# Which great circle around the world touches the most solid ground?

Discussion in 'Earth Science' started by iroQuai, Oct 4, 2006.

1. ### iroQuaiRegistered Member

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Hello. I hope I can explain what I am looking for in the right way in English. I’m involved in the first attempt of an global art project. A part of this project is the (virtual) visualization of a circle around the earth. This circle had to touch as much solid ground as possible. It is preferable, not necessary, that this circle is a great circle, like the equator is. Which way this (great) circle is going does not matter.

Is there somebody around here maybe that can easily calculate how this circle should go? You could help me a lot!

3. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Welcome, and thanks for an interesting question. Are you planning a globe circling highway with the least requirements for floating sections?
I suggest you get a globe and with string loop circle of circumference equal to the globe's great circles, try to find your circle experimentally.

Perhaps, if necessary, using several such string loops to discriminate between reasonable "final choices." - Mark each when on the globe with a felt tip marker where it is over land and then measure and add up the total marked portions of the string.

If you are concerned that this is not an exact procedure, do not be. The exact answer is neither known nor constant, but a function of the tides and the winds. This is very dramatically illustrated where the beach is very nearly flat going into the sea. For example, at Mount St. Marchant on the French coast where the shoreline moves by miles with each tide.

PS you English is fine - better than some who post here - come back again.

Last edited by a moderator: Oct 4, 2006

5. ### iroQuaiRegistered Member

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Thank you,

I'm going to play with some strings and a globe tomorrow, so then I'll find out. your last remark was really good by the way, probably it is inpossible to be very exact, because of the reasons you just mentioned

7. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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Please let me know the result. (I have added a few more comments to my first reply while you were posting, so you may want to read it again.)

8. ### Fraggle RockerStaff Member

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This sounds like an interesting project. Intuitively, just looking at a globe, it seems that starting at almost any point on land, the exact opposite point on the other side is water. Yet the opposite is not true. It is not difficult to find two points of water that are directly opposite each other.

The Western Hemisphere is your big problem. Our land masses are so narrow. Choosing a great circle that is more or less longitudinal, it's hard to plot a course through the Western Hemisphere that is even half land, and it will greatly constrain your choice of routes on the other side of the globe. And a great circle of a more east-west orientation can't help traversing some huge expanses of ocean.

I wonder what the result of the opposite assignment would be. What is the maximum amount of water you could cover with a great circle? I'll bet it's huge.

9. ### NickelodeonBannedBanned

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The Pacific really screws things up. Looks like South Africa -> Saudi Arabia -> far eastern edge of Russia makes at least half the circle.

Last edited: Oct 4, 2006
10. ### phoneticstroking my banjoRegistered Senior Member

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Does ice count as land?

I'd say roughly between 60 and 75 degrees west. Take the line around Antarctica, up S American, across some of the Caribbean islands, east coast of USA and canada, over the ice in winter and Greenland. Over the Arctic, into Russia..... but then when I think about it, the Indian Ocean is fairly huge back down to the Antarctic...

Since you say the size doesn't matter, The Arctic Circle looks like it would have the most land along it's line, especially with ice.

Or, if you can get away with it, make a circle around the furthest points of the Antarctic.

11. ### NickelodeonBannedBanned

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Only in Iceland

12. ### Fraggle RockerStaff Member

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It certainly would not if I were the teacher because ice is water, not land. But it's not my test.
Size does matter because it has to be a great circle. That means it must be the largest possible circle and bisect the surface area. It doesn't have to go in any particular direction so it does not need to touch the poles. But any two opposite points on the circle must be at exactly opposite points on the sphere.

All of the meridians (lines of longitude) are great circles because they pass through both poles. But the only parallel (line of latitude) that is a great circle is the equator. Neither the Tropics nor the Arctic and Antarctic Circles qualify. Every great circle crosses the equator twice, at opposite points.

13. ### phoneticstroking my banjoRegistered Senior Member

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I'm familiar with the lingo and concepts. Thanks anyway, Fraggle.

14. ### valichRegistered Senior Member

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Define what you mean by solid ground. Take a circle that goes over the Himalayas and the Andes, down into the Mid-Atlantic Ridge, then over the Rockies. The earth is wider in the equatorial regions and not really a sphere.

