Page 2 of 8 FirstFirst 1234 ... LastLast
Results 31 to 60 of 235

Thread: Gravitational Wave Rumors Rumble Social Media

  1. #31
    Join Date
    May 2003
    Posts
    6,084
    Quote Originally Posted by StupendousMan View Post
    From the LIGO paper itself (which you can read for free at http://journals.aps.org/prl/pdf/10.1...ett.116.061102)
    Thanks, that's great to see. The graphs on page 2, comparing the actual strain data to a theoretical prediction from general relativity, are really very pretty.
    Conserve energy. Commute with the Hamiltonian.

  2. #32
    Join Date
    Jun 2002
    Posts
    1,989
    So, when's the announcement that ESA is moving up the launch date of eLISA?

  3. #33
    Join Date
    Aug 2003
    Location
    The Wild West
    Posts
    9,443
    Quote Originally Posted by StupendousMan View Post
    From the LIGO paper itself (which you can read for free at http://journals.aps.org/prl/pdf/10.1...ett.116.061102)
    What a paper! An instant classic.
    Everyone is entitled to his own opinion, but not his own facts.

  4. #34
    Join Date
    Oct 2004
    Posts
    517
    Soon to be cited like a gazillion times.

    I wonder why they published in PhysRevLett and not Science.

    My best guess: Science would never have allowed open access to the paper.

    Well, off to read it now.

  5. #35
    Join Date
    Jun 2005
    Posts
    13,858
    Quote Originally Posted by trinitree88 View Post
    Grey. That's cool indeed. I'll extend that confirmation to predict that a search of the neutrino detector database...IMB, SuperKamiokande, etc. will yield a 5 sigma coincidence of events with the timing of the seen BH merger. Betting a hot fudge sundae, three scoops, whip cream, and three cherries on top. pete
    That's certainly an interesting idea. In fact, since it was apparently a billion light years away, the arrival of a neutrino flux might give us an idea about the speed of neutrinos.
    As above, so below

  6. #36
    Join Date
    May 2008
    Location
    The Netherlands
    Posts
    15,384
    I'm at page 3 and already trying to visualize how enormously massive this event must be.. 70 solar masses worth of black hole rotating around each other 75 times per second in the space of the country I live in. And then merged in what looks to us to be half a second. Blink and you miss it.
    ____________
    "Dumb all over, a little ugly on the side." -- Frank Zappa
    "Your right to hold an opinion is not being contested. Your expectation that it be taken seriously is." -- Jason Thompson
    "This is really very simple, but unfortunately it's very complicated." -- publius

    Moderator comments in this color | Get moderator attention using the lower left icon:
    Recommended reading: Forum Rules * Forum FAQs * Conspiracy Theory Advice * Alternate Theory Advocates Advice

  7. #37
    Join Date
    Aug 2003
    Location
    The Wild West
    Posts
    9,443
    Quote Originally Posted by slang View Post
    I'm at page 3 and already trying to visualize how enormously massive this event must be....
    An energy release (in gravitational waves) equivalent to about (200 solar masses * c2) per second! I guess that's how, after rippling through about a billion lightyears of space, we could still detect it. I wonder how the neighbors fared.
    Everyone is entitled to his own opinion, but not his own facts.

  8. #38
    Join Date
    Oct 2004
    Posts
    517
    https://dcc.ligo.org/LIGO-P1500213/public

    Here's the LIGO page for the paper. I also contains links to a bunch of other papers offering more details. All these papers are open access (at least in their LIGO preprint versions).

    Anyway. Finished it.

    Wow.

    There's a special feeling to reading a paper that is likely to still be cited a hundred years from now, on the day it is published. The first of its kind, and all that. A moment of magnitude comparable to the 1919 report of how the Sun bent starlight following GR's rules, comparable to Hubble's discovery of the expanding Universe, to the discovery of the CMB... In this century, I guess only the Higgs boson compares.
    Last edited by Don Alexander; 2016-Feb-11 at 10:01 PM.

