Size Comparism Of The Moons Of The Gas Planets, Moon Systems of the gas giants compared |
Size Comparism Of The Moons Of The Gas Planets, Moon Systems of the gas giants compared |
Guest_spaceffm_* |
Nov 15 2005, 12:10 AM
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Nov 18 2005, 07:09 PM
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Member Group: Members Posts: 648 Joined: 9-May 05 From: Subotica Member No.: 384 |
QUOTE (jski423 @ Nov 18 2005, 09:36 PM) Since the only purpose of these images are to show scale, some artistic licence was taken to make them more attractive. Celestia was used to create the idvidual images with textures taken from various sources to include but not limited to, Nasa/JPL and Steve Albers along with some I've created myself. OK!! That's just great but if you don't mind ;I have one question: -Why did you write radiuses instead of diameters ? Maybe this is the "Stupid question of the day"..... -------------------- The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful.
Jules H. Poincare My "Astrophotos" gallery on flickr... |
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Nov 18 2005, 08:42 PM
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
QUOTE (Toma B @ Nov 18 2005, 07:09 PM) OK!! That's just great but if you don't mind ;I have one question: -Why did you write radiuses instead of diameters ? Maybe this is the "Stupid question of the day"..... I know it is a pretty common practice - many tables use radius instead of diameter. I am not really sure if it is just a preference thing or if there is a real reason, but it does mean you have to be careful when comparing the size of two worlds to make sure you aren't comparing a radius to a diameter and thinking both are diameters or radii., -------------------- |
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Nov 18 2005, 09:18 PM
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
QUOTE (tedstryk @ Nov 18 2005, 01:42 PM) I know it is a pretty common practice - many tables use radius instead of diameter. I am not really sure if it is just a preference thing or if there is a real reason, but it does mean you have to be careful when comparing the size of two worlds to make sure you aren't comparing a radius to a diameter and thinking both are diameters or radii., I think it has to do with what the constants are used for by scientists -- physical studies of the bodies, navigation, that kind of thing. If you're interested in the force of gravity or pressure or something within or just outside a body you're interested in the radial distance from the center. Same with navigation. Most geophysical modeling (at least mathematical modeling) is done in polar coordinate systems, which measure spatial positions in radial distance from some center point, typically the center of gravity. Also many of these things are triaxial ellipsoids, which are described mathematically using their semi-axes, that is, their radii. You do have to be very careful. My favorite single source for solar system physical data, the National Space Science Data Center, uses radii for planets/moons and diameters for asteroids -- and I have repeatedly forgotten that fact. Oops. --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Nov 18 2005, 09:40 PM
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
QUOTE (elakdawalla @ Nov 18 2005, 04:18 PM) I think it has to do with what the constants are used for by scientists -- physical studies of the bodies, navigation, that kind of thing. If you're interested in the force of gravity or pressure or something within or just outside a body you're interested in the radial distance from the center. Same with navigation. Most geophysical modeling (at least mathematical modeling) is done in polar coordinate systems, which measure spatial positions in radial distance from some center point, typically the center of gravity. Also many of these things are triaxial ellipsoids, which are described mathematically using their semi-axes, that is, their radii. You do have to be very careful. My favorite single source for solar system physical data, the National Space Science Data Center, uses radii for planets/moons and diameters for asteroids -- and I have repeatedly forgotten that fact. Oops. --Emily Radius for planets and diameters for comet, asteroide or meteor sound logical to me. The smaller bodies do not have a constant radius. Rodolfo |
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