Comments on: A hex on Saturn http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/ I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog. Fri, 09 Jan 2009 04:38:24 +0000 http://wordpress.org/?v=2.3.1 By: Jeff Allen http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-133821 Jeff Allen Wed, 12 Nov 2008 22:11:14 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-133821 Following on the discussion and the question of "walls" to the container. I think we'd find that a combination of gravity and pressure produce a very nice "virtual" container. In stead of thinking of the atmosphere pressing against the planet surface as a limit, think instead of gravity and the volume of atmosphere as producing a shell instead. In fact, you could consider it in terms of three rotations. 1) that of the planet surface 2) the different rotation rate of gas moving around the same axis of rotation and 3) the effectively "non-rotating" limit presented by attenuation of atmosphere and Saturn's gravity. Might be an opportunity for some fluid physicist to see what patterns emerge in a fluid when you have a sphere rotating within a second sphere, with the fluid sandwiched between them. Following on the discussion and the question of “walls” to the container.

I think we’d find that a combination of gravity and pressure produce a very nice “virtual” container. In stead of thinking of the atmosphere pressing against the planet surface as a limit, think instead of gravity and the volume of atmosphere as producing a shell instead. In fact, you could consider it in terms of three rotations. 1) that of the planet surface 2) the different rotation rate of gas moving around the same axis of rotation and 3) the effectively “non-rotating” limit presented by attenuation of atmosphere and Saturn’s gravity.

Might be an opportunity for some fluid physicist to see what patterns emerge in a fluid when you have a sphere rotating within a second sphere, with the fluid sandwiched between them.

]]> By: George http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-100409 George Sun, 13 Jul 2008 15:47:53 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-100409 The article: “Saturn's north polar hexagon” Mar. 28, 2007, by Emily Lakdawalla, in The Planetary Society Weblog, and the comment by DoctorAtlantis [May 28th, 2008 at 5:10 pm] in Blogs/Bad Astronomy (http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/) require clarifications. Richard Hendricks, a space enthusiast, pointed out in Emily’s article an arXiv paper, published in 2006, titled "Polygons on a Rotating Fluid Surface", by Thomas Jansson et al. This paper was the precursor of a subsequent article that appeared in Physical Review Letters [Phys. Rev. Lett. 96, 2006, 174502] by the same authors: http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000096000017174502000001&idtype=cvips&gifs=yes. The erratum that accompanies the previously mentioned paper clarifies DoctorAtlantis’s comment. Emily’s hesitation whether or not the bucket experiments is applicable to Saturn’s stable hexagon because the planet “has no edges” can be argued as follows. The first to study mathematically the problem with an arbitrary number of polygon sides was J.J. Thomson [Treatise on Vortex Rings (Macmillan, London, 1883), p. 94]. Havelock [Philos. Mag. 11, 1931, 617] generalized Thomson’s treatment including also (among other things) an external confining wall. His analytical results indicated that besides the heptagon (N = 7), an external retaining wall is not expected to change the 'quality' of the rest of the N-gons. Furthermore, based on the work of Polvani et al. [J. Fluid Mech. 255, 1993, 35-64] we can also conclude that the planetary curvature is not anticipated to affect the basic features of the event either. The article: “Saturn’s north polar hexagon” Mar. 28, 2007, by Emily Lakdawalla, in The Planetary Society Weblog, and the comment by DoctorAtlantis [May 28th, 2008 at 5:10 pm] in Blogs/Bad Astronomy (http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/) require clarifications. Richard Hendricks, a space enthusiast, pointed out in Emily’s article an arXiv paper, published in 2006, titled “Polygons on a Rotating Fluid Surface”, by Thomas Jansson et al. This paper was the precursor of a subsequent article that appeared in Physical Review Letters [Phys. Rev. Lett. 96, 2006, 174502] by the same authors: http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000096000017174502000001&idtype=cvips&gifs=yes. The erratum that accompanies the previously mentioned paper clarifies DoctorAtlantis’s comment.

Emily’s hesitation whether or not the bucket experiments is applicable to Saturn’s stable hexagon because the planet “has no edges” can be argued as follows. The first to study mathematically the problem with an arbitrary number of polygon sides was J.J. Thomson [Treatise on Vortex Rings (Macmillan, London, 1883), p. 94]. Havelock [Philos. Mag. 11, 1931, 617] generalized Thomson’s treatment including also (among other things) an external confining wall. His analytical results indicated that besides the heptagon (N = 7), an external retaining wall is not expected to change the ‘quality’ of the rest of the N-gons. Furthermore, based on the work of Polvani et al. [J. Fluid Mech. 255, 1993, 35-64] we can also conclude that the planetary curvature is not anticipated to affect the basic features of the event either.