  9. #39
    Join Date
    Oct 2005
    Posts
    26,823
    Quote Originally Posted by trinitree88 View Post
    Grey. That's cool indeed. I'll extend that confirmation to predict that a search of the neutrino detector database...IMB, SuperKamiokande, etc. will yield a 5 sigma coincidence of events with the timing of the seen BH merger. Betting a hot fudge sundae, three scoops, whip cream, and three cherries on top. pete
    I'll take that bet-- LIGO thinks the source is 1.3 billion light years away. Not gonna get neutrinos from that.

  10. #40
    Join Date
    May 2008
    Location
    The Netherlands
    Posts
    15,384
    Did I understand correctly that they estimate this sort of thing happening once every few years in a supercluster of galaxies, or less?
    ____________
    "Dumb all over, a little ugly on the side." -- Frank Zappa
    "Your right to hold an opinion is not being contested. Your expectation that it be taken seriously is." -- Jason Thompson
    "This is really very simple, but unfortunately it's very complicated." -- publius

    Moderator comments in this color | Get moderator attention using the lower left icon:
    Recommended reading: Forum Rules * Forum FAQs * Conspiracy Theory Advice * Alternate Theory Advocates Advice

  11. #41
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    21,884
    Quote Originally Posted by slang View Post
    Did I understand correctly that they estimate this sort of thing happening once every few years in a supercluster of galaxies, or less?
    Some rumors have indicated that three to five such events have been observed since September, the rumors haven't given quality of signal information about the others, but it appears this is a several times a year kind of event.
    Forming opinions as we speak

  12. #42
    Join Date
    Jun 2008
    Posts
    718
    Quote Originally Posted by Ken G View Post
    I'll take that bet-- LIGO thinks the source is 1.3 billion light years away. Not gonna get neutrinos from that.
    Why not?
    “Of all the sciences cultivated by mankind, Astronomy is acknowledged to be, and undoubtedly is, the most sublime, the most interesting, and the most useful. For, by knowledge derived from this science, not only the bulk of the Earth is discovered, but our very faculties are enlarged with the grandeur of the ideas it conveys, our minds exalted above their low contracted prejudices.” - James Ferguson

  13. #43
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    21,884
    Quote Originally Posted by Fiery Phoenix View Post
    Why not?
    Well, the idea is that there wouldn't be a high likelihood of one being detected from the event. This was perhaps 10,000 times as far away as SN1987A, which was the only event with any significant number of neutrinos detected, so it would need to have generated 100 Million times as many neutrinos to be detected in the same way ... but also, two merging black holes don't need to generate neutrinos anyway.
    Forming opinions as we speak

  14. #44
    Join Date
    Sep 2005
    Posts
    564
    Biosci here, i have not posted for some time and have a question regarding LIGO.

    In all the descriptions of how LIGO detects gravitational waves that I have seen, they talk about length changes (from the passing gravitational wave) resulting in changes in the time for the beams to traverse the instrument but I do not recall discussions regarding gravitational wave effects on time and how that may effect the speed of the laser beams.

    Would such time effects add to or reduce the ability to detect length changes?

    Thanks!

    Biosci

  15. #45
    Join Date
    May 2008
    Location
    The Netherlands
    Posts
    15,384
    Quote Originally Posted by antoniseb View Post
    Some rumors have indicated that three to five such events have been observed since September, the rumors haven't given quality of signal information about the others, but it appears this is a several times a year kind of event.
    Wikipedia lists 8 superclusters as "near", and a twenty'ish more as "distant" with one at z=0.06. The paper says:

    These observational results constrain the rate of stellarmass
    binary black hole mergers in the local universe. Using
    several different models of the underlying binary black hole
    mass distribution, we obtain rate estimates ranging from
    2–400 Gpc−3 yr−1 in the comoving frame
    I think I read in one of the cited papers something like 1 Gpc-3 yr-1 as a high frequency estimate. Superclusers are OOM 100 million ly?

