That can’t be right - Ringword has about 3 million times more surface area than the Earth, but the galactic empire had (Googling…) 25 million planets; hmmm, closer than I expected… So 8 or 10 Ringworlds would do it.
It might just be the population figure I’m remembering, then… I think Ringworld is probably more densely populated than the average Galactic Empire planet, especially considering that humans have filled all of the ecological niches. Unfortunately, I can’t seem to dig up the population of the Empire offhand (though I know it’s in the books somewhere).
Ummm, how do you keep the shell centered on the star, and not impacted by it as it orbits the galactic center (and possibly other motions within the galaxy or galactic group, but IANA physicist/cosmologist/astronomer, just a SF-loving bio/anthro person)?
Nitpick: Not humans, but hominids also descended from the Pak, which have speciated to become everything from grazers to scavengers. Although most of them seem also to have evolved to become neotenous, and therefore more or less sapient without the Protector transformation - unlike the Pak.
Orbits around other objects (like the galactic center) are no problem. The central star won’t feel any net gravitational field from the shell itself, but it will still feel the field from things outside the shell as normal. So both the shell and the star inside will orbit the galactic center together.
Aren’t most of them still considered to be genus Homo, though? I’d call everything in Homo a “human”, not just H. sapiens.
Pak themselves (at least the breeders) are referred to as Homo habilis in “Protector”, so it’s likely that all their descendants would be lumped under genus Homo. Which doesn’t explain the other primates on Earth, but works for Ringworld.
Didn’t they also want to move the Ringworld because the galactic core was exploding and in ~20,000 years most of the galaxy would be uninhabitable?
The ringworld was in the same plane as the galaxy, and scrith blocks neutrinos, so it’s the only safe place to be when the radiation front hits. That’s why (at the end of the first book at least) Teela Brown was lucky enough to go there - she’ll survive the core explosion.
I shouldn’t read these threads.
…wanders off to download the Ringworld and Foundation series’ to his iPhone…
Okay, if you say so. I still don’t understand how it can track the star if there’s no gravitic interaction, but that’s okay. I wouldn’t understand the math if you tried.
I wasn’t doubting whether the star would continue its normal orbit around the galactic center, or that its response to other gravitational attractions would differ. However, that business about Ringworld being unstable and, without the thrusters, due to eventually brush against the star, made me wonder whether a Dyson sphere wouldn’t be equally unstable. That’s where the question came from, if you were wondering.
Frankly, I don’t think that chimps, et al, should be in other genera. Chimps and bonobos, for certain, and probably gorillas, and likely orangs. Not that my opinion counts for anything. But I consider them hominoids, at least. There’s entirely too much genetic similarity.
OTOH, I certainly wouldn’t call any of the hominids on Ringworld humans; sorry. For me (and I think any biologist), “human” is shorthand for H. sapiens sapiens, and for anything else to be human would mean interfertile with humans. You may or may not be aware that many people speculate that humans could be interfertile with chimps (there is a chromosome number difference, though, IIRC, so any hypothetical offspring would be “mules”). I decline to take a position, personally.
Niven was most specific that inter-hominid breeding - whether with humans or with other hominids - is not fertile. Indeed, it’s a means of satisfying appetite without the potential hazard of reproduction - as well as a matter of diplomacy, etc.
Also - stars die. Even Sun-sized stars expand into red giants, and then go nova. If you can swing it, it’s a good idea to be elsewhere when that happens.
(Who cares if it’ll happen billions of years in the future? The Ringworld was pretty clearly built to last).
That, and the Galactic Core was exploding; as I recall eventually it was intended for the Ringworld to head for the Magellanic Clouds at sublight like the Fleet of Worlds, using the Ringworld’s star as a fusion engine. It had to be out of range of human and Kzin attacks first though.
As I recall, it was due to the original Protectors, when they knew they couldn’t survive deliberately exposing the breeders to radiation, to produce mutations that might survive without them.
Here’s one thing I can’t figure out about gravity inside such a shell. I get it, that the shell effectively cancels its own attraction to objects inside it. But in spite of that does the shell still exert a measurable gravitational effect to objects inside it by friction?
I’m not sure friction is the right term. But bear with me.
I’m looking at this like an object being pulled by (and I realize I’m simplifying here) two ropes in opposite directions. Because the pull is equally strong in each direction, the object being pulled goes nowhere. In fact, it’s more stable than it was before someone tied a couple of ropes to it: try to pull it in a third direction, and it will resist that movement because the first two ropes are holding it in place.
Does the rope analogy make sense in this context? Will objects inside the shell resist other forces because of the gravitational pull in all directions from the shell’s mass?
No.
Thanks. Well played. :rolleyes:
I can get how gravity cancels things out inside the sphere, even if it’s nonintuitive, but if the sphere was orbiting a central sun, wouldn’t things still be drawn towards that sun? Then again… here on earth we’re drawn towards the earth and not the sun. I’m guessing distance matters a lot more than mass when it comes to gravity?
Somebody pass the bong before my head asplodes.
The analogy is no good. If you try to move the rope-held ball (or whatever) in one direction, the rope on that side would slacken and the rope on the other side would tighen, resulting in a non-cancelling rope force on the ball. The force is such that it tries to restore the position of the ball.
For gravity in a shell, the force in one direction is always exactly the same as the force in the other, even as you push the ball around. You shouldn’t think of the cancelling effect as being like two ropes. You should think of it as being like the shell isn’t even there.
Why are you here?
-FrL-
We’re drawn towards both. Our attraction to the sun does work out to be only 0.1 pounds or so, but without that pull, we would feel 0.1 pounds lighter at midnight (as we tried to move in a straight line while the earth stayed on its curved solar orbit) and we would feel 0.1 pounds at high noon (as the earth curved into us). As it is, we follow the same orbit around the sun as the earth – we just happen to be stuck to the earth, too.
The Ringworld does have a net interaction, and it’s such that if it gets a little bit out of whack, it tends to get even more out of whack. It’s like a marble sitting on the top of a dome: You can, in principle, balance it right on the top, but if it’s nudged just the slightest bit off-center, it’ll tend to roll further in that direction, faster and faster, until it falls off. That’s what we mean when we say something is unstable.
A complete sphere, though, has no net interaction at all. It’s like a marble sitting on a flat tabletop. If something nudges it slightly, it’ll start rolling slowly, but it’ll stay slow, and never get any faster. This is what we call neutral stability. You would still need some sort of thrusters to cancel out any slight nudges it might get, but it’s a lot easier than doing the same thing for an unstable system.
Finally, there are stable systems. These are like a marble in the bottom of a bowl: If you nudge the marble a little bit one way, it’ll roll that way, but then it’ll slow down, stop, and roll back to the bottom of the bowl. It’s not leaving the bowl unless it gets a really big push to start with. In a system like that, you wouldn’t have to do anything to correct for nudges, since the system is self-correcting.
Probably not to give a lecture on fundamental physics. The analogy listed out by Subway Prophet just doesn’t make any sense and is useful only as an example of why trying to reason via analogy is a poor means of trying to understand the world versus the empirical scientific method or the analytical ontological approach. The fact is–and this is apparent from a basic reading of classical Newtonian mechanics–the gravitational potential at any point within a sphere by the field created by the mass of that sphere will be neutral in all directions. I don’t have a physics text at hand but any university level calculus-based text will develop this in detail. There is no “friction” or anything like (and indeed, mechanical friction is the result of coupled forces) and the only resistance an object within will have to movement is based on its own inertia which is proportional to the mass. A more appropriate analogy–although again only suited to illustrative purposes–is to imagine the effect of air pressuring in a balloon on objects inside. While a pressure differential in air can cause objects to move, a static and uniform pressure increase won’t result in any movement whatsoever.
Stranger