Size Comparism Of The Moons Of The Gas Planets, Moon Systems of the gas giants compared Options

[Phillip]

These are wonderful posts! Here is a link to a University of Indiana site, which also has some pictures of relative sizes -- but only the "big boys" of the solar system and none of the moons. I found their verbal description a nice complement to the photos (and to work well for my small, food oriented brain): if the solar system were reduced by the order of one billion, then the earth would be the size of a grape, the sun would be 1.5 meters tall about one "city block" away from earth, Jupiter would be the size of a grapefruit -- five blocks away from the sun. Saturn would be an orange, ten blocks away and Uranus/Neptune would report in as lemons, 30 blocks away. But here is the kicker: how far away is the closest star? Still 40,000 KM away! Is the answer to Fermi's Paradox simply distance?? ( Anyway, I leave it to the others to assign our other (smaller) celestial bodies with their proper food symbol (peanuts and pistachios come to mind for the bigger ones).

http://www.indiana.edu/~geol105/1425chap2.htm

As to the discussions above regarding copyright, we should always be mindful, at least in the U.S. and other common law jurisdictions, of the "fair use" doctrine, which allows certain uses of copywritten materials even without consent of the creator/author. While this is a common law doctine, and hence no hard and fast rules (and the internet has introduced even more ambiguity until the courts sort it all out), some factors in favor of permitting use of copywritten material as "fair use" include, first, use for scientific or education purposes in lieu of commercial ones, second, giving proper attribution to the creator, third, use of only so much of the material as is necessary for the new use, and fourth, use of the material in a manner that does not "compete" with the work of the original creator (i.e. does not diminish the market available to the original creator). There are other factors, but applied more in literary than photographic contexts. Uses that a court would consider against a finding of "fair use" include first, is a non-copywritten or a reasonably priced copywritten substitute available (in which case the "fair user" should have used that instead), and, second, did the user make the material publicly available (a factor that made a lot more sense pre-internet, but which is is the sticky wicket in internet cases for the time being). Note however, none of the factors are determinative and a court would consider them as a whole under the given facts and circumstances. I did not see the original posts, but to the extent this is a collaborative scientific forum, we may want to consider the "fair use" aspects.

The concerns raised by "other" Doug (his hard work at creating scientifically sound reproductions should not be kidnapped by tr*lls to expound c*nspiracy theories) are very valid and are protected by "moral rights" that an author/creator retains -- even if he or she has assigned or released the copyrights. The doctrine of "moral rights" protects an artist from any intentional distortion or modification to the work if it would harm the artist's reputation. It protects the author from the extreme scenario of selling a work of art and assigning all copyrights in the work and then waking up the next morning to find the art, which everyone attributes to the artist, on billboards promoting an offensive political agenda or being descrated. Moral rights cannot be transferred and survive for as long as the author survives. So, the tr*lls can't go painting little green men on "Other" Doug's pictures. That's a no- no. Or, depending on where you live, a non-non.

But all of this raises perhaps an even more important point: if someone posts materials that infringes the copyrights of a third party, then the poster may have liability, but the real "publisher" of the infringing material is, unfortunately, the forum itself. Gulp. In the U.S., the Digital Millenium Copyright Act provides protection to certain forums (read: Ebay) who do not control what individuals are posting, BUT to secure that protection, the forum has to have in place a policy whereby if anyone thinks their copywritten materials are being posted improperly on the forum, there is a clear procedure to follow for notice to the forum, removal of the materials and opportunity for the "poster" to rebut the claim, etc.

As I do not have a scientific background, I tend to be a "lurker" on this forum in respect of the atmosphere of promoting scientific debate and analysis (versus speculation and hijinks), but if Doug would like when he returns, I would be happy to assist in the (pro bono) preparation of a "DMCA" notice procedure that would, at least in the U.S., provide a defense to possible copyright infringement claims. I would love to find a way to contribute to this excellent forum.

Sorry for the long post

Phillip

[helvick]

Great work elakdawalla!

Loved the site!

Look folks, Spaceffm's compilations are a good effort with good intentions.

If there are copyright issues lets try to pull together and assist spaceffm in resolving any copyright issues _if_ they exist. That shouldn't be too hard and we will all benefit.

I like the result and I think it's worthwhile. I also would like to think that we have proven that we like to work together and so providing assistance to folks who want to make their contribution is the sort of thing we should try to make a habit of rather than jumping up and down and just pointing out the flaws.

If there are possible problems with copyright\attirbution then lets help get them resolved rather than picking a fight.

[elakdawalla]

Sorry for the long post

Phillip

No apologies necessary! I think it an excellent example of why it's worthwhile to cultivate friendships with people who may not share ALL of the same interests I do! And also of how most people have many dimensions to them. (I could treat you all to an extremely detailed explanation based on experience as a city planning consultant of why Los Angeles does not have much in the way of public transportation, for example, but it's both frustrating and boring, so I won't. )

Getting back to the size comparisons, I've started putting together those pages I mentioned above...again, these are a work in progress. So far I've only done 1,000 km, 500 km, 200 km, and 100 km.

