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"Size" of Black Holes Misleading -- They Are Points
Latest comment: 15 years ago6 comments5 people in discussion
The article needs to emphasize more clearly that non-rotating black holes are always points -- and that there is no structure to the black hole other than the point (the event horizon being conceptual only).
That depends on your point of view. Literally. From the point of view of distant observers, nothing can reach the center of black hole in finite time. Actually, nothing can reach event horizon in finite time! See this picture: http://busybox.net/~vda/blackhole_1d.png - anything falling into the hole experiences time dilation and never reaches the horizon (although practically it is redshifted so much that distant observers see it "disappearing" very quickly). Therefore, from the point of view of distant observer, the matter of collapsed star does NOT collapse into infinitely dense point, it is similarly "falling forever" in strongly time-dilated region of space. VZ9 (talk) 16:12, 29 June 2008 (UTC). This begs the question as to how a black hole could ever form. Any object approaching an emerging event horizon would take a longer and longer time (from the point of view of an external observer) to fall through it. Thus, we would be waiting until the end of time to see a black hole form.
The use without clarifying commentary of the terms "size", "large", "micro" etc. for different masses of black holes is very misleading -- as is the description of non-rotating black holes as "spherically symmetric objects". All black holes are "micro" in size (though not mass), and a point of course is not a sphere. —Preceding unsigned comment added by 76.199.66.94 (talk) 12:54, 29 June 2008 (UTC)
But there is no such thing as a point unless there is another point somewhere else. The issue, here, is whether black holes can exist in isolation from other points that are not points. Or other black holes, for that matter. For any given volume, a nearly infinite number of black holes can be postulated to fill it. And if there are that many black holes in a given volume, the space is going to behave like a foam, isn't it? To illustrate this more aptly, five or six black holes may be point like, but there is a real quandary declaring one or more of them to be in orbit around the others. Or vice versa. 198.177.27.32 (talk) 05:35, 24 August 2008 (UTC)
If you want to get into topology then points can of course be defined as separate from other points - if they coincide, then they are one and equal. The point is that there is a singularity at the center, mathematically. However, physically, singularities do not exist, which is why a theory of quantum gravity is necessary. So I feel like the question of "size" of black holes accepts the notion that singularities are nonexistent, so size is a matter of the volume of the Euclidean space enclosed within the event horizon. SamuelRiv (talk) 05:42, 25 August 2008 (UTC)
I think the key problem here is you guys think black holes have infinite mass, or somehow a singularity contains infinite mass. It has a finite mass in a definite, but internally unquantifiable volume. This does not mean that a black hole is a point - it means there's an event horizon, where stuff can't escape, and at some coordinate inside the blackhole (the "singularity"), regardless of total mass, rotation, etc, there is a section of maximum density that is obtainable by whatever pieces/fields/w.e you believe makes up the inside. Otherwise black holes would collapse to a point of an evergrowing mass, that is volumeless. It would mean literally that directly outside the "point" there would be perfectly empty space, that space in between the singularity, and the event horizon. To clarify, the space which contains a gravitational field more powerful than the speed of light, but which wouldn't contain mass because the black hole would bring it to the point. And a point on what the the guy two posts before me said, if black holes were points, they couldn't combine, as that would require a volume to overlap. Part of my argument is wholly based on my interpretation, where a singularity is an density of mass so large that it exceeds the speed-of-light gravitational barrier, but has a definite maximum potential, not exceeding a gravitational speed-of-light-attraction when it reaches that barrier, or only going a distance past it, which is what requires quantum stuff to come into play (that of course along with the matter-wave spectrum being well, broken by the "greater than light" proposed speeds). —Preceding unsigned comment added by 69.205.97.220 (talk) 21:49, 10 December 2008 (UTC)
I'd also like to mention what I meant by "maximum" density, is the point where if it goes further, it would have to change into something else. Like how temp, pressure, and volume are for the maxes/mins of states of matter, and if I said "minimum" temperature of something, it would be the point before it goes into a supercooled state. —Preceding unsigned comment added by 69.205.97.220 (talk) 22:16, 10 December 2008 (UTC)
Wrong picture!
Latest comment: 16 years ago10 comments2 people in discussion
"What makes it impossible to escape from black holes?" section contains a picture whose author obviously did not even try to depict null geodetics of Schwarzschild equations! This one is more correct: http://busybox.net/~vda/blackhole_1d.png
blackhole_1d.png unfortunately does not have test particle wordlines inside light cones, having those would show how that wordlines are bending towards black hole inside symmetrical light cone. VZ9 (talk) 15:59, 29 June 2008 (UTC)
First of all the the picture you say is more correct show exactly the same thing as the one in the article.
No. In the article, "Closer to the black hole spacetime starts to deform" picture shows a light cone which has tilted to the right. That is, "left" light ray's angle from vertical is less than 45 deg. while "right" ray's angle from vertical is more than 45. In my picture, both rays have the same angle. How's that exactly the same?
Take Schwarzschild equations, pick arbitrary point in space with R > Rs and solve the equation for ds^2 = 0. IOW, find out under which angle null geodetics cross your chosen point. You will find that there are two solutions (for "left" and "right" light ray) and they are symmetrical - that is, both rays should have the SAME angle from vertical and it will be less than 45 deg. This is intuitively correct too - if angle between null geodetic and vertical is less than 45 deg., it means that light moves "slower" there - in other words, we have time dilation. If your two null geodetics have DIFFERENT angles, you have two DIFFERENT values for time dilation in the same point, which makes no sense! VZ9 (talk) 09:35, 30 June 2008 (UTC)
"Angle with the vertical" has no intrinsic meaning in GR. The only way to give meaning to such a phrase is by choosing a "time function" and defining vertical as constant time surfaces. Implicit in your reasoning is using the "schwarzschild time" as a time function. This time function has the awkward property that no geodesic reaches the horizon in finite Schwarzschild time, making it useless for discussing the (im)possibility of escaping from a black hole. There exist much more suitable time functions such as the "outgoing null coordinate" v featured in Eddington-Finkelstein coordinates, in such coordinates with such a time function lightcones are completely regular across the horizon and feature lightcone tilting {although not quite as in the picture).
