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

I downloaded the universal "Sun Graph" from
http://www.analemma.com/Pages/framesPage.html
and poked in the co-ordinates for Dublin. It appears the "grand stretch" has just exceeded two minutes since the earliest sunset eight days ago on Dec 14.

Okay, I'm tenatively done. I believe I got everything, although all can feel free to poke holes in my editing abilities. A2152766
-MotDoc

Looking good, MotDoc.

I'm wondering whether it might be good to include the bit about places having local times until the introduction of the railways, which led to standardised time.

Oh, and there's a typo: independantly > independently.

You don't clearly distinguish between noon by the clock (12:00) and noon by the sun (when the sun is due south and half way between sunrise and sunset. You'll have to distinguish between these two so as not to confuse people.

Well done MotDoc, you show that it is possible to get the essential information into a short entry without diagrams.

We can clarify a bit here:

>"at some points in its orbit the Earth is closer to the sun (winter in the northern hemisphere) and at some points it is farther away."

--wouldn't it be shorter to say "January" than "winter in the northern hemisphere"?

>"In addition to not being circular, the earth's orbit is also not flat"

--is this true? Even if it is, is it relevant? It seems to me that you mean something else by "not flat" viz. "not orthogonal to the earth's axis"

>"Depending on how you wish to visualize it, either the earth's axis is tilted toward the sun's position in the celestial sphere, or the earth's orbit is tilted with respect to the sun"

--it's unnecessary to introduce the celestial sphere at all; highly confusing. And I can't see what you mean by "tilted with respect to the sun". As I understand it, what you're talking about is the earth's rotation (spin) being around an axis which is tilted with respect to the plane of its orbit round the sun.


>"the effect is that the angle of the sun toward the earth varies over the course of the year"

--this bit is important; we need to single out those ways in which it (the sun's apparent position) varies so as to produce the analemma. More concise language than this is needed. You might say something like "in winter the sun shows less in the sky, in summer more; and this affects not only the hours of daylight, the rising and setting points on the horizon, and the height of the sun at noon, but also the apparent speed of the sun's transit across the sky." Someone more astronomically hip might choose better than I have what salient points to fix on, and how to get it across, but this kind of language seems to be both readable and exact enough for the job.

>"At the point at which the earth is exactly over the equator"

--for earth read sun? And would "on the days" be more concise than "at the point" -- "point" refers too indiscriminately to time and place.

Thank you everybody, I have been working on your comments.
Recumbentman:
winter in the northern hemisphere-
I would actually prefer to do months, but I don't know specifically which months are the closer ones. But it is more than just January.

All others have been incorporated as best I can. Overall, I have done my best to translate complex astronomical concepts into simple language that anyone can understand. I suppose the measure of my success will come if the entry goes up for review, since everyone involved here presumably already knows what I am talking about.
-MotDoc

"if the entry goes up for review" -- that's up to you the writer, isn't it? "Submit for review"

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