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

[Guest_spaceffm_*]

edited out

[David]

Nice. I see you squeezed Mars, Pluto and Charon in for comparison as well as the Earth and the Moon. Just to be perfect you could find a place to put Ceres in for comparison as well.

[Decepticon]

Excellent work!

I've been wanted images like this.

[deglr6328]

Ohhhh nice! Would you consider releasing these under public license so that they can be added to the Wikipedia?

[tedstryk]

Well, considering several of these images are from Welcome to the Planets, including several of what appear to be Tayfun Oner's images, I think the copyright issues are a bit deeper.

[deglr6328]

Tayfun Oner? Ugh, copyrighting these probe images is so ludicrously silly anyway. I just don't get it. oh well.

[tedstryk]

Tayfun Oner? Ugh, copyrighting these probe images is so ludicrously silly anyway. I just don't get it. oh well.

To me, it matters in two ways. First, I have used it on more occasions than I can count to stop anomalists from using my images. Secondly, if someone else claims to have processed them. If they are used on a non-anomalist site without credit, I don't complain, but when someone else claims to process them, that makes me angry.

[tasp]

If this post is deemed not on topic for the thread, I pre-emptively accept your gentle rebuke.

What of Jupiters smallest possible satellites?

I have been toying with an idea, if it is of no consequence, let me know.

After comet Shoemaker-Levi was 'zorched' into Jupiters atmosphere, I wondered about the 'tail'. Or the tail of any other 'cometary' body orbiting Jupiter. Would the tail materials manifest themselves similarly to a meteoroid stream in orbit around the sun, but instead around Jupiter?

Granted such a 'swarm' would probably not stay collimated very well for very long, and I suspect solar radiation pressure and gravitational perturbations would 'flush' them out of the system fairly quickly.

However, as we saw, recently, comets might happen by to 'restock the shelves'.

Are these possible swarms of tiny moonlets orbiting Jupiter of any import?

Well, not having any appreciable atmospheres around any satellites of Jupiter rules out any naked eye confirmation by eventual astronauts there. But if a mechanism is found that keeps these streams in any way concentrated any where, such places may not be where we would want a space craft to traverse at high speed. Would a stream interact with the magnetosphere of Jupiter, perhaps characteristic changes of radio emissions of Jupiter might result.

But perhaps a spacecraft might view them via scatterring effects on light or perhaps in a way analagous to seeing zodiacal light.

[hendric]

THX tedstryk,
for taking away all the fun.
All Pics have been NASA / JPL Pictures.
Whats Tayfun Oner anyway, never heard of it.

Anyway pics are edited out.

That's a little unfair, and uncalled for. You could have spent 15 seconds on Google, like I just did, and found out who Tayfun Oner is. I bet if you asked him his permission to use his images, he would be more than happy to oblige with appropriate credit. How would you feel if someone did the same to you? Not too happy I imagine, looking at post #1.

[tedstryk]

Let me get this straight. You made a bunch of copyright threats after taking a bunch of processed images from the internet without tracing their origins, and I ruined the fun?

[Decepticon]

[Toma B]

Let me get this straight.  You made a bunch of copyright threats after taking a bunch of processed images from the internet without tracing their origins, and I ruined the fun? 

Just a thought...
Maybe you should make agreement with "spaceffm":

-He should delete all his copyrighting nonsence from his posts and in return you return his modified posts back...

I don't care much about those images , but I know it is not good to lose a member...

BTW.
I didn't meen to be mesing with your administration tedstryk...


You can just ignore this anyway...

[dvandorn]

Yeah -- insisting you're in the clear because you took images "from Google" is like a cop asking a robber where he got his loot, and the robber saying "I got it from the road." No, he didn't -- the road took him somewhere, where he then stole something.

Google takes you to websites. At many websites, there are copyrighted materials on display. You can no more just lift that copyrighted material and use it for your own purposes (with no attribution) than you can walk in a store and just take what you want without paying.

It's a good point to remember -- just because something is displayed on a website doesn't mean you're free to use it for whatever purpose. Until the copyright laws are changed, anyway.

-the other Doug

[mike]

It seems odd to me too to copyright something as simple as putting publically-available pictures of planets and moons together.. What if I then make my own such mosaic, am I breaking your copyright? It's like copyrighting a drawing of a stick figure - I doubt whatever court handles copyrights would support either one.

[tedstryk]

Just a thought...
Maybe you should make agreement with "spaceffm":

-He should delete all his copyrighting nonsence from his posts and in return you return his modified posts back...

I don't care much about those images , but I know it is not good to lose a member...

BTW.
I didn't meen to be mesing with your administration tedstryk...


You can just ignore this anyway...

I am a bit confused Toma B...how did I modify his posts? I am not a moderator.

[tedstryk]

It seems odd to me too to copyright something as simple as putting publically-available pictures of planets and moons together..  What if I then make my own such mosaic, am I breaking your copyright?  It's like copyrighting a drawing of a stick figure - I doubt whatever court handles copyrights would support either one.

Where you would run into trouble is if you took someone else's work and then claimed the copyright on it for yourself. That is the issue here.

[dvandorn]

A copyright recognizes any significant value added to an intellectual property.

In the case here, spaceffm put together some very nice comparison murals. But *if* the work of scaling the images so that they were in proper scale to each other was done by someone else (especially by someone who took out a copyright, not on the images, but on the work he did to adjust each image to the proper scale), and *then* spaceffm claimed that he did the work to accurately scale the images, he would be making a false claim. It would be trying to take credit for someone else's work -- work that the someone else spent enough time and energy on, and added enough value to the images' presentations by doing the scaling calculations and manipulating the images accordingly, that he felt the value he added was worthy of its own copyright.

So, if spaceffm were to produce paper copies of these murals and sell them, or even if he were to insist on being credited if the murals were shown elsewhere on the Internet, the issue a copyright court would consider would be whether or not spaceffm had added any significant value to the images, as manipulated and copyrighted by Tayfun Oner. If spaceffm could prove that he did all the work to scale and manipulate all the images in his own murals, then he would win the suit. Just because Oner had made such scaled images doesn't preclude anyone else from doing it -- as long as they do the work and don't just use Oner's pre-scaled images without attribution. However, if all spaceffm did was re-arrange the elements of similar comparison murals made by Oner, without actually doing any of the scaling and image manipulation itself, then he would lose the suit.

In fact, even if spaceffm did almost all of the scaling himself, if he used even *one* pre-scaled image taken from someone else's work and deliberately passed it off as his own work, he would lose the suit.

-the other Doug

[elakdawalla]

Hey, now, let's all play nice while Doug is away.

I, too was once very irritated by copyrights being splashed all over space images, which do all come from publicly supported missions. And I still think it's a bit much to claim copyright for doing something as simple as, say, adjusting the contrast in an image. But it's also true that some of the processing that is done to make these pictures is a tremendous amount of work, for which the worker should get credit. Furthermore, a lot of the processing work done by the so-called "amateur" community crosses the line into art. By calling it "art" I'm implying both positive and negative connotations -- the positive is that the images they create are truly beautiful; the negative is that they have to make up or fudge some information in the image to edit out blemishes, noise, seams, etc. Most scientists would never do that, and you'll rarely see images released by official agencies that have been fudged in that way. By indicating who gets the credit for the image you also inform whoever is looking at the picture how literally "true" the image is, and acknowledge the work of the artist.

Really, though, I'm not interested in the legalistic stuff; for me this debate comes down to being polite. It is polite and kind to ask permission from someone before taking an image from his or her website. For the most part, you will find these people to be delighted that you are interested in the work that they spent many hours producing. All they ask in return is that you give them credit for their work. In effect, this permission has already been asked for, and granted, from NASA/JPL; they have given a blanket permission to all who use their images -- themselves the product of an incredible amount of work on the part of hundreds of scientists, engineers, and IT people -- for educational purposes for the reuse of their images -- and they should be credited! I've already asked permission from Ted Stryk and Mattias Malmer and Doug Ellison and Olivier de Goursac to use the images that they've worked on on my website, and they have given their permission enthusiastically. What's the harm in asking permission? In the end, it's a way of opening a friendly dialogue among all of us who, after all, share interests in gazing at the beautiful images returned from our robot explorers. Many of you might find this asking of permission to be a great way to make contact with the scientists who produce the official images too. It's a very polite way to open a dialogue, and I'll bet you'd find that you'd either get a pleased response or be ignored, that you'd probably never be denied permission.

