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

Entry: Dyson spheres – How big are your balls? - A9186537
Author: The_Jon_m - Scout, I am the only and only, nobody I'd rather be. Wibble - U204330

pop science entry

I love the title!

This is good, but it concentrates on formulas too much, and not enough on giving the reader an understanding of what Dyson spheres are all about. For example, you dismiss in one sentence the problem of the sphere being unstable. That will mean nothing to most readers, and certainly could do with a section on steering the sphere to keep it in place.

Similarly, you quote Gauss's law in a form that most people will not understand but don't point out what it would be like to live on the inside of a rotating sphere. Instead, you introduce magical "artificial gravity". Since the rest of the entry is about something which is at least within the laws of physics if not practical at the moment, you should avoid artificial gravity since it is completely impossible by all the known laws of physics.

I think an entry like this should have no formulas whatsoever. It's enough to say that the shell would have to be 8cm or 8m thick without quoting the formulas you used to work it out.

There are very few typos and grammar problems in this. I'll point them out later.

Yeah good entry...the minute I saw the title I immediately thought of Larry Niven's Ringworld as I have only just finished rereading it. A stunning book and it mentions Dyson Spheres in it a lot.

You may like to mention the Xbox video game Halo at that point in the text. As that is set on a ring world it enables the contemporary to understand the concept immediately.

I agree you need to cut out about 90-% of the maths as that information is not really suitable for the edited guide otherwise its a great entry...

While I too think the title is funny, 'Dyson Spheres' would have to be the actual title.

Yeah, I know, 'No Fun zone'

sulks at Jimster and changes title and removes the maths.

Shocking. Gnomon's allowed to be proud of his hairy balls, but you get harrassed for asking a simple question of your readers. I'd complain if I were you

it looks like in jimster's world, balls can be hairy but not big

The things you are describing are called "Dyson Spheres". The thing I was describing is called "The Hairy Ball Theorem". Titles are supposed to be short.

OK. You've removed all the mathematics. Now start putting all the other stuff in. Describe things rather than just mentioning them.

Living on the inside of a Dyson sphere - do we want to be able to stand on the inside surface as if it were the ground? If so, what are the conditions required? What would it be like? Talk about sunrise and sunset, or rather the lack of them; how would we have night? Would there be mountains? In a spun sphere, the land would gradually rise as you got further from the equator, until the land would be above the atmosphere. But the rest of the sphere could still be used for solar collection.

Living on the outside of the sphere - could it be done on a sphere of 1AU radius? Why not? What size would it have to be before there was reasonable surface gravity?

Stability in the sphere and the Ringworld. (Larry Niven didn't spot this in the first book and had to have it pointed out to him. I always got the impression that the second book was just an excuse to correct that mistake in the first book.) Your description doesn't really explain the problem to people who know nothing about orbital mechanics. Talk about how the earth is held in orbit and how the Dyson sphere isn't. Talk about how the thrusters would work. Perhaps even mention Niven's thrusters on his Ringworld.

*miffed that she missed the maths*

"Born in Berkshire on December 15, 1923, Freeman Dyson is no relation to the Astronomer Royal, Frank Watson Dyson." or the vaccumm cleaner guy?

Good entry

you removed the mathematics, but still say: "The mathematics behind a Dyson shell is explained below."

milliard -> billion


Dancer

Darn, I thought this was a Star Trek entry

<<...the only gravity acting on a point will be the star’s itself, which is about 1000 times smaller than Earth’s gravity>>>

I'm a bit confused by this. Should this read 1000 times *bigger*, or do you mean at the Earth's surface while earth is in free-fall around the sun?

Otherwise excellent

dancer, do not get me started with millards and billions

I am using the correct term, it's not my fault that the language was been corrupted.

The milliard has never been a word in English. The correct term, if you don't like the new-fangled billion, is "thousand million".

waves the OED at Gnomon, milliard is in there

but the point, surely, is that nobody uses it?

so yes, factually correct but plenty of people (like me) will be going " what's he on about? a billion?"

apart from that, this is fascinating.
(oh, and is he related to the vacuum cleaner bloke?)

what I meant is the term, not the OED. Lots of people use that

I don't really mind - Milliard is used to say a thousand million in Hebrew.