Talk:Oort cloud

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Argument from Ignorance

...Doesn't the whole concept of the Oort Cloud fall under the Wiki definition of "Argument from Ignorance"? >_> ~Dah Cheese —Preceding unsigned comment added by 76.179.137.176 (talk) 03:43, 23 August 2010 (UTC)

The argument from ignorance is "It has never been disproven, therefore it must be true." The key word there is must. "It has never been disproven, therefore it may be true (or in the case of the Oort cloud, very likely is true, given the evidence), is not an argument from ignorance. Serendi^podous 19:48, 23 August 2010 (UTC)

However, it is taught and put forth in particularly this article as binding and very real truth, with no alternative at all proposed or theorized. At least it seemed that way when I read it. ~Dah Cheese —Preceding unsigned comment added by 76.179.137.176 (talk) 01:33, 28 August 2010 (UTC)

The very opening line says, "hypothesized spherical cloud of comets". It then goes on to say it may lie roughly 50,000 AU from the Sun and that there has been "no confirmed direct observations of the Oort cloud". As the modern accepted theory what-else do you want it to say without getting off topic? -- Kheider (talk) 04:41, 28 August 2010 (UTC)

An imaginary cloud of comets is about as scientific as leprechauns. I wouldn't object at all, if not for the heavy handed way the writers make the hypothesis out as if it is a real thing. I suggest editing it with a view to making it seem more like a tidy story, that has no evidence whatsoever, Because that is what it is. —Preceding unsigned comment added by 98.212.63.192 (talk) 19:54, 12 December 2010 (UTC)

It has plenty of evidence. Every long period comet ever observed is evidence for its existence. Serendi^podous 21:04, 12 December 2010 (UTC)

This should be something that will be shortly resolved by advancing capabilities to image and assay in fine detail the matter in the region in question. There needs to be something connecting the hypothesis with current science in the way that Higgs boson has. My sense is that the current text understates the evidence and/or overstates the hypotheticality. 72.228.177.92 (talk) 11:56, 21 February 2011 (UTC)

I know of no telescope even in the planning stages that is powerful enough to observe the Oort cloud. This region will remain hypothetical for the forseeable future; that said, because, as you say, it is still possible to observe it, given adequate technological advances, the Oort cloud remains a falsifiable hypothesis. Serendi^podous 14:28, 23 February 2011 (UTC)

Do you mean optical telescope? I doubt that's the proper instrumentation for this purpose. 72.228.177.92 (talk) 07:18, 25 February 2011 (UTC)

No telescope, no matter what its wavelength, could spot an object the size of Halley's Comet from a distance of 20,000 AU. Serendi^podous 08:08, 25 February 2011 (UTC)

The only reason something like Tyche (planet) in the Oort Cloud would be observable in the infrared is because as a gas giant Tyche generates its own internal heat. -- Kheider (talk) 09:55, 25 February 2011 (UTC)

I presume the imaging in question will use an active signal to detect the matter in question rather than relying on radiation or any other force (other than gravity) of which it (the cloud) is the source. 72.228.177.92 (talk) 09:23, 26 February 2011 (UTC)

Absolute Magnitude

It seems to me that the two normalizations of absolute magnitude can cause confusion. In "Structure and composition" and reference 14, the 1 AU distance normalization is used. Perhaps this could be clarified by stating non-stellar absolute magnitude. Filiulodimeapatro (talk) 04:10, 21 September 2010 (UTC)

Absolute magnitude in this sentence links to Absolute_magnitude#Solar_System_bodies_.28H.29. Ruslik_Zero 15:39, 21 September 2010 (UTC)

Criticism Section

The article needs a little bit of coverage of criticism to insure that it is upholding the principle of scientific falsifiability. My suggestion is below--Novus Orator 03:06, 7 November 2010 (UTC)

Criticism

The Oort Cloud theory, while generally accepted in the scientific community, has come under some criticism. R. A. Lyttleton questioned the procedures behind adopting a comet shell model in a 1974 research paper:

