Reminds me of how orthogonally polarized waves can inhabit the same bit of space without interfering with each other (and can be cleanly separated later using 2 polarized filters at 90 degrees).
"After my one course in linear algebra, I knew eigenvectors and eigenvalues like the back of my head. If your instructor was anything like mine, you recall solving problems involving eigendoohickeys, but you never really understood them."
-- Jonathan Richard Shewchuk, from An Introduction to
the Conjugate Gradient Method Without the Agonizing Pain
