Earth, Moon, and Sun
by: Rachel Flack
Take a tour of the moon.
Earth in Space
How does Earth move in space?
When Earth moves around the sun it's called a revolution. Revolution is when an object moves around another object. Earth also rotates on its axis. Rotation is the spinning motion around an imaginary line, such as: a figure skater when s/he spins. This process causes day and night: when one side of the Earth is facing the sun it is day time but because the other half is facing away from the sun and no sunlight can reach it, it is night.
What causes the cycle of seasons on Earth?
The seasons are caused by the tilt of Earth's axis. When the Northern Hemisphere is pointed toward the sun it is summer there and winter in the Southern Hemisphere. On the opposing side, when the Southern Hemisphere is pointed toward the sun it is summer. The summer and winters very in temperature because the closer to the equator you are the more direct the sun rays, also the closer you are to the poles the less direct rays hit Earth.
Gravity and Motion
What determines the strength of the force of gravity between two objects?
The strength of gravity between two objects depends on two things: the mass of each object and the distance between the two objects. The greater the mass of each object the more gravity that will be present and the less mass the less gravity. Then, when the distance is greater the force decreases and when the distance decreases the gravity increases.
What two factors combine to keep the moon and Earth in orbit?
The moon (around Earth) and the Earth (around the sun) stay in orbit because of inertia and gravity. Inertia keeps the moon and Earth going in a straight continuous line with the same speed and direction. Gravity pulls the moon to the Earth and the Earth to the sun, this makes the moon and Earth stay in a circular orbit.
Phases, Eclipses, and Tides
What causes the phases of the moon?
The phases of the moon are causes by the relative position of the moon, Earth, and sun. The phases of the moon are the new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, and waning crescent. The phases are caused when the moon revolves around the Earth and you can see the lit side of the moon. When the moon is located between the sun and the Earth it is a new moon because the lit-up part of the moon is facing away from Earth. As the moon circles Earth in a counter-clockwise circle the moon becomes more visible do to the sun lighting up the part of the moon that is visible from Earth. Once the Earth is between the sun and the moon, the moon closest to Earth is fully lit and it is a full moon. As the moon keeps going around the Earth counter-clockwise the moon has less light visible by Earth until it is between the sun and Earth again, then the process repeats. These positions also cause the tides and eclipses.
What are solar and lunar eclipses?
To start an eclipse is the shadow of the moon on Earth or the shadow of Earth on the moon. In a solar eclipse the moon passes between the sun and the Earth, this casts a shadow on Earth and blocks the sunlight. When the Earth casts a shadow and blocks the sun from moon it is a lunar eclipse.
What causes the tides?
Earth has tides: tides are when the water in bodies of waters rise and fall. These tides are caused by the differences in the moon's gravitational pull on the different parts of Earth and its bodies of water. When the moon pulls on the Earth and the water is pulled more easily a hide tide occurs, this also happens when the moon pulls Earth and the water is 'left behind'. When this happens it causes a low tide between the two high tides. This is shown in the image below.
Image: The moon pulls both the Earth and water toward it but has an easier time pulling the water causing a high tide such as in location A. In location C the Earth is more easily pulled which 'leaves the water behind' and causes high tide. In locations B and D it is low tide because all the water in the high tides are taking up the water giving less for these two locations.
What features are found on the moon's surface?
There are three features on the surface of the moon. Recent pictures have shown maria, craters, and highlands. Maria means "seas" in Latin; they are hardened rocks from lava flows that occurred between 3 and 4 billion years ago. Craters are round pits that can be hundreds of kilometers across and are created from the impact of meteoroids. Finally, highlands are high areas or mountains on the moon.
What are some characteristics of the moon?
The moon is dry and airless. Compared to Earth it is small with large differences of surface temperature. It is about one-forth the diameter of Earth, one-eighth of Earth's mass, but the moon's average density is similar to Earth's. Since the moon has no atmosphere to surface temperature ranges from 130 degrees to -180 degrees Celsius. The moon has no liquid water, but there is evidence of there being frozen water at the poles.
How did the moon form?
There are many theories about how the moon formed, lots have reasons for rejection, but one seems to be the best fit for the evidence found. This theory is called the collision ring theory. When Earth was young and lots of rocky debris was fly around, some of it collided with Earth and was ejected away from Earth. