On Mon, 26 Nov 2012, Frederick Williams wrote: > William Elliot wrote: > > > > If into a field with five cows, you add > > a bull, how much bull will you get? > > The word problem for groups is (recursively) unsolvable. I've never > heard of a word problem for fields. I do recall a school physics > teacher asking "What do you find in magnetic fields?" I do not know > what answer he was expecting, but the answer he got was "Magnetic > cows." Oh, how we laughed. > For practical purposes, such as directing migratory birds across the field, it's naturally magnetized by Earth's magnetic field.