tag:blogger.com,1999:blog-22973357.post7289726414553398286..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: OJ 287Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger20125tag:blogger.com,1999:blog-22973357.post-32570959485850325242010-04-13T02:14:07.820-04:002010-04-13T02:14:07.820-04:00Hi Phil,
Well, I wouldn't say stuff is "...Hi Phil,<br /><br />Well, I wouldn't say stuff is "drawn" into the singularity because the singularity doesn't exist on all space-like hypersurfaces, thus you could plausibly say it doesn't exist yet, so how can stuff be drawn into something that doesn't exist. It would be more accurate to say that all world-lines end in the singularity (see posts on causal diagrams) or Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66738641195574456312010-04-13T00:20:53.024-04:002010-04-13T00:20:53.024-04:00Hi Bee,
If we look at things simplistically, just...Hi Bee,<br /><br />If we look at things simplistically, just before a mass shrinks below its <a href="http://en.wikipedia.org/wiki/Schwarzschild_radius" rel="nofollow">Schwartzchild Radius</a>, the greatest gravitational force encountered would be what it is at the surface of the collapsing sphere, with the force diminishing to zero as one moves to the centre of the mass, since the pull of Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71223247902479522302010-04-12T14:45:14.718-04:002010-04-12T14:45:14.718-04:00What confused me Bee was the last bits: "we c...What confused me Bee was the last bits: "we call this surface the event horizon" which relates earlier in the sentence to "on the surface." It's a silly semantic thing Bee, I'm sorry for being a weenie on this, and hoo-boy I'm glad I was right as Black Holes ain't my current thing (but they will be soon ... I'm just re-remembering/studying that which I Steven Colyerhttps://www.blogger.com/profile/10435759210177642257noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-79093942915978428192010-04-12T14:10:44.975-04:002010-04-12T14:10:44.975-04:00Hi Steven,
What you say is correct. I don't k...Hi Steven,<br /><br />What you say is correct. I don't know what confused you about my sentence. The word "surface" doesn't imply there actually "is" something at this surface. Every point in space is on some surface. It's just a subset of points. (Every point "is" on some "holographic screen" harharharharhar.) Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-17376264048663246202010-04-12T14:08:59.904-04:002010-04-12T14:08:59.904-04:00I found that interesting, but one sentence in the ...I found that interesting, but one sentence in the first long paragraph confused me based on my understanding, possibly misunderstanding, of black holes:<br /><br /><i>If the gravitational force on the surface gets so strong not even light can escape, we call this surface an event horizon.</i><br /><br />Here is my confusion. Irrespective of what a black hole actually <i>is</i> (a singularity &Steven Colyerhttps://www.blogger.com/profile/10435759210177642257noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-11082306752692953572010-04-12T14:06:40.426-04:002010-04-12T14:06:40.426-04:00This comment has been removed by the author.Steven Colyerhttps://www.blogger.com/profile/10435759210177642257noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-84218297135489306402010-04-12T12:56:10.805-04:002010-04-12T12:56:10.805-04:00William: Stopped watching at 1:46. The defining pr...William: Stopped watching at 1:46. The defining property of a black hole is not the singularity but the horizon. <a href="http://backreaction.blogspot.com/2009/02/evidence-for-black-hole-event-horizon.html" rel="nofollow">You might find this interesting</a>. Apologies if that came later in the video. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25341576363131632772010-04-12T11:45:47.839-04:002010-04-12T11:45:47.839-04:00Phil, Bee, etal, have you seen these? ...
Black h...Phil, Bee, etal, have you seen these? ...<br /><br />Black holes don't exist: <a href="http://www.youtube.com/watch?v=A4GFAjX62Yg" rel="nofollow">http://www.youtube.com/watch?v=A4GFAjX62Yg</a><br /> <br /><br />A primer in important math concepts: <a href="http://www.youtube.com/watch?v=PSJjs4l_FHU" rel="nofollow">http://www.youtube.com/watch?v=PSJjs4l_FHU</a><br /><br />Besides making me Williamhttps://www.blogger.com/profile/15991841830350137397noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-73446109251043834492010-04-11T17:36:10.606-04:002010-04-11T17:36:10.606-04:00Hi tspin,
I read through the paper "Predict...Hi tspin,<br /><br /><br />I read through the paper "<a href="http://iopscience.iop.org/0004-637X/646/1/36/" rel="nofollow">Predicting the Next Outbursts of OJ 287 in 2006-2010</a>" today and was a bit disappointed that I couldn't find a very precise prediction - but this seems not to have been the point of that paper. Instead, it discusses in detail the complicated processes stefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-3177476632219185862010-04-11T17:27:37.901-04:002010-04-11T17:27:37.901-04:00William:
Actually, Kerr singularities are two-dim...William: <br />Actually, Kerr singularities are two-dimensional. <br /><br />The <i>three</i>-dimensional version would be the toroidal singularity at the heart of a (purely mathematical) toroidal black hole. A tbh has major-axis rotation keeping the ring open, and minor-axis rotation keeping the ring "fat". <br /><br />There've been some research papers on these beasties, but they&ErkDemon (Eric Baird)https://www.blogger.com/profile/00430413494529535159noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-14586534731426274392010-04-11T12:16:26.665-04:002010-04-11T12:16:26.665-04:00Hi Bee, thanks for clarification.
