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Classroom Use of Deep Space

[The Help file for Deep Space contains three narative sections entitled Overview for Beginners, Overview for Active Observers, and Overview for Teachers. The following is based on the Overview for Teachers section.]

I have taught science and math from the Jr. High to the Jr. College level since 1972. (Programming is what I do late at night and during vacations.) Many of the features of Deep Space and Planet Tracker have been motivated by my classroom experience. I have built whole courses around activities produced with these two programs.

How can you use Deep Space for an astronomy unit? Try the following suggestions for starters. If you find innovative ways to use Deep Space or Planet Tracker, I would like to hear about it.

(If you make regular use of Deep Space in your classes, please find it in your budget to register your copy. If you make it available for multiple machines or put it on a network, please obtain the site license. Feel free to give shareware copies to interested students and colleagues.)

Blank Star Maps

If students can find the constellations on star maps with nothing but dots, they can find them in the sky. Start them with the Circular Sky View map for the current date. Limit the magnitude to about 4.5. Print out one copy with lines and labels, and another with the everything but stars removed. Teach them the bright stars first. Have them circle the 6 or 8 brightest stars and try to find them at night even before learning the constellations. Learn the first magnitude stars in patterns: "Summer Triangle", "Winter Hexagon", "Arc (from the Big Dipper) to Arcturus then spike to Spica", use the Big Dipper to point to Polaris, Arcturus, Regulus, etc. Once the brightest stars have been identified, use them as a framework for learning the surrounding constellations.

Match-the-Sky Maps

[Match-the-Sky Maps are maps plotted with the correct scale and projection so that when held at a specified distance from the eye they exactly match the sky. Deep Space has a feature which allows you to produce Match-the-Sky Maps for a selected hand-to-eye distance, centered on any constellation or any other point in the sky.]

Your students will love making and using "Star Frames". Bend a coat hanger into a rectangle with the hook made into a loop/handle at one corner. Cover it with plastic wrap. Print out Match-the-Sky Maps of the brighter constellations to be used as masters. Trace the main dots for the constellation onto the plastic wrap with white correction fluid or luminous paint (available from hobby shops or electronics shops). For a more durable set, use a laser printer to print the charts directly onto transparencies. (You will still have to go over the main stars with white correction fluid or luminous paint to make them visible with a dim red flashlight at night.) Make a set for all the bright constellations visible at one time of the year and have a schoolyard star party.

If the Match-the-Sky Maps are intended to be used for a single occasion, they can be produced in Horizon Mode using the chosen day and time. This will produce maps with the correct orientation at that particular time.

Orbit Murals

I know one 4th grade teacher who did a mural of the zodiac across the whole back wall of his classroom and had his students update the positions of the sun, moon, and planets each day. Similar murals or posters can be done with orbit diagrams. Make transparencies from printouts and project them onto butcher paper with an overhead projector.

The Daytime Moon

One celestial body (besides the sun) that can be observed during the school day is the moon. For planning purposes, go to Day and Time, set the observing time for the hour of the day you want to do the activity, then plot a Circular Sky View map. The constellations will be "wrong" for that time of year because these are the stars out when daylight obscures them. Now plot the sun and moon for a one month period. There will be progressively more offset between the moon images and the X's, since the background stars shift about a degree per day. The X's show where to expect the moon, the corresponding image shows the phase.

Lunar Parallax

Another instructive printout involving the moon is to print out its position at 1/10 day intervals for several days (about 30 positions). Note that it does not move in a smooth path. This is because your position on the earth is taken into account. As the earth spins you are moving forward and backward relative to the motion of the moon, so the moon appears to move backward and forward relative to its average motion. By measuring the deviations from the average motion and taking into account the latitude of his observatory, Tycho Brahe (in the 16th century) was able to measure the distance to the moon. (A good project for a bright student with a good high school math background would be to use this simulated data to reconstruct Tycho's measurement.) It is the closeness of the moon that makes the parallax visible. The lack of parallax in the motion of comets is what led Tycho to conclude that they were farther from the earth than the moon.

A simpler form of parallax is observable by printing out two identical maps with observing sites at very different latitudes. (Use the north and south poles for maximum effect.) Knowing the distance between the observing sites and measuring the angular shift of the moon allows this data to be used for a slightly simpler distance measurement.

