Celestia Forums

I am really getting into this now... but let me disclaim: I know this is like using a
very delicate tool for a very crude job, but that's part of the anarchistic fun of it.
I am not serious. This is why I am posting on the User, not the Development,
forum. So if I am annoying, feel free to ignore this.

I think for geocentricity, rather than making the Earth a star, it is better
to put a very small neutron star (called Origo) at the center of the cosmos
and to make the earth a planet of that with a very small orbit. so the Origo
"star" will stay well inside the Earth. This doesn't solve the problem of the light
source, though. But for a geocentric Universe, I think all of the planets are
supposed to have their own light anyway, so this is just a problem of moon
and earth. I think this is the best I can do until geocentric universes become part
of official development (and that would be asking a bit much )

FLAT EARTH: could somebody maybe send me a .3ds file of a disc? I don't have
the necessary gl-tools here and I would like to try and fit a historical map on such a model.
Also a .3ds model of a flat square would be appreciated (since I believe Ptolemy
thought the earth was rectangular, hence "the 4 corners of the world")
thus, I could come up with "babylonian", "aristotelian" and "ptolemaic" flavours
of geocentric universes

Actually, Ptolemy knew the earth is round.

- Hank

that's right. I think the round earth became popular with
aristotle, but even erathostenes did an estimate of the earth
radius. but for a long time it was an open question and it seems
not very clear who believed what. the options were disk, rectangle,
hemisphere, sphere. after a brief web search it appears

Hekataios (also, Bablyon,...): disc
Dikaiarchos (also, Chinese): rectangle
Aristotle: speculations on sphere, everybody after Aristotle
open to this idea because of The Philosopher's prestige.

Ptolemy is notable because he came up with the epicycles (which
artificially prolongued the life of a doomed concept)


dab

Hmmm.... a flat Earth sounds interesting. This may be sad/pointless, but I'm going to suggest it anyway : instead of a simple disc, why not have a disc supported by four giant elephants on top of a turtle, make the sun and moon really small and orbit the turtle, and have the disc turning ? If you've never read Terry Pratchet you'll just think I'm a nutter, if you have then you'll know I am. A Pratcheterian universe may be a far cry from Ptolemy's SLIGHTLY more believable model, but the giant turlte/elephants were based on real, ancient beliefs. Even weirder ideas included an infinite tower of turtles supporting the flat Earth (no, I am NOT making this up, it is mentioned in the beggining of "A Brief History Of Time" by Stephen Hawking)
Of course there are a whole plethora of ways to model the Universe, both ones of total fantasy (such as Dune and Star Wars, already suggested by others) and ones that were once thought correct (such as the Ptolomeic and Copernican models). I think Chris should continue to develop Celestia to be as accurate as is curently known (which is what he wants to do, from what I gather from other parts of the forum) - this is likely to be far more challenging than modelling a fantasy reality (because there is so much data available for the real universe compared to fictional ones, and accuracy fans will expect as much of this as possible. Fantasy universes are fun, but don't require (except to the hardcore fans, the kind who can name Star Trek episodes by stardates) the same wealth of detail to the level that Celestia currently presents, let alone any future versions). But if anyone out there is working on on a Celestia-based fantasy I'd love to hear about it.
Going back to the original post, why should the neutron star be called Origo ?

Origo:
check Perseus: it's just the origin of the coordinate system.
but apart from that, the small star at the center of the cosmos struck me as tolkienian:
"And I will send forth into the Void the Flame Imperishable, and it shall be at the heart of the World, and the World shall Be"


turtles and what not, hm, I was going at historical models, but while we're at it...
just somebody has to sit down and make a 3d model of it...

dab

I think this is getting slightly insane but i'm pleased my idea has spawned it... Just to add fuel to the fire, (and this idea is quite possibly impossible) how about a Earth based on the idea that at the poles are giant holes into a second earth, inside? I heard about it somewhere...

Hollow Earth theory ? Wish I'd thought of that.... There are lots of variations on this. Some say the Earth is just hollow and that's it, others say there are worlds within worlds down to infinity, and the craziest say that OUR earth is inside others...
Perhaps you are right and it IS going slightly insane, but only in a logical way As far as I can tell, the only real value of former solar system / universe models is for fun. Now that we know they are wrong, surely fantasy realities are just as valid as Ptolomey ? The planets don't whizz about in crazy epicyclic orbits any more that Atlas holds up the world. So we might as well have some fun if we change the nature of reality in our little toy universe....
Just as a matter of interest, which book, specifically, does the "Flame Imperishable" quote come from ?

About the turtles...

As I recall, the story goes that an elderly woman approached a young astronomer after his public lecture on our place in the universe, and informed him that he had got it all wrong, that in fact the earth rested on the back of a huge turtle.

"Oh, really?" said the astronomer, somewhat snidely. "And what is the turtle supported by?" he asked.

"Another turtle," the woman replied.

"And what is THAT turtle supported by?" the astronomer inquired.

"Another turtle," said the woman.

The astronmer started to speak again but the woman cut him off.

"Save your breath, sonny," she said. "It's turtles all the way down."

- Hank

Very much so, this is all just for fun. Even celestia itself -- fun and education;
Two reasons! Fun and education and an almost fanatical devotion to accuracy.
Ah!

seriously, though, The further you go from the standard solar system,
the less convenient the program will become. To render this earths-inside-earths
business, any old game engine would be more appropriate.

With fantasy worlds, it is also the amount of things you have to make up
increases. While for historical models, you know exactly where to put each
star, namely so the model coincides with the modern one for observers on
the earth's surface as much as the model allows, for a diskworld universe,
you might as well distribute stars with a random generator, it doesn't matter.

But of course the for-fun argument clearly outweighs the convenience/feasibility stuff

To get back to the technical side, 3ds geometrical primitives handy,
anyone? If not, I'll just have to google around for convenient tools.

cheers

dab

PS: the "Imperishable Flame" quote is of course from the creation myth (beginning
of Silmarillion)

Personally, I think that whole "space" idea is a little mad. I mean, look up at the night sky. I see what appears to be white dots on a black roof. Where did the unimaginable distances of vacuum come from? Who thought that those dots were actually glowing balls of gas millions and millions of miles away? Why do people believe that there is all that stuff up there, contrary to everything they've every seen? For such a farfectched idea (a infinate amount of nothing with things in it?) is seems to be strangely popular. How do we know that the Voyager probes won't smack into a wall at the edge of our solar system? How do we know the Voyager probes exist? I suppose when you start doubting, there's no end to it...

Well, I never expected a Celestia user to say that !

We know the Voyager probes exist because NASA told us they do. We know there's no wall because NASA told us there isn't one. When it comes to fundamental judgments about the nature of the Universe, it's much easier to let someone else (preferably, but not necessarily, someone cleverer than you) do the thinking for you.

Space may be a little mad, but consider this :
We live on a tiny little rock whose core is hotter than the surface of the sun, spinning endlessly. On this rock live six billion beings who have been locked in a debate about life, the Universe and everything since they came out of the trees. Thousands of years ago, their chief scientist decided that matter could not be made of fundamental building blocks because there would be spaces between them. Other ancients believed the SunRecently their most powerful nation decided to elect as its leader, a man with hundreds of nuclear missiles capable of anhillating.... well, everyone, a man who can't spell "potato". Even more recently another leader of the same nation has declared "If we don't succed we run the risk of failure." One major nation has decided, for no apparent reason, that a 101 year old (who happend to marry a head of state) who lived a life of luxury as being one of nature's greatest miracles. Another nation favours nuking the atolls and others believe chopping down a wacking great load of trees igrowing in poor soil is the best way to get more farmland.

If space is a little mad, the Earth is TOTALLY LOOPY !!!