    So putting together several tentative detections in a year, and 30'ish "local" superclusters... oh wait, I'm mixing parsecs and lightyears. Why is this so difficult, and not easy like computers?
    ____________
    "Dumb all over, a little ugly on the side." -- Frank Zappa
    "Your right to hold an opinion is not being contested. Your expectation that it be taken seriously is." -- Jason Thompson
    "This is really very simple, but unfortunately it's very complicated." -- publius

    Moderator comments in this color | Get moderator attention using the lower left icon:
    Recommended reading: Forum Rules * Forum FAQs * Conspiracy Theory Advice * Alternate Theory Advocates Advice

  16. #46
    Join Date
    Jun 2002
    Posts
    1,989
    Quote Originally Posted by SRH View Post
    Site detection separation was 7 milleseconds, btw
    Light, and presumably gravity, would travel 1260km in that time and distance (great circle) between the two detectors is about 3040 km. so they must have a fairly decent circle in the sky to look along. Perhaps we'll get lucky and someone will have pix of the afterglow.
    Last edited by Squink; 2016-Feb-12 at 04:13 PM.

  17. #47
    Join Date
    Jan 2014
    Location
    Klang, Malaysia
    Posts
    7,608
    India claims some credit in the detection of gravity waves.

    http://www.business-standard.com/art...1200053_1.html

    Indian scientists played a crucial role, including in-data analysis, in the path-breaking project for the detection of gravitational waves, or ripples in space-time, which Albert Einstein predicted a century ago.

    Several institutes, including Institute of Plasma Research (IPR) Gandhinagar, Inter University Centre for Astronomy and Astrophysics (IUCAA), Pune, and Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, were involved in the research.

    The announcement of detection of gravitational waves was made simultaneously at IUCAA, Pune, and by scientists in Washington DC, USA.

  18. #48
    Join Date
    Mar 2004
    Location
    Ocean Shores, Wa
    Posts
    5,648
    Quote Originally Posted by selvaarchi View Post
    India claims some credit in the detection of gravity waves.

    http://www.business-standard.com/art...1200053_1.html
    Very appropriate, given how much has been invested in this enormous project.

    The clarity is stunning; and as Don intimated, eye opening in that the resolving power is only about a factor of five greater than the previous version of LIGO. This is such a clear signature that over-time (1-6 years) we should see many events; and quickly determined if this is an unexpected artifact.

    - it sure looks like the real McCoy- .
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  19. #49
    Join Date
    Mar 2004
    Location
    Ocean Shores, Wa
    Posts
    5,648
    Quote Originally Posted by SRH View Post
    I hope they accounted for solar flare interference...

    http://www.spaceweather.com/images20...q47kpq90k0q6p2
    Wow. Check out the shape of the aurora waves on 15 September.

    http://www.spaceweather.com/archive....h=09&year=2015

    That is just what many would expect a pair of collapsing black holes to look like.
    “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.” ― Arthur Conan Doyle, Sherlock Holmes

  20. #50
    Join Date
    Jun 2005
    Posts
    1,759
    So the gravitational waves exist.
    What are the expectations regarding them?


    * Would they penetrate matter undisturbed?
    * Would they have different speeds in different media like electromagnetic waves?
    * Would they refract or interfere wavelike?
    * Would gravitational lensing bend their path?


    Thanks in advance.

  21. #51
    Join Date
    May 2003
    Posts
    6,084
    Quote Originally Posted by a1call View Post
    * Would they penetrate matter undisturbed?
    There should be some interaction, but just like it takes enormous masses moving quickly to create measurable gravitational waves in the first place, it would similarly take a very large mass to have a noticeable effect on an existing wave.

    Quote Originally Posted by a1call View Post
    * Would they have different speeds in different media like electromagnetic waves?
    I think the answer should be yes, but with the gravitational interaction so much weaker than the electromagnetic interaction, I think there would be very little difference between the "gravitational index of refraction" of empty space and that of anything but extremely dense objects. So, travelling through a neutron star might have some effect, but passing through the Earth would probably have an unmeasurably small effect.

    Quote Originally Posted by a1call View Post
    * Would they refract or interfere wavelike?
    They should, but again, actually observing this would be a lot harder than just observing the waves in the first place. We usually observe refraction or interference by working with a continuous source of light and seeing how it changes, and it seems unlikely that we could find a source like that for gravitational waves.

