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  #1  
Old 03-10-2012, 10:45 AM
Ignatz Ignatz is offline
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How many miles to circumnavigate the Earth by boat?

I saw a tv documentary to break the time record for circumnavigation of the globe by the purpose-built Earthrace Kevlar-clad motor-poweredtrimaran by Pete Bethune. That report indicated that the attempt failed due to mechanical problems. Wikipedia gives more details about the wave-penetrating ship/boat (as MY Ady Gil) and says that a 2008 retry was successful, from/to Sagunto, Spain.

The ship was later sold and became the MY (Motor Yacht) Ady Gil and fought against whaling ships, was rammed by one (or it rammed one)(?) and sank from the damage in 2010.

This got me wondering about the minimum distance a boat would need to travel, on the water, to circumnavigate the globe.
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Old 03-10-2012, 11:05 AM
gazpacho gazpacho is online now
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The minimum distance is 21,600 nautical miles. It is not completely obvious what it means to circumnavigate the globe. You could hug Antarctica and travel much less than 21,600 nautical miles. But people that officiate records don't think that is within the spirit of circumnavigating.

Quote:
a. RTW - Round the World, eastbound and westbound 21600NM. 2 separate records.
To sail around the World, a vessel must start from and return to the same point, must cross all meridians of longitude and must cross the Equator. It may cross some but not all meridians more than once (i.e. two roundings of Antarctica do not count). The shortest orthodromic track of the vessel must be at least 21,600 nautical miles in length calculated based on a 'perfect sphere'. In calculating this distance, it is to be assumed that the vessel will sail around Antarctica in latitude 63 degrees south.
A vessel starting from any point where the direct orthodromic distance is too short shall pass one single island or other fixed point on a required side so as to lengthen his orthodromic track to the minimum distance.
No starting point will be permitted more south than 45 south.
1 degree of longitude at 63 degrees south will be taken as 27.24NM
http://www.sailspeedrecords.com/the-...-offshore.html
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Old 03-10-2012, 11:07 AM
psychonaut psychonaut is offline
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Quote:
Originally Posted by Ignatz View Post
This got me wondering about the minimum distance a boat would need to travel, on the water, to circumnavigate the globe.
Your question isn't possible to answer unless you more clearly say what you mean by "circumnavigate". The Earth is roughly a sphere, and so its circumference ranges from 0 to nearly 40,000 km. I could therefore circumnavigate the globe, with a minimum distance of 0, simply by standing in place. On the other hand, the World Sailing Speed Record Council has arbitrarily defined a round-the-world circumnavigation as a transequatorial journey of at least 21,600 nautical miles (about 40,000 km), where the starting and ending points are the same but not lower than 45S, every meridian is crossed at least once, not all meridians are crossed more than once, land is not crossed, and the vessel sails no lower than 63S. Under that definition, the minimum distance is 40,000 km.
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Old 03-10-2012, 11:32 AM
gazpacho gazpacho is online now
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21,600 nautical is the circumference of the earth, so it not a number just pulled out of the air.
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Old 03-10-2012, 06:40 PM
Fiendish Astronaut Fiendish Astronaut is offline
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Quote:
Originally Posted by gazpacho View Post
21,600 nautical is the circumference of the earth, so it not a number just pulled out of the air.
True, but it's not the answer to the OP either as there's all that pesky land in the way. In practice it must be impossible to circumnavigate the globe obeying the conditions in that link in as few a number of miles as that. Or am I mistaken?

Last edited by Fiendish Astronaut; 03-10-2012 at 06:41 PM..
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Old 03-10-2012, 07:06 PM
septimus septimus is online now
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The definition quoted above by gazpacho ("The shortest orthodromic track of the vessel must be at least 21,600 nautical miles in length") seems somewhat arbitrary. It may be a fun exercise to construct a "purer" criterion.

How about:
A voyage is a proper circumnavigation if it intersects every great circle.

Last edited by septimus; 03-10-2012 at 07:10 PM..
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Old 03-10-2012, 07:30 PM
septimus septimus is online now
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Looking at the globe, it seems clear that the shortest circumnavigation will be to visit the Arctic Circle and approach Antarctica. (Closer study is needed to decide whether to use the Northwest Passage or the Northeast Passage.) Alternatives are much longer, even if you're allowed to use Panama and Suez Canals.

Of course this may not be a practical route for a sailboat.
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Old 03-10-2012, 08:21 PM
bluezooky bluezooky is offline
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Following the trade winds and using the Suez and Panama canals seems fairer circumnavigation until you factory in the danger of piracy hence the trend to take the Antarctic route, easier to dodge whales and waves than bullets.
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  #9  
Old 03-10-2012, 10:39 PM
gazpacho gazpacho is online now
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Quote:
Originally Posted by septimus View Post
Looking at the globe, it seems clear that the shortest circumnavigation will be to visit the Arctic Circle and approach Antarctica. (Closer study is needed to decide whether to use the Northwest Passage or the Northeast Passage.) Alternatives are much longer, even if you're allowed to use Panama and Suez Canals.

Of course this may not be a practical route for a sailboat.
People find that doing this violates the spirit of circumnavigating the globe. But they are just one organization you are free to choose your own ideas. You could start from Perth Australia take a quick jaunt up to the equator and then continue going in the southern latitudes and travel less than 21,600 nautical miles. You are of course entitled to think that this counts but others will not be impressed.
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  #10  
Old 03-10-2012, 10:59 PM
snowmaster snowmaster is offline
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Using Google Map's Ruler I get 24,987.5 (non-nautical) miles, 21,713.6 nautical miles over what I assume is a popular route through the Panama Canal, S. of Africa, between Aurtrailia and Papua New Guinea. Mighty close the the "required" number.

Last edited by snowmaster; 03-10-2012 at 11:00 PM..
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  #11  
Old 03-10-2012, 11:29 PM
Chronos Chronos is offline
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Quote:
How about:
A voyage is a proper circumnavigation if it intersects every great circle.
I think this is equivalent to my criterion, which is that at least one pair of points on the route be antipodal to each other.
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  #12  
Old 03-11-2012, 12:02 AM
septimus septimus is online now
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Quote:
Originally Posted by Chronos View Post
Quote:
A voyage is a proper circumnavigation if it intersects every great circle.
I think this is equivalent to my criterion, which is that at least one pair of points on the route be antipodal to each other.
Yes, though come to think of it either definition would allow you to travel West from Ecuador to Singapore and then turn around, never visiting Indian or Atlantic Oceans. Adding the requirement "Visit every meridian" is insufficient since it allows you to start from Antarctica, circumnavigate the Arctic and come back, never visiting the Pacific.

Back to the drawing board.

ETA: Perhaps the key is to intersect each great circle twice.

Last edited by septimus; 03-11-2012 at 12:05 AM..
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