# IS Ringworld Stable? **URL:** \ **Category:** Great Debates\ **Created:** [October 9, 2000, 11:41pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327 "2000-10-09T23:41:35Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Scylla](https://avatars.discourse-cdn.com/v4/letter/s/a5b964/32.png) [@Scylla](https://boards.straightdope.com/u/Scylla)\ **Post date:** [October 11, 2000, 7:30pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/21 "2000-10-11T19:30:27Z")
I think the actual floor material of Ringworld is only supposed to be 20 feet thick. Niven supposes that you could build it out of the mass of the planets in the solar system provided you had some kind of transmutation technology. ---
**Author:** ![Fiver](https://avatars.discourse-cdn.com/v4/letter/f/e274bd/32.png) [@Fiver](https://boards.straightdope.com/u/Fiver)\ **Post date:** [October 11, 2000, 7:49pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/22 "2000-10-11T19:49:21Z")
**Tristan** : > [@](#): > > There is also a 3rd book that I have not read yet called Ringworld throne. Do yourself a favor: **don’t** read The Ringworld Throne! It is a steaming pile of excrement, and qualifies as a “novel” only in that it is fiction, made of paper and bound between covers. I hated it, and I say that as a rare individual who liked Ringworld Engineers better than the original. ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [October 11, 2000, 8:43pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/23 "2000-10-11T20:43:46Z")
> [@](#): > > \*Originally posted by \*\*\*SPOOFE Bo Diddly \*\* > > > [@](#): > > > > 40% as dense as neutron star matter?! That would mean it would weigh, what, as much as both Magellanic Clouds combined? Maybe half as much as the whole damn Milky Way?! > > Aw, c’mon, Tracer, you’re exaggerating. In zero gravity, it wouldn’t have _any_ weight at all 😃 It wouldn’t have any weight, but neither do the Megellanic Clouds or the whole damn Milky Way. So Tracer is correct. It would weigh as much as both clouds and _exactly_ half as much as the Milky Way. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [October 12, 2000, 2:51am UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/24 "2000-10-12T02:51:28Z")
First time poster here. You all might be interested in my material on Ringworld stability found on this site [http://members.optushome.com.au/guests/PhysicsinSF.html](http://members.optushome.com.au/guests/PhysicsinSF.html) (please forgive if I don’t have the codes right). Among other things the site talks about the differences between RW pseudogravity and real planetary gravity. BTW, the RW’s building material does block 40% of neutrinos (who knows how!) but it’s explicitly not 40% the density of a neutron star. The mass of the whole RW is about 0.1% of the mass of the Sun. Andy L. ---
**Author:** ![andros](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@andros](https://boards.straightdope.com/u/andros)\ **Post date:** [October 12, 2000, 4:24pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/25 "2000-10-12T16:24:22Z")
Welcome, **Andy** , and thanks a bunch for the link. As I said, scrith is _magic_. 🙂 ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [October 13, 2000, 4:00am UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/26 "2000-10-13T04:00:55Z")
Jeez, Andros, how’d I know, as soon as I saw the thread title, that you’d be putting your 11 1/2 cents in? What I’d still like to know about the Ringworld (and the Dyson Sphere, for that matter) is how would the Solar Wind be deflected? On Earth, the magnetic field takes care of that. But does the Ring also have a magnetic field? Is that explained in the third or fourth book? I couldn’t stomach finishing them–I tried, but I just couldn’t bring myself to give a shit about the characters. ---
**Author:** ![Satchmo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/satchmo/32/4223_2.png) [@Satchmo](https://boards.straightdope.com/u/Satchmo)\ **Post date:** [October 13, 2000, 1:21pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/27 "2000-10-13T13:21:35Z")
Hi All, I do remember in one of the collections, (Playgrounds of the mind, maybe) Niven talks about someone calculating the tensile strength of scrith. It was on the same order of magnitude as the force that holds the nucleus of an atom together, (though I don’t remember if that’s the strong or the weak nuclear force, I know it’s the force that holds protons together in close proximity). So, scrith isn’t really magic, you just need to consider the ringworld as one very big nucleus. ---
**Author:** ![speakertohumans](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@speakertohumans](https://boards.straightdope.com/u/speakertohumans)\ **Post date:** [October 13, 2000, 1:57pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/28 "2000-10-13T13:57:31Z")
Seems to me that if the ring was as dense as star stuff, meer (mir?) attitude jets, let alone a small meteorite would be able to puncture it, let alone move it. I am on the l-niven mailing list and Larry has decided to write Ringworld Child, so I say hold on for more canon information cause he has heard all the chatter and wants to set the record (ring?) straight. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [October 13, 2000, 2:53pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/29 "2000-10-13T14:53:58Z")
Sounds like the actual engineering instructions for building a time machine: “First, take 18,000,000 cubic feet of neutronium…” (And it theoretically works, too, if you happen to be able to have the capacity to work with neutronium in a vacuum without having it catastrophically expand to normal-space dimensions.) I’m glad to hear of Ringworld Child – there are too many loose ends left in the series. ---
**Author:** ![Fiver](https://avatars.discourse-cdn.com/v4/letter/f/e274bd/32.png) [@Fiver](https://boards.straightdope.com/u/Fiver)\ **Post date:** [October 13, 2000, 4:04pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/30 "2000-10-13T16:04:26Z")
Niven invented _scrith_ because he thought only a fictional substance could have the properties he needed for the Ringworld. But I read somewhere that he needn’t have. If the Ringworld were smaller, say, the size of Mercury’s orbit instead of Earth’s orbit, it could be made of buckminsterfullerenes and be sturdy enough to survive. ---
**Author:** ![speakertohumans](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@speakertohumans](https://boards.straightdope.com/u/speakertohumans)\ **Post date:** [October 13, 2000, 5:47pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/31 "2000-10-13T17:47:41Z")
There was a recent conversation on the web with larry included. He like to give his characters the time to improve their own tools. (Example: The improved stepping disc technology 11 years later in the series used by puppeteers.) So, if he wants to make changes based on up to date technology, more power to him. It _is_ his playground. I just can’t get around that protectors would want their kith and kin on something so unweildy… ---
**Author:** ![andros](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@andros](https://boards.straightdope.com/u/andros)\ **Post date:** [October 13, 2000, 10:39pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/32 "2000-10-13T22:39:34Z")
**Blessedwolf** : be lucky 11 cents is all you get, pally. No, solar crap was never discussed IIRC. **Speaker** , welcome! Thanks for the info, although I cannot share **Poly** ’s enthusiasm for another Ringword novel. I’ve been a rabid Niven fan since I was 11 and even I thought _Throne_ sucked ass. Relatively speaking, of course. 'Fact, until recently I had been fairly disappointed in much of his more recent work. _Gripping Hand_ was good, but didn’t live up to _Mote_, IMHO. I had lots of trouble with the Svetz book, _Rainbow Mars_, was it? And _Beowulf’s Children_ put me to sleep. But I just finished _The Burning City_. Damn. I don’t know if it’s Jerry or Larry, or both, but I thought the book was just fantastic. I was afraid the Warlock thing would be too heavy-handed, but the story and characters were paramount and the mythology wasn’t at all overplayed. Well worth the read, for those of you who might be interested. Niven and Pournelle do high fantasy. ( **Blessedwolf** , consider that an official recommendation.) **Five** : while a Ring in Mercury’s orbit made of fullerine would be stable, I don’t reckon it would support much life. Something about those 400[sup]o[/sup] temperatures. Unless we build a second ring, just inside the other, to deflect most of the energy (which begins to defeat Dyson’s Hypothesis). Even then, it would have to be sturdy enough to withstand the temperatures and be heavily anchored to the other ring (or have many more and better attitude jets). ---
**Author:** ![andros](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@andros](https://boards.straightdope.com/u/andros)\ **Post date:** [October 13, 2000, 10:44pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/33 "2000-10-13T22:44:11Z")
Er, that would be 800 degrees. Farenheit. ---
