# How many miles to circumnavigate the Earth by boat?

**URL:** <https://boards.straightdope.com/t/how-many-miles-to-circumnavigate-the-earth-by-boat/615387>\
**Category:** Factual Questions\
**Created:** [March 10, 2012, 4:45pm UTC](https://boards.straightdope.com/t/how-many-miles-to-circumnavigate-the-earth-by-boat/615387 "2012-03-10T16:45:45Z")\
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**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:** [March 11, 2012, 6:02am UTC](https://boards.straightdope.com/t/how-many-miles-to-circumnavigate-the-earth-by-boat/615387/12 "2012-03-11T06:02:21Z")

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> [@Chronos](#):
>
> > [@](#):
> >
> > 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. :dubious:

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

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