I prefer "schwarzschild time" because it coincides with usual perception of time for the distant observer. In many cases, it's distant observer that matters most. For one, any observable physical effects we can possibly ever see around black hole are, by definition, seen by "distant observers". Thus, it is quite useful if this article would mention that from the POV of distant observers, matter does not cross event horizon (in finite time), it is not compressed in infinitely dense point of space (in finite time), and thus, for distant ovserver, black hole actually has no singularity (it "did not form yet") and therefore GR can fully describe it. The current picture with light cone does not show this. As I see it, it misleads the reader into thinking that object falls into the hole in finite time. Text is misleading in places. For example, read "Hitting the singularity" section. It literally says that "as soon as an object passes within the hole's event horizon, it is lost to the outside universe" etc. But from the POV of outside universe, this never happens! VZ9 (talk) 22:30, 3 July 2008 (UTC)
The picture is used to help explain why something cannot escape from a black hole. This is an inherently local discussion and has nothing to do with what a distant observer sees. Schwarzschild time is very bad for this discussion because you cannot cross the horizon in finite Schwarzschild time let alone again escape from it again. To discuss this properly you need a time coordinate that is regular at the horizon. This also means that the picture does not show infinite red-shifts and other effects particular to distant observers. The article does in fact mention explicitly that it takes infinite time to cross the horizon from the POV of a distant observer. Actually it does this several times. (See the "effects of falling in a black hole" section, this section needs some work btw, so if you see someway of improving it please do. But I also need to stress that object do indeed fall into the black hole in a finite proper time, as the article also clearly states. (TimothyRias (talk) 07:03, 4 July 2008 (UTC))
Namely, the outgoing null geodesic continuously deforming from moving away from the black hole, to point towards the singularity. Second, it uses Schwarzschild coordinates, which have a coordinate singularity at the horizon making them not so good for describing what happens at the horizon. (the "lightcone stretching" described in that picture is a result of this.)
The exact way the situation is visualized depends strongly on the chosen coordinates, although the main qualitative behaviour (i.e. outgoing null rays continuously deforming from moving away to moving towards the singularity) is always similar. I chose, to depict the situation in coordinates that minimize odd behaviour at the horizon, such as lightcone squeezing (schwarzschild coords), the black hole seeming infinitely big (kruskal) or geodesics moving backwards wrt time at infinity. But, the current picture is correct in some coordinate system. (TimothyRias (talk) 09:21, 30 June 2008 (UTC)(
For me distant observer's coordinate system would be the preferred choice. After all, how events look in this coordinate system is the most important because that's what we are seeing when we observe black hole. VZ9 (talk) 09:39, 30 June 2008 (UTC)
The distant observer's coordinate frame does not uniquely define the coordinates for the whole spacetime. The a litterally infinitely many ways to continue those coordinates towards the black hole. Schwarzschild coordinates use the distant observer's proper time as a global time coordinate, which is bad in this discussion for very obvious reasons. Other frequently used coordinate schemes (such as Eddinton-Finkelstein or Kruskal-Szekers coordinates) feature other coordinate specific non-intuitive features and are thus also not suitable in a lay discussion of the issue. Luckily, because at this point we are only drawing pretty pictures, we can choose different coordinates, in which the metric would look quite messy, but the picture only features the qualitative behaviour we were try to explain. Namely, that space deforms in such a way that inside the black hole outgoin light rays will actually move towards the black hole. (TimothyRias (talk) 08:48, 1 July 2008 (UTC))
I find it pointless to argue with you Tim, because we talk past each other. You say what I already know (e.g. as above about "infinitely many ways" to define coordinate systems). I KNOW THAT. You are totally failing to understand what I say - that while there are many coordinate systems possible indeed, and when you put them into equations, they are all equally valid, when we look at black hole thru our telescopes, we want compare our observations with what theory says what *we* should see, not what falling observer should see (or whoever else). If I'll throw a mirror into black hole, did it cross the horizon *from my POV*? Since I can send send a ray of light and it will still bounce off it and get back to me - obviously not. And since I can do it even one million years later - the mirror never reaches the horizon. Yes, it's from my POV, but this is POV that matters. VZ9 (talk) 08:07, 6 July 2008 (UTC)
And if you are flying a space ship through the horizon of a black hole, it is important to know why you can't escape from the black hole from your POV. It is pointless to discuss this from the POV of distant observer, cause as you rightly point out from his POV you would have never reached the horizon in the first place. So, if you are discussing the (im)possibilty of escape from a black hole, you better do this in coordinate system in which reaching the black hole makes sense in the first place. Since this is what the picture you were criticizing is discussing, I don't really see what you are throwing a fuss about. (TimothyRias (talk) 15:18, 6 July 2008 (UTC))
What next?
Latest comment: 15 years ago4 comments4 people in discussion
I am just a high schooler so it was hard for me to understand much of the article. My question could have been already answered by the article but not interpreted by my simple brain. Can someone answer this in simple English? I understand that it is impossible to create or destroy energy. So once something is pulled by the gravity of a black hole and crushed where does it go next? —Preceding unsigned comment added by 222.153.21.181 (talk) 10:29, 3 July 2008 (UTC)
After the Object that is entering the black hole passes the singularity, what happens next is open to theory. Since no one knows any way to get past the singularity without being crushed. I am a middle school student and that is as simple an answer as you get in middle school so, enjoy.3rd captian Gin Ichimaru (talk) 11:09, 10 August 2008 (UTC)
One answer could be, when viewed from outside, the time stops at the event horizon. So an object can not be seen or scientifically measured (like a radar or so) to actually enter the black hole. So the energy stays outside, at least as seen from a distance. A similar answer is to the question how the force of gravity (and electric charge) can come from the hole. The matter stays on the outside, as least when measured from a distance. A completely different view is seen onboard a vessel entering the hole. That is a strange effect, but time is not fixed, especially not when it comes to black holes. --BIL (talk) 11:47, 11 September 2008 (UTC)
I am also just a "high schooler" but as far as I know, when a black hole tears apart things that begin to enter they are torn down to there elementary particles they continue to enter the black hole until they reach the singularity, at which point they "join" it and are added to it's infinity, but, I think the real question is indeed the where, if the theory is correct in stating that a black hole does not sit in time/space where is the singularity? It undoubtedly sits within the hole but seeing as the hole is a sphere where is it? I may be wrong with this, but if anyone can see what i am trying to say, and has the answer I would be appreciative. —Preceding unsigned comment added by JackCopple (talk • contribs) 01:24, 13 December 2008 (UTC)
Integrating Effects and features sections
Latest comment: 16 years ago2 comments2 people in discussion
I feel that the two sections "Features" and "Effects of falling into a black hole" tend to overlap on many points, especially when discussing the horizon. I think it might be better to try to integrate the two sections into a single section. (In the process we might reduce some overall length of the article.)
The best approach may be to incorporate the information from the effects section in the features section (which may need a new name). The stuff about crossing the horizon and gravitational time dilation can probably be integrated in the section about the event horizon. The hitting the singularity, subsection can probably be integrated in the subsection about the singularity. I'm not yet sure about the stuff about tidal forces, this may need a new subsection in the features section.
Do others agree? (TimothyRias (talk) 08:31, 9 July 2008 (UTC))
for some reason I cant fix it, but there is a typo...
"such a small black holes"
a small black hole or such small black holes —Preceding unsigned comment added by 66.82.9.92 (talk) 04:02, 12 July 2008 (UTC)
NAME subsection clarification
Latest comment: 16 years ago1 comment1 person in discussion
In the NAME section of the black hole article, Ann Ewin is correctly (as far as I know) given credit for using the term, black hole, in 1964, before Wheeler adopted it in 1967. However, the Wiki article refers to Ewing's writing as a "letter," whereas it was a report on a meeting of the American Association for the Advancement of Science, in the January 18 issue of [Science News Letter]. The article title is "Black Holes" in Space."
Latest comment: 16 years ago1 comment1 person in discussion
Just a suggestion, but some qualified individuals from here might want to go over the Magnetospheric_eternally_collapsing_object article. The article was clearly written by a rather enthusiastic proponent of the idea, and it's in serious need of review and balancing. Alsee (talk) 18:52, 24 July 2008 (UTC)
theories
Latest comment: 16 years ago3 comments3 people in discussion
hi, I would just like to say that I am only 13 so found it hard to find the right info in this article.
I am doing a study at school on different aspects of black holes and am trying to find out a range of theories on how they are formed. One theory I have found states that some people believe black holes form when large stars begin to shrink at the end of their lives. No idea whos theory this is, so any theories found would be a great help, Missy315 (talk) 04:28, 26 July 2008 (UTC)
Ok I am 13 as well as this is the theory that I got from studying black holes. As a supermassive star neers the end of its life and runs out of fuel, it begins to collapse into itself. This is because when the star is converting its feul from one element to another, the atoms get heavier and heavier. This process is like this Hydrogen-Helium-Oxygen-Iron, After the star runs out of fuel to continue expanding, the gavitional pull from the core and the iron atoms make the star "Implode" in some respects. This in turn results in a black hole.3rd captian Gin Ichimaru (talk) 11:17, 10 August 2008 (UTC)
"In fact, the Earth could be passing through an event horizon at just this moment without our ever noticing"
Latest comment: 15 years ago6 comments5 people in discussion
Everyone would notice. The entire sky would be black except for a small spot of light, caused by gravitational lensing. unless the black hole was unreasonably large (like 10^30 solar masses or 10,000 light years in circumference) the tidal forces would rip the earth apart. —Preceding unsigned comment added by 69.37.38.45 (talk) 21:10, 27 July 2008 (UTC)
The sentence you objected to has been removed, which is probably for the best since we know enough about the matter around us to know that it's not forming a black hole. But you certainly can fall though the event horizon of a very large black hole without noticing anything. The sky does not go black. To pick a more realistic example, assuming the Lambda-CDM model is correct there's a cosmological event horizon surrounding every galaxy at a distance of around 16 billion light years; the galaxy becomes permanently unreachable to anything that falls through the horizon. We're falling through the cosmological event horizons of distant galaxies at a rate of about one per year without noticing. Even our view of the galaxy in question is uninterrupted. It's a different kind of event horizon but the same general idea. -- BenRG (talk) 11:52, 11 August 2008 (UTC)
Well, he could have a point, however... According to Stephen Hawking, one who was within a black hole would not be able to communicate with one outside, so he could somewhat determine if it were an extremely small one... Another thing that must be considered is that in a black hole, the effect of gravity would (theoretically, obviously) be greatest at the center of the black hole, and NOT the earth. So, should you not be compacted into oblivion, you would notice that a basket ball would stop bouncing towards the center of the earth, and more than likely towards the center of the black hole. Also, outside observers and inside observers would notice that the other's time would have appeared to stop completely, due to time relativity, and that each would appear to gradually be further and further redshifted as one is pulled towards the center of the black hole. KeineLust90 (talk) 22:49, 17 November 2008 (UTC)
One *theory* is that everything is compressed as tightly as the atoms will allow, possibly causing atom deformation? (See magnetar) As more material is compressed the 'object at the centre'?'star'? expands, the event horizon expands occordingly. —Preceding unsigned comment added by GamesMaxter (talk • contribs) 19:14, 3 November 2008 (UTC)
"This article may be too long" template?
Latest comment: 16 years ago10 comments5 people in discussion
In order to shorten this article (per the template), I'd like to suggest splitting it between theoretical properties versus astronomical objects. The latter article could then include the "Formation and evolution", "Techniques for finding black holes", "Black hole candidates", "Black holes and Earth" and most of the "Sizes" sections. As a title, perhaps "Black holes in astronomy" would be suitable? Following the split, this article can then focus entirely on the physics of black holes, and those of us with a primary interest in astronomy (like me) can work on the other page. Any thoughts?—RJH (talk) 21:08, 8 August 2008 (UTC)
A while ago I suggested moving "Techniques for finding black holes" and "Black hole candidates" to a separate article, and your suggestion "Black holes in astronomy" looks a good title. I think it would be a mistake to move "Formation and evolution", because the article needs to show that BHs are a natural phenomenon rather than just a theoretical construct. "Sizes" would be too small for a separate if not accompanied by "Formation and evolution". "Black holes and Earth" is too small and I see no other sections that make natural partners for it. -- Philcha (talk) 21:48, 8 August 2008 (UTC)
Well a split article on black holes in astronomy must still be summarized here, so this step wouldn't be completely removing the information about formation; it is merely converting the article entry to briefer, summary style. (Per Wikipedia:Summary style as the technique suggested for over-long articles of this nature.) A dedicated article on black holes in astronomy will definitely need more in-depth information on their formation and evolution, as this relates to galaxy formation and the evolution of massive stars. Hence, moving substantial parts of "Formation and evolution" to the second page seems a logical step. Thanks.—RJH (talk) 18:17, 10 August 2008 (UTC)
I agree that it might be best to defer some of the material to other article(s). It might however be a better idea to move some of the content to already existing articles instead of making new ones. I think most of the content on techniques for finding black holes and black hole candidates could be moved to the stellar black hole and supermassive black hole articles. This might be better than a new article since this topics already natural split between the different size classes of black holes.
With respect to the "formation and evolution" section. This section actually contains some very key parts of black hole physics and should remain pretty much as it is here. (The articles on stellar black holes and supermassive black holes should however give a more in depth discussion of the processes leading to their creation.)
As for the BHs and earth section, I believe this section to be unencyclopedic. And feel that it should be left out altogether. (TimothyRias (talk) 08:17, 11 August 2008 (UTC))
- Well a black hole isn't really "black", since light cannot escape the black hole it is invisible. Also no one would be alive when we get close to the event horizen since spegetification would have already split us into atoms.3rd captian Gin Ichimaru (talk) 11:00, 10 August 2008 (UTC)
What about content forking the section on Einsteins' Theory. It also appears to go into minute details which may be more appropriate within it's own article? That would probably reduce 3 paragraphs. --CyclePat (talk) 00:35, 18 August 2008 (UTC)
Ah, yes the history section. As it is, most of the section is just a listing of dates of various discoveries. I think this purpose is better served by just attributing the discoveries and there dates when explained in the rest of the article. If we really want a narrative discussing the historical development of the topic it might be better to do so in a separate article in more detail. (writing such an article will be challenging though since the development of the topic is probably hard to explain without requiring some knowledge of the concepts being discussed.
Latest comment: 15 years ago4 comments4 people in discussion
The simulated view of black hole in front of the milky way shows black hole as perfectly black. Matter just outside event horizon must be present in all directions, not just like disk form. In that case, the disk of the black hole must look little blur. If the simulation is simplified to demonstrate that the body of black hole is black, it must be mentioned that apparent disk like shape of surrounding matter is not real.
Or is it that the matter around black hole actually forms disk like shape (like spiral galaxies do)? manya (talk) 04:30, 14 August 2008 (UTC)
The simulated view shows a black hole with no matter surrounding it at all. In particular there is no matter between the observer and the black hole. Nor is there anything to emit or reflect light in the immediate vicinity of the black hole. Thus no light will reach the observer from the direction of the photon sphere. (Following any potential lightray coming from that direction back in time will lead to the (past) event horizon of the black hole.) (TimothyRias (talk) 10:26, 14 August 2008 (UTC))
Actually, the matter isn't spiraling out of it, it's just the way the video rotates view while the black hole is spiraling, creating an illusion.
Black holes and Earth section: remove?
Latest comment: 16 years ago6 comments4 people in discussion
I think that there is no need for the BH and earth section. It currently discusses 2 topics: the first is BH moving through our solar system. I don't think that is a very notable subject, and with the lack of citation claiming supporting that this is a notable concern, I think it should be removed. The second part discusses BH cration in the LHC. This is mentioned elsewhere in the article and is treated in much more debt in the Safety of the Large Hadron Collider article. Hence I see no need to discuss it here in seperate section. If there are no objections I will remove this entire section from the article saving space. (TimothyRias (talk) 11:50, 18 August 2008 (UTC))
Aren't there tests happening in Europe which could see the creation of a black hole on earth? I though I remember seeing that in my local news paper and how scientists are working with huge particule accelerators. What about naturally colliding particules? I haven't read the section, but I think it could be fairly notable.--CyclePat (talk) 18:06, 18 August 2008 (UTC)
Then again, maybe it's more of a subject matter that deal with the Hadron Collider... and a small mention in this article (with a link to the main article) (an okay content fork, according to me!). --CyclePat (talk) 18:09, 18 August 2008 (UTC)
Jeppe here: I love this Timothy: The wonderful thing is that if a black hole was ever to trespass our solar system, we would all be doomed (ironically), and thus a wikipedia article serves no other purpose than inform posterity about the ridiculous in this idea, and of the fanciful notion that a mini-black hole can be created with the large hadron collider.
But I think a fortune could be made about publishing a book on hillarious misunderstandings and freaks of the science world and beyond. It would be a best-seller! —Preceding unsigned comment added by Jjjjc (talk • contribs) 22:09, 11 September 2008 (UTC)
Einstein thought Black Holes were impossible
Latest comment: 15 years ago7 comments6 people in discussion
And you should mention there, instead of claiming that his theory predicted Black Hole. At best, it was Kerr's theory of BH to predict Black Holes. But I know you will refuse to debate that. You need to say that Einstein predicted BH while he said the opposite. Boys will be boys. Wiki will be wiki.83.103.38.68 (talk) 15:27, 18 August 2008 (UTC)
I think it is wrong to say Einsteins general theory of relativity predicted black holes. At the time he proposed his theory this (such derivations) were not foreseen. The person who derived the existence (and the process of how black holes are formed) was Subramaniam Chandrasekhar. Ironically he is not at all mentioned in this page.Unsigned contribution by 155.53.76.194 (talk) 21:40, 15 September 2008
The article doesn't currently say anything about Einstein's personal views. Every occurrence of the word "Einstein" is in reference to "Einstein's theory of general relativity" or "Einstein's field equations" or some variation on that theme. The article does say that black holes are a prediction of general relativity (aka "Einstein's general relativity"), and that's true. It wasn't Einstein who proved that, and he may not even have believed it, but the article never claims that he did. That said, it does seem pointless and potentially confusing to mention Einstein's name so much. I removed half a dozen particularly pointless mentions, and I think we could stand to remove more. -- BenRG (talk) 17:57, 18 August 2008 (UTC)
Ok let's go to the point:
"Black holes, as currently understood, are described by the general theory of relativity."