Constellations and 3-D

Teach constellations then show the stars in 3-D. Certain questions arise naturally. Why can't we see the constellations in the sky like in the 3-D views? Why does the sky appear to be a dome rather than open space? (The answer is our depth perception fails at great distances, so beyond a certain distance everything looks the same distance away. If everything appears to be the same distance away, we see ourselves to be at the center of an sphere. The sky is an illusion. There is no sky!) To reinforce the concept do activities with 3-D photography. Take a picture of a stationary scene. Move to one side a few inches or a few feet and take another picture. Increasing the distance between the two viewpoints increases the depth perception. Look at the pictures under a stereo viewer, one picture for each eye. (Get wallet-size prints or crop the pictures to fit together with the same separation as the lenses in the stereo viewer.) What would space look like if we were giants with eyes half a light year apart? That is exactly what the 3-D printouts show. (We give price breaks for 20 or more stereo viewers classroom sets.)

Full Moon Births

Many hospital workers will tell you there are more births at full moon than at other times of the month. Is it a myth? Check it out. Print out the moon phase data in the Almanac option for the range of years when your students were born. Have each student figure out how many days past new moon they were born. Make a chart. Is there a pattern? Enlarge the sample. Do patterns emerge or disappear when different classes are sampled? What about when the data are combined?

Understanding Eclipses

Why isn't every new moon a solar eclipse? Print out an almanac for the year. Use the Day and Time option to set the time for each successive new moon. Plot the planets on the Default Map and zoom in on the sun/moon until they are large enough to show their true scale. (The sun and moon are shown at a certain minimum size, so they are out of proportion on large scale star maps.) You might have to adjust the time setting a few minutes by trial and error. Try to show the moon just before and just after it passes the sun. By how far does it miss the sun each time? Can you tell when an eclipse will occur?

Changing Moon Size

How much does the moon change size during the month? Why does it change size? (It doesn't have a perfectly circular orbit.) In the Modify Configuration option set one of the eyepiece fields to 0.5°. Plot a series of moon images a day or two apart for a month overall. Recenter the map on one of them. Change the map scale to 1°= 8 inches to make the narrow dimension of the 8 x 10 inch printout equal 1°. Put the cursor near the center of the moon's disk and jump to the exact center. Place the 1/2° target on top of the moon image for comparison or step off the moon's diameter with the cursor in measuring mode. Print out the moon images and overlay them. Repeat for each of the moon images in the month. When is the moon largest? Is there a pattern? Does the size of the moon's disk depend on the phase of the moon? (No) Repeat for a different month to see if the pattern is the same. (The time the moon is closest to the earth is called Perigee. The time it is farthest from the earth is called Apogee. Deep Space does not print out times of Perigee and Apogee directly, but it shows up in the moon images. If you took pictures of the moon at different times of the month with a telephoto lens you would see variation in its size as predicted by Deep Space.

Expanding Universe Demo

I came up with a creative use of Deep Space while I was participating in Project SPICA, an astronomy mentor program for teachers at the Harvard Center for Astrophysics. Think of printed star maps as random dot patterns representing the distribution of galaxies in the universe. Two star maps printed at slightly different scale can represent the state of the expanding universe at the present and another time, say a billion years in the past. Look at the maps independently. There is no apparent order or "center" to the pattern. Now print the maps on transparencies and overlay them. You will see a spray pattern suddenly emerge, a dramatic graphical representation of the expansion of the universe. The apparent center of the expansion represents our viewpoint here on earth. However, if you shift the overlays relative to each other, the pattern re-arranges itself centered on a different point! Line up any dot on one sheet with the corresponding dot on the other and it will appear to become the center of the expanding universe! In other words, the center is an illusion: observers anywhere in the universe see themselves as being at the center of the expansion.

The effect is striking! You have to see it to get the full effect. A pair of pre-computed maps has been saved on the distribution disk. To access them choose the Load Saved Map option, then print them out. They can be Xeroxed onto transparencies, or if you have a laser printer you may be able to print directly onto transparencies. For use by students in a lab setting, print out copies of the current universe on paper and the earlier universe on transparencies, or vice versa. These can be overlaid on a desk without the use of an overhead projector.

The age of this simulated universe can be easily determined, and understood, by even younger students. The distance of a dot from the center is how far it has traveled since the Big Bang. The separation between the pair of dots on the two transparencies is how far the galaxy traveled outward in 1 billion years. Divide the small distance into the large distance and you have how many billion years old the universe is. Different galaxies are traveling at different speeds (the farther out the faster they are traveling) but the ratio of distance in one billion years to total distance remains the same for them all. Shift the center and try it again. The ratio should stay the same. In other words, the age of the universe is the same for observers in any galaxy.)

To create your own pair of printouts, set one map to 10° per inch and the other to 18/17ths of that value--180° per 17 inches--to give you an 18 billion year old universe. Try universes of different age and have students measure the age of each one. (To make a universe Y billion years old, the scale of the second map should be 10xY° per Y-1 inches.)