Which reminds me...at the risk of being hopelessly sentimental, I'd like to advocate that those robot explorers be acknowledged in image credits too, where space allows of course. They gave their 'lives' to us to return these images.

--Emily

[tedstryk]

I was referring to the image processing - coloring, reprojecting. A few I recognize as Oner's, a few as others. I agree about free distribution, with a few exceptions, but it just struck a nerve to take images that others had processed, even if he scaled them himself, give those who processed them no credit, and then claim copyright over the product.

Here are the instances in which I have asserted copyright claims in the past. First, when someone else posted, in unaltered form, one of my images and claimed to have done the work. I have made requests that have been honored to anomalist websites, when I see my images posted there, to get them removed. The only time I have ever threatened legal action (and I did get a lawyer who is a friend of mine to send a letter, which worked) was when an anomalist site posted my Phobos 2 images WITH credit, and claimed that I was doing work with the images to investigate the nature of alien spaceships and artifacts seen in them. I only involved the laywer because the site owner, who I won't name (I am not sure I still even have the name) refused to remove the references to me or my images. The reason I took this so seriously is that when dealing with old data and foreign data not found on the PDS, I have been fortunate in that scientists and archivists have been more than helpful in providing me with material - for example, Francis Graham's finding me the matrices to make the Pioneer-11 Io images. If my name was spread over the internet as being connected to the anomalists, I fear that scientists would be less willing to respond to my inquiries for data, which would greatly damage my work. But, other than that, I have never, even if I legally could, tried to stop others from using my images, even without credit. My whole purpose of doing the work is to resurrect images that (in the case of Soviet images) never reached the west in proper form, were lost among a myriad of other images, were processed decades ago and are in need of touchups, and occasionally a famous image that I think could be processed better. This is so that some of the many vistas of the Solar System can be shared by more people, not just those of us who obsessively process the data. And, therefore, my goal is to see it spread around as much as possible. My only concern is that it not be used by anomalists to distract people with their utter nonsense from the true wonders of the solar system.

[tedstryk]

I've already asked permission from Ted Stryk and Mattias Malmer and Doug Ellison and Olivier de Goursac to use the images that they've worked on on my website, and they have given their permission enthusiastically.

I will add something. While I much appreciated being asked, I would not have been angry if my images just turned up there.
I would have only become angry if Emily had tweaked one of them a bit and then claimed copyright for herself without mentioning me, or if she had made anomalist claims, particularly if she associated me with them, for the reason stated in my previous post.

I think a lot of this boils down to MOTIVATION and the need for a bit of control over one's work that is connected to that. I process images to allow people to see visions of the solar system, with my favorite thing being to extract views from obscure sources or from degraded or low-quality data. I do this because I believe that our Solar System is a beautiful and inspiring place, and I want to create something to make that beauty and inspiration more accessible to people. That is why I do my work. If it is instead used to promote kooky anomalist views that distort much of the public discussion space exploration from what really matters, MY REASON FOR PRODUCING AND DISTRIBUTING IMAGES IS GONE.

[Toma B]

I am a bit confused Toma B...how did I modify his posts?  I  am not a moderator.

UPS!?!?!?!
I... I..... I thought.... I thought that you are the ONE...
Sorry tedstryk I seam to be even more confused than you are...

"MODERATOR" please excuse me...
Not my busines anyway...

[elakdawalla]

Where did i threat ??? anyone?
U are threatrening me with a sueing case..am i getting crazy or what?

Please, please, spaceffm, no one is threatening anybody. My own response wasn't directed at you specifically, it was my general thoughs on the issues of copyright, which have come up in this forum before. I apologize if I seemed to be directing them at you specifically. In fact I have not seen the images that were at issue because they seem to have been removed from your original posts. You should have been given the opportunity to edit or remove them yourself, I can definitely understand why their disappearance has upset you. I would be very sad to see you depart the forum over this misunderstanding.

