How does our Sun affect temperature on each of the planets?
The closer a planet is toward the Sun, the hotter it will be. Let’s conduct an experiment to see how. You will need a student desk lamp with a 75 watt bulb, three mounted Fahrenheit thermometers, and a yardstick. Lay the yardstick on a cleared desk. Place one thermometer the 4” mark, another at 14” and another at the 36” mark. Turn on the desk lamp, aiming it at the front end of the yardstick. Keep the lamp on for approximately 10 minutes. Thereafter, record the temperature at each yardstick marking. You should notice that the temperature on the thermometer closest to the lamp is higher than those farther away. The heat from the Sun, similarly, provides more heat and light energy to closer planets.
How can the Sun’s light hurt our eyes if we look at it directly or through a lens?
This experiment should only be conducted by the teacher in an open area like a school play yard. You will need a sheet of paper, a bright, sunny day and a simple hand lens to conduct this experiment. Place the sheet of paper on the ground. Using the hand lens, focus the sunlight onto the sheet of paper. A perfectly round, very tiny circle will form on the paper when the light is focused. You may have to squint your eyes, for reflected sunlight may interfere with your vision. It will not, however, harm your eyes. Hold the focused light in place for about five minutes. Just for a moment, have a student quickly touch the area of the paper on which the light was focused. What did he/she notice? (The student should find the area on which the light was concentrated is much hotter than the surrounding paper.) Have the student remove his/her finger, and continue to focus the sunlight in the same spot. After a while, something else will happen? (If focused correctly and long enough, the paper will begin to burn.)
Telescope and binocular lenses and the lens in your eye, just like the hand lens, focus light. Other components of your eye, just like that paper, could be damaged with prolonged contact with light. So remember, NEVER LOOK DIRECTLY INTO THE SUN!
If stars are big, why do they appear to be so tiny in our night shy?
When the night sky and our eyes get together, they play tricks on us. Let’s discover how! (This tried and true exercise is best conducted in a large space, like your school corridor or gymnasium.) You will need three grapefruits and three oranges, two “large feet” for estimated measurement purposes, and three students. Have the children determine which person in the class has feet closest in size to the length of a 12-inch ruler. (The teacher will probably be selected.) Using the chosen individual, measure an approximate 12-foot distance, marking that point with tape. Repeat the same distance three more times, and correspondingly mark each noted distance. Have three students, each with a grapefruit and orange in each hand, stand along the strategic points so that each child is visible to onlookers at the extreme opposite end of the hall. Have them hold the fruit up. What do you notice? The citrus fruits, despite their actual size, appear to be much smaller. The angle and distance from which the observer stands impacts the way we see size of an object. This principle applies to the stars we observe in the sky.
Why do stars twinkle?
Have you ever been in a house during a cold winter’s day, and the radiator was on full blast. Notice how objects around that radiator appear to shimmy even though you know they are standing still. Or have you ever seen water boiling on a stove? The hot air rising out of the pot appears to make the area around the stove wave. The moving air in both instances make you think the objects behind them are wiggling. That’s similar to the principle behind why stars twinkle. It’s called scintillation. Let’s conduct two experiments to take a closer look. (Although the two experiments that follow can be conducted in class, they make great homework assignments and are best conducted in a very dark room.)
The following presentations should initially be teacher-guided. Before conducting the scintillation portion of the experiment, first introduce the concept of light traveling in a straight line
You will need a flashlight and a table top, wall and floor. With flashlight off, aim it straight in front of you, directly at a wall. Where do you think the light will land? Try it and see. (The light should fall directly on the wall where aimed.) Again, flashlight off.
This time, hold the flashlight overhead towards the top of the table. Where do you think the light will land? Turn it on. (The light should land where targeted.) Flashlight off. Point it directly overhead towards the ceiling. Where do you think the beam of light will appear? (Again, the light should land where directed.) You’ve guessed it! Turn on the light. (In each instance, the children will discover that you can determine where the light will land, for it traveled in a straight line towards the object on which it was directed.) Conclusion: Light does travel in a straight line.
So, how does this concept affect stars seen from our planet? You will need to use the flashlight once again, along with a 10” by 10” sheet of aluminum foil, a 2-quart glass mixing bowl filled midway with water, and a darkened room to discover why. First, crumple the square piece of foil and reopen it, laying it outstretched beneath the water-filled bowl. Let it set until the water within is absolutely still. Hold the flashlight approximately 12” above the bowl. Focus it towards the center of the bowl. Turn it on, and take a look at how the light reflected from the foil looks. (Students should see a clear, circular patch of light.) Continuing to hold the light overhead, carefully move the bowl so that the water moves within. Look down on the circle of light inside of the bowl. (Students will notice the light appears blurred and jiggly. Actually light is bending and bouncing off of the moving water creating a shimmery effect.) This occurrence is similar to what happens in the night sky. Light rays that usually travel in a straight line are slightly bent because of air and atmospheric movement.
: As a conclusion to this unit, take your class on a trip to a major or local college-housed planetarium.