That's false.
Einsein made an article claiming that Black Holes would make particles go faster than the speed of light: A. Einstein, Annals of Mathematics, 2nd Ser., Vol. 40, No. 4. (Oct. 1939), p. 936 thus if you speak of Black Holes you are not speaking of the general realtivity, you speak about other theories which are not in "Einstein's relativity". Please reply precisely, thanks.83.103.38.68 (talk) 13:45, 19 August 2008 (UTC)
General relativity is not limited to Einstein's work or beliefs, just as the study of evolution is not limited to Darwin's. Science is not a cult of personality, and no field of study belongs to an individual. -- Coneslayer (talk) 14:01, 19 August 2008 (UTC)
So you are trying to claim that the schwarzschild metric is NOT a solution to the Einstein equation (=== General Relativity)? That's quite easily disproven.
Anyway, a priori, relativity does not exculde the possibility of faster than light travel. It is a result from relativity that faster than light travel is generally not possible. But there exist loop holes in GR that would circumvent this, such as the possibilty of geometries with timelike loops. (TimothyRias (talk) 14:22, 19 August 2008 (UTC))
Coneslayer is correct. But if you can dig up some sources about Einstein's opposition to the Black Hole theory I'd like to see it in the article. --IronMaidenRocks (talk) 01:08, 22 September 2008 (UTC)
Einstein clearly recognized that black holes indicated a probable error in his equations. This is present throughout his writings on the topic. 134.217.96.252 (talk) 22:10, 28 January 2009 (UTC)
pictures lead
Latest comment: 16 years ago5 comments4 people in discussion
I messed around with the pictures in the lead to reduce the white space created by the freakishly long table of contents. Is this working OK for people viewing the page in different resolutions (and/or different window setups/skins/etc.)? (The pics may need to be downscaled some more. I am also not a very big fan of the picture I added. Does somebody have any suggestions for a better picture? (TimothyRias (talk) 10:02, 19 August 2008 (UTC))
My screen is a LCD rectangle screen and it looks okay. There of course a little bit of a gap between the table of contents and the pictures. I'll read up to see how I could put the table of contents on the right side and the images on the left. I actually like the larger images. It makes a better impression. I wonder how it would look like if we could center the table of contents and put the images on both sides... on the other hand maybe not. Meuh! Just my meandering thoughts. --CyclePat (talk) 20:51, 19 August 2008 (UTC)
You can float the TOC using Template:TOCright and Template:TOCleft. I think I favor putting it on the right with article text on the left. Unfortunately the first section after the introduction is short and the section after that has its own right-floating box (as does the intro), so there are nontrivial formatting issues to be worked out. -- BenRG (talk) 17:06, 20 August 2008 (UTC)
It's pretty simple, the black hole grows by gathering more mass. Let's say that the object never cross the event horizon. Mass would approach it, and stay there, and new mass would get closer, but never completely overlap if it took infinite time. However, as it got closer, eventually, the gravitational attraction would grow enough to either "break" the infinite-time idea, or it would grow dense enough to have it's own event horizon. Sort of a like a contour map, except the contours are gravity potentials. Even if the mass was spread around the black hole almost infinitely thin, that almost would eventually have mass overlapping enough to the point where the event horizon would grow. On the contour map the comparison would be spreading dirt at the rate of a pound of dirt a day, outside say of a certain elevation. Eventually the dirt would change the elevation of the land. Hope that helps.
spelling error
Latest comment: 16 years ago2 comments2 people in discussion
Latest comment: 16 years ago7 comments3 people in discussion
When the article clearly states that black holes are theoretical speculations not directly observed, whose existence are not proven, then it is most inappropriate to show fanciful illustrations. These artists' conceptions are speculations, they misguide the uneducated reader and should be instantaneously removed, as well as NASA's simulated view.
More appropriate would be a photograph of the Milkyway that has not been tampered with, and then a text in the direction of:
According to General relativity, our galaxy The Milky Way is thought to revolve around a supermassive black hole.
You also badly need to make the criticism section more visible; where is it?
Funny how you object to illustrations of black holes, and in the same sentence promote artist impressions of the milky way. (For good order, we cannot make picture of the Milky way because we are inside it. A classical example of not being able to see the forest through the trees. (TimothyRias (talk) 11:57, 11 September 2008 (UTC))
Haha, blunder! Logically I did not mean a photograph, but an ARTISTS IMPRESSION that has not been modified in any way, or a close-up of the center of the galaxy with the suggested comments. But I still propose that they be removed unless we want wikipedia to go to discovery channel standards. —Preceding unsigned comment added by Jjjjc (talk • contribs) 13:48, 11 September 2008 (UTC)
Okay, here's my personal impression of all the non-purely-technical images that are in the article at the time of this complaint.
This is not exactly art, it's a simulation of lensing. I'm inclined to get rid of it, actually, because the animated GIF farther down the page is both prettier and does a better job of showing the lensing.
I'd rather remove this too unless it usefully illustrates some property of black holes, in which case it should have a caption to that effect.
Overly artsy, but seems fine as a diagram.
Enh. Not enough science, too much Thomas Kinkade.
I like this one.
Another Kinkade, but it does usefully illustrate some properties of black hole binaries.
I tend to agree at least to some extent. (I have numbered the pictures above for easy referencing.) About 1. I agree that the animated gif does a better job at illustrating lensing, but I still like this as a picture for the lead. The lead of such a large article needs a picture that illustrates what the article is about. This picture does a pretty OK job at this.
Number 2. was pretty much a placeholder until I found something better. I haven't so it can go.
Number 3. not a big fan of this one, we might want to look for a better picture for accretion disks.
Number 4. not a big fan. (note that the section it is in needs to be redone.)
Number 5. is a good illustration I say keep it.
Number 6 has its use as an illustration of binary system.
Number 7. I don't think we need a particle detector pic here, so it can probably go. (We need to look at that section anyway since it repeats a lot of what has been said earlier in the article.
Number 1. It has to go. The GIF is far better at illustrating the concept. Which is only a concept - had we some direct evidence from another galaxy where lensing could be observed, we could put it there. But it is photoshopping illustrating a speculated concept, and has to go.
