Earth, Moon, and Sun
By: Marissa Gebeau
Section 1: Earth in Space
How does Earth move in space?
Earth moves through space by rotation and revolution.
Rotation is the spinning of Earth on its axis. It takes 24 hours for Earth to rotate once. Each 24-hour cycle of day and night is called a night.
Revolution is the movement of one object around another. One complete revolution of Earth around the sun is called a year. It takes 365.25 days to make a revolution around the sun.
What causes the cycle of the seasons on Earth?
Earth has seasons because its axis is tilted as it revolves around the sun.
As Earth revolves around the sun, the north end of its axis is tilted away from the sun for part of the year (winter) and toward the sun for the other part of the year (summer). It is the opposite for people on the south end of the axis. The change in seasons is not caused by the distance between Earth and the sun.
Section 2: Gravity and Motion
What determines the strength of the force of gravity between two objects?
The strength of the forces of gravity between two objects depends on the masses of the objects and the distance between them.
The force of gravity is measures in units called newtons, named after Isaac Newton.
All objects around you, including Earth, are pulling on you, just as you are pulling on them. You don't notice the pull because the strength of gravity depends on the masses of each object.
The strength of gravity is affected by the distance between two objects as well as their masses. The force of gravity decreases rapidly as distance increases.
What two factors combine to keep the moon and Earth in orbit?
Inertia and gravity combine to keep the moon and Earth in orbit.
Inertia is the tendency of an object to resist a change in motion.
Gravity is a force that attracts all objects toward each other
Earth's gravity pulls the moon toward it, preventing the moon from moving away. At the same time, the moon continues moving ahead because of its inertia. If Earth didn't have gravity, inertia would cause the moon to move off through space. Same thing with Earth and the sun.
Section 3: Phases, Eclipses, and Tides
What causes the phases of the moon?
The phases of the moon are caused by the changing relative positions of the moon, Earth, and sun. The sun lights the moon so half the moon is almost always in sunlight, since the moon revolves around Earth, you see the moon from different angles. The phases of the moon you see depends on how much of the sunlit side of the moon faces Earth.
What are solar and lunar eclipses?
When the moon's shadow hits Earth or Earth's shadow hits the moon, an eclipse occurs.
Eclipse-when an object in space comes between the sun and a third object, it casts a shadow on that object
Solar eclipse-occurs when the moon passes directly between Earth and the sun, blocking sunlight from Earth
The moons umbra reaches a little spot of Earth and in that area there is a total solar eclipse. This can happen at any time of day. Another cast of the moons shadow is the penumbra, where part of the sun is visible from Earth. People in this area only receive partial eclipse.
Lunar eclipse-during this, Earth blocks sunlight from reaching the moon
When the moon is in the Earth's umbra, you see a total lunar eclipse. Before and after a lunar eclipse, you can see the edge of Earth's shadow on the moon. A total lunar eclipse can be seen anywhere on Earth that the moon is visible.
What causes the tides?
The tides are caused mainly by differences in how much the moons gravity pulls on different parts of Earth. The area of Earth, where moon is closest to, has the strongest force of gravity with high tides. At the opposite end of the world, the force of the moons gravity is weaker and high tides also form there.
Section 4: Earth's Moon
What features are found on the moon's surface?
Maria, craters, and highlands are features found on the Earth's surface.
Maria-dark, flat areas on the moons surface
Craters-large round pits on the moon
Highlands- light colored features on the moons surface
What are some characteristics of the moon?
The moon is dry and airless. It is small and has large variations in its surface temperature, compared to Earth.
The moon is 3,476 kilometers in diameter, which is about one-fourth Earth's diameter. The moon's average density is similar to the density of Earth's outer layers. The temperature on the moon changes so much because it has no atmosphere. They range from 130 degrees Celsius in direct sunlight to -180 degrees Celsius at night. The moon has no liquid water but there may be large patches of ice near its' poles.
How did the moon form?
Scientist theorize that a planet-sized object collided with Earth to form the moon. Material from the object and Earth's outer layer was ejected into orbit around Earth, where it formed a ring. Gravity then caused this material to combine to form the moon.