Education.com
Try
Brainzy
Try
Plus

# Sky Distances

based on 2 ratings
Source:
Author: Janice VanCleave

So You Want to Do a Project about Sky Measurement!

### Purpose

To use your hands to measure sky distances.

### Procedure

1. Stand outdoors in a clear area so that the horizon, where the sky appears to touch Earth, is visible.
2. Measure the distance from the point directly overhead to the horizon. Do this using the following steps:

• Make a fist with one hand and hold this hand at arm's length over your head.
• Make a fist with your other hand and put this fist under the first as shown.
• Keeping your arms extended, lower your fists to the horizon by moving one fist under the other, counting each one until the bottom of one fist appears to touch the horizon. How many fists did you use?

### Results

Nine fists are generally needed to make the measurement.

### Why?

You used your hands to measure the angular distance from the zenith (the point directly overhead) to the horizon (an imaginary line where the sky seems to meet Earth). Angular distance is the apparent or observed distance between distant objects, usually measured in degrees. For measuring angular distances in the sky, the width of a person's fist held at arm's length measures about 10°. A person with longer arms generally has wider hands, so generally everyone's fist measures an angular distance of 10°. Thus, a measurement of nine fists from the zenith to the horizon is an angular measurement of 90°.

### For Further Investigation

Other parts of the hand can be used to measure larger or smaller angular distances, such as distances between stars. Do the distances between stars in a constellation (a group of stars that form a pattern in the sky) change? A project question might be, How do the distances between the stars in the Big Dipper (part of the Ursa Major Constellation) compare from one hour to the next during the night?

1. On a clear, moonless night, and as early in the evening as possible, use the hand measurements shown here to measure the angular distance between the end stars of the Big Dipper or between any two stars. Decide on a consistent method of measuring. For example, you may wish to measure the distance between the centers of the stars, as shown here.
2. Repeat the measurement every hour for 3 or more hours.
3. For the most accurate results, make four or more measurements, recording them in an Angular Distance Data table like the one shown. Average the measurements for each observation time and compare them.
4. You may wish to make a drawing indicating the stars and hand measurements used, similar to the figure shown for clue 1.

### References and Project Books

• Berry, Richard. Discover the Stars. New York: Harmony Books, 1987.
• Couper, Heather, and Nigel Henbest. How the Universe Works. Pleasantville, N.Y.: Reader's Digest, 1994.
• Dickinson, Terence. Exploring the Night Sky. Buffalo, N.Y.: Firefly Books, 1987.
• Estalella, Robert. The Stars. Hauppauge, N.Y.: Barron's, 1993.
• Rey, H. A The Stars. Boston: Houghton Mifflin, 1976. Ridpath, Ian. Stars and Planets Atlas. New York: Facts on File, 1997.
• VanCleave, Janice. Janice VanCleave's Constellations for Every Kid. New York: Wiley, 1997.
• janice VanCleave's Solar System. New York: Wiley, 2000.
• Wood, Robert W. Science for Kids: 39 Easy Astronomy Experiments. Blue Ridge Summit, Pa.: Tab Books, 1991.