![]() | This is an archive of past discussions. 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. |
Archive 1 |
This Accretion Disk page says that quasars "can convert about 10 percent of the mass of an object into energy as compared to around 0.5 percent for nuclear fusion processes." However, the quasar page states that quasars "can convert about half of the mass of an object into energy as compared to a few percent for nuclear fusion processes."
The wording of both sentences is identical, just the numbers have changed. One of these has to be wrong, no? I am in no position to say which, but maybe someone smarter than I can clear this up? Patbert 05:48, 9 January 2007 (UTC) patbert
I recall reading a short article about a year ago announcing that Stephen Hawking had retracted his assertions of belief in the theory of black holes. He had done some work to reexamine the correctness of his math, and came to the realization that it wasn't necessarily true that the phenomenon we call a black hole constituted a space-time singularity. I'll try to dig up the article... Infinite.ki 00:05, 26 January 2006 (UTC)
You are mistaken. His recent work was involved with the problem of unitarity with the formation / destruction of black holes, not whether black holes as a class of objects exist or not. (Although his proof involves the fact that an observer far enough away cannot know for certain if a given black hole exists at a given location.) Anyway, accretion disks can form around neutron stars, white dwarfs, in T-tauri stars and even in the formation of a planet - so whether or not black holes exist isn't really important for this particular article. Sfuerst
I think the spelling should be changed to 'disk', though, in all references. In my experience as a trained astronomer, and as a native american english speaker, the only time the spelling 'disc' is preferred is for 'compact disc'. I cannot recall seeing 'accretion disk', 'galactic disk', 'protoplanetary disk', etc spelled any other way, in american publications. Probably happens, but certainly in the minority. Any agreement to change the name? Myrrhlin
"Accretion disk" is much more common than "Accretion disc" in the scientific literature, even though technically the word "disc" is more correct. Changing it to the more common form would probably be a good idea. Sfuerst 20:22, 18 March 2006 (UTC)
The reason I changed 'protoplanetary disk' to 'nova' is that there is an accretion process going on in a protoplanetary disk which has nothing to do with accretion disks. While there _may_ continue to be accretion of H/He gas onto the protostar, this is (I would argue) not the 'accretion' one would usually be talking about in the protoplanetary disk. Use of the term 'accretion disk' to describe a protoplanetary disk leads to confusion. Please see my comments on the solar nebula.
Also, you reverted away the other edits I made, which may have needed some polishing, but added more information about accretion disks in close binaries with stellar remnants. I also had a sentence specifically addressing the possible confusion over the term accretion when referring to protoplanetary disks. Any comment why you removed these changes by reversion, instead of incorporating them? You marked your edit as minor. perhaps you did not notice those other changes? Myrrhlin 04:40, 21 March 2006 (UTC)
Both of these issues lead me to really question more generally what the tone and direction of scientific articles should take. Should it represent current "traditional" scientific thinking, or a broader spectrum of ideas including largely untested or even unlikely (but still "possible") explanations? In the solar nebula article i edited, there was already a reference to a theory i'd never heard of, which i guess was placed there by a proponent (or perhaps even THE proponent). If a model has little support by the relevant scientific community, should it be included, without a discussion of why it is not accepted as credible? I left it there, not being one to censor anything, and not knowing enough to write anything about problems with it. To be balanced, an article should allow mention of any crackpot theory, but only when a discussion of its failings is also present. Myrrhlin 14:01, 24 March 2006 (UTC)
Why do accredition disks form, instead of accretion spheres, or some other shape? This rather basic question is not answered in the article. -- Beland 07:32, 22 April 2007 (UTC)
Well, sounds like a good question, but all you have to do is a little reasoning. All it takes is an understanding about angular momentum. Not that I've ever even taken a physics class before, so I could be absotely wrong, but it seems to me that because the Roche Lobe is tear-drop shaped, the matter being fed into the accretion disk is kinda funneled down into a thin stream, as it is in the pictures. Now, the stream is crazy. Instead of going straight from the companion star to the primary, because they're both spinning, it misses. If you spin in a chair with a friend, try and throw a ball at him or her when you're directly facing them. It's going to miss because the ball will keep its momentum. So that stream misses, but the primary catches it on the rebound. Now the matter's spinning like crazy because it's getting pulled in hard while it spins really fast. So it's being flattened out like spinning a pizza crust in the air, while at the same time being pulled in. Now, keep spinning in that chair of yours. Give one good push, then pull your arms in. You'll notice that the closer you pull in, the faster you spin. That's because the closer you