Thursday, August 19, 2010

Palm Pilot*

*Any resemblance to any gizmo living or dead is purely coincidental. No similarity to any gizmo living or dead is intended or should be inferred.

What I am about to share will put you in the category of "smarter than the average bear". At the very least, it will earn bonus points for you with your nephews.
I am going to teach you how to tell time with a stick.

Long before Timex came along, the cavemen still needed some sort of gadget to tell them what time it was so that they wouldn't miss their favorite programs on TV. They would pull their hand out of the pocket of their saber-tooth overalls, stab a stick through it, then go and watch "As the World Revolves" or" CSI: Pangea", depending on what time it was. This was the first pocket watch model available. Later models required fewer trips to the ER, but were more likely to get lost.

What you need:
  • A straight stick (string will work too)
  • Your hand
  • Sunlight
  • A little old fashioned know-how
What you must know first:
  • Which way is North?
  • Your latitude (Chicago is at 42*N, Seattle is at 47*N, and Miami is at 25*N)

 What to do:
  • Stand in the sunshine.
  • Hold your hand level with your palm facing upward.
  • Grasp the stick with your thumb.
  • Hold the stick so that it is at the same angle as your latitude (near Chicago it would be close to 45*)-on a sundial, the sticky-up part that casts the shadow is called a gnomon.
  • Point the stick directly North. 
  • In the morning, use your left hand and point your fingers west. In the afternoon, use your right hand and point your fingers east. (If you don't know whether it's morning or evening, what are the odds that you'll care about making a sundial with your hand?)
  • Note where the shadow falls on your hand. Use the chart below to determine the time.
  • If you can't see the stick, it's time to go home.

Of course, some of this is relative to your hand size, as well as the seasonal cycle and adjustements for Daylight Savings Time.
For greater accuracy allowing for hand size, take a day and physically mark out the hours on your own hand. The best time of year to do this is one of few days where no correction is necessary (use the graph below). I know it gets a little technical, but the graph below shows the appropriate corrections to make to your sundial given the time of year. The Equation of Time is universal. Latitude and time zone don't matter.

The Equation of Time
Can you tell about what time it is in the photo below?

If you're trying to catch a plane, I recommend that you stick with your Blackberry or iTouch. If you want to impress your hiking buddy, then your very own Palm Pilot is the way to go.

Conversely, if you know what time it is, you can use this app (ha!) to determine direction. Simply line up the stick's shadow with the matching time position on your hand and it will be pointing North.

Well, it looks like it's about time for "Ace of Caves". See you later.