tag:blogger.com,1999:blog-22973357.post4819085306255353409..comments2021-05-08T00:25:31.451-04:00Comments on Sabine Hossenfelder: Backreaction: Are Singularities Real?Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger61125tag:blogger.com,1999:blog-22973357.post-54356195070421315912020-12-23T12:02:18.108-05:002020-12-23T12:02:18.108-05:00Yet another highly interesting function is
f(x) =...Yet another highly interesting function is<br /><br />f(x) = (sin(x) - x cos(x)) / (x - sin(x)) <br />= cos(x) (tan(x) - x) / (x - sin(x))<br /><br />(1) The zeroes are the Eigenvalues of the differential equation y''+ k y = 0 (e.g. F = m a)<br />(2) It has a single (removable) singularity at x=0 with f(0)=2<br />(3) For large x the function approaches f(x) = -cos(x) Gerd Termathehttps://www.blogger.com/profile/01718262823488014650noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-64509199435411092422020-12-20T08:46:16.724-05:002020-12-20T08:46:16.724-05:00This comment has been removed by the author.Timm Deeghttps://www.blogger.com/profile/13181230067763830910noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91097560895094536342020-12-19T15:44:09.184-05:002020-12-19T15:44:09.184-05:00It's good to drive prople think what are real ...It's good to drive prople think what are real things. In physic the only real thing is to compare observations to predictions, nothing more.<br /><br />Singularities are math. Is the number theory full of singularities? Mad idea. But the quantum measurable world can be very connected to the number theory. Applying range rules out direct measurability of pure math in phenomena but it's notEusahttps://www.blogger.com/profile/14114706429392111062noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71072168628825463942020-12-19T11:53:39.071-05:002020-12-19T11:53:39.071-05:00This comment has been removed by the author.Timm Deeghttps://www.blogger.com/profile/13181230067763830910noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59325029419473825162020-12-19T11:48:18.712-05:002020-12-19T11:48:18.712-05:00@ Terry Bollinger
"Question 1: As she peers ...@ Terry Bollinger<br /><br />"Question 1: As she peers upwards through her ever-dwindling cone of observation, will she see time speed up for events in the outside universe?<br /><br />Question 2: At the instant before crossing the absolute event horizon, just as her observation cone becomes infinitely thin, will time for outside events appear to speed up infinitely? If so…<br /><br />Timm Deeghttps://www.blogger.com/profile/13181230067763830910noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-79474563595142079112020-12-18T12:47:30.457-05:002020-12-18T12:47:30.457-05:00Hi Steve,
I believe you are confusing the escape ...Hi Steve,<br /><br />I believe you are confusing the escape velocity with acceleration. Also, the event horizon is not a point. It's a surface. In the simplest case it's a sphere. And no, neither space nor time stop there. There is nothing in particular happening at an event horizon. It is merely the boundary of a region from which you cannot escape. There is no singularity at the event Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-46141364196461342602020-12-18T12:41:14.989-05:002020-12-18T12:41:14.989-05:00The Event Horizon is for simplicity sake the "...<i>The Event Horizon is for simplicity sake the "point" where the acceleration of gravity equals the speed of light. At this "point" doesn't the physics we accept say that time and space come to a stop and any mass goes infinite?</i><br /><br />They do not.Scotthttps://www.blogger.com/profile/16914985126761335721noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-63862015271182594612020-12-18T05:21:03.342-05:002020-12-18T05:21:03.342-05:00The only waves that are currently fundamental are ...The only waves that are currently fundamental are gravitational waves. That doesn't mean other waves are not real. It just means they're not fundamental. They derive from something else. They "can be reduced to" something else, as the philosophers would have it.<br /><br />As I already said above a point is not a singularity. A point has zero size. You can interpret this as Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28171616254747600842020-12-18T04:28:17.260-05:002020-12-18T04:28:17.260-05:00Mozibur7:24 AM, December 17, 2020