**Author:** ![InkBlot](https://avatars.discourse-cdn.com/v4/letter/i/b5e925/32.png) [@InkBlot](https://boards.straightdope.com/u/InkBlot)\ **Post date:** [October 13, 2000, 10:47pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/34 "2000-10-13T22:47:58Z")
So move to Discworld instead. Sure, it’s unstable, but that’s all part of the charm! inkblot (besides, YOU try balancing a planet on the back of four elephants and tell me how easy it is) ---
**Author:** ![andros](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@andros](https://boards.straightdope.com/u/andros)\ **Post date:** [October 13, 2000, 10:57pm UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/35 "2000-10-13T22:57:26Z")
And I hear Riverworld’s nice this time of year . . . ---
**Author:** ![djbdjb](https://avatars.discourse-cdn.com/v4/letter/d/a87d85/32.png) [@djbdjb](https://boards.straightdope.com/u/djbdjb)\ **Post date:** [October 14, 2000, 12:19am UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/36 "2000-10-14T00:19:39Z")
Why can’t one get around the tensile-strength-of-scrith problem by spinning RW slower? Who needs (much) gravity anyway. How does the height of the wall needed to keep the atmosphere in vary with rotational speed? ---
**Author:** ![andros](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@andros](https://boards.straightdope.com/u/andros)\ **Post date:** [October 14, 2000, 12:30am UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/37 "2000-10-14T00:30:46Z")
> [@](#): > > \*Originally posted by djbdjb \* > \*\*Why can’t one get around the tensile-strength-of-scrith problem by spinning RW slower? Who needs (much) gravity anyway. How does the height of the wall needed to keep the atmosphere in vary with rotational speed? \*\* You’re right, people would be fine in a lower gravity. But the slower the spin, the greater the instability (back to the OP!). I’m not sure how much effect the slower rotational velocity would have on required tensile strength. Engineers? As for the atmosphere, the Ring cannot afford to lose much (relatively speaking, of course), as it has no way of replacing it once it’s gone. So it’s a matter of making sure an equilibrium is reached–lower walls just mean a thinner atmosphere on the ring floor. I suspect the wall height would go like the square as G decreased. I’ll grab my calculator when I get home and see if I can work up some numbers. Or I may not. Depende on how much of a geek I’m feeling. 😉 ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [October 14, 2000, 1:58am UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/38 "2000-10-14T01:58:35Z")
> [@](#): > > \*Originally posted by andros \* > [BBut I just finished _The Burning City_. Damn. I don’t know if it’s Jerry or Larry, or both, but I thought the book was just fantastic. I was afraid the Warlock thing would be too heavy-handed, but the story and characters were paramount and the mythology wasn’t at all overplayed. Well worth the read, for those of you who might be interested. Niven and Pournelle do high fantasy. ( **Blessedwolf** , consider that an official recommendation.) > \*\* Consider it done, my hoopy frood. But only if you consider the _Enchantment_ book I told you about. I’m going to go ahead and assume that you’ve read _The Integral Trees_ I know Niven and I think Pournelle wrote. ---
**Author:** ![2sense](https://avatars.discourse-cdn.com/v4/letter/2/e47774/32.png) [@2sense](https://boards.straightdope.com/u/2sense)\ **Post date:** [October 14, 2000, 5:08am UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/39 "2000-10-14T05:08:29Z")
Actually, Niven wrote _The Integral Trees_ and the sequel _The Smoke Ring_ all by his lonesome. ---
**Author:** ![Scylla](https://avatars.discourse-cdn.com/v4/letter/s/a5b964/32.png) [@Scylla](https://boards.straightdope.com/u/Scylla)\ **Post date:** [October 14, 2000, 6:30am UTC](https://boards.straightdope.com/t/is-ringworld-stable/36327/40 "2000-10-14T06:30:27Z")
_Lucifer’s Hammer_ and _Footfall_ remain my favorites. [Previous page](https://boards.straightdope.com/t/is-ringworld-stable/36327.md?page=1) [Next page](https://boards.straightdope.com/t/is-ringworld-stable/36327.md?page=3)