What keeps a train on the tracks? How sure are you?

What keeps a train on the tracks? Yeah, right, that flange on the inside of the wheels. Obvious right?

Wrong.

What I like about this information is not just how the truth of the matter, despite it having seemed obvious to me since I was a kid, is incorrect, but how the truth of the matter is so subtle and elegant and beautiful.

And isn't this always the pattern of discovery?  And how many other much more complicated truths do I hold that might be debunked by subtle, elegant, and beautiful re-understanding?  Lots, I hope.

First seen at www.boingboing.net