# What proportion of the earth's land surface has land at its antipodeal point? **URL:** \ **Category:** Factual Questions\ **Created:** [June 25, 2010, 4:17am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448 "2010-06-25T04:17:32Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Dervorin](https://avatars.discourse-cdn.com/v4/letter/d/eb8c5e/32.png) [@Dervorin](https://boards.straightdope.com/u/Dervorin)\ **Post date:** [June 25, 2010, 4:17am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/1 "2010-06-25T04:17:32Z")
I was playing around with the antipodes map the other day, and this question came to me. Given that about 70% of the earth’s surface is water, and that there is more land surface in the northern hemisphere, I expect that the percentage isn’t high, but can anyone put a number to it? ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [June 25, 2010, 4:37am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/2 "2010-06-25T04:37:34Z")
If you draw an antipodal map this way, rather than using an interactive point locator like you were probably playing with, you can get a good idea: [http://bartonhome.ca/antipodal\_map.png](http://bartonhome.ca/antipodal_map.png) What percentage is brown, representing the bits that overlap? I’m eyeballing it as about 24%. South America is about 12% of the Earth’s land surface, and it looks like the other bits are enough to finish filling up SA. Remember that Greenland is distorted by the projection. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [June 25, 2010, 4:55am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/3 "2010-06-25T04:55:27Z")
In fact, I’m adjusting my guess down a little, because of the distortion of Greenland. Say 22-23%. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [June 25, 2010, 5:25am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/4 "2010-06-25T05:25:47Z")
> [@yabob](#): > > If you draw an antipodal map this way … > > What percentage is brown, representing the bits that overlap? Fun! The brown percentage would be easy to derive: just let the computer count colored pixels. As you imply, however, it would be better to start with equal-area projection. Maybe I’ll try that for fun. A fun puzzle I worked on once is to find eight vertices of a cube on the Earth’s surface, where each vertex is on land. Or, easier, the four vertices of a tetrahedron. ---
**Author:** ![Desert\_Nomad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desert_nomad/32/177_2.png) [@Desert\_Nomad](https://boards.straightdope.com/u/Desert_Nomad)\ **Post date:** [June 25, 2010, 5:43am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/5 "2010-06-25T05:43:05Z")
You need an equarectangular projection… look at Japan in the linked png - it is different in place vs the one shown in the South America overlap. ---
**Author:** ![Anomie](https://avatars.discourse-cdn.com/v4/letter/a/4491bb/32.png) [@Anomie](https://boards.straightdope.com/u/Anomie)\ **Post date:** [June 25, 2010, 5:56am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/6 "2010-06-25T05:56:40Z")
Here’s another map: > **[Expedition 360 - Definition of a True Circumnavigation](http://www.expedition360.com/home/circumnavigation.htm)** > > expedition 360; around the world; human power; expedition; circumnavigation; exploration; explorer; x-plorer!; adventure; discovery; first around the world; man power; education; experiential learning; kids; outdoor adventure; curriculum Given the distortion at the poles, I’m guessing less than 5%. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [June 25, 2010, 6:28am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/7 "2010-06-25T06:28:24Z")
> [@Desert\_Nomad](#): > > You need an equarectangular projection… look at Japan in the linked png - it is different in place vs the one shown in the South America overlap. I realize something like the equal-area [Goode homolosine projection](http://en.wikipedia.org/wiki/Goode_homolosine_projection) would be very difficult to work with, but wouldn’t any equal-area projection with adequate mathematical regularity work OK, assuming I map antipodes correctly? (I won’t try to define “adequate mathematical regularity”, but think it’s weaker than equarectangular.) The linked image must have had its antipodes miscalculated. But I think that calculation should be easy on any equal-area projection “with adequate regularity.” I’d like to start with a big map (i.e., many pixels), perhaps [this cylindrical equal-area map](http://cmsa.uah.edu/files/earth_cyl.jpg). It’s Jpeg, which is inconvenient (best would be only 2 colors: blue and brown!), but I think I can fix that in about an hour. ---
**Author:** ![EdwardLost](https://avatars.discourse-cdn.com/v4/letter/e/bbe5ce/32.png) [@EdwardLost](https://boards.straightdope.com/u/EdwardLost)\ **Post date:** [June 25, 2010, 10:30am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/8 "2010-06-25T10:30:04Z")
I read some article years ago, musing about this subject. He author was impressed with how neatly the continents seem to fit into their antipodal oceans (S. America excepted): N. America into the Indian Ocean, Australian into the N. Atlantic, Asia into the S. Pacific, and Antarctica into the Arctic Ocean. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [June 25, 2010, 11:29am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/9 "2010-06-25T11:29:45Z")
'Netting around I found [this](http://fabpedigree.com/james/eanti.htm), probably as good as I would have done. The guy claims “5.17% land-to-land diameters”, but he admits to missing some water, so the correct figure is probably slightly less than 5%. ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [June 25, 2010, 12:41pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/10 "2010-06-25T12:41:49Z")
> [@septimus](#): > > A fun puzzle I worked on once is to find eight vertices of a cube on the Earth’s surface, where each vertex is on land. Or, easier, the four vertices of a tetrahedron. David Brin didn’t happen to give you this puzzle, did he? Part of his novel _Earth_ involves setting up scientific stations on the Earth that are arranged in a cube; IIRC, in the novel some of the locations required are politically unfeasible, so they go with a tetrahedron instead. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [June 25, 2010, 2:16pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/11 "2010-06-25T14:16:46Z")