are to the center, the less distance you have to travel, so that same amount of energy will spin you faster. It's what ice skaters do to spin faster without pushing off again. So the matter is pulled in and spins faster, and because it spins faster, it's pushed out. It's like my relationships: the closer you get in, the faster you spin, the harder you're pushed out. The farther you're out, the slower you spin, and the easier you get pulled in. Push and pull, push and pull, lots of friction causing heat between all the particals, until something gives. In the case of a disk, it's thought to be that the streams being shot out at the poles (remember how it doesn't have to move as much when it's close in? It's kinda like being on a merry-go-round in the center where you can stand up) to release the energy of spinning, trying to balance it out, finding the easiest path. And in my relationships, it usually ends in bad memories and a court fee. Either way, it's fun to watch. ElijahD 11:12, 10 May 2007 (UTC)
I added the "confusing" tag right before the "α-Disc Model" section because it comes out of nowhere. More context would be helpful about what attributes of accretion disks are well-understood, and what bulk properties are correctly predicted by gravitional models. Context about the scientific status of the α-Disc Model and the magnetic turbulence mechanism (has it been accepted by scientific consensus? still only a proposal?) is also needed. -- Beland 07:37, 22 April 2007 (UTC)
The external link to Jeong's so-called theory of dipole-gravity has been removed. The terms used and claims made by the author are misleading and confusing. Please refer to Jeong’s contributions at [1] (Wikipedia:Articles for deletion) to see that Jeong’s model of “dipole antigravity,” which he now refers to as “dipole gravity,” is deemed unfit for Wikipedia, citing serious flaws in his paper. —Preceding unsigned comment added by Djily ( talk • contribs) 20:53, 31 January 2008 (UTC)
Dipole gravity literally means two pole gravity. One pole is attractive and the other pole is repulsive. What would you call a repulsive gravity? Antigravity!!!
What else?
So, dipole gavity is the same name for dipole antigravity. But Antigravity sounds like a pure Scifi?
Not really. Has it ever occurred to your mind that the jets could be due to the antigravity effect from the rotating core of the galaxies?
If you have a true gravitomagnetism, wouldn't it be like two opposite mass poles that one side is attractive and the other side is repulsive?
That's exactly what is happening in the theory of dipole gravity although it is not even a "theory". It is a self evident general relativity. You have to study it in detail to understand it fully. The paper is available at [2]. —Preceding unsigned comment added by 70.128.226.243 ( talk) 11:28, 31 March 2008 (UTC)
"This process can convert about 10 percent of the mass of an object into energy as compared to around 0.5 percent for nuclear fusion processes."
This statement contradicts the mass-energy equivilent article that states that black holes can convert mass into energy, and has it listed under the "perfect conversion" section, insinuating that the process is 100% efficient. ScienceApe ( talk) 16:48, 13 June 2008 (UTC)
I don't understand why the black hole is leeching a stream of gas from the star, rather than the entire star just falling into it. —Preceding unsigned comment added by 82.4.15.210 ( talk) 20:18, 3 July 2009 (UTC)
Accretion discs seem to exist at the planetary scale (eg formation of Saturn and its moons) and stellar level and also at the galactic level - but not at intermediate levels. There are, for example, no globular clusters in the form of accretion discs or any Intermediate-mass black holes with proportionate accretion discs. Should the article explain this - or highlight the matter? -- Tediouspedant ( talk) 13:19, 7 February 2010 (UTC)
Does anyone have more detailed input regarding radation jets. Perhaps we are observing is simply occuring because it could not occur any other way as easily. The jets may just be taking the path of least resistance. —Preceding unsigned comment added by 58.107.48.83 ( talk) 18:11, 26 June 2010 (UTC)
The (non-redirect) page title is "Accretion disc" but the article starts "An accretion disk is a structure..." and then seems to use both forms throughout the article. I think it would be preferable to stick to one form, even if the choice as to which one, is arbitrary. MSUGRA ( talk) 17:20, 3 July 2015 (UTC)
The second paragraph of manifestations says that the gravitational gradient of the black hole is responsible for the friction heating of material, yet super massive black holes have very little gravitational gradient. This apparent contradiction needs to be explained. 2A01:E35:2E68:4F50:FADB:7FFF:FE9E:34E7 ( talk) 07:18, 26 June 2013 (UTC)
Updated the explanation. — Preceding unsigned comment added by 178.15.151.163 ( talk) 09:57, 28 January 2016 (UTC)
The intro was recently redone. I reverted the changes because I felt they made it less clear. What's wrong with the current intro, and how can we improve it? -- Parejkoj ( talk) 16:28, 12 December 2008 (UTC)
Different 'colours' emitted in different directions from accretion disk - eg in quasars Another quasar mystery solved - Could describe here (with a better source) ? - Rod57 ( talk) 12:07, 28 June 2017 (UTC)
I think the article should also mention General Relativity's result of a Innermost stable circular orbit as a mechanism why matter ultimately ends up falling into the black hole. — OttoMäkelä ( talk) 09:19, 23 February 2018 (UTC)