Worlds of the Solar System: 1,000 km to 10 km per pixel
Worlds of the Solar System: 1,000 km per pixel
Worlds of the Solar System: 500 km per pixel
Worlds of the Solar System: 200 km per pixel
Worlds of the Solar System: 100 km per pixel

More tomorrow...

--Emily

[tedstryk]

Great work! Both to Emily and spaceffm.

[dvandorn]

First off, thanks to Phillip for his insightful review of copyrights. Don't hesitate to contribute in any way you can, Phillip -- it's great to have all kinds of people here!

Secondly, what I'd love to see in terms of a comparative size display would be something like World Wind or Google Earth -- something that zooms back to show you real, scaled images of all of the bodies we've photographed with any kind of resolution (as far away as the Kuiper Belt or as small as Itokawa). Allow the user to zoom in until they get a good balance between resolution and display, and let them rotate and manipulate each object.

You could even take Steve Albers' maps and project them onto appropriately shaped wire-frame objects -- and every time new images are received and the maps are updated, you just re-project them and, voila, you have a properly scaled Solar System model that updates itself.

I know, I know -- nice idea, but a lot of work. It's times like this I wish I was a programmer.

-the other Doug

[helvick]

You could even take Steve Albers' maps and project them onto appropriately shaped wire-frame objects -- and every time new images are received and the maps are updated, you just re-project them and, voila, you have a properly scaled Solar System model that updates itself.

You should take a look at Celestia if you haven't already. It allows you to do all of the above and doesn't stop at the solar system.

[lyford]

OMG??!@?#
These images are so incredibly beautiful.... please don't harsh my buzz with the copywrong bit - who let the lawyers in here?

Unless you are privileged enough to be primarily involved in these missions, we all are standing on the shoulders of giants.... Though I do agree that combining images in a new mosaic referenced to scale constitutes "adding value" whatever that means. But you must admit the skill involved in coaxing Photoshop (or whatever) into displaying images at the same resolution pales in comparison to that involved in creating the spacecraft that acquired the images... touche!

[Bill Harris]

I always had a mental image of the Galilean satellites as being larger; seeing them compared to our Moon, they look like rather mundane rock/ice/sulfur balls.

Don't worrry about bringing up the copyright issue; as imagers/photographers many of us have been affected by mis-use incidents, so thatis a collective "short fuse".

--Bill

[David]

I always had a mental image of the Galilean satellites as being larger; seeing them compared to our Moon, they look like rather mundane rock/ice/sulfur balls.

Well, they are large: just not particularly large in comparison with Earth. But the Earth is big, something we're disposed to forget when we've been told so often just how small and insignificant we are -- it's the largest terrestrial planet, and the biggest thing in the Solar System that isn't a star or a 'gas giant'. By the way, it occurs to me that, although I am used to thinking of Uranus and Neptune as miniature Jupiters, they are -- in both size and structure -- almost as different from Jupiter and Saturn as they are from Earth.

I think mundane is a good word for objects of this size, though; mundanus in Latin means "of or relating to the world", and they are worlds in themselves, even if not big ones. Maybe the IAU guys who are coming up with classifications for the solar system can employ a category, "mundane objects".

[elakdawalla]

Well, they are large: just not particularly large in comparison with Earth.  But the Earth is big, something we're disposed to forget when we've been told so often just how small and insignificant we are    -- it's the largest terrestrial planet, and the biggest thing in the Solar System that isn't a star or a 'gas giant'.  By the way, it occurs to me that, although I am used to thinking of Uranus and Neptune as miniature Jupiters, they are -- in both size and structure -- almost as different from Jupiter and Saturn as they are from Earth. 

I think one thing that surprises me is how many scales there are. You've got the scales of Jupiter and Saturn, and the one of Uranus and Neptune, and the one of Earth and Venus, and the one of Ganymede and Titan, and the one of Europa and Triton, and the one of Rhea and Oberon, and the one of Enceladus and Mimas -- Jupiter is more than 300 times the diameter of Enceladus yet you are still dealing with spherical worlds from one end to the other. And we've barely scratched the surface of the study of the geology of any of these other worlds except Earth. The Moon is the only other place we've left seismometers on or brought samples back from. All those other places -- they're still mysteries. Even Mars.

Here's the next page, 50 km/pixel
--Emily

[jski423]

Here have some fun with these.

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.

Use these as you like.

[Toma B]

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".....

[mike]

I'd like to give thanks to everyone who has put together these mosaics - I wasn't aware just how big these various objects are, and seeing them next to each other makes it incredibly easy. They're also very colorful.

[tedstryk]

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.,

[elakdawalla]

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