"Physicall...Mozibur7:24 AM, December 17, 2020<br /><br />"Physically, that doesn't make sense" <br />Yes, but the idea of a point is useful in models. Have you heard of Geometry or Calculus?<br /><br />"His criticism is still calid today."<br />Zeno's paradoxes are avoided using Calculus. Have you heard of it?<br /><br />"its one reason why I like string theory"<br /><brSteven Evanshttps://www.blogger.com/profile/13898046706669437332noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-90079437867485383252020-12-17T13:40:52.921-05:002020-12-17T13:40:52.921-05:00Dr. Hossenfelder,
As always a very interesting re...Dr. Hossenfelder,<br /><br />As always a very interesting read of all of the comments. The various theories and modeling that go into explaining a black hole and its singularity provide for great thought. The most interesting comment to me was that the event horizon was a "gateway." I believe that this is the most important point that we can think about. The Event Horizon is for Steve Guderianhttps://www.blogger.com/profile/09572661573643389505noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-41519016443661678362020-12-17T12:36:53.701-05:002020-12-17T12:36:53.701-05:00Hi Sabine,
It's true Michael Berry's sing...Hi Sabine,<br /><br />It's true Michael Berry's singularities are only within waves. Are you arguing that waves are not real on a fundamental level? If we should regard only elementary particles as fundamental constituents of the universe, well, what are those? Many of their properties and interactions can be modeled with soliton waves -- including their singular nature. Also, as FeynmanKris Kroghhttps://www.blogger.com/profile/07340827856086381459noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-58764541805157475362020-12-17T10:00:53.370-05:002020-12-17T10:00:53.370-05:00A point per se isn't a singularity. It's a...A point per se isn't a singularity. It's an example for something that has size zero, which is unphysical. I talked about last week. That in and by itself doesn't mean every point is a singularity. In fact that statement is entirely meaningless. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74111739743985808282020-12-17T07:24:47.907-05:002020-12-17T07:24:47.907-05:00Actually, it has occured to me that the simplest e...Actually, it has occured to me that the simplest example of a singularity is that most ubiquitous thing in physics, a point. As Euclid defined it, it is extensionless. Physically, that doesn't make sense either spatially, as a position; temporally, as a moment; or in terms of matter, as a point particle like an electron is supposed to be.<br /><br />Zeno was the first to realise that singularMoziburhttps://www.blogger.com/profile/11836761141351221660noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27546454078506550532020-12-17T04:22:00.273-05:002020-12-17T04:22:00.273-05:00Couldn't agree more Lawrence. I've identif...Couldn't agree more Lawrence. I've identified the repulsive force as equivalent to a soliton or 'Mexican Hat' profile, reversing within the torus to emerge at the cusp. We then get what we actually find; all accreted matter is re-ionized and ejected in the 'quasar' jets. Indeed we find slightly MORE matter in the jet columns! Possibly due to pair production at the shear Peter Jacksonhttps://www.blogger.com/profile/13905359947213961259noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-61134954741054086412020-12-17T02:40:12.096-05:002020-12-17T02:40:12.096-05:00Still sore about Gentzen. Some people prefer being...Still sore about Gentzen. Some people prefer being right to the truth. All Helbig 1.0 has to do to avoid deprecation in favour of Helbig 2.0 is provide evidence of universal fine-tuning.<br /><br />Strange that so many physicists claim universal fine-tuning - the UK Astronomer Royal, Brian Schmidt, Helbig 1.0, Luke Barnes, Geraint Lewis, etc. - but can provide zero evidence. <br /><br />I think Steven Evanshttps://www.blogger.com/profile/13898046706669437332noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56056336688615192542020-12-17T01:12:04.285-05:002020-12-17T01:12:04.285-05:00All these theories are effective theories, meaning...All these theories are effective theories, meaning they break down on small scales. On small scales there's just atoms (or subatomic particles) and nothing is singular, so all the singularities in effective theories are mathematical artifacts. <br /><br />As I said, the only instance we currently know of that could be a true singularity is the black hole singularity (or other singularities inSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-13643661740738267552020-12-16T19:47:31.462-05:002020-12-16T19:47:31.462-05:00@Lawrence Crowell:
