Measuring The Moon

The moon has been the object of much interpretation and affection for centuries. The earliest myths developed by early man involved primitive “scientific” theories about its waxing, waning, and constant chase of the sun.

Today, modern science has taught us much about its control on the sea and sky, and its beauty still captivates. Let your inner astronomer free – why not measure the moon?

You will need a ruler, a calculator, a window, a table, and a few books to discover its diameter and become a true scientist:

On a clear evening shortly before a full moon, select a window through which the moon can be seen an hour of two after it rises. Then stick two strips of adhesive tape horizontally upon the glass about an inch and a quarter apart.

Place a pile of several books on the corner of a movable table, like a card table or TV tray, and you are ready to observe. The books should be about eye-level when you, or the lucky observer, places their chin on the table.

The idea is to look at the moon between the two pieces of tape. Move backward (bring the table with you) until the moon’s image just exactly fills the space between them, and then measure accurately the distance of your eye from the tapes. The corner of the top book on the pile can help – just bring it closer to your eye. Don’t poke it! Safety first.

When you’ve marked the location of your eye to the moon, measure carefully the exact distance from the book corner to where your eye was to the tapes on the windowpane. Also measure the exact width of the space between the tape.

Now you can calculate the diameter of the moon. Grab your calculator, and start to multiply. Make sure your measurements are correct. First, multiply the distance between the two tapes by the moon’s diameter. 1.25 x 239,000 = 298,750

Then divide this figure by the distance from your eye to the two tapes on the window. We will use 137.5 inches as an example: 298,750 / 137.5 = 2,170 miles

The moon’s diameter, 2,170 miles, comes out only slightly larger than professional astronomers figure it using precise methods and fancy gadgets. This project is great to do with kids, or with a loved one. Perhaps you’ll spot a shooting star – make a wish!