I think everyone needs to relax a little bit and continue the discussion when they are calmer.

--Emily

[dvandorn]

And believe me, I was simply proposing a what-if and using the example of the size comparison chart to discuss what *could* be actionable, and under what conditions. I *wasn't* stating that spaceffm stole *anyone's* copyrighted work -- I don't know this Oner's work well enough to recognize anything spaceffm used that might have been copyrighted.

I'm just trying to point out that if you put together something that seems very similar, or almost identical, to copyrighted material, you need to be able to prove that you did the work and you did not use any of the copyrighted material, or else the holder of the copyright on the similar work *might* decide to sue you. I never said anyone wanted to sue spaceffm, and certainly didn't mean to suggest that anyone ought to try.

I would rather see spaceffm stay here in the forum, too... and if I said anything that sounded like I was accusing him of anything, I most certainly apologize.

-the other Doug

[deglr6328]

Oh goodness, now look what I've gone and done with my simple question.....

[Bill Harris]

Great discussion on copyright and intellectual property. I had no idea that the discussion had turned in this direction.

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This is the freebie you get from NASA. But the instant you add value, tweak, crop or resize, the image created from this data becomes yours, as attached.

--Bill

[Phil Stooke]

Maybe we could recover this thread by actually making some size comparisons from scratch! They would be highly informative - everyone accepts that, I'm sure. A whole series is needed, really - from the (traditional) planets down to the comet nuclei and asteroids etc., at appropriate scales.

Phil

[Bill Harris]

A whole series is needed, really...

I've thought about something along the concept of "Powers of Ten" going from the Sun to ??whatever. Or maybe from ??whatever to the Oort cloud...

That might be too much though...

--Bill

[lyford]

Which reminds me...at the risk of being hopelessly sentimental,  I'd like to advocate that those robot explorers be acknowledged in image credits too, where space allows of course.  They gave their 'lives' to us to return these images.

--Emily

I don't think it's too sentimental - especially if one has invested so much personal time following each spacecraft - they become anthropomorphized and linked to memories like a favorite pet.

There's a lot of emotional drama as well on each of these missions, and they are symbols the tremendous ingenuity and hard work of thousands - so it's entirely appropriate to credit the images to reflect that. It's a nice touch and makes you think....

[lyford]

I've thought about something along the concept of "Powers of Ten" going from the Sun to ??whatever.  Or maybe from ??whatever to the Oort cloud...

That might be too much though...

--Bill

Something like this, but with all the solar system...
He does actually include the Moon and Phobos and Deimos, IIRC...

[elakdawalla]

Maybe we could recover this thread by actually making some size comparisons from scratch!  They would be highly informative - everyone accepts that, I'm sure.  A whole series is needed, really - from the (traditional) planets down to the comet nuclei and asteroids etc., at appropriate scales.

I'm working on exactly this sort of thing for the Society's website -- you can see the work in progress here. I've created sets of images within our image library for the scales: {1,000 km/pixel, 500 km/pixel, 200 km/pixel, 100 km/pixel...down to 1 km/pixel}. I haven't gotten to the very smallest bodies yet (just a smattering below Hyperion's size) but I'm working on it. The current page only shows the 1,000, 100, and 10 km/pixel images. Since this seems to be a popular idea maybe I should throw together a page at each of the scales I created images for. I find it really informative to be able to compare all the little bodies this way.

--Emily

[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

[RNeuhaus]

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

[jski423]

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".....

No, not a stupid question. I'm just used to working with radius versus diameters.

When I put this together a while ago it wasn't meant for distribution, I made it for myself and my daughter to get her interested in the Solar System. I didn't bother to update anything before posting here.

I am sure this is pretty common knowledge and I don't mean to isult anyone's inteligence but just multiply the radius by 2 to get the diameter. For smaller bodies
I have used the maximum radius and not the mean.

Like I said do what you would like with these and if diameter is what you like you are free to change it. Just do not take credit for it.

