That we ALL take for granted...as far as knowledge about specific things... be it big things or trivial.

It just did not occur to me that using the word 'magnetic south' with that crew today would cause a problem... but it only makes sense that it would.

I'm a pilot, (or was), and I also love maps and orienteering... so knowing how to factor in magnetic north is a must... but other than flying or maps when does a person really need that info? hell, I can't think of any other reason at the moment.