Number 2. Agree, it can go.
Number 3. Agree, it can stay.
Number 4. Agree, it can go.
Number 5. Agree, it can stay.
Number 6. Disagree, it is Kinkade, it must go. Just because it is beautiful it does not mean that it becomes less useless; Hubble space telescope images of binary stars please.
Number 7. It can stay - since it is actually a 'photograph' documenting a real experiment. Whether it serves an instructional purpose for the article must be discussed by others, I am not going to meddle in that.
The bottom line: Illustrations of speculations are malplaced. What if it turns out that lensing or any other aspect works in a different way? Then the image is stuck in the mind of the student (private or connected to a recognized instution) who endeavours to study the subject, and is representing a false conception.
I battle this with my students all the time; Wikipedia is the single greatest source of information for beginners. Misconceptions from the start can be fatal. I suggest we maintain 3,5 and seven, and remove the others.
By the way, the single most hillarious phrase from the article is the formerly critizised: "allowing the photon to escape or sending it spiraling to its doom." Please, please, please remove or rephrase this. Immediately. —Preceding unsigned comment added by Jjjjc (talk • contribs) 21:50, 11 September 2008 (UTC)
(fixed the sentence it should be a little better now.)
I clearly disagree with you on number 1. First of all it is not a photoshop (see the referenced source). It is the simulated result of what you would see if you were to look directly look at a black hole, done by ray tracing in an actual black hole (schwarzschild) metric. It is good science and there is very little speculative about it. Moreover, illustrates a couple of features of black holes. Besides gravity lensing it also clearly shows the visual effect of the photon sphere. It also gives a good visual illustration of why black holes are called "black". This makes it a very good illustation for the lead.
File:800px-Cygnus X-1.jpgAn artist's impression of the HDE 226868–Cygnus X-1 binary system. ESA/Hubble illustration.
On the subject of number 6. I don't think there actually exist hubble picture of star-compact object binaries with enough angular resolution to distinguish between the two objects. And if they do, they will be of type blurry blob-blob and not very illustrative to the untrained eye. Hence such an illustration is out of the question. However, there is at least some need to illustrate the concept of such a system, an artist impression can be a usefully alternative. I agree that the current illustration is bit to fanta. The picture here on the right is slightly (although not much) better.
While we are on the subject of images 3-6. These are part of a section that is in dire need of rewrite. (Some of the information is blatantly wrong, the "objects orbeting possible black holes" being the most blatant. Moreover the section is missing any sort of disussion of the general strategy for looking for black holes, i.e. find an estimate for the mass and an upper bound for the physical extend and show that it is too dense to be anything else. Also due to changes in the preceding section it needs a more thorough discussion of accretion disks.) I am a theorist first and formost and as such I find that I have quite a particular view on this part of the subject. It would be extremely useful if somebody with a more astronomical background could help rewrite the section. (TimothyRias (talk) 12:32, 13 September 2008 (UTC))
New article can be linked
Latest comment: 16 years ago1 comment1 person in discussion
Latest comment: 16 years ago1 comment1 person in discussion
Somebody split of large portions of the article in an attempt to reduce the overal length. I feel he (or she) was a bit overly zealous in his (or her) attempt and have reverted for the time being. After the split this article no longer contained any information on the event horizon and hawking radiation and many other essential topics. It may be a good idea to split off some of the material that was split off. Lets discuss. (note I will be away until next week so it may take some time for me to respond.) (TimothyRias (talk) 07:09, 2 October 2008 (UTC))
Inside event horizon
Latest comment: 15 years ago2 comments2 people in discussion
I removed this line because I don't think it is correct:
Objects closer to the singularity aren't seen, as all paths light could take from objects farther in point inwards towards the singularity.
However, I could not think of a better replacement line. Specifically, you can run into a light path from a point ahead of you, but you would have fallen to a point past where that light was first irradiated. Relativity still works. Light still measures out as 300,000 km/s in all directions. It is space that is sliding towards the singularity. All objects in front will be severely red-shifted and would eventually disappear from red shift as you got closer to the singularity. Kind of like looking at the cosmic background radiation.Swlenz (talk) 22:39, 2 October 2008 (UTC)
They are red shifted and visually disappear not as they approach the singularity, but the event horizon. The speed of light certainly is still the same here, but within the event horizon all light falls into the singularity. That quote is not completely clear, but it is correct. Within the event horizon nothing can be seen as all light that exists within the event horizon travels to only one place--the singularity. Andrew Nutter Talk | Contribs 14:07, 10 February 2009 (UTC)
Objects orbiting possible black holes
Latest comment: 16 years ago3 comments2 people in discussion
In the Techniques for finding black holes section: It seems to me this whole discussion needs to be improved or deleted. The discussion in terms of circular orbits is unhelpful and not really correct. In general relativity, orbits are not even elliptical, as the radial and azimuthal periods differ, so the perihelia precess, as for Mercury. There is no discussion of real specific astronomical objects (thought the Galactic center "S"-stars come to mind as good candidates that should be discussed). There are no sources, so that the whole section is un-encyclopedic. If there is no objection I am going to smite it soon. Wwheaton (talk) 03:47, 13 October 2008 (UTC)
Nice job on improving the section. I like the addition of examples. Using more examples in the observation section may make the "candidates" section redundant. (especially as most of that section is better treated in stellar black hole and supermassive black hole. One thought should it also say something about using orbital characteristics to obtain estimates for the mass of the compact object. This has been very central in identifying BH candidates by showing that the observed compact object are too heavy to be neutron stars. (TimothyRias (talk) 08:33, 15 October 2008 (UTC))
Black Hole creation in LHC
Latest comment: 16 years ago6 comments3 people in discussion
Scattered throughout the article are various claims relating to black hole creation in particle accelerateors. They're writting in a fairly neutral-sounding tone, but still, do these belong in a serious article?
