Did you know that the moon doesn't give off its own light—that it merely reflects light from the sun? Or have you noticed that the moon seems to change every few days? Some nights it’s so large it appears to occupy the entire sky, but other nights, you can’t even see it at all! Those changes are called phases. Try this experiment to see why they occur.
Moon Phases Science Project***
What You Need:
What You Do:
It takes around 29 days for the moon to orbit the Earth once and the same amount of time for the moon to spin around one complete time on its axis. That means that we always see the same side of the Moon! However, we do see the moon changing as it goes through its phases.
While facing the lamp (sun), the surface of the orange (moon) facing you (Earth) was dark, even though the other half of the orange, facing toward the lamp was bright. This is the first phase of the moon, called new moon. We can’t see the moon at all during this phase!
As you began to turn away from the lamp, a shadow still covered most of the orange, but you probably saw a small crescent shape of light on the right side of the orange. This phase is called waxing crescent.
The next phase is called the first quarter: the light (sun) shone on the half of the orange (moon) facing it. From Earth, we see half of the light side and half of the dark side during this phase so sometimes it is called a "half moon."
As you continued to turn to the left, the light shone on more of the side of the orange you could see, lighting up all of the orange except for a small crescent. This is the waxing gibbous phase.
Once you had turned halfway around so that the lamp was directly behind you, the light (sun) shone directly on the orange (moon) making the whole side facing you bright. This is a full moon. During a full moon, the side facing away from Earth is dark. This phase is the exact opposite of new moon.
(Note: if the orange isn’t fully illuminated, try moving your head or shoulders so you aren’t blocking the lamp. If you are blocking it, you’ve created a lunar eclipse – which happens when the Earth blocks the sun’s light from hitting the moon. Normally, the moon is just above or just below Earth so an eclipse doesn’t happen every time there is a full moon.)
At this point, the amount of the light side of the moon that we can see begins to decrease, or wane. The next phase is called waning gibbous. Most of the moon is still light during this phase.
Next is the last quarter (also called third quarter) where only half of the illuminated side of the moon is visible. This phase is opposite of first quarter. Notice that your back is facing toward the direction you were facing when you saw the first quarter phase!
The last visible phase is the waning crescent, where only a sliver of light is visible. This phase is opposite the waxing crescent. After this, you will be facing toward the lamp (sun) again, and the orange (moon) will be back to the new moon phase!
If you’re having difficulty remembering the difference between waxing and waning moon phases, these rhymes might help:
Waxing: “Moon on the right, getting bigger every night.” (Leading to a full moon.)
Waning: “When the moon is waning, it is fading to the left until there’s no moon remaining.” (Leading to a new moon.)
***For younger kids, show the moon's phases using this fun Oreo cookie activity instead.
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The Sun and Stars
Did you know that the sun is actually a star? It is the closest star to the Earth, which is why it seems so big and bright. Compared to some stars though, the sun is just medium-sized! Any star that has planets and other celestial bodies orbiting around it can be called a solar system. The Earth, other planets, their moons, various stars, comets, and asteroids that revolve around the sun are all part of our solar system. The word "sol" means sun, so our solar system could be called a sun system.
But why is the sun so important? Without the light, heat, and energy it imparts, the Earth would be so cold that no living thing could survive on it! And the sun's gravity keeps the Earth and the rest of the planets moving in their orbits—without it, the planets would move randomly through space like comets. Even though our solar system is huge, it is a very small part of a much larger system called the Milky Way galaxy. Even the whole galaxy is small compared to what else is out there. There are many galaxies in the universe containing many other solar system!
If you look at a star chart, you'll see that stars are often shown in groups or patterns called constellations. To help keep track of where stars and locate constellations, astronomers have created something called the celestial sphere, which is an imaginary clear ball surrounding the Earth. You can think of it like this: all of the stars and groups of stars that form constellations are attached to a clear sphere surrounding the Earth. Even while Earth rotates, the sphere stays still, causing it to seem like the stars are moving across the sky! In reality, the stars are not on a sphere and are not even moving. They are simply located in outer space and Earth is simply rotating on its axis and orbiting the sun. Because the imaginary sphere stays still, astronomers are able to use it to keep track of where objects are located in the night sky even as the Earth moves.
Learn how to locate some stars this summer with the simple printable constellation maps on this site. Read mythical stories about constellations, too! Go here to learn more about stargazing including the summer triangle and meteor showers.