Ringworld Construction and Livability

[Reaper]

After having just read Larry Niven's Ringworld (A very good book by the way), it got me thinking about how one might actually go about building and living on one.

 

In the novel, Larry assumes the ring would be about a million miles wide, and 600 hundred million miles in circumference. To keep in all the air, the Ringworld edges are about 1000 miles high. He calculated that it would take about a mass of Jupiter to create such a structure. Not only would there be virtually limitless supplies of energy, but there would also be quite a bit of space. And much sturdier than a Dyson Sphere.

 

Now, assuming those dimensions, how would some alien or future society go about actually planning and building one? As much mass as Jupiter sounds great, but it is also worth noting that most of the mass (> 90%) in the solar system is just hydrogen, so a lot of the material would have to come from somewhere else (One could then question why such a structure would be built, if they could just settle on other star systems?). The second issue is that of gravity; such a structure would probably be very difficult to keep from being torn to shreds by gravitational forces. I know Niven has a computer (and a super-strong alloy) to keep in in check, but unless it is intentionally not a perfect circle, I don't see how one can keep it from falling apart.

 

I also wonder about the habitability of such a structure. While it is said to be about the same distance from it's parent star as the Earth is from the Sun, the fact that the Earth has an active interior, a large moon, liquid water, is rotating, and seasons all contribute as well. A Ringworld wouldn't have any of that, so it would definitely need a way to shield from radiation. It also turns out that the Earth rotates much slower than Ringworld would (about 1000 mph compared to Ringworld's 770 mps, unless you opted for < 1g surface gravity), so I would imagine that weather patterns would not be equivalent to Earth's. Indeed, I don't think that climate patterns would even be the same on such a structure; unless most of the Ringworld was covered with water, I would imagine that large sections of it would be very arid and just simply not habitable.

 

The other thing, then, is if we were to stand on it, what would we see? My book cover has that you can indeed see the "world" curve upwards into the distance, but that is from a considerable altitude. Since the structure is about 600 million miles in circumference, would anyone living on it have a clue as to the world's true nature? It is already difficult enough to see the curvature of the Earth, and it is only 40,000 km in circumference. Also, since it is always facing it's star, and Niven's proposed night cycles are just solid lumps of sheet metal orbiting the Ringworld, it would be very difficult, if not impossible, to see the stars. Of course, in Niven's book, most of the societies on Ringworld have largely forgotten the true nature of their world and have reverted to using supernatural explanations for various phenomenon....

 

 

So, what do you all think?

Edited June 4, 2009 by Reaper

[CaptainPanic]

Regarding gravity and the whole thing being torn to shreds: we had a discussion here about a year ago about the rings of Saturn. I'm assuming that this ring world is positioned around the sun: you might want to look at the Roche limit. It's an interesting law. I'm not sure if it applies though, since you said it orbits at the same distance as the earth.

 

And I agree that even if the Roche limit doesn't ruin the fun, then the ring might collapse into several spheres that will all have the same orbit.

 

You also mentioned the day/night cycles: it's possible to create night with some disks moving around the ring. But how does one create day on the backside of the ring? Mirrors?

 

However, I think that the greatest challenge is indeed the weather system and/or the water system. I have no clue about that actually... but with such a massive surface area (the mass of Jupiter, but in the shape of a ring will create an enormous surface area) the place will have an astonishingly large amount of atmosphere which will have some funky day night cycles, possibly some "pole" on the back side where it's always dark and freezing...

 

Does the ring in the book have oceans? That seems like an incredible risk in the design: water can move! Therefore water will be attracted by whatever gravitational imbalance there is and gather in 1 place, and form a sphere somewhere on the ring (and that will most likely destroy the thing).

[Sisyphus]

CaptainPanic, only the inner surface of the Ringworld is habitable. It isn't in orbit around the sun, but is spinning quite a bit faster - fast enough that the centrifugal effect experience by someone standing on the inner surface approximates Earth gravity. It's held in place purely by the tensile strength of the material, which obviously is enormous. The day and night cycle is accomplished with a smaller ring similarly spinning at about half the radius, this one composed of large solid sections connected by ridiculously strong tethers. There are large bodies of water interspersed throughout the ring (though not connected, and tiny relative to the size of the ring itself, as well as two huge oceans on opposite sides. And yes, the surface area would be huge, which is the point: 3 million times the surface area of the Earth.

 

Anyway, I read that book many years ago, but I'm pretty sure I remember some of those questions addressed. (If not there, then in the first sequel, The Ringworld Engineers). Curvature would be completely indetectable at the surface, creating the illusion of an infinitely distant horizon. The atmosphere would become opaque at a distance when anything noticeable would happen. However, the ring would still be visible overhead, appearing as an arch (with the sun under it!). I'm pretty sure stars would be visible at "night," too, as they are in a solar ecclipse. The construction is left deliberately mysterious, although I think allusions are made to "a suspension bridge with no endpoints." Weather patterns are addressed, too, I'm sure, in the discussion about the "eye storm," although I don't remember the details. The radiation shield bit is also addressed, although I think in the second book. So too is the gravitational instability. I won't talk about it, though, cus they're actually kind of key plot points...

[CaptainPanic]

Ah, so they live in a tube?

 

Hmm... I tihnk I'll just apologize for replying to a (fictional) topic that I had not sufficient knowledge about. If you guys think this is a fun book to read, I'll add it to my yet-to-read list (which unfortunately always grows - I cannot read fast enough).

[Sisyphus]

Ah, so they live in a tube?

 

Hmm... I tihnk I'll just apologize for replying to a (fictional) topic that I had not sufficient knowledge about. If you guys think this is a fun book to read, I'll add it to my yet-to-read list (which unfortunately always grows - I cannot read fast enough).

 

No, it's not a tube. It's flat, like a fan belt. In the book it's described as like a circular loop of ribbon, an inch wide and 50 feet long, with a candle in the center (the candle being the sun). "Inner" as in facing towards the sun, as opposed to away from the sun. The atmosphere is prevented from escaping by thousand mile tall walls at the edges, pointing towards the sun. A "ceiling" is thus unnecessary.

 

And yeah, it's a sci fi classic and a quick read, so give it a look.

[Reaper]

And I agree that even if the Roche limit doesn't ruin the fun, then the ring might collapse into several spheres that will all have the same orbit.

 

That's ultimately what would probably happen. In the book itself, though, it is made from a super-strong alloy known as Scrith, and while strong enough to make super-structures of this kind, even with that they have a hard time maintaining stability of it.

 

You also mentioned the day/night cycles: it's possible to create night with some disks moving around the ring. But how does one create day on the backside of the ring? Mirrors?

 

Only the inside of the ring is livable, as Sisyphus mentioned, not the backside. So it's not a problem if the backside is not lit.

 

However, I think that the greatest challenge is indeed the weather system and/or the water system. I have no clue about that actually... but with such a massive surface area (the mass of Jupiter, but in the shape of a ring will create an enormous surface area) the place will have an astonishingly large amount of atmosphere which will have some funky day night cycles,

 

and

 

Weather patterns are addressed' date=' too, I'm sure, in the discussion about the "eye storm," although I don't remember the details.

[/quote']

 

@Sisyphus: They do talk about it in the first book; the engineers of the ringworld did put some sort of air-circulation and climate control system, but I think it is said to have malfunctioned long ago. And that's where I find a major issue as to it's habitability. And I doubt even with the air-circulation you could create climates that are more or less like that of Earth's.

 

CaptainPanic is indeed correct, weather and water circulation systems would certainly be a formidable challenge. Because of it's massive surface area, not only is there a fantastic amount of air in general, but also it would most certainly have landmasses that dwarf that of Pangaea, and super-oceans that would make the Pacific look like a small puddle.

 

Not only that, but the air would probably not be circulating all too much. The reason the air circulates on planets has largely to do with the fact that it is spinning. Ringworld spins too, but only so that it could create centripedal acceleration to match that of Earth's gravitational pull. So, in effect, the air is largely just sitting there.

 

possibly some "pole" on the back side where it's always dark and freezing...

 

Well' date=' since the backside is not inhabited, the point is moot. However, I would imagine that there would probably be some freezing near the edges though. Although, since it would be impossible to circulate all the heat on the supercontinents that would likely cover the world, possibly large areas of center would also be very cold too.

 

Does the ring in the book have oceans? That seems like an incredible risk in the design: water can move! Therefore water will be attracted by whatever gravitational imbalance there is and gather in 1 place, and form a sphere somewhere on the ring (and that will most likely destroy the thing).

 

 

Yes it does. It would be an incredible risk to put them there while building it, but since the Ringworld is spinning the water would likely just stay on the ring. If the far future humans or some advanced alien civilizations were to have any hope of making Ringworld more Earth-like, you absolutely need oceans. I think the most problematic thing about this is the oceans themselves; unless the oceans were truely gigantic, large portions of Ringworld would be drier than the Atacama Desert. But then, the problem with the oceans would be the size of the oceans themselves; one could only imagine what type of climate such oceans with little circulation would create.

 

Personally, I don't think it would matter what the size of the oceans are, or how many of them there are. Large portions of the Ringworld land masses would probably be arid anyway due to the geometry of the thing.

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However, the ring would still be visible overhead, appearing as an arch (with the sun under it!).

 

How visible would the arch be though? The "other-side" would be more than 300 million km (about 200 million miles) away. Sure, it's a million miles in width, but at such a large distance it would still appear to be very small. Also, the glare of the star (as it is assumed to be a yellow star like the Sun) would probably make it difficult, if not impossible, to actually see the arches. At least not without the aid of instruments.

 

I'm pretty sure stars would be visible at "night," too, as they are in a solar ecclipse.

 

How so? "Night time" occurs when a big metal sheet happens to cover a particular patch of the ring. There would be no solar eclipse, since the metal sheet is already much larger than the diameter of the sun. It would completely block out the sky.

 

Although, it might be possible to see stars during "twilight hours", as the atmosphere might refract some of the light...

Edited June 5, 2009 by Reaper
Consecutive posts merged.

[insane_alien]

reaper, the metal plate doesn't cover the whole sky, the blocks that allow for day night cycles are about halfway between the ringworld and the star. it is much more like a solar eclipse than you imply.

[Sisyphus]

A good comparison of the visibility of the arch would be with Earth's moon. The moon's diameter is about 1/100th its distance from us. It is quite large in the sky and clearly visible in the daytime. Assuming our dimensions, the width of the ring at its farthest point would be about 1/200th its distance from an observer. Obviously this particular point would be behind the sun and thus always invisible, but most of it would be clearly visible. A quarter away around the ring would be almost as wide as the moon is to us, and it wouldn't be just a circle, but a huge band across the sky, widening down to meet fully half the horizon. So yes, it would certainly be visible, day and night. If anything, the "archlight" would be inconveniently bright at night.

[Reaper]

reaper, the metal plate doesn't cover the whole sky, the blocks that allow for day night cycles are about halfway between the ringworld and the star. it is much more like a solar eclipse than you imply.

 

Ah, ok, never mind then. I read very quickly, and sometimes I miss some details...

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A good comparison of the visibility of the arch would be with Earth's moon. The moon's diameter is about 1/100th its distance from us. It is quite large in the sky and clearly visible in the daytime. Assuming our dimensions, the width of the ring at its farthest point would be about 1/200th its distance from an observer. Obviously this particular point would be behind the sun and thus always invisible, but most of it would be clearly visible. A quarter away around the ring would be almost as wide as the moon is to us, and it wouldn't be just a circle, but a huge band across the sky, widening down to meet fully half the horizon. So yes, it would certainly be visible, day and night. If anything, the "archlight" would be inconveniently bright at night.

 

Actually, after my last post I did some more thinking about it and realized that you would see it. A different line of reasoning, but same conclusion nonetheless.

 

On the side note, while it might be inconvenient bright at night, it would be far easier to observe the details on the other side during that time.

[Pangloss]

Scrith also stops 40% of neutrinos, if memory serves. An amusing side-note that later turns out to be a plot-point in one of the sequels, I believe.

 

I actually asked Larry Niven, at a SF convention in 1984, whether he originally planned for _____ (don't want to spoil it for Reaper) to be the creators of the ringworld. He made a sarcastic remark about writers and readers knowing their respective places, as I recall (basically he didn't want to say). Oh well.

 

I think the thing I loved most about it was the distorted sense of scale that Louis Wu keeps fretting over. Lots of fun.

 

In the 2004 novel (the fourth sequel) he gets a bit into the problems of moving the Ringworld, which is an imaginative bit. That book turned out to be pretty decent, after the disappointing "Ringworld Throne" sequel from 1996.

Edited June 6, 2009 by Pangloss