Try This: Seasons in the Sun
Another way of measuring time is to mark the changing seasons. From the heat of summer, to cool crisp days in autumn when the leaves fall, to the snows of winter, to the first blooms of spring, seasons show us that time is passing and that we are indeed making our way around the sun. It's a journey that takes a full year to complete. Many people believe that the reason why it is warm in the summer and cold in the winter is because the earth is so much closer to the sun in the summer than in the winter. However, this isn't so.
The earth is actually farther from the sun in the summer (94.6 million miles in June) than in the winter (91.4 million miles in December).
The earth is tilted at an angle of 23º from vertical. This is why we have seasons.
Why do we have seasons?
Medium or large Styrofoam ball, available at a craft supply store
Desk lamp without a shade
Pencil or long knitting needle
Mark the top and bottom of the ball with the letters N (on top) and S (on the bottom). These marks indicate the north and south poles.
Draw a circle around the middle of the ball to indicate the equator of the earth.
Place the lamp in the middle of your room.
Push the pencil through the N and S markings on the ball and tilt the top of the ball slightly toward the lamp.
Turn the light on and notice what parts of the ball are illuminated. This represents the beginning of summer in the Northern Hemisphere (location I).
Notice which wall of the room the ball is tilted toward. You will want to keep the ball tilted toward the same wall throughout the experiment. Move to a position 90º away from your starting position (location II). Again, notice what parts of the ball are illuminated. This represents the first day of fall in the Northern Hemisphere.
Now move another 90º around the lamp and again notice what parts of the ball are illuminated (location III). This is the beginning of winter in the Northern Hemisphere.
Finally, move another 90º around the lamp and note the illuminated parts of the ball (location IV). This is the first day of spring in the Northern Hemisphere.
We have seasons with longer and shorter days not because the earth is any closer to the sun, but because of the tilt of the earth. When the north is tilted toward the sun, the Northern Hemisphere has summer. Days are longer and warmer and you can see this effect if you rotate the ball and notice how long the northern parts of the earth are illuminated. In the Southern Hemisphere, however, little sun reaches the ball. Days are shorter and colder and this is when they have winter. Six months later (location III), the north has winter and the south has summer. You can see how the tilt of the earth gives the south much more sunlight and how the north gets little. In spring and fall, days are about the same length all over the earth. You can see this in locations II and IV.
Two scientists want to arrange a secret meeting to discuss a new solar energy experiment. Use the sundial decoder to figure out the message that one scientist sent to the other. Write the secret message on the lines provided.
If you look into the sky a little beyond the sun, you'll see thousands of stars. Some of the stars appear to be connected with other stars, as if they formed a particular shape. In fact, ancient civilizations believed that the shapes formed by stars meant something, and they made up stories about the shapes. The shapes are called constellations. Can you find some of the more common ones?5
QUESTION Why do we see only part of the moon?
EXPERIMENT OVERVIEW In this experiment, you'll set up a model of the sun, the moon, and the earth and track the phases of the moon through drawings and a hands-on activity.
SCIENCE CONCEPT Surprisingly, the same half of the moon always faces Earth. We can never see the “dark side of the moon” except from a spaceship. The only reason we can see the moon is because light from the sun reflects off its surface and back to our eyes.
As the moon orbits the earth (a journey that takes about 29 days), half of it always faces the sun. However, it isn't always the same half! So as the moon travels around the earth, we see any amount from 0 percent of the side that faces us to 100 percent of that side. These percentages are called the phases of the moon.
Formally, the phases are labeled as new moon (we can't see it), first quarter (we see the right half), full moon (we see the entire face), and third quarter (we see the left half). Every once in a while, the moon during its “new” phase crosses the line between the sun and the earth and we experience a solar eclipse. Not as rare are lunar eclipses, when, during the moon's “full” phase, the earth passes between the sun and the moon and casts a shadow on the moon.
There are 88 constellations recognized by astronomers.
Desk lamp as bright as possible, without a shade
Small ball, a little larger than your hand
Clean sheet of paper
Time (This experiment will take up to a month to complete, but only requires a few minutes each day.)
Check in your local paper to find the date of the new moon. Start your experiment on this day.
On the paper plate, draw marks around the outer edge representing 28 days. You might want to draw lines that cut your plate in quarters and make seven marks per quarter of the circle. You will use this as your guide for locating the ball when you begin your experiment. Start at 0/28 and begin numbering in a counter-clockwise direction.
Set your lamp on the side of your room against one wall. Make sure this is a location you can easily keep the lamp or place it each day for your test.
Turn off the light in your room and turn on the lamp.
Set the plate on the floor in the middle of your room and stand on it. Point Day 0/28 toward the lamp.
Face in the direction of the day you are recording (beginning at Day 0 and counting upward for 28 days) and hold your ball at arm's length.
Take a close look at the illumination of the ball. For Day 0, there should be no illumination, as this corresponds to the new moon.
Record the ball's illumination on your sheet of paper in a table that allows you to track the phases of the moon over the course of one month.
Repeat this step each day for 28 days. When you finish, you should have 29 drawings (Day 0 through Day 28) showing the phases of the moon.
Periodically, check your results with the actual moon outside at night.
The moon actually looks a reddish color during alunar eclipse due to sunlight passing through the earth's atmosphere and being bent toward the moon — in effect, a “sunset” during an eclipse.
QUESTIONS FOR THE SCIENTIST
Did your drawings match the actual phases of the moon?________________
What effect did the fact that the moon's orbit is actually a little longer than 28 days have on the accuracy of your data?_______________________
What does the fact that solar and lunar eclipses are rare tell you about the orbit of the moon? Think about how this would look in your experiment.______________
FOLLOW-UP Research the history of man's attempts to fly to the moon. What objects were left on the moon by those who visited? For a powerful look at a failed moon voyage that almost cost three astronauts their lives, rent the movie Apollo 13.
Giant Science Kriss-Kross
How can you find the answers to these science questions? If you've looked through all the chapters in this book, you will have no problem! Fill each answer into the numbered grid. The words in the shaded row will answer this riddle: What is the best part about being a scientist? We left you a few A-T-O-M-S to get you started. Need more help? Check out the Experiment Overviews.
A mixture of two or more liquids.
Animals use _____________ to blend into their surroundings.
When you heat air in a bottle, you can _____________ a balloon.
Scientists use this form of energy to light up their laboratories. You use it at home, too!
Isaac ___________ is the scientist who defined the laws of gravity.
A _____________ points toward the magnetic north.
The sun gives us _______ in the form of heat and light.
A process that uses one metal to coat another metal.
An ___________ is a picture that shows you the inside of your body.
Barometers are devices used to measure air __________.
Albert _________ is a scientist whose theories and experiments led to new ways of thinking about time, space, matter, energy, and gravity!
One of the Laws of Motion says that every action has an equal but opposite _____________.
___________ only form when it is cold enough for water to freeze, but at the same time there is a way for water to drip.
Electricity flowing through a wire turns the wire into an electro___________.
A seismologist is a scientist who uses a Ricter Scale to measure the strength of __________________.
The _________ _________ (2 words) controls all the actions and reactions of the body.
An astronomer is a scientist who uses a __________ to look at the stars and planets.
A ___________ grows up from the ground.