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chanilover



Joined: 19 Oct 2006
Posts: 1451
Location: London

I read a post on here somewhere about how Arrakis is a really small planet on the basis of the measurements at the beginning of Dune.

How small is it and would the horizon be curved or flat?

I have no idea why I'm interested in this, I really can't explain it.

By the way, the signature has reverted to Sloe Man. I knew that polite post you did was a trick.
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Tleilax Master B



Joined: 05 Jun 2006
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Sandchigger has done a lot of work on this. Quite a bit of that is presented on his Hairy Ticks of Dune blog.
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SandChigger
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Based on the Map and Cartographic Notes at the beginning of Dune, the planet is WAY too small to be a suitable setting for the novels.



It's just a wee bit larger than Earth's moon, so forget about normal gravity or an atmosphere and any sort of protection from radiation (from a sun with a gland problem, btw).

In the end, size does matter.

(We're also told somewhere that the gravity of Arrakis is 9/10 that of Earth. Assuming a similar composition and calculating the radius using the gravity formulas is another possible, but not really valid, approach. I'm still muddling over it all.)

The horizon would appear as flat as it does on the moon.

If you're looking for a vacation spot where you can definitely tell your horizon is curved, I suggest Deimos:



Lovely in the northern spring (Martian I mean, of course). And I hear there's a new concessions area at the base. Wink

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guildnavigator



Joined: 26 Aug 2006
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Location: Rhode Island. Kretinga, Lithuania in summer.

Well, aren't their sources in FHs books( I believe we had a thread about this along time ago) and one source said 9/10s earths size, the other said something like 1/10s earths size. Their was also some stuff in the dune encyclopedia, but that can probably be ignored. The answer of your question lies with which source you choose to believe.

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SandChigger
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I decided to throw out everything from the Encyclopedia even though it provides a lot more information about the planet and Canopus system—none of it has any basis in FH's writings.

One big problem is the change in scientific knowledge between the time when FH chose Canopus for Dune's sun and today.

My own approach is to take the textual as the final word, so the Cartographic Notes trump the map itself (which evidently was based on a sketch by FH himself and possibly just redrawn to look more professional by de Fontaine) and Carthag is 200 km northeast of Arrakeen; Arrakeen gravity is 0.9 G; etc.

Unfortunately there isn't enough data in the books to arrive at a definite final result. Any answer will reflect a certain amount of fudging. Wink

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SandChigger
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I got bored and played with Celestia some more....

Here's what I meant about a "sun with a gland problem":



Canopus is a big sucker. (Normally, that would be a good thing in my book, but in this case....) And it's bright...Wikipedia gives a luminosity of 20,000 x Sol's but Celestia's database uses a more conservative 13,800 x. Either way, that translates into HOT HOT HOT. At 1 AU, Celestia reports a temperature of 279 K for Earth; at 15 AU in my current set up, the same reading for Arrakis is 519 K.

The main problem with Canopus is that its mass of 8~10 x Sol means it will have a much shorter lifetime than a smaller star. The probability of its eventually going supernova is also very high. (Not something we ever have to worry about with little ole Sol.)

If Canopus could form a system of planets, there would probably not be time for complex life to arise before the star exploded. That isn't a big problem for the Duniverse, however, if we assume (based on evidence in the texts) that all life was brought to the planet from elsewhere (sandtrout and various Terran forms like kangaroo rats, bats, and, well, sand chiggers! Very Happy ).

I'm working on a version of the StarGen program that will hopefully generate realistic solar systems for a star as large as Canopus. (The current version cuts off the star size/mass at 2.0 x Sol.) One thing that the original programmer, Jim Burrows, has warned me about, though, is to expect "gadzillions" of planets.

But I figure I'll burn that Bridge of Hrethgir when I come to it.... Wink

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chanilover



Joined: 19 Oct 2006
Posts: 1451
Location: London

Wow, that's sizzling.

Will you name a planet after me, preferably an important one. Thanks.

Will there be pictures of what the scenery might look like? It would be cool to have a green sun.
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Eru



Joined: 08 Jun 2006
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Isn't there a quote somewhere which says something about Arrakis' rotation or orbit being "artificial" or something? Maybe that explains the gravity problem. Or maybe Dune is just really, really dense.
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SandChigger
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First epigraph in House Corrino:

Quote:
The axis of spin for the planet Arrakis is at right angles to the radius of its orbit. The world itself is not a globe, but more a spinning top somewhat fat at the equator and concave toward the poles. There is a sense that this may be artificial, the product of some ancient artifice.
—Report of the Third Imperial Commission on Arrakis


Back in mid-August, I PMed Byron about this:

Quote:
Hey, Byron, the next time you talk to Brian or Kevin, could you ask them about the inclusion of the information on the "axis of spin" at the beginning of House Corrino? Was it something they realized and worked in or was it in Frank's notes.

It seems like such a little thing, but it's absolutely essential for the environmental setting to behave as presented in Dune.


He replied:

Quote:
Here ya go! I spoke with Brian and Kevin yesterday and here is what they said...

"That came directly from Frank’s notes. He had a few pages where he drew up some basics about the planet, so we included the details in House Corrino."


So, unlike many things, this is "real worm spice", not the tank stuff. (ACCEPT NO SUBSTITUTES!)

(Note, I won't go into the issue of the inclusion of otherwise irrelevant detail just because it's in The Notes. In this case, I'm glad they did. Wink )

The divergence from a perfect sphere is nothing unusual; it is quite common, in fact, and is the natural result of the centrifugal force from rotation on a non-completely solid body. That's why you science textbook in school should have told you the Earth is an "oblate spheroid", larger diameter at the equator, slightly flattened at the poles. The effect is even more pronounced in the outer gas giants because they are even less solid than the terrestrial planets.

The non-spherical shape does give rise to miniscule differences in gravity across the surface of the planet. (But then, so does the composition of the crust and inner layers of the Earth at any given point.) I don't think this ties in with the earlier stuff about gravity, though. But yeah, if it's the size shown above, Arrakis would have to be incredibly dense to achieve 0.9 G average gravity.

The part about the axis of spin was a very clever "catch" by FH. Arrakeen is at about 62 degree north latitude. If Arrakis had an inclination like Earth (about 23 degrees or so), that would place it very close to the arctic cirlce. (Compare Rejkjavik, Iceland, at 64 N.) And that would have very direct consequences on the setting for the story. Like...really long dark winters. As it is, Canopus never rises very high in the sky over Arrakeen. And at the north pole it is just above the horizon year round. (Given the mountains around the pole, it's highly likely that the sun never shines there at all, making a residual ice cap more believable.)

Again, a perfect inclination of 0 degrees is unusual, but not impossible. In my opinion, the bit about "ancient artifice" is just a red herring. There are no aliens in the Duniverse, no Hitchhiker-style planet builders hiding in the wings. Wink

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Freakzilla



Joined: 02 Jun 2006
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The Earth's oblate sheroid shape is evident in pictures from space:



Maybe Arrakis was made by pan-dimensional mice too?

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SandChigger
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Unfortunately, the difference isn't one that would probably show up in a photo of that size:

Earth radii (from WP):
6,378.137 km (equatorial)
6,356.752 km (polar)
6,372.797 km (mean)

Or roughly 5 km wider at the equator and 8 km "flatter" at each pole than would be expected for a perfect sphere.

(The Earth in the photo can be covered by a circle with axes 236 (w) and 238 (h) pixels; the N-S axis is wrong to show what we want. Maybe an effect of perspective? Lens artifact? To show what we want, a picture would have to be taken from orbit exactly over the equator; it wouldn't show as much of Antarctica and Africa would be much lower. Sorry...you just tweaked my chiggey sense. Sad )

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Freakzilla



Joined: 02 Jun 2006
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Location: Atlanta, GA

Dude, I found that picture on the Regents Exam website, it HAS to be true!

Laughing

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SandChigger
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Is it safe to assume that I now know how you voted on the old "Can you trust the Internet?" poll? (AKA the "Let's bash Wikipedia!" thread.) Wink

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Freakzilla



Joined: 02 Jun 2006
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I have absolutely no faith.

I don't even believe in states or countries I've never been to.

Wink

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scyfe eye



Joined: 10 Jun 2006
Posts: 329

Freakzilla:

Quote:
Maybe Arrakis was made by pan-dimensional mice too?


yeah, i know the guy that designed the coastline for Denmark. Laughing
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SandChigger
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I think I fell victim to the ole radius/diameter confusion and boffed those earlier figures

Earth radii (from WP):
6,378.137 km (equatorial)
6,356.752 km (polar)
6,372.797 km (mean)

So...the equatorial diameter is 10.68 km wider than expected. The two poles are 32.09 km closer together than expected.

D'oh.

Now let's sing with Maria:

I feel stupid, oh so stupid....

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SandChigger
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Damn. I thought for a while I had it solved:

FH in GEoD wrote:
Leto knew the innermost sensation of what she saw. Except for that insignificant, blurred blip of his tower's base, there was not the slightest lift of horizon-flat, everywhere flat. No plants, no living movement. From her vantage, there was a limit of approximately eight kilometers to the line where the planet's curvature hid everything beyond.

It's fairly simple to calculate the distance to the horizon IF you know your (eye) height above sea level (approx. = average radius of the planet).

There's no indication of the height of the dune they were on, so I fudged and assumed 5 m (the winds being weaker than in the old days, dunes wouldn't be very high; I'm not sure if the large dunes mentioned later in the passage would really be possible) + 1.75 m for Sionna's eye height. And got a very reasonable 6400 km, just a little larger than Earth. (Which if we assumed a similar mass for Arrakis, could account for the lesser gravity...but I haven't done that calculation yet.)

UNfortunately, if you increase the dune height to 10 m, the radius drops to around 2723 km. Use 100 m and it's a paltry 300-some km.

VERDICT: not enough info provided. Again.

