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Earth, Sun, and Moon
Transcript of Earth, Sun, and Moon
California Science - MacMillan 3rd grade
Earth, Sun, and Moon
Day and Night
The position of the Sun in the sky appears to change during the day. Earth's
ROTATION causes day and night.
around the Sun causes the seasons. The position of the Sun in the sky seems to change from season to season.
The Phases of the Moon
What are the phases of the Moon?
Each day the Moon seems to change shape. Sometimes you can only see a small part of the Moon. At other times you cannot see it at all. Each shape that we see is called a phase. Scientists have names for each phase of the Moon.
Lunar and Solar Eclipse
How does the Sun's position seem to change?
Each day the Sun seems to move across the sky in a giant arc. In the morning the Sun appears low on the eastern horizon. At midday, it appears high overhead. In the evening, it appears low on the western horizon.
Have you ever noticed how the shadows change during the day? Sometimes they are long and at other times they are very short.
Go outside with a partner and talk about your shadows. Is it long or short? Why?
Your shadow will be shorter at midday.
Your shadow will be longer both during the sunrise and during sunset.
So what causes
day and night?
Earth rotates like a giant top that is spinning in space. To rotate means to turn. It is the rotating of the Earth that causes day and night. As Earth rotates, one side faces the Sun. That side of Earth has daytime. At the same time the other side of Earth faces away from the Sun. That side of Earth has nighttime.
As Earth turns, the Sun's position seems to move in the sky. What you actually see is caused by Earth's rotation.
Every 24 hours, Earth makes on complete rotation. A full day is 24 hours long, or all of the daytime hours plus all of the nightime hours
What is an axis?
Have you ever seen a basketball spinning on a fingertip? Think of a line drawn from the fingertip to the top of the ball. The line would be straight up and down. The ball spins around this line.
Earth's shape is a
sphere. Earth's axis
is not straight up and down. It is slightly tilted. North Pole is at the north end and South Pole is at the south end.
Review of the causes of day and night:
Activity: Draw a picture of the Earth and
it's axis. Then label the North, South,
East, and West. Then draw an arrow
showing the direction of the rotation.
In your your journal, write a 3 - 4 sentence paragraph telling where the Sun is when you wake up. Where is it when you get home? Check your spelling and punctuation.
Why do seasons change?
You learned that Earth rotates around its axis. This is not the only way Earth moves in space. It aslo
An object that moves around another object revolves.
Earth travels, or revolves in a regular path around the Sun This path is called Earth's
. It takes Earth one year, or about 365 days, to complete one orbit around the Sun.
Season change as Earth rotates and revolves around the Sun because of Earth's tilted axis. Look at the diagram. No matter where Earth is in its obit, its axisis always tilted in the same direction.
In June, the North Pole is tilted toward the Sun. This means sunlight is more direct. More of the Sun's energy reaches the North Pole. Days are longer. Temperatures are warmer. It is Summer there.
By December, Earth has moved to a different position in its orbit. Now the North Pole is tilted away from the Sun. Less direct sunlight and less energy reaches the North Pole. Days are shorter and it is colder. It is Winter.
How does the Sun's path change from season to season?
You learned that on a single day, the Sun appears to rise and follow a path across the horizon. Day, night, and changing shadows are caused by Earth's rotation. Now let's see why the position seems to change from season to season.
The Sun's position seems to change from season to season. While it is summer in California, the Sun is high overhead at noon. That is because the northern half of Earth is tilted toward the Sun.
When it is winter in California, the path of the Sun appears low in the sky. California is tilted away from the Sun. The Sun at noon is lower. The southern half of Earth is tilted toward the Sun.
In the spring and fall, the path of the Sun is in between high and low. In the spring days are growing longer, and temperatures are higher in California. In the fall days are growing shorter and temperatures are lower in California.
So, what are the seasons like in other places?
June in sunny California
June near the equator
June in Argentina
Bill Nye the Science Guy
There are Eight Phases of the Moon
As we see more of the Moon's lit surface, we say the Moon is a waxing moon.
means that something is
As we see less of the lit surface of the Moon, we say the Moon is a waning moon.
means that something is
Why does the Moon shape seem to change?
The Moon, like the Earth, moves through space. The Moon orbits Earth, much like Earth orbits the Sun. The Moon's shape seems to change because of this orbit. Look at the diagram. One half of the moon faces the Sun. The other half faces away from the Sun and is in darkness. The Moon does not make its own light. As the Moon orbits Earth, we see different parts of its lighted half. These lighted parts are the different shapes, or phases, we see.
It takes the Moon about four weeks to orbit Earth. During this time it passes through all of its phases. The four-week cycle of the changing phases is called the lunar cycle.
Like the Sun, the Moon seems to rise, move across the sky and set. This happens because of Earth's rotation around its axis.
Here is a calendar showing how the Moon moves through all the phases all month long.
Why do we see the Moon during the day?
The reason we see the Moon during the day is because of its orbit around the Sun. During the lunar cycle it makes a circuit across the sky. At the full Moon it is exactly opposite of the Sun. However, as it gets closer to the New Moon, the Moon gets closer to the Sun. This may make the moon less visible at night and makes it more visible during the day. The Moon however, does not give off light. The Moon reflects light like a mirror, making it very visible day or night.
The Sun and our Shadows