SharkD wrote:
> Warp wrote:
>>   A more complicated invention of antiquity is the so-called
>> south-pointing
>> chariot. A Chinese invention which is, basically, a chariot with a figure
>> on top which always points in the same geographical direction
>> regardless of
>> how the chariot is moved and turned. In other words, the figure acts as a
>> non-magnetic compass, obviously very useful for travelling long
>> distances.
>> The invention might be as old as from 2600 BC (although with certainty
>> it's
>> at least from 200 AD).
> 
> It would have to be very heavy, otherwise it might bounce instead of
> roll around corners, and rotation information would then be lost.
> 
> Also, I am having trouble visualizing how the device behaves differently
> on curved surfaces (i.e. the Earth) as opposed to a flat plane. I wish
> the article had some diagrams or animations.
> 
> -Mike

I don't think the the curved surface causes the distance that each wheel
travels to vary. It is more the geometry of the problem. Start at a
point on the equator, with the compass pointing south, and go directly
north till you hit the pole. Turn 90 degrees left, and the compass
should point to your left. Walk to the equator. By now, the compass
would be pointing to the east.

Also it is a good example of how a triangle is not limited to 180
degrees outside of Euclidean geometry.

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