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

Are you going to answer my comments about your entry, The_Jon_m? If you don't agree, then just say so and I'll go away.

Living on inside - talked over night / day, atmosphere only in a small section. Also about if we'd live on surface or in domes

will try and figure out some text on terrain but I'm assuming it would be flat since we've used all the matter in the solar system to build the shell, there isn't much left for mountains.

explaned the living on the outside a bit

will have another bit about stability of a ringworld



On imaginary numbers, yep they are simple, but they are not taught in america, you can easily get into post-doc physics without encountering them. all my phyiscs text books have rather crazyily complicated equations for realtivity because they won't use imaginary numbers

We use imaginary numbers in advanced algebra pretty regularly, provided they're the ones with 'i' in them that I'm thinking of.

Electrical Engineers use imaginary numbers to represent the phase angle between voltage and current in alternating current (AC) systems.

Traveller in Time waving a coil
"< A316739 > 'imaginary numbers' < C63 >.
Before someone posts an external link. "

in uni our floors were lettered rather than numbers

A was basement, B ground, C 1st floor etc.

none of the buildings had a floor I, so it was taken as an imaganary floor

OK, here are some detailed comments.

1. Are the numbers Type 1 and Type 2 ones that you've come up with or are they the standard terminology?

2. I'd like to see you expand on the sentence "Once it is complete, it will need to have thrusters on the outside, otherwise any impact will drift the shell into the star."

This could do with at least a paragraph, as I doubt anybody would understand it unless it is spelled out.

3. "A ringworld is not dynamically stable" -- this should be "Live a Type 2 Dyson Sphere, a ringworld is not dynamically stable", or even use different words so that people will realise what you mean.

4. unregarded yellow sun - actually the sun isn't yellow, it is green. But nobody will believe me. I suggest you change this to "unregarded G-type star".

5. "Constructing a spinning shell would seem to be the answer" -- this comes immediately after a sentence saying the the shell will drift off course, and suggests that spinning the shell keeps it in place. In fact, it is the answer to an entirely different question, how to stick people to the inside of the sphere.

6. To achieve earth gravity on the inside of a sphere of radius 1 AU, I reckon it would have to spin once every 5.46 days.

7. "rendering most of the surface of the sphere uninhabitable." -- most of the ground would be not horizontal anyway, unless the inside of the sphere was terraced.

8. "as we do on Earth, wandering free across the surface" -- make it clear that it is the inner surface.

9. I don't understand why the Dyson sphere would have any more problem with heating up than the earth. The earth absorbs heat on one side and emits it on the other side. Each part of hte sphere would also absorb heat on one side and emit on the other (outer) side.

That's enough for the moment.

G

I think the referance...

unregarded yellow sun - actually the sun isn't yellow, it is green. But nobody will believe me. I suggest you change this to "unregarded G-type star".


is a reference to the opening paragrtaph of DNA's Hitchikers guide to the Galaxy ...

'in the slightly less fashionable end of the western spiral arm of the galaxy lies a small unregarded yellow sun. Orbiting this at a speed of roughly 92 million miles per hour is a small insignificant bluey-green planet.Its ape descended life forms are so amazingly primitive that they still think digital watches are a pretty neat idea.'

Oh. Didn't spot that. In that case, leave it.

I've done my calculations a bit more carefully and I now reckon the sphere would have to rotate once every 9 days. That's using a value of the radius of the sphere r as 150 million km, acceleration due to gravity on Earth's surface g as 9.81 and the period of rotation given by:

T = 2.Pi.Sqrt(r/g)

Say, regarding milliard vs billion. Why not say 'billiard'? Then, when you mean to say that there are more than this already astoundingly large number, you can say 'billiards.' Then we Americans will understand that you mean lots of balls knocking about. All in fun. Good entry

Why not say billiard? Because billiard means 10 to the power of 15.

you got me there.

Why don't we just use greek prefixes instead (kilo, mega, giga, tera, peta, exa)???

I was also thinking that billiard balls are a bit small to live on

In post 47 Gnomon talks about horizontal surfaces.

Earth is an approximate sphere, so no surface on it is horizontal. It's smaller than a Dyson sphere, and Humans manage to live on it. What would be interesting about a Dyson sphere's insides, is that you'd be able to see the next roofs of the next county by looking up at an angle as it curves into view.

Yep - you get that sort of effect with the ring-shaped world in the PC game Halo - you can see the land curving upwards in the distance

I was just having a think about wether or not you would see the curvature above you. I thought no perhaps youd see a 'normal' horizon like on earth and then perhaps just a faint black line streching up into the sky. So I set up an experiment to see if I was wrong or not.

Using my 3D CAD software I created a ring world 1000km diameter, with a 1 km thick crust and with it 1 km wide. I then modelled a 1 metre x 1 metre x 1 metre cube and placed it on the ground inside the ring. By switching on the perspective viewer and standing next to the ring you get an idea of what you would see...heres the snap shot I took

http://images.fotopic.net/y4hvb8.jpg

So it appears I was wrong you do see the world curving.With a caveat though this view does not include any atmosphereic and I'm not sure how accurately the software breaks down a circle but it still gives a good idea

I think you missed my point, Sea CHange. If the earth was a perfect sphere, every point on the surface would be horizontal. That is, the surface would be perpendicular to gravity. But on the inside of a spinning Dyson sphere, only the points on the equator are horizontal (perpendicular to the perceived gravity. If you poured water onto the ground anywhere inside the rotating sphere, it would flow until it reached the equator.

which is why if you span it, it would be more useful as a ringworld