15. ### iroQuaiRegistered Member

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As told, I used a globe and a string to find out some lines that are possible.
I've tried to estimate for how many kilometers (or miles) these circles touched solid ground. Not ice, because ice melts quite easely and moves also. (I know, the continents are moving too, but not as fast and unpredictable as ice)

The measurements arn't too accurate because I've used quite a small globe (scale 1cm:510km) and I rounded off at half centimeters. But anyway, it gives quite a good idea of the possible routes

1. Bering Strait – Russia – Finland – Sweden – Norway – Greenland – Canada – Alaska (17340 Km or 10.774,58 mi)
2. South Africa – Red Sea (okay, this is not land, I know) - Saudi Arabia – Russia – Alaska (16830 Km or 10.457,68 mi)
3. Southern East Australia – Indonesia – Thailand – Vietnam – Birma – Himalaya – Russia – Europe – Brazil – Argentina – Antartica (27030 Km or 16.795,66 mi)
4. Chili – Bolivia – Argentina – Brazil – Venezuela – Cuba – United States – Canada – North pole – Russia – Mongolia – Philippines – a part of Australia (24990 Km or 15.528,07 mi)
5. Mexico – United States – Canada – Artic Ocean (okay, again no land here..) – India (16830 Km or 10.457,68 mi)
6. Macdonald Island or Kerguelen Island (somewhere in the pacific ocean) – India – Russia – North pole – Canada – California (20400 Km or 12.675,97 mi) (this is a great circle – Macdonalds island is on the exact other and of the world as California is. It would be a nice to end at a McDonnalds building – just for fun

)

7. The Equator (only 8670 Km or 5.387,29 mi)
8. South Africa – Zaïre – Sudan – Saudi Arabia – Irak – Iran – Russia – Hawaii (20910 Km or 12.992,87 mi) (another great circle, starting on Hawaii, going somewhere to a place in south Africa)

Please give some comments about these options, or maybe some advice or other possible lines? Two interesting points right at the other end of the world are interesting to hear too - like the Macdonalds islands and a Macdonalds establishment somewhere in california

16. ### Billy TUse Sugar Cane Alcohol car FuelValued Senior Member

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I was betting on your #4 without even looking at a globe, but admit the land of Mexico (instead of passing thru the Caribbean sea/ Cuba etc) which I know about made me not appreciate the fact that on other side of globe I would probably enter the ocean too soon.

I will extend your geography game - I would like to know what percent of each hemisphere is ocean. In my book, Dark Visitor I make use of the fact that there is much more ocean in the Southern Hemisphere than in the northern one.

Story predicts the "dark visitor" (probably a black hole of a few solar masses, never visible of course, but just detected by very minor perturbation of Pluto's orbit.) will pass by solar system and slightly change Earth orbit in a few years.

New (only computed now) orbit has milder winters in Northern Hemisphere as Earth is nearer to sun then and the S. Hemisphere's ocean are evaporating more rapidly, covering most of the Earth with clouds. Big snow storms always come in mild winter weather when it is cloudy. - I.e. almost every day in N. Hemisphere new milder winters.

Unfortunately, 6 months later, the Earth is farther from sun and not all or the accumulated snow from prior winter melts. The albedo in the N. Hemisphere is steadily increasing as a result of this and the N. Hemisphere is plunged rapidly into new permanent ice age (>100 feet of ice covers Washington Dc in less than 100 years).

We S. Hemisphere dwellers survive but the torrential rains every eve in our summers, wash away many cities. Both hemispheres lose all their ports in less than a decade as ice accumulates on land and oceans levels drop.

Unfortunately this is not only all possible, but probably more likely than Earth ever being hit by comet, etc large enough to kill even 1% as many people. This because the number of small black holes is greater than all the stars that have ever existed! - More details at web site under my name.

Last edited by a moderator: Oct 6, 2006
17. ### valichRegistered Senior Member

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3,501
Why are you considering "solid ground" as only ground above sea level? This is not correct. Ground is defined as "rock or rock material in which a mineral deposit occurs." This is why I stated that you need to consider the depths of oceanic ridges and trenches too according to be accurate and consistent with your post.

Okay, so are only measuring continental land masses above sea level.

If it were strictly lateral, I believe Antarctica has the longest flat dimensions, followed by Antarctica, then Russia then Canada. So if the circle doesn't have to be centered, the two most widely separated points in Russia are over 8,000 km (5,000 mi) apart along a geodesic - Poland and the Kurile Islands off Hokkaido Island, Japan. The coastline of Antarctica measures 17,968 km (11,160 miles), but Mount Vinson is its highest peak at 16,600 feet. Canada is about 9,700 km (6,000 miles) wide from the Pacific Ocean to the Atlantic.

Why don't you try a circle - a spherical line - that goes across the U.S., slightly to the Northeast across some of the New England states so that it then goes across France and all of Russia, and then across most of Antarctica. I don't have a globe so I don't know if this would work.

18. ### iroQuaiRegistered Member

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@BillyT - Interesting theory

I'll keep that in mind

@Valich - You are right, I didn't use the term correct. Indeed, I ment continental land masses above sea level

thanks for correcting me.

I found this quite funny, but still useful tool on the net. It's a tool you can use to make the world a sandwich.

with this tool you can find the two coördinations on the planet that are the exact opposite