Getting Your Bearings

Using the Sun to Find Compass Directions

INTRODUCTION. If you were blindfolded and whisked away and set down in the middle of an ocean or a forest, you would look around, wondering where you are, and trying to get your bearings - your directions. While this is a bit far-fetched in your own life, it is not too far from what would happen when a Mars lander sets down in an emergency situation due to loss of radio communication. The emerging earthlings would wander out and wonder which way they should start going in hopes of finding that second base that was being set up when they landed. They didn't take any pocket magnetic compasses because they knew that Mars does not have a magnet field. All they have are the sun and stars. Ah, ha! Astronomy! There is hope if they are smart!

In another scenario which you may have heard about - the building of the ancient pyramids in Egypt, there have been a number of mysteries put forth. How were those ancient Eqyptians able to make such a precise four-sided pyramid? How were they able to make its expansive foundation platform so perfectly flat? How were they able to align the four sides so precisely with the primary compass directions? Even the Discovery Channel on television has voiced these wonderments, and that in itself indicates how few people understand basic physical, mathematical and astronomical principles. Even talk persists that space aliens had to have been present to show the ancients how do to these things, just because the TV authors themselves could not conceive of a way to do these various activities of design and construction. But let's not get too side-tracked! Let's only look at a way that these ancients could get their bearings - long, long before the magnetic compass was discovered. (You might wonder if they used the North Star, but (a) the North Star (Polaris) was not at that time above the north pole (the earth has since wobbled (precessed) a little!), and (b) any star over the north pole cannot be seen from Egypt as those stars are so close to the horizon that they are lost in the haze.)

What you need are:

Yourself
Some rocks, bricks, sticks, chalk
A flat area in the sun all day.
Something that stands up straight with a point on top - a stick stuck in the ground.
A sunny day - all day long.

Now that's a list conceivable of either a lost Mars wanderer or an ancient Egyptian, right?

What you need to do:

On a sunny mid-morning, plant your stick in the middle of the flat area you have chosen. This stick will stand there all day.
Notice where the shaddow of the stick's tip is located in the field. Go place a marker there (one of your rocks, bricks, sticks or a chalk "X" if it is a parking lot).
About every hour until mid-afternoon, place additional markers down at where the tip's shaddow is.
By the time you are halfway through, you should be noticing that a pattern is becoming apparent. Which of the following is it most like:

1 2 3 4 5 6 7

Does it...

have any relationship to the major compass directions?
matter what the season is? Consider what the differences would be for June 21 and December 21.
What results would you get if you did this on either March 21 or September 21?
matter what latitude you are? (And what is the latitude of the pyramids?)
You now see how the ancient Egyptians could use simple equipment very precisely to determine the cardinal compass directions. Now come some "what if's" because these may help our lost wanderers on Mars. Does it matter that our earth's axis is tilted 23° from the plane of its orbit around the sun? (Here you might want to make use of a globe and bright lamp.) You can take a globe and tilt it more or less, and see how a shaddow behaves on its surface. If the degree of tilting doesn't matter, then this technique should work for ANY planet! Like Dr. Kuiper said, if it works for earth, it might work elsewhere!

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