-- "Tesla" is a unit for the strength of a magnetic field.
The Earth's magnetic field at the surface ... the one that makes
compasses work ... averages roughly 45 microteslas.
So 1 Tesla = somewhere around 20,000 times the magnitude
of Earth's magnetic field at the surface.
There's a smaller, more convenient unit, called the 'Gauss'.
1 Tesla = 10,000 Gauss. The Earth's magnetic field ranges
between 0.25 to 0.65 Gauss at various places on the surface.
-- Newton is a unit of force, equal to about 3.6 ounces.
1 pound of force is about 4.45 newtons.