I don't understand what yo...@Lawrence Crowell:<br /><br />I don't understand what you mean by 'the two test masses are arrayed perpendicular to the radial direction'.<br /><br />Generally, I think of test masses as ideal point masses. But that can't be the case here as they are arrayed 'perpendicularly'. Are they ideal rods instead?<br /><br />Given your description, a black hole sounds like a tardisMoziburhttps://www.blogger.com/profile/11836761141351221660noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-84504634887689734792020-12-16T19:21:04.293-05:002020-12-16T19:21:04.293-05:00@Phillip Helbig:
It's worse. It's not an ...@Phillip Helbig:<br /><br />It's worse. It's not an AI. Nor even the imitation of an AI. It's a sock-puppet and I think I can see the wiring ...Moziburhttps://www.blogger.com/profile/11836761141351221660noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37505755134785632762020-12-16T19:15:17.961-05:002020-12-16T19:15:17.961-05:00By the way, do you work with optical vortices expe...By the way, do you work with optical vortices experimentally? I hadn't heard of them before and just looked them up on wikipedia and they seem fascinating - and the pictures don't look bad either. There were some pictures in Berry's article too, as I recall.Moziburhttps://www.blogger.com/profile/11836761141351221660noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69281502202136285542020-12-16T18:19:36.057-05:002020-12-16T18:19:36.057-05:00The 'topological protection' is there so t...The 'topological protection' is there so that the so-called singularity doesn't vanish. The situation is modelled by vector bundles. <br /><br />There's an easy physical analogue which shows what happens: a Mobius strip has a twist and no matter how you stretch and pull the band that twist remains there. This is the 'topological protection'. The same is true for additionalMoziburhttps://www.blogger.com/profile/11836761141351221660noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53799926621633262042020-12-16T15:43:43.351-05:002020-12-16T15:43:43.351-05:00Hi Sabine,
Michael Berry's article cites Will...Hi Sabine,<br /><br />Michael Berry's article cites William Whewell's discovery of a singular point (or "catastrophe") in the pattern of tides between the coasts of England and Holland. Is that a real thing or an artifact of the approximation?<br /><br />You could compare Whewell's analysis to the problem of identifying the highest point on a mountain peak. Assuming it hasKris Kroghhttps://www.blogger.com/profile/07340827856086381459noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-11947799043689681142020-12-16T14:32:16.343-05:002020-12-16T14:32:16.343-05:00The singularity in a Kerr or RN metric is actually...The singularity in a Kerr or RN metric is actually repulsive. Orbits around them are closed timelike curves. These are identified with some sort of monodromy, but I have not seen this worked out and for myself ponder this some. In this setting what is really important is the monodromy; the singularity is just an artifact of our mathematical language. Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-13225911737830429612020-12-16T13:12:16.414-05:002020-12-16T13:12:16.414-05:00Addendum 2: Observational implications of the dark...Addendum 2: Observational implications of the dark mirror interpretation<br /><br />This literally was not on my agenda for the rest of this week, but some part of my brain refuses to ignore dangling strings. So, if only to get on to other things…<br /><br />-----<br /><br />The most significant implication of the dark mirror model is that there is no such thing as Hawking radiation, and that itsTerry Bollingerhttps://www.blogger.com/profile/03915136249111338024noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33155194257679840132020-12-16T12:59:42.209-05:002020-12-16T12:59:42.209-05:00Is "topological protection" sufficient t...Is "topological protection" sufficient to produce the production of hawking radiation as deminstated by some types of optical solitons or is there some other factors involved?Axilhttps://www.blogger.com/profile/07190120527431077518noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-10715702388886080412020-12-16T12:01:48.497-05:002020-12-16T12:01:48.497-05:00Mozibur,
You're right that Berry's singul...Mozibur,<br /><br />You're right that Berry's singularities are not the type where density goes to infinity. However, as Sabine noted, "certain types of singularities do not even require any quantity to become infinite."<br /><br />The objects Berry is describing have a feature called "topological protection." That guarantees the existence of singular points in their Kris Kroghhttps://www.blogger.com/profile/07340827856086381459noreply@blogger.com