"The procedures adopted as theory for a shell of comets are shown to be invalid. Any plot of numbers of Long-period comets against 1/a will automatically exhibit a peak at small values of this parameter, and cannot be inverted to demonstrate a high volume-density of aphelia in space. The positions of actual aphelion-points show no sign of any concentration at any range. Further, the aphelion-distance undergoes large almost random changes owing to planetary perturbations at each return, and present values can yield no indication of original positions. That a group of some forty, or even twenty, comets selected for other reasons would all be coming in for the first time has such evanescent probability as to be an entirely inadmissible assumption...The plain conclusions emerge that the shell-theory is devoid of any support by facts, and that the alleged shell of comets is non-existent. "-R.A. Lyttleton

Young earth creationist Danny Faulkner claimed that comets should be all gone if the universe is billions of years old:

"Comets are continually being lost through decay, collisions with planets, and ejections from the solar system. If the solar system were billions of years old, then all comets would have long ago ceased to exist if they were not continually being replaced"-(Faulkner 2001).

The article already says that the Oort cloud comets formed at planetary distances and then were sent out into the shell by planetary action. I don't really understand what the difference is. Serendi^podous 07:55, 7 November 2010 (UTC)

What Novus Orator means is that some (such as Lyttleton) view this hypothesis as implausible, and that this fact should be mentioned in the article. CielProfond (talk) 18:41, 7 November 2010 (UTC)

Does it offer an alternative explanation? Plus, that paper is 36 years old; I would prefer a more modern objection, since science tends to reject older hypotheses. Serendi^podous 18:43, 7 November 2010 (UTC)

I'm open to a different critic. All that matters is that a little bit of ink is given to some of the issues with the theory.--Novus Orator 05:40, 8 November 2010 (UTC)

Assuming there currently are any. This guy's ideas may have been thrown out by another paper. Plus, refutation isn't enough in science; you have to offer your own plausible explanation. Does he? Serendi^podous 08:09, 8 November 2010 (UTC)

I will add more quotes from his paper that detail his explanation (See Above)..--Novus Orator 09:02, 8 November 2010 (UTC)

Yes, he makes the case that there is no Oort cloud, but as far as I can tell he makes no case as to how the long-period comets are appearing in our skies. Serendi^podous 09:11, 8 November 2010 (UTC)

I added a quote from Faulkner that gives the Young-earth creationist solution to the problem.--Novus Orator 09:22, 8 November 2010 (UTC)

Uh, yeah. That's why scientists proposed the Oort cloud as a solution to the problem. This is a scientific article. If the only alternative to the Oort cloud is to endorse YEC, then we can't do that, as YEC is not a scientific hypothesis. Oh, and by the way, I typed "lyttleton" and "oort cloud" into Google, and this article, published 3 years later, came up, refuting Lyttleton's assertions. Serendi^podous 09:24, 8 November 2010 (UTC)

Faulkner may not be notable enough, though you might want to actually include a quote from that refutation of Lyttleton at least. It seems that the principle behind this article is that it must exist rather than accepting the unthinkable alternative that the universe is young.:) I'll leave for now (I don't actually edit creation/evolution related articles due to a strong personal bias towards creationism) but I just wanted to bring it up so you guys can discuss it...--Novus Orator 09:45, 8 November 2010 (UTC)

As long as your not an extreme fundamentalist, God can exists not matter how old (or big) the Universe is. I know priests that happily accept and teach the age of the Universe. This is a scientific article that needs scientific explanations. Twenty years from now science may have a better theory, but for now... -- Kheider (talk) 13:56, 8 November 2010 (UTC)

I have problem with "2. Their orbits could have been disrupted by an as-yet-unknown planet-sized body within the Oort cloud.[48]" in the Oort cloud objects (OCOs) section. Given distance from the sun involved and the expected planetary discriminant, The body in question would have to be 4 MJup or greater to have cleared it's orbit, and an outer (super) Jovian has been both effectively ruled out by WISE and that it could not be in a highly inclined orbit or there would be noticeable effect on the other outer system objects. Abyssoft 74.202.23.198 (talk) 21:13, 15 November 2011 (UTC)

The WISE data hasn't been fully released yet, so I wouldn't say it's effectively ruled it out. Serendi^podous 21:19, 15 November 2011 (UTC)