]]> By: DoctorAtlantis http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33977 DoctorAtlantis Wed, 28 May 2008 23:10:58 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33977 Funny that Emily found a group doing that fluid theory study. I just heard a different guy (Dr. Georgios Vatistas ) on CBC's Quirks and Quarks doing the same thing, finding stable geometric shapes in a fluid vortex, and he said he was merely validating the work of Nobel Prize winner J.J. Thomson. But it certainly does seem like various pressure regions could serve the purpose of generating the same effects that a beaker-wall serves in the lab. Or it's a very big Carbon molecule. Funny that Emily found a group doing that fluid theory study. I just heard a different guy (Dr. Georgios Vatistas ) on CBC’s Quirks and Quarks doing the same thing, finding stable geometric shapes in a fluid vortex, and he said he was merely validating the work of Nobel Prize winner J.J. Thomson.

But it certainly does seem like various pressure regions could serve the purpose of generating the same effects that a beaker-wall serves in the lab.

Or it’s a very big Carbon molecule.

]]> By: Jim McDade http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33976 Jim McDade Wed, 02 Apr 2008 22:52:38 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33976 What a beautiful sight! We will continue to discover amazing things as we continue our exploration of space. I can't wait. What a beautiful sight! We will continue to discover amazing things as we continue our exploration of space. I can’t wait.

]]> By: ceticismoaberto.com » Blog Archive » O Grande Hexágono de Saturno http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33975 ceticismoaberto.com » Blog Archive » O Grande Hexágono de Saturno Tue, 10 Apr 2007 10:07:49 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33975 [...] Saturno não é um cilindro com um fundo giratório, e seus gases não são líquidos, mas o trabalho de Hendricks mostra que fluidos rotatórios podem sim produzir polígonos regulares de forma espontânea nas condições adequadas. Como exatamente isto ocorre em Saturno parece assim um mistério especial solúvel através da exploração espacial. [via The Planetary Society blog, do qual este post é um plágio, visto no Bad Astronomy blog] [...] […] Saturno não é um cilindro com um fundo giratório, e seus gases não são líquidos, mas o trabalho de Hendricks mostra que fluidos rotatórios podem sim produzir polígonos regulares de forma espontânea nas condições adequadas. Como exatamente isto ocorre em Saturno parece assim um mistério especial solúvel através da exploração espacial. [via The Planetary Society blog, do qual este post é um plágio, visto no Bad Astronomy blog] […]

]]> By: Tormenta hexagonal en Saturno « Un pequeño paso para Neil http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33974 Tormenta hexagonal en Saturno « Un pequeño paso para Neil Sun, 08 Apr 2007 10:19:14 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33974 [...] Tormenta hexagonal en Saturno 8 abril 2007 Posted by Javier Arántegui in Espacio, Humor. trackback Hace unos días apareció en todas partes la imagen de una gigantesca tormenta hexagonal en el polo norte de Saturno: [...] […] Tormenta hexagonal en Saturno 8 abril 2007 Posted by Javier Arántegui in Espacio, Humor. trackback Hace unos días apareció en todas partes la imagen de una gigantesca tormenta hexagonal en el polo norte de Saturno: […]

]]> By: Irene http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33973 Irene Fri, 06 Apr 2007 16:10:20 +0000 http://blogs.discovermagazine.com/badastronomy/2007/04/03/a-hex-on-saturn/#comment-33973 Josie Says: April 3rd, 2007 at 1:34 pm I always think it’s funny when people see something with angles, and assume it has to be ‘unnatural’ in some way. Haven’t these people ever looked at a bee’s hive, or a sunflower? I wonder what it is about our brains that assume things like that have to be messed with by something outside natural forces? Well, Saturn is a gas planet, You would expect gas plantets to have a swirl. Yes, A lot of things in nature are geometric, I agree, but in this particular case, it is interesting, because it has been going on for a while(I think at least 30 years) and it's on a different planet made of gases Josie Says:
April 3rd, 2007 at 1:34 pm
I always think it’s funny when people see something with angles, and assume it has to be ‘unnatural’ in some way. Haven’t these people ever looked at a bee’s hive, or a sunflower?

I wonder what it is about our brains that assume things like that have to be messed with by something outside natural forces?

Well, Saturn is a gas planet, You would expect gas plantets to have a swirl. Yes, A lot of things in nature are geometric, I agree, but in this particular case, it is interesting, because it has been going on for a while(I think at least 30 years) and it’s on a different planet made of gases

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