    Quote Originally Posted by a1call View Post
    * Would gravitational lensing bend their path?
    It should, since gravity curves spacetime, which affects everything travelling through it. Gravitational waves should be affected in the same way as light.
    Conserve energy. Commute with the Hamiltonian.

  22. #52
    Join Date
    Jun 2005
    Posts
    1,759
    Thank you very much Grey.

  23. #53
    Join Date
    Jun 2005
    Posts
    1,759
    Could we consider gravity a gravitational wave with a frequency of 0?
    And expect it to behave as a gravitational wave with an infinitely low frequency?
    Would all this explain the "Allais effect":


    After analysis of Foucault pendulum data during the solar eclipse of July 11, 1991, L. Savrov suggested that the "pendulum responded to the remanent shock wave at the maximum of the total eclipse phase".[13]
    https://en.m.wikipedia.org/wiki/Allais_effect


    Or is the gravitational wave observed too weak to account for such anomalies?

  24. #54
    Join Date
    May 2003
    Posts
    6,084
    Quote Originally Posted by a1call View Post
    Could we consider gravity a gravitational wave with a frequency of 0?
    And expect it to behave as a gravitational wave with an infinitely low frequency?
    Would all this explain the "Allais effect":

    Or is the gravitational wave observed too weak to account for such anomalies?
    Gravitational waves from the Earth-Sun system would be much too weak to measure without equipment that is orders of magnitude more sensitive than LIGO. Also, reading the Wikipedia article, it's not clear that the Allais Effect has been conclusively demonstrated to exist at all. So before we go looking for an explanation, we'd probably want to verify that there's something that needs explaining.
    Conserve energy. Commute with the Hamiltonian.

  25. #55
    Join Date
    Jun 2005
    Posts
    1,759
    Agreed. Thank you again for your replies Grey.

  26. #56
    Join Date
    Feb 2005
    Location
    Boulder, Colorado
    Posts
    6,269
    Just want to join in and say how cool this detection is!
    My travel blog Mostly about riding a motorcycle across the US and Europe. Also has cool things that happen in between.

  27. #57
    Join Date
    Dec 2009
    Location
    Oklahoma City
    Posts
    448
    Quote Originally Posted by Cougar View Post
    An energy release (in gravitational waves) equivalent to about (200 solar masses * c2) per second! I guess that's how, after rippling through about a billion lightyears of space, we could still detect it. I wonder how the neighbors fared.
    So I read ~3 solar masses of energy went into the wave. What are the effects on local matter, excluding peripheral EM radiation to the event?

    What is the minimal safe radius for human-like life?

    What is the chunky salsa radius?

  28. #58
    Join Date
    Oct 2004
    Posts
    517
    Quote Originally Posted by Grey View Post
    It should, since gravity curves spacetime, which affects everything travelling through it. Gravitational waves should be affected in the same way as light.
    The latter actually leads to an interesting thought: If the GW signal were lensed, would this lead to a higher mass estimation for the black holes?

    On the other hand, if the redshift estimation is correct, lensing is very unlikely to have taken place, even if there were an intervening mass, the lensing would be small.

  29. #59
    Join Date
    Aug 2003
    Location
    The Wild West
    Posts
    9,443
    Quote Originally Posted by JCoyote View Post
    So I read ~3 solar masses of energy went into the wave.
    Right, sorry. I was reading at page 7 of the paper - it's the peak gravitational wave luminosity that's equivalent to about 200 solar masses times c2 per second.

    Quote Originally Posted by JCoyote View Post
    What are the effects on local matter, excluding peripheral EM radiation to the event?

    What is the minimal safe radius for human-like life?

    What is the chunky salsa radius?
    All good questions. The wave "strength" has to drop off exponentially, I expect.
    Everyone is entitled to his own opinion, but not his own facts.

  30. #60
    Join Date
    Jul 2012
    Posts
    308
    Why would the merging of 2 black holes of approximately 70 solar masses in total only give a detectable signal in the last 0.5 seconds of the merger, and not for the 5 minutes before, or even 10,000 years before, and up to the merger?

    How many times per second were these black holes spinning around each other, say 30 seconds before the merger?

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •