Talk:Horizon
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[edit] Refraction
I added brief mention at the end of the fact that the actual visual horizon is a little further than the calculation in the article would suggest, because of refraction.
Actually, I would like to have changed the nomenclature completely here, but I didn't feel like taking the time to redraw the picture. The word "visual horizon" ought to include the effect of refraction, while "geometric horizon" is the horizon for a spherical planet, but without the effect of atmosphere. I don't know of a phrase meaning "where the horizon would be if the Earth were a plane," but "geometrical horizon" isn't it.
[edit] Unheadered stuff
so why is it purple then?
I came to this page to see if it said anything about why the sky (during a clear day) gets grayer as it gets closer to the horizon. If anyone has a good treatment or link, that would be swell. Jake 00:02, 19 Aug 2004 (UTC)
- Maybe this would be better treated on sky since that is where they talk a little about the color? Jake
See airmass or extinction (astronomy) for an explanation of this phenomenon. --Lasunncty 00:18, 29 January 2006 (UTC)
[edit] Added gemoetrical horizon
I added the part about perspective drawing and the "geometrical horizon". In a way, it is similar to the description of "astronomical horizon". However, astronomical horizon was described as a plane, while I believe the horizon is alway a line. Note that it compares the astronomical horizon to the true horizon (one being lower than the other), even though one is described as a line and one as a plane. It seems like this could use some clean up to clarify this distinction.
Robbrown 21:06, 29 January 2006 (UTC)
[edit] Mushroom cloud
Why does the horizon picture look like it has a mushroom cloud in the background? User:fresheneesz
[edit] Metric?
How about a formula using miles. Why is there only formulas using the lame metric system?
How about performing a simple conversion you lazy person Graemec2 13:13, 13 November 2006 (UTC)
[edit] Mental Calculation
What if you do not have a calculator? Naval officers often use a thumb rule calculation that you can do in your head, that is:
The distance to the horizon in miles is equal to the square root of the height of eye in feet, multiplied by 1.1.
It usually suffices to choose a height of eye that is a square of a round number, like 4, 9, 16, 25, 36, etc. If in a small boat or looking through a periscope, assume a height of eye of 4 feet, the square root of 4 is 2, multiply by 1.1 to get the distance to the horizon of 2.2 miles. If you are on a larger boat, use 9 feet [3.3 miles], a bigger boat, 16 feet [4.4 miles], and so on. If your height if eye is mid-way between 9 and 16 feet, the distance would be half way between 4.4 and 5.5 miles, say 5 miles.
The distance provided by this thumb rule is roughly 10 percent shorter than the exact distance. That accuracy is usually quite sufficient for an eye-ball approximation of a ship or lighthouse that far away.
24.15.3.112 18:22, 24 February 2007 (UTC)tvbanfield
