MadSci Network: Earth Sciences
Query:

Re: Does a compass point to the South Pole south of the equator?

Date: Thu Feb 17 16:28:54 2000
Posted By: John Christie, Faculty, School of Chemistry, La Trobe University, Bundoora, Victoria, Australia
Area of science: Earth Sciences
ID: 950797747.Es
Message:

Greetings from South of the equator.

Have a good look at your compass. The needle has two ends. Typically one is 
coloured red, and the other one silver. The red end is what points to the North 
(Magnetic) Pole, and the silver end therefore points to the South Magnetic Pole. 
That is what happens in the Southern Hemisphere as well.

If you have a good quality compass, there is one important difference. In the 
Northern hemisphere, the Northern (red) end of the compass needle wants to dip 
downward. The dip is stronger the further North you go. Compass makers 
compensate for this by putting extra weight on the southern end of the compass 
needle or card. They even make different compasses with different amounts of 
compensating weight for Canada and Florida. But here in Australia, the Southern 
end of the compass needle is what wants to dip downward, and the needle or card 
must be weighted at the other end. If I bring a good compass here from Europe or 
North America it is almost unusable because the North end wants to point up into 
the sky! The southern side of the card is weighted heavier anyway, because it 
was designed for use in the Northern hemisphere, and then the Earth's magnetic 
field makes it want to dip even more.




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