I just thought...Hi Bee, thanks for clarification. <br /><br />I just thought it unlikely they had enough data to predict next flare but not enough to detect energy loss due to GR waves. But if that's the case then ok.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-63926837923703929462010-04-09T21:34:00.238-04:002010-04-09T21:34:00.238-04:00Phil Warnell said... "However it is amazing r...<i>Phil Warnell said... "However it is amazing really just how far in the last while we’ve gone in understanding what not long ago Einstein said just couldn’t exist."</i><br /><br />Perhaps it was the 0-D, singularity, of no size at all but enormous mass which Einstein objected to? <br /><br />And isn't it true that a zero-dimensional object, aka singularity, can never be proved to Williamhttps://www.blogger.com/profile/15991841830350137397noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-77788122759687841722010-04-09T09:02:48.776-04:002010-04-09T09:02:48.776-04:00Regarding competing GR theories ....
MOND has all...Regarding competing GR theories ....<br /><br />MOND has allegedly been recently falsified.<br /><br />What about John Moffat's MOG, is that still in play? (This is a response to Uncle Al's reply, which got me thinking ...)Steven Colyerhttps://www.blogger.com/profile/10435759210177642257noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72046518442451832372010-04-09T08:31:05.047-04:002010-04-09T08:31:05.047-04:00Make sure it's exactly 287 ml :-)Make sure it's exactly 287 ml :-)Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27807876002644393772010-04-09T08:17:49.698-04:002010-04-09T08:17:49.698-04:00I won't be able to drink another glass of oran...I won't be able to drink another glass of orange juice now without remembering binary blackhole systems. How cool is that?!Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-54887697482054975882010-04-09T05:55:16.774-04:002010-04-09T05:55:16.774-04:00Hi Bee,
Thanks for this truly interesting piece a...Hi Bee,<br /><br />Thanks for this truly interesting piece about the observations and progress in understanding celestial objects like OJ 287. I do wish however they would offer up a more inspirational name for something that is so immensely attractive in nature. That is I can just see myself trying to strike up a conversation today with someone beginning with saying ‘what do you think about Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44523301215150148742010-04-09T02:08:57.537-04:002010-04-09T02:08:57.537-04:00Hi Tspin:
The results of the Fourier trafo are i...Hi Tspin: <br /><br />The results of the Fourier trafo are in the <a href="http://iopscience.iop.org/0004-637X/646/1/36/" rel="nofollow">ApJ paper</a> (it's open access), see table 1, Fig 2 & 3, Section 2.2 & 2.3 (I left out most details in the post for obvious reasons). The point is that the events are not strictly periodic (otherwise the prediction of the time of the outburst would Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-64300278147403445322010-04-08T20:39:09.777-04:002010-04-08T20:39:09.777-04:00Nice post, but I have some reservations. First the...Nice post, but I have some reservations. First there is really no way to tell from your post or the paper how impressive the prediction really is as we cannot see the Fourier transform. If there is a clear periodicity on FT then predicting next event may be easier then it looks based on time-domain data. <br /><br />The actual graph in the arxiv paper is quite different from the one embedded in Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-6995799104638734422010-04-08T15:26:48.587-04:002010-04-08T15:26:48.587-04:00If Sept 2007 was the emergent flare, the next ente...If Sept 2007 was the emergent flare, the next entering flare is in 2016. Patience - and a space telescope or two taking a long hard look across the spectrum!<br /><br />Any gravitation theory competing with GR requires a surpassingly perfect strong field ansatz. Either that, or a GR founding postulate must be selectively falsified under heretofore unobserved circumstances.<br /><br />http://Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91861609492074568992010-04-08T14:33:20.248-04:002010-04-08T14:33:20.248-04:00Dear Bee,
thanks for sharing :-). I have never he...Dear Bee,<br /><br />thanks for sharing :-). I have never heard of OJ 287 before - a pity, as it is a fascinating object indeed!<br /><br />Cheers, Stefanstefanhttps://www.blogger.com/profile/09495628046446378453noreply@blogger.com