Sorry, that last paragraph needs a few corrections :

Space may be a little mad, but consider this :
We live on a tiny little rock whose core is hotter than the surface of the sun, spinning endlessly. On this rock live six billion beings who have been locked in a debate about life, the Universe and everything since they came out of the trees. Thousands of years ago, their chief scientist decided that matter could not be made of fundamental building blocks because there would be spaces between them. Other ancients believed the Sun went round the Earth because people lived on Earth, hence it must be importance. And it had to go in a perfect circle, because they didn't hold with ellipses. "None of that sort of thing in OUR solar system !" they said. Recently their most powerful nation decided to elect as its leader, a man with hundreds of nuclear missiles capable of anhillating.... well, everyone, a man who can't spell "potato". Even more recently another leader of the same nation has declared "If we don't succed we run the risk of failure." One major nation has decided, for no apparent reason, that a 101 year old (who happend to marry a head of state) who lived a life of luxury as being one of nature's greatest miracles. Another nation favours nuking the atolls and others believe chopping down a wacking great load of trees growing in poor soil is the best way to get more farmland.

If space is a little mad, the Earth is TOTALLY LOOPY !!!

This is getting a little weird... but Space has to be as loopy as Earth, because the loopy Earthmen thought of it! As a subject of the daughter of that 101-year old, let me just say - "Well, well, well. Your daughter, born a humble princess, has grown up to be queen."

Who'd have thought a simple request for a flat earth model could incite such a phillosophical discussion ! I too am I "subject" of that 101 year old's evil reptillian daughter (go David Icke ! Only joking.... he's even more mad than the monarchy) but I'm afraid I don't understand that quote at all. Perhaps you, unlike the press, could enlighten me as to the reason some old bat who lived in a palace is worthy of my respect ? Or even attention ? Seriously, I'd really like to know this. And please don't mention the War. Either of 'em. Or her wonderful personality because (I say, taking a foolish risk) you never knew her. At best you met her for five minutes back in 1953 when she was waving to everyone on some kind of visit to your home city/town/village/hamlet/remote farmhouse.

I think I should get back to the topic of Celestia just to justify this whole topic, which doesn't seem to relate to the flat Earth, space, or even Celestia at all any more. In that respect, err.......
ummm.......
urrr...........
Well I tried.
Actually, here's a thought for a knew feature (don't know if it's already been suggested). I downloaded yesterday an NEO .ssc file. Would it be possible to complie a similar file for all currently know NEOs and their orbits (as accuractely as is known), and have Celestia bring up a message when, allowing for the errors in measuring the orbits, a collision is possible ? Logically this would lead to some kind of "collision simulator".... it wouldn't have to be blindingly accurate, just enough to look good. It could perhaps involve the most likely site for a collision, or allow the user to select from a range of possible areas. Or use some kind of probability function biased towards the most likely area, but would give you slightly different collision sites each time. As with all my suggestions this is not high priority, but eveyone else has already thought of the important updates. It would be purely for entertainment (well, watching some country you don't like get blasted is always good entertainment, in a stupid, thoughlessly cruel kind of way), of course.

Apologies for the long-winded post, anyone who's read all this should reward themselves and go and eat some chocolate.

Grrrr......

The forum doesn't seem to want to post my Username. So I'm just saying that the last three anonymous posts are mine.


---Mad Boris

Are we perhaps going a little-off topic? Flat Earth, Hollow Earth, conspiracy, madness, the Queen (btw, I hope that those mad people queuing to see the body did NOT speak for the nation, otherwise we are doomed), and now planet destruction? What I think Celestia should do is simulate sun expansion - e.g in 5 billion years our sun would expand and swallow up Mercury and Venus (according to new data the Earth would survive by a mere few million km - a little close for comfort). And I don't want a dialog box to warn me... sitting on 2002 EM7, tracking the earth as it passes through the Moon's orbit in March is warning enough!

Off-topic ? Well, maybe a little...
1) The flat-earth etc, are just historical/psuedo-historical/fun ways to model the planet instead of a boring old sphere. Besides, this topic is entiled flat earth !
2) Conspiracy ? I don't remember any conspiracy discussion !
3)Madness - OK I'll give you that one.
4) The Queen - same again.
5) Planet destruction. I don't see how that death-by-asteroid doesn't relate to Celestia. I tried downloading 2002 EM7 and set the date to March the Eighth, 2002. It was millions of miles from earth (about 1.5au, I think). Must be a bug somewhere. A warning box might be nice, but only if the Earth/potential hazard is selected. Optional, of course.

An expanding sun would be great ! Except Celestia's orbits, I hear, go crazy after about 50,000 years. There would also have to be some kind of triggering command in the program itself that gets rid of Mercury and Venus at the appropriate times (better yet, replaces them with balls of lava first). It wouldn't do simply to expand the Sun's radius, it's atmosphere would also have to grow. And there would have to be a planetery nebula and a white dwarf left behind after the Sun's destruction.
And this process would have to take millions of years (also the sun would have to pulse in size, not grow linearly). Since Celestia can't cope with a a few thousand years (yet), let's wait a bit on that one. Asteroid collisions sound easier to me (but I'm not a programmer).

-Mad Boris

Anonymous wrote:5) Planet destruction. I don't see how that death-by-asteroid doesn't relate to Celestia. I tried downloading 2002 EM7 and set the date to March the Eighth, 2002. It was millions of miles from earth (about 1.5au, I think). Must be a bug somewhere. A warning box might be nice, but only if the Earth/potential hazard is selected. Optional, of course.

The incorrect location of 2002 EM7 was due to a sign error in Celestia 1.2.3. Get the 1.2.4 prerelease for the fix.

Anonymous wrote:An expanding sun would be great ! Except Celestia's orbits, I hear, go crazy after about 50,000 years. There would also have to be some kind of triggering command in the program itself that gets rid of Mercury and Venus at the appropriate times (better yet, replaces them with balls of lava first). It wouldn't do simply to expand the Sun's radius, it's atmosphere would also have to grow. And there would have to be a planetery nebula and a white dwarf left behind after the Sun's destruction.
And this process would have to take millions of years (also the sun would have to pulse in size, not grow linearly). Since Celestia can't cope with a a few thousand years (yet), let's wait a bit on that one. Asteroid collisions sound easier to me (but I'm not a programmer).

I've got an idea for a way to keep the planets orbits stable for a lot longer than they are now. After a while however, you run into a wall because of the limitatations of double precision floating point arithmetic--I'll have to do some more calculations to be sure, but I believe that a billion years into the future, motion will become rather jittery unless I stop using IEEE doubles.

--Chris

It's the end of the world --
>And I don't want a dialog box to warn me...
well said! there is only so much the welfare state (and proprietary OSs)
can do for you!

I have commented on celestia's longterm behaviour before, but I didn't
quite think of continental drift and stellar evolution! In principle it should
be easy to set some sort of threshold before the series-expanded orbits
go completely berserk and fall back to the kepler ellipses. This wouldn't allow
you to accurately simulate eclipses thousands of years into the past/future,
but it would keep up the appearance of a well-behaved solar system while
these other interesting things take place...

dab

PS: re, royals/old bats, I don't think being privileged and being admirable are
mtually exclusive. In fact, you need to be reasonably privileged, i.e. surviving
your birth without major brain damage or massive malnutrition for long
enough to even get a chance to develop admirable qualities. And with somebody
as ridiculously over-privileged as the dead QM, I think it is admirable already
if you don't turn into a complete bitch in early childhood. But of course the brits
are not mourning the woman so much as the passing of the last trace that they
ever ran an empire. And then I suppose she was a nice woman, even if I never
set eyes on her. But certainly it wouldn't appeal to me to be expected to consider
myself anybody's subject.

Well said ! I could not agree more.

I don't remember anyone mentioning continental drift, but it's a damn good idea if Chris' better long-term orbits work as expected.
That gives me another idea albeit one rather dependednt on others - how about the Dinosaur killing asteroid ? The orbit could be anything as long as it hit the planet at the right point (Yucatan). Who wouldn't want to see that ?

A question for Chris : any idea about the release date for 1.2.4 ?