I recommend concentrating this subject in Safety of particle collisions at the Large Hadron Collider, which specifically addresses the issue in a fairly comprehensive way and has lately been promoted to good article status. The question does of course need to be mentioned when it is natural to do so, but then a link to the specialized article should try to treat it fully, rather than scattering less complete coverage everywhere across many articles—IMHO. Editors here may see improvements to make in Safety of particle collisions at the Large Hadron Collider, which would be most welcome, but I think it is better to have one mature article reflecting all our combined expertise and wisdom, rather many less solid discussions in may articles. Wwheaton (talk) 06:11, 14 October 2008 (UTC)
The possible existence of micro black holes is an open research question that deserves a mention in this article. This certainly is a topic that is taken seriously by the scientific community. (The LHC data will for example be screened for the typical signature left by the evaporation of a micro black hole.) To Wwheaton, note that the topic of the creation of micro black holes goes beyond any possible safety concerns. I will however look around in this article for any stuff that is covered more comprhensively in the Safety of particle collisions at the Large Hadron Collider article and insert appropriate links. (TimothyRias (talk) 07:55, 14 October 2008 (UTC))
I have no problem with the creation of micro BHs in accelerators being treated here, I just don't want the planetary safety issue to be needlessly duplicated. As far as I know the possibility of creating BHs in accelerator experiments remains open, and could provide valuable information on compacted dimensions, etc. Sorry if I reacted with knee-jerk negativity.... Wwheaton (talk) 03:06, 15 October 2008 (UTC)
I agree with Bill, we need to write about the possibilty of these micro black holes but we need not compicate things by discussing the whole planetary saftey issue which belongs in another article. Josh 19:05, 17 October 2008 (UTC) —Preceding unsigned comment added by 11341134a (talk • contribs)
Maybe I am missing something, but I don't think the article at present discusses the "planetary safety" issue, nor have I seen anybody suggest that it should. So why are we even dicussing this? (TimothyRias (talk) 21:05, 17 October 2008 (UTC))
Sorry if I reacted with knee-jerk negativity...., as I said earlier. The original query here concerned the seriousness of the issue, and I thought the safety question might have been in the mind of the editor who posted it. Anyhow, the possible creation of micro BHs does seem to be a serious possibility, though not a safety concern. Wwheaton (talk) 03:50, 18 October 2008 (UTC)
CPT symmetry
Latest comment: 16 years ago10 comments6 people in discussion
Well, since black holes aren't a law of nature, that is hardly relevant. Theories that are CPT invariant may very well have no CPT invariant solutions. Also, I'd love to see proper source of that claim.(TimothyRias (talk) 13:43, 23 October 2008 (UTC))
I also would like to see a physically convincing explanation (reliably sourced, of course) of how BHs violate CPT symmetry before I'd believe it, since CPT is almost universally accepted as a bedrock feature of current physical theories and both BHs and CPT have been intensively studied for many decades. I believe that argument would have to show that a Charge—, Parity—, and Time—reversed BH solution could not be a solution of the underlying equations of quantum mechanics and general relativity? I see no problem with C or P, and I believe time-reversed BHs have long been understood as White holes, of which the Big Bang is the prime example. Wwheaton (talk) 16:15, 23 October 2008 (UTC)
I consider a system of two particles, an electron and a black hole in its center of mass. The electron crosses the event horizon from outside the black hole. After a parity transformation P , that is a simultaneous flip of all spatialcoordinates, there is still an electron crossing the event horizon from outside the black hole. After a charge transformation C, I observe a positron still crossing the event horizon from the outside. Finally, after a time transformation T, I can see a positron leaving a black hole, that is in fact no black hole. Therefore, black holes violate CPT symmetry. --84.59.224.16 (talk) 09:32, 24 October 2008 (UTC)
Actually after a "T reversal" (note that in the context of GR this a somewhat ambiguous notion), the black hole becomes a white hole. So, still no problem. (TimothyRias (talk) 12:42, 24 October 2008 (UTC))
Agree. A time-reversed BH is a white hole (WH), still physically a valid solution in GR. (Note that white holes are possible physically since they expand so fast that although they are in some sense inside their own Schwarzschild radius, the mass on one side [say the right] can never get the word about the mass on the other [left, say] side needed to complete the BH, because the gravitational signals cannot travel fast enough. Both BH & WH solutions have a singularity, but for a BH it is in the future, while for a WH it is in the past. An obscure and delicate point, but I think the issue here is semantic.) Wwheaton (talk) 17:09, 24 October 2008 (UTC)
If really a time reversed – just think of a movie running backwards – black hole (BH), that might be called a white hole (WH), is still physically a valid solution in general relativity (GR), an object having the same size and mass as a BH might not have enough gravity to be a BH. That means, the gravity is not exclusively caused by the mass or energy. You can explain that? —Preceding unsigned comment added by 88.68.98.182 (talk) 09:20, 27 October 2008 (UTC)
You are making no sense what so ever. Also, this is NOT the place to discuss these issues. Find yourself a physics forum and that your nonsense there. This page is discussing changes to the Black hole wikipedia article, not for discussing BH's themselves. (TimothyRias (talk) 11:29, 27 October 2008 (UTC))
You are right, the story about the WH makes no sense. BHs violate CPT symmetry. A CPT transformed BH has same size and mass. It must be a BH too or the whole theory about BHs does not make any sense. --84.59.226.254 (talk) 13:56, 27 October 2008 (UTC)
(If you knew what you were talking about, you would know they make sense.) Now take this discussion elsewhere, as it has absolutely no relation to improving the article. Wikipedia is not a forum. (TimothyRias (talk) 15:44, 27 October 2008 (UTC))
Multiple issues
Latest comment: 16 years ago2 comments2 people in discussion
Sorry but this article:
is missing citations in many sections;
has too much unexplained jargon;
repeats article subject in section titles (per WP:HEAD);
has single-paragraph sections and single sentence paragraphs (per WP:LAY);
is too long and needs to be split up or further summarized, (per WP:SS).