[JRehling]

Here is a scale diagram of the satellite orbital distances. The planets are to scale, but each satellite is only one pixel (so dust off your screen). This includes every satellite over some threshold (I forget what that was)... plus Phobos and Deimos. The real upshot here is the revelation that Iapetus is so far out! Also, it's interesting to see that the orbits of Deimos and Charon would fit inside the gas giants.

http://www.cogsci.indiana.edu/farg/rehling...moon-orbits.gif

[Bob Shaw]

Solor Sytsem?

Ooops!

Bob Shaw

[David]

Here is a scale diagram of the satellite orbital distances. The planets are to scale, but each satellite is only one pixel (so dust off your screen).
http://www.cogsci.indiana.edu/farg/rehling...moon-orbits.gif

I think that it needs a few labels! Here's what I can figure out:

MERCURY
VENUS
EARTH: The Moon
MARS: Phobos, Deimos
JUPITER: Amalthea, Io, Europa, Ganymede, Callisto
SATURN: Janus(?), Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion, and (way over on the right) Iapetus
URANUS: Miranda, Ariel, Umbriel, Titania, Oberon
NEPTUNE: Larissa(?), Proteus, Triton
PLUTO: Charon

The cutoff appears to be around 95km radius.

Now, if I may be so bold as to render the smallest grumble of disapproval about this fine diagram: I realize that it's more artistic to depict Saturn with tilted rings, but in this particular case, when you are showing the satellite systems, and considering that the rings are really part and parcel of Saturn's satellite system and not merely an adornment, it might be more appropriate to straighten them out and get the rings (and Saturn's equator) in line with the satellites' orbital disk.

[tedstryk]

I have been searching and haven't found much in the way of Pallas imagery. Here is an image I constructed through super-res processing of an HST sequenc. The disk is only a few pixels, so it does not show surface details (it missed the planetary camera chip, so it is imaged by the Wide Field portion of WFPC2. The only thing of sigificance is that it does seem to be a pretty round little world, which is consistent with occultation data.

[Patteroast]

Wow, that little orbit comparison reminded me of something I made a while ago.. even more hard to read, though. Pretty much just shows the general idea of the relative distances of the outer planets' moons. I made it some time in 2004. Take a look.

Link

I didn't embed it because it's over 10000 pixels wide.

If it does anything, it really drive home are incredibly far away Neptune's outermost moons are.

[Gsnorgathon]

Say - not to drag things off topic here - and it's sort of a size question, in the generic (not technical) sense of magnitude - but...

Has anyone here ever seen a graphical comparison of the albedos of various solar system bodies?

One's always reading about how the Moon's albedo is really quite low, so that images of the Earth and Moon have to amp up the Moon's relative brightness so it can be seen, or about how such-and-such object (comet, asteroid, TNO) is "black as coal". But I've never seen a graphical comparison, or an attempt to relate albedos other than coal or fresh snow to ordinary objects.

[JRehling]

Say - not to drag things off topic here - and it's sort of a size question, in the generic (not technical) sense of magnitude - but...

Has anyone here ever seen a graphical comparison of the albedos of various solar system bodies?

One's always reading about how the Moon's albedo is really quite low, so that images of the Earth and Moon have to amp up the Moon's relative brightness so it can be seen, or about how such-and-such object (comet, asteroid, TNO) is "black as coal". But I've never seen a graphical comparison, or an attempt to relate albedos other than coal or fresh snow to ordinary objects.

FWIW, the different bodies receive different levels of solar illumination, so the Moon is actually brighter per unit surface area than, say, Uranus.

One thing that makes it hard to display albedos accurately is that monitors just aren't bright enough -- not even close. A white screen in a dark room is much dimmer than coal in daylight. As it happens, Uranus is about the brightness of a monitor, but the first six planets and their moons are lit significantly more brightly. So you'd have to use bar graphs or something to represent the brightnesses.

I once observed seven planets and the Moon through my telescope on the same night, sometimes getting a peek at two planets as fast as I could point (~2 min). Of course, rare (unless the Moon is one body) conjunctions let you compare two bodies at the same time through a low magnification. You can find pictures of Moon-planet occultations and compare away...

[Gsnorgathon]

FWIW, the different bodies receive different levels of solar illumination, so the Moon is actually brighter per unit surface area than, say, Uranus.
...

You're right - that's a whole 'nuther kettle o' fish. There's albedo, and then there's brightness.