Just don't time travel back to Shakespeare's day and address someone as "Sirrah" if you don't want a rapier through your liver. It's a term of contempt, roughly the equivalent of "Hey, douchebag". OTOH, it's an ideal word if you're involved in a flame war today.
Among other things, Isaac Newton hypothesized that colour perception is caused by pressure on the eye. To test this, he once stuck a needle into his eye socket past the eyeball and poked around back there.
https://upload.wikimedia.org/wikipedia/en/thumb/1/11/CN_Railway_logo.svg/250px-CN_Railway_logo.svg.png
https://en.wikipedia.org/wiki/Allan_Fleming
http://www.youtube.com/watch?v=pDY6bWT5oTM
Maybe Van Gogh just couldn't hear him.
Couldn't find pictures of the whole set (12 I think), but here's a few.
http://lyspeth.com/gallery2update/v/toronto/DSCF0460.jpg.html
http://www.bikingtoronto.com/2008/06/rom-adds-public-art-bike-racks.html
http://torontoist.com/2008/05/lawrence_of_ara.php
Good philosophy. Reminds me of the Possum Lodge Man's Prayer on the Red Green Show:
I'm a man. But I can change. If I have to. I guess.