&c. Thus I tagged with a multiple issues template. To get back to GA, I believe needs a thorough going over. Thank you. =) —RJH (talk) 21:56, 30 October 2008 (UTC)
The article does have a large number of issues. I have been trying to get at least the content up to par, but have gotten stuck on the section on observations. (There is just too much going, and it is hard to get a good representation of everything that is out there.) By all means help out wherever you can. (TimothyRias (talk) 12:56, 31 October 2008 (UTC))
evaporation
Latest comment: 15 years ago3 comments2 people in discussion
hi;
i've gone through the whole article, & the stuff about evaporation is kind of a mess.
the same info is repeated several times, unnecessarily
i haven't changed anything yet, but it does need work.
i'm starting a talk section here, to discuss how best to do that (rather than battle to the death); if i don't get any replies within a few days, i'll start revising & see how it goes...
all comments are welcome :)
the use of the term evaporation is being blurred between the process of the black hole emitting radiation, & the (eventual) end result of the black hole disappearing completely. all black holes evaporate by emitting hawking radiation, regardless of their size/mass, but black holes above a certain mass emit their mass via hawking radiation more slowly than they absorb mass from the cosmic background radiation. so they are, at this time, gradually increasing in mass, instead of reducing.
however, when the c.b.r. of the universe has cooled enough, all black holes will eventually emit more mass than they absorb, & will eventually disappear via hawking radiation evaporation.
there are several explanations of this written into the text,but none of them is complete & the number of them is redundant.
the part about c.b.r. cooling over time, causing all black holes, even the largest, to eventually boil away, was included in this article previously, & seems to have disappeared
it should be restored; it's immediately relevant to the article, dealing with the life cycle of black holes.
there is also what appears to be an unsubstantiated claim, & certainly an inadequately explained one in the section on micro black holes:
"However, if micro black holes can be created by other means, such as by cosmic ray impacts or in colliders, that does not imply that they must evaporate."
i think that should require a citation, & at the very least needs to be explained further (in this section, not just on its separate article page).
finally, off-topic; there used to be a rather well-written bit about the probability of black holes colliding with the earth/sun.
Replying to the last remark first. There was a section about that, but it definately was not well written. Nor was it notable in any sense. Issie of collidng with a black hole simply is a non issue from a scientific point of view, and has never had any real notable coverage. There was a quite general consensus to get rid of the entire section.
About evaporation, you seem to have a very gung ho attitude about the subject. Please, not that Hawking radiation has never been observed, and it is nowhere near a theoretical certainty that it must exist. It is even more uncertain that if it exists it must actually lead to evaporation. So some caution is needed when discussing it. You do however raise a valid point about the redundancy of its treatment. The "Hawking radiation" subsection in the features section probably should just talk about hawking radiation without really mentioning evaporation. The "evaporation" subsection in the evolution section should probably say a little more about the different theoretical possibilities for the end stage of the evaporation and that its is subject of scientific debate. Then theres is the somewhat troublesome "advanced topics" section which just has a lot of redundant information, this section probably needs to be completely integrated with the rest of the text. (TimothyRias (talk) 22:01, 8 November 2008 (UTC))
Lol, hence you understand my dread about tackling this single-handed. Re: The risk of being hit by a black hole. I disagree; i think it was reasonably well-written & fun, without violating wikipolicy. It certainly didn't count as high science, but it was something of relevance & interest to the reader, & i'm not aware of it having been factually incorrect. Maybe we are thinking of different things, or different versions? The one i read was something like 1 yr + ago, & i believe the article had not be de-listed as a featured article yet. Lx 121 (talk) 21:35, 1 December 2008 (UTC)
Someone might like to bring the article up to date
Latest comment: 15 years ago5 comments3 people in discussion
Is there a boffin who regularly edits this page who might like to include info such as that here (and similar sources}? The article's second paragraph -(last sentence in particular) - needs amendment to bring it up to date. 222.152.164.206 (talk) 20:01, 10 December 2008 (UTC)
All the PR blatter aside. Nothing really new has been proven. The observations of Sgr A just show that there is an object of extremly large mass and very little spacial extend. The best candidate for such an object would be a black hole. However it doesn't really prove that there is a black hole. It does not for example prove that no light can escape from the region, etc. It could however be any of a large class of exotic hypothetical objects. Maybe it is a fuzzball (which I would count as a BH) or a Q-star or a gravastar or something we haven't thought of yet. (TimothyRias (talk) 23:11, 10 December 2008 (UTC))
Well now. Wikipedia is supposed to give all p'sov, providing they are referenced. TimothyRias, you say " However it doesn't really prove that there is a black hole." The link I gave says the following --
"Researchers from the Max Planck Institute for Extraterrestrial Physics used two telescopes operated by the European Southern Observatory in Chile to watch stars as they circled the centre of the Milky Way. The 16-year study, now published in the Astrophysical Journal, has proved beyond doubt that lurking at the very centre of the galaxy is a black hole."
You might well be right TimothyRias, but so might the people who carried out a study for 16 years and say they have established beyond doubt that black holes do exist. That claim can be fully referenced. PhySusie, I believe the sentence I referred to should be expanded by adding after "black holes do exist in our universe", something along the lines that this was confirmed by the Max Plank 16 year study. That (fully referenced), would give more authority to that sentence. Is all. 222.152.164.206 (talk) 20:22, 11 December 2008 (UTC)
Well the media have been widely misquoting the article in the Astrophysical journal. Partly because journalists tend to have no clue about physics (even the science reporters), but probably because an overly optimistic press release from the communication department of the Max Planck instistitute for Extraterrestrial Physics. The actual journal article is much more nuanced. It basically states that their study is the best evidence so far for the existence of supermassive black holes. But even that argument basically realies on the assumption (which is the general concensus among the astronomy community) that stellar black holes exist. I agree that the report should definitly be referenced in the article, probably in the section on supermassive black hole candidates. But the report doesn't really say anything new about the actual existence of black holes. (TimothyRias (talk) 21:58, 11 December 2008 (UTC))
Recommended Split Idea.
Latest comment: 15 years ago2 comments2 people in discussion
Latest comment: 15 years ago2 comments2 people in discussion
In the third paragraph of the subsection Black hole types, it says, ...Q^2+(J/M)^2 ≤ M^2 for a black hole of mass M. Black holes saturating this inequality are called extremal. Can someone please clarify what 'saturating the inequality' means. At first, I thought it meant equality. Or does it mean that the RHS is very huge compared to the LHS of the inequality ? Either way, I think it needs to be reworded. Thanks. MP(talk•contribs)16:42, 22 December 2008 (UTC)
This is an archive of past discussions about Black hole. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.
DoneIt's been fixed. It's actually spelled absorption, but thanks for the pointer! ~ mazca t | c 22:21, 10 September 2008 (UTC)
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