h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Surely the easiest way to create gravity on a Dyson Sphere would be to spin it. As the rate of spin increses it exerts centrifugal forces away from the the point of rotation. It would need a lot of energy to keep this spinning though

Sean

Scotty had indeed stored himself in the pattern buffer of a transporter. I'd hate to be stored in the pattern buffer of my PC. I'd be lost if the machine ever needed to be restarted (i.e. I'd last about 3 hours).

Dyson spheres were invented by Freeman Dyson. He is a different bloke from the guy who invented the centrifugal filter-less vacuum cleaner.

The trouble with spinning a Dyson sphere to make gravity is that it is only the right strength at one lattitude. If you spin it so that gravity is just right at the equator, then it will be much less at 45 degrees north, and it will be at an angle, too, so that the ground will appear to be a very steep hill. In effect you will only be able to use the bit of the sphere around the equator. But you could use the rest of it for solar panels to harness 100% of the sun's energy.

I can't be bothered doing the math just now, but if you were to spin it so that gravity was too strong at the equator, surely you would get two "bands" of acceptable gravity instead of one? (one "above", one "below")

Somebody with a lot of time on their hands could probably calculate the optimum amount to go over standard gravity at the equator to maximise the percentage of the internal surface which fell within acceptable limits of "normal" gravity.

I'm not a clever person but spinning woudl create normal gravity over only the equator. Bear in mind that earths spinning does not create its gravity, its preasance in teh unibverse does. The problem on a dyson sphere is that if you loose gravity or spinning tenn everything falls in towards the sun. I don't know what woudl ahppen away from teh equator though, probably a feeling of being dragged to teh outside as per centrefugial force.

In star trek they probably used an artificial grivity machine. Which is a n easy non-tech way of saying how you'd work it.

In teh end, isn't it easyer to build an artificial planet?

I'm feeling a bit more awake, so I can expand on my last posting...

33337, spinning creates a sort of "gravity" effect which is strongest at the equator, and lessens (and becomes at more of an angle to the surface) as you move away from the equator. If, for the sake of argument, we defined a range of +/- 5% of Earth gravity to be acceptable for human habitation, then by spinning the sphere so the equator appeared to have a gravity of 5% above "Earth normal", there would be a band reaching from the equator to the points above and below where gravity was 5% below "Earth normal" which would be suitable for habitation. Beyond that point, say to the region which was 50% of "Earth Normal" people would still be able to travel and function, so those areas would be used for two "Agricultural bands" where edible foliage would grow larger than normal in the reduced gravity, with more of the plant's energies going into making leaf matter and less into stalk.

The downside of building an artificial planet is that you need an artificial sun too, and keeping them the right distance apart can be tricky in the initial stages... Also, you need matter to fill the planet with, unless it's hollow, in which case you've just built a Dyson sphere again! Also, a hollow "planet" wouldn't have nearly enough mass to remain in a life-sustaining orbit, or indeed to provide sufficient surface gravity. Unless you build a Dyson sphere with a mini-black-hole in the exact centre...?

Makes a little more sense. Wish I was cleverer.

As for artificial planet. How about finding/manufacturing a big lump of material teh size of earth and then "Dropping" it into orbit of a similar sun at about earths distnace. If you can somehow match all of earths orbital characteristics (Very difficult because composition matters so I hear) and then add on the life support stuff. Of course, it wouldn't hold anywhere near as many people as a dyson sphere. (Where your adavntage is that over teh ideal gravity area you have a huge amount of land. (Enough to take a year of fast travel around)

I had a drunken conversation with a friend earlier which led to an expansion of the "plant-growing" theory above...

Basically, grow Bamboo! It'll grow straighter and taller than on Earth, and will make the ideal structural material for constructing the shell of the *next* Dyson sphere...

Just think how man Giant Pandas you could raise in a bamboo forest that size. The World Wildlife Fund would probably give you knighthood for that!

The trouble with the low gravity forests, is that since the sun is fixed, they would all lean towards the sun instead of growing straight up. (Up here means perpendicular to the axis of rotation of the sphere). We might end up with curved rather than straight bamboo.

Woudl taht actually matter, with bamboo if you were going to feed pandas with it? Obviously it reduces its value as a construction material but Are pandas actually bothered about eating bent bamboo? Has anyone asked them?

the problem with the spining dyson sphere idea is that no matter how fast it spins there will never be any gravity at the poles. also if you live too close to the poles for a long period of time then your body will deteriate to such an extent that you will never be able to go to the equator as the gravity will be too strong.

how about if you gave the actural sphere incredible mass. then you might be able to create gravity like that on earth.

No matter how massive the sphere is, you will not get any gravity at all inside it. This is a consequence of the way gravity decreases with distance. The near side of the sphere and the far side of the sphere exactly cancel out each other's pull. You will get gravity on the outside, but since the sphere is very large in diameter and not very massive, it will be fairly negligible.

I still think the Velcro boots are the best solution.

of course. i didn't think of that. the velcro boots might help but it will probally be a little uncomfortable having to walk around like that all the time.
basically it could never realistically be done.

There's a wonderful demonstration of how to walk with velcro boots in the film "2001 - A Space Odyssey". The stewardess on the space liner brings a tray of refreshments to Dr Floyd, the only passenger.

i know. but she never looked very comfortable when she was doing it and i don't think anyone could do that all the time. besides they also had the the spining dome idea in 2001 on board the descovery.

Plus velcro is never a good solution. It woudl get full of bits of fluff and lose its stickyness. Then you'd fall screaming into teh sun, which isn't nice.

thats true. mind you the sun would have to be fairly strange (i.e. very small) inorder to fit into the sphere in the first place. i don't think stars can acturally form if they go bellow a certain mass.

Maybe you are imagining a smaller sphere than I am. I was thinking of one with the same radius as the Earth's orbit around the sun, that is, a radius of about 150 million kilometres.

Ah I see. That’ll definitely be a very big world. You’ll have to excuse me; I wasn't familiar with this theory before so I’m trying to pick up what I can as I go along.

i don't know why my computer put those numbers in there.

With a 150million Km radius I suppose you wouldn't really need the poles. You coukld keep machinery there, and solar panels. Otherwise it would just be really wasteful.