Wrist Compass

If you wear an analog watch, you can use it as a compass:

Hold it flat in the palm of your hand, with the hour hand pointing in the direction of the sun. The point midway between the hour hand and the figure 12 is due south.

(In the Southern Hemisphere, point the figure 12 toward the sun. The midpoint between the 12 and the hour hand points north.)

Decibel Levels

Decibel levels:

  • 0 – Threshold of human hearing (with good ears)
  • 10 – Human breathing at 3 meters
  • 30 – Theater, with no talking
  • 40 – Residential area at night
  • 50 – Quiet restaurant
  • 60 – Office or restaurant
  • 70 – Busy traffic at 5 meters
  • 80 – Vacuum cleaner at 1 meter; curbside of busy street
  • 90 – Loud factory, heavy truck at 1 meter
  • 100 – Pneumatic hammer at 2 meters; inside a disco
  • 110 – Accelerating motorcycle at 5 meters; chainsaw at 1 meter
  • 120 – Rock concert; jet aircraft taking off at 100 meters
  • 130 – Threshold of pain; train horn at 10 meters
  • 140 – Rifle being fired at 1 meter
  • 150 – Jet engine at 30 meters
  • 180 – Rocket engine at 30 meters
  • 250 – Inside a tornado
  • 1,000 – Eruption of Krakatoa

Schopenhauer wrote, “The amount of noise which anyone can bear undisturbed stands in inverse proportion to his mental capacity.”



This is The Ambassadors (1533), the celebrated painting by Hans Holbein the Younger. It’s full of noteworthy symbols of exploration, but what’s that odd skewed element at the bottom?

If you view the canvas from a narrow angle, the image resolves into a skull:


This is an early example of anamorphic perspective, an invention of the early Renaissance. It’s thought that Holbein intended that the painting would be hung in a stairwell, when people ascending the stairs would view the image from the proper angle and get a gruesome surprise.

Why? That’s an unanswered question.

Cat as Coauthor

Physicist J.H. Hetherington had already typed up a physics paper in 1975 when he learned of an unfortunate style rule: Physical Review Letters does not accept the pronoun we in single-author papers.

Hetherington didn’t want to retype the paper — this was before word processors had become widespread — so he added his cat as a second author (“F.D.C. Willard,” for “Felis Domesticus Chester Willard.”)

“Why was I willing to do such an irreverent thing? Against it was the fact that most of us are paid partly by how many papers we publish, and there is some dilution of the effect of the paper on one’s reputation when it is shared by another author. On the other hand, I did not ignore completely the publicity value, either. If it eventually proved to be correct, people would remember the paper more if the anomalous authorship were known. In any case I went ahead and did it and have generally not been sorry. Most people are amused by the concept, only editors, for some reason, seem to find little humour in the story.”

Chester is believed to be the only cat who has published research in low-temperature physics. “When reprints arrived, I inked F.D.C. Willard’s paw and he and I signed about 10 reprints which I sent to a few friends,” Hetherington later recalled. “The story has now been told many times and my wife can add that she sleeps with both authors!”

Simpson’s Paradox

Baseball is a game of statistics, but numbers can be deceiving. It’s possible for one batter to outperform another in both halves of the season and still receive a lower batting average:

First Half Second Half Total Season
Player A 4/10 (.400) 25/100 (.250) 29/110 (.264)
Player B 35/100 (.350) 2/10 (.200) 37/110 (.336)

This is an example of Simpson’s paradox, a mathematical quirk that arises occasionally in social science and medical statistics.