Actually, the equator goes through the mouth of the Amazon in South America. I would think that you need to adjust the maps so the equator on each map line up. One map is a bit too high for the other. It looks OK longitude-wise, with the Alaska-Siberia gap of the Bering straight about even with Greenwich. Then you can adjust for the mercator distortion. Just by stats, the odds that 1/4 lines up with 1/4 is about 1/16. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [June 25, 2010, 2:26pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/12 "2010-06-25T14:26:44Z")
> [@septimus](#): > > 'Netting around I found [this](http://fabpedigree.com/james/eanti.htm), probably as good as I would have done. The guy claims “5.17% land-to-land diameters”, but he admits to missing some water, so the correct figure is probably slightly less than 5%. Are you giving percentage of the Earth’s total surface, or percentage of the land area? The OP asked for the latter, which is what I was estimating above. ---
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [June 25, 2010, 2:44pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/13 "2010-06-25T14:44:31Z")
> [@EdwardLost](#): > > how neatly the continents seem to fit into their antipodal oceans (S. America excepted): N. America into the Indian Ocean, Australian into the N. Atlantic, Asia into the S. Pacific, and Antarctica into the Arctic Ocean. Which means the actual land-to-land antipodal points are far fewer than would be expected by chance, e.g. one of those randomly-generated continent world maps in the Civilization game having 24% land surface. Although I don’t know how to calculate how much that would be. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [June 25, 2010, 3:48pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/14 "2010-06-25T15:48:07Z")
> [@yabob](#): > > Are you giving percentage of the Earth’s total surface, or percentage of the land area? The OP asked for the latter, which is what I was estimating above. Oops. In that case my quote should have been 17%. But I’d better double-check the whole thing. :dubious: (I’ve been blundering dazedly lately – can no longer blame it on brain damage since I just had a clean CT brain scan. 😃 ) > [@MikeS](#): > > David Brin didn’t happen to give you this puzzle, did he? Part of his novel _Earth_ involves setting up scientific stations on the Earth that are arranged in a cube … Thought of it myself about 6 years ago. … But was probably reacting to a subconsciously-remembered puzzle years earlier, perhaps by David Brin. (By the way for geometry puzzlers, the 8 vertices of a cube are _not_ the solution to “place 8 points on a sphere maximizing smallest point-to-point distance.”) ---
**Author:** ![AWB](https://avatars.discourse-cdn.com/v4/letter/a/bb73d2/32.png) [@AWB](https://boards.straightdope.com/u/AWB)\ **Post date:** [June 25, 2010, 3:55pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/15 "2010-06-25T15:55:55Z")
Nat’l Geographic had a 1-page article about this very thing. It’s maps (2 hemisperical ones with antipodals overlaid in gray) indicated a very small of land-land antipodal amount. 5% sounds about right. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [June 25, 2010, 7:18pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/16 "2010-06-25T19:18:56Z")
Covered in “Right Beneath Your Feet” by I. Asimov. _The Magazine of Fantasy and Science Fiction_ (Jan. 1967) collected in Science, Numbers, and I (1968). I have this but not nearby. Anyone want me to dig it out? I’ll need an incentive. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [June 25, 2010, 8:08pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/17 "2010-06-25T20:08:25Z")
Is our respect and gratitude insufficient? ---
**Author:** ![Johanna](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johanna/32/8318_2.png) [@Johanna](https://boards.straightdope.com/u/Johanna)\ **Post date:** [June 25, 2010, 11:57pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/18 "2010-06-25T23:57:37Z")
I read that many years ago. It was written during the Vietnam War. I remember Asimov saying that if anybody wanted to get as far away from Vietnam as possible, that would be the antipodes in Ecuador. A subtle antiwar message. ---
**Author:** ![bizerta](https://avatars.discourse-cdn.com/v4/letter/b/3be4f8/32.png) [@bizerta](https://boards.straightdope.com/u/bizerta)\ **Post date:** [June 27, 2010, 11:22am UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/19 "2010-06-27T11:22:51Z")
> [@yabob](#): > > If you draw an antipodal map this way, rather than using an interactive point locator like you were probably playing with, you can get a good idea: > > [http://bartonhome.ca/antipodal\_map.png](http://bartonhome.ca/antipodal_map.png) I question the validity of that map (or my interpretation of antipodal). [ul] [li]On one side, Lake Baikal is antipodal with portions of South America. On the other side, Lake Baikal is in the Pacific Ocean off the coast of Chile. [/li][li]The antipodal of Hawaii is in a portion of Africa which, like Hawaii, is in the northern hemisphere.[/li][/ul] ---
**Author:** ![Manwich](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Manwich](https://boards.straightdope.com/u/Manwich)\ **Post date:** [June 27, 2010, 12:10pm UTC](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448/20 "2010-06-27T12:10:46Z")
> [@bizerta](#): > > I question the validity of that map (or my interpretation of antipodal). > [ul] > [li]On one side, Lake Baikal is antipodal with portions of South America. On the other side, Lake Baikal is in the Pacific Ocean off the coast of Chile. [/li][li]The antipodal of Hawaii is in a portion of Africa which, like Hawaii, is in the northern hemisphere.[/li][/ul] Yeah, I was just going to say something is screwy there. Australia’s antipodal shadow is way too far north for a start. [Next page](https://boards.straightdope.com/t/what-proportion-of-the-earths-land-surface-has-land-at-its-antipodeal-point/544448.md?page=2)