then light; what it is actually doing is remaining at rest relative to an inertialess quantum field. You still can't send bulk energy, whether it is bound like electrons in an atom, or unbound like a pair of entangled photons used in these experiments, any faster than the speed of light, but entanglement states may flip in the instant that is "NOW" everywhere in this inertialess quantum field once the entangled photons start arriving between locations you may wish to send an entangled message. Entanglement may not be absolute space or absolute time, but it does seems to have a definite origin "instant" of time itself built into whatever it does. NOT a time INTERVAL. We're talking about an instant of time with no measurable duration.

    I think it is the Higgs field that may be responsible for entanglement, but this is just a crank theory of mine based on the idea that the basis of time itself is sourced in the only quantum field that can transfer linear inertia at +/- c to rotational inertia at +/- c between bound and unbound forms of energy, by means of an excitation of that field which is the only known particle that has zero quantum spin. It is part of the theory of the Higgs mechanism that the Higgs field is entangled everywhere.

    And it does look as though, if we can communicate via entanglement, the next logical step technologically would be to develop a means for utilizing entanglement to synchronize clocks. This might make GPS clock synchronization easier than it currently is using periodic corrections to their respective time bases based on relativity's predictions of their time dilation.

    And since gravity wave energy causes time dilation, and because entanglement synchronized clocks would be a minimum 10,000 times more accurate than ones based on synchronization mechanisms limited by the speed of light, this might finally offer us a means to detect something that perturbs time dilation on scales comparable to those of a passing gravity wave, a prospect we can be reasonably certain Einstein himself never dreamed possible.

    Sometimes I worry my posts aren't quite "cranky" enough. Nah...
     
    Last edited: Jan 20, 2016
  21. danshawen Valued Senior Member

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    The accuracy you quoted (100,000 times smaller than a nucleus) bothered me until I found this:

    http://www.iflscience.com/physics/t...mic-scale-could-help-find-gravitational-waves

    Interesting reference. I've never imagined using vibrating squid mirrors in an interferometry setup to quiet things down. So that's why LIGO is so much more sensitive than it was before. They really pulled out all of the stops; they must be desperate.

    This definitely won't work.
     
  22. PhysBang Valued Senior Member

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    OK, stop.

    You are citing The Daily Mail.

    Sigh.

    Let's see what the actual journal article said?

    Fortunately, I have access.

    Hmm... nothing about information at all.

    Sure. But entanglement doesn't transmit information. And nothing in that article says that it does.
    So says you, with your vague fantasy physics. This doesn't help us understand anything.

    You need to read the basics of quantum information. One simply cannot use entanglement as you suggest.
    I agree, if we could communicate with entanglement, we should use it to synchronize clocks.

    https://en.wikipedia.org/wiki/No-communication_theorem

    http://curious.astro.cornell.edu/ab...-faster-than-light-communication-intermediate
     
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  23. danshawen Valued Senior Member

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    In a sense, what you say is correct. You supposedly cannot transmit information in an instant. So, go fix your definitions of information, because I think this might actually work. It requires BOTH entangled photons in order to transmit or assert a single state. Does this make sense?

    I don't wonder, Nature has a difficult time putting this in terms experts in the field will understand.
     
    Last edited: Jan 20, 2016

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