MOND

As I recall, MOND is a fairly contentious hypothesis, and is not accepted by the majority of physicists. This reference to MOND will have to be qualified somehow, and I'm not sure it deserves its own section. Serendi^podous 22:40, 22 February 2011 (UTC)

This should go into a note. In addition, this section does not contain any references that actually discuss Oort cloud. Ruslik_Zero 09:53, 23 February 2011 (UTC)

Then this is OR and should be removed. Serendi^podous 10:14, 23 February 2011 (UTC)

Sorry, the paper of Milgrom (1983) considers solar system tests. So, the section should be made into a note. Ruslik_Zero 16:22, 23 February 2011 (UTC)

I've rephrased the note; however some reference to the experimental validity of MOND should be added. Serendi^podous 16:57, 23 February 2011 (UTC)

Density of Oort cloud

Regarding the image caption change, the surface area of the outer edge of the Oort cloud would be about 30 billion square AU (4 * pi * (50000 AU)^2 ). Even with billions of comets that would be less than one comet per square AU, an extremely sparse density. The image makes it look like you could barely poke your finger into the cloud without hitting a bunch of comets, so I believe that noting that the density is exaggerated is helpful. Miraculouschaos (talk) 04:17, 8 August 2011 (UTC)

The image depicts the entire Oort cloud, which actually contains many billions of comets. Only an infinitesimal fraction of these are shown. The only way the density could be exaggerated would be if the number of spots in the image exceeded the actual number of comets. Density simply refers to the number of comets per unit volume. How the image "looks" is not relevant; in actual fact, the true density is far higher than shown. This might be more obvious if a scale bar were present in the image, along with an indication of the actual size of a comet. WolfmanSF (talk) 05:42, 8 August 2011 (UTC)

Objection against the Nemesis theory.

As I recall in reading what may well have been the original Nemesis theory article in Scientific American nearly thirty years ago, its claim to fame was that it gave AN explanation to the 26 million year periodic mass extinctions of dinosaurs and their friends. Even then its argument was very weak: essentially, it said that any kind of periodic event with a period as long as 26 million years "could only have an astronomical cause".

And straight away there was an objection that an orbit that far away from the Sun would be utterly unstable (by a mechanism such as that described in the "Tidal effects" section of this article) and would not show any kind of regular periodicity. So isn't this Nemesis dude a hypothesis that has been discredited for a long term? Is it therefore really worthy of mention? Old_Wombat (talk) 09:14, 8 August 2011 (UTC)

I have a tendency to agree that Nemesis as defined in 1984 is all but dead. See: Nemesis is a myth (Max Planck August 01, 2011) -- Kheider (talk) 09:36, 8 August 2011 (UTC)

New Section - Are Voyager/Pioneer in or near the Oort Cloud?

Thumbs up on the article reaching FA status, it's a very interesting read. I had a question that I thought I'd post here. Where are the Viking and Pioneer probes in relation to the Oort Cloud and will they reach it eventually? (If so, how long?). I can't quite work it out from the articles as the Viking 2 talk about "...studying the boundaries of the Solar System, including the Kuiper belt, the heliosphere and interstellar space" but this article doesn't mention the heliosphere so I can't quite rationalise the distance.

Thanks for any info you can provide, I read a lot of the astronomy articles on Wikipedia purely as they are very interesting. CaptRik (talk) 15:05, 8 August 2011 (UTC)

The Voyagers will reach the Oort cloud in about 12,000 years. It's WAAY out there. Serendi^podous 15:07, 8 August 2011 (UTC)

Pronunciation is wrong

Could someone add a ː after the vowel? Thanks. I'd do it myself but the article is protected. — Preceding unsigned comment added by 82.139.87.39 (talk) 02:40, 21 September 2011 (UTC)

I hope you're right. Serendi^podous 05:35, 21 September 2011 (UTC)

You might want to take a look at the result. — kwami (talk) 08:26, 21 September 2011 (UTC)

Never mind. They have a 3rd transcription in the OED. — kwami (talk) 08:27, 21 September 2011 (UTC)