So close....

(Byron, could you ask Brian if there is anything about Arrakis' radius or diameter in The Notes?!)

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Freakzilla



Joined: 02 Jun 2006
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I believe it's 15 miles from horizon to horizon here on Earth, so 8 miles would be slightly larger.

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SandChigger
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Have you ever seen Great Moments in Architecture by David Macaulay (I think that's where I saw it)? He's got a great drawing showing the meeting of two train lines in the Old West, one with wide tracks and an enormous locomotive, the other small and dainty. The caption reads something like "When Imperial met metric...."

(Ahem Wink)

Seriously, though, mon ami, the distance to the horizon is not an absolute. It really is relative to your height.

If I have seen farther than others it is only because I have stood upon the giant pile of books beside my bed.

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SandChigger
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Nothing proves a point like an illustration!



As you can see, if Sionna...wait a minute, that's not Sionna...THAT'S KAILEA! Damn, how did she get back on Arrakis?! CHANILOVER! ONE GOT OUT OF THE MENAGERIE! HELP!

Anyway, as I was saying, if the bint stands at the base surface level (since "sea level" has no meaning here, right?), her eyes are at height R(adius of planet) + h1 (= height of her eyes above the ground). Her line of sight is tangential to the curvature of the planet; the point of intersection is distance R from the center of the planet and distance D1 from her eyes. Since the lines form a right triangle, we know that (R+h1)^2 = R^2 + D1^2.

Compare this to the second situation in which she is standing on the sand dune. R+h2 is the Radius + her eye height + the height of the dune. R+h2 is obviously greater than R+h1. Since R is fixed, D2 must also be greater than D1. (Shown by the thickened copies of the lines above. ... Pity those aren't Clarkian monoliths that could crash down on the slag. Oh well, would probably only get one of her.... Kailea...the human version of Velveeta, the Cheese That Never Dies!)

Seeing is believing!

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chanilover



Joined: 19 Oct 2006
Posts: 1451
Location: London

Thanks! This is all interesting stuff.

As for Kailea resurfacing, her antics during the Butlerian Jihad are currently in draft stage, almost finished. I haven't looked at it in weeks so I suppose I should get on with it really, I keep getting distracted by other fanfic threads and tedious on-line arguments with Australian ice cream vendors.

I liked the reference to the monoliths - that's from 2001, right? My favourite part of that film was the pre-human monkeys hitting each other over the head with bones. Probably what it's like at dinner time chez Sloe Man.
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SandChigger
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chanilover wrote:
... tedious on-line arguments with Australian ice cream vendors. ... Probably what it's like at dinner time chez Sloe Man.

Your sheer, unrelenting biatchiness has got to be one of your most endearing qualities. Very Happy

I realize most people are bored stif...er, silly by this sort of thing; also that there is a strong "Gahd, do you have to overanalyze EVERYthing?!" contingent among us, but I get off on it and that's enough for me. If someone else thinks it's interesting, that's just gravy on the cream pie.

Er...something like that.

That reminds me, I've got another book cover to prepare, don't I! Embarassed

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chanilover



Joined: 19 Oct 2006
Posts: 1451
Location: London

SandChigger wrote:
Your sheer, unrelenting biatchiness has got to be one of your most endearing qualities. Very Happy

I realize most people are bored stif...er, silly by this sort of thing; also that there is a strong "Gahd, do you have to overanalyze EVERYthing?!" contingent among us,


What can one do? You can't please all the people all the time, so anyone who doesn't like it can kiss my semi-pinoy bum.

There are plenty of other threads to entertain people. Some of them mentally stimulating, others which involve rummaging through the sewers of humanity. You tend to find me in the latter.
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Omphalos
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Freakzilla wrote:
I believe it's 15 miles from horizon to horizon here on Earth, so 8 miles would be slightly larger.


Not to be a nitpicker, but gramps always told me it was 14 miles, not 15.

And can 6" really add more miles to the horizon?

And, not to be an a$$, Sandchigger, but is R constant on oblong planets?

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SandChigger
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I don't feel like doing the conversions and equations at the moment, but yes, the distance to the horizon would be mathematically greater if your height increased even just 6".

Would you be able to perceive the difference? Unless your eyes are incredibly better than mine, no.

You're not being an a$$; it's a good point: R as a constant is an abstraction. The oblate shape of most planets would have an effect on the calculations, but I'm thinking it's probably going to be minor enough that you can ignore it. (Again, there's the actual difference in measurements and what you can perceive.) Very Happy

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Omphalos
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Ah...I love the sweet smell of precision in the morning! Wink

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Dunester



Joined: 22 Mar 2007
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I wonder if they had the whole "sea-level" thing before Paul? Or was it dune-level back then? Razz

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SandChigger
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Actually it would more correctly have been "Bled-level", since the Great Bled was used as the basis for altitude determination, according to the map notes in Dune.

Like sea-level, though, it would be a best an approximation. The depth of the sand at any point would vary to some degree with time, as a result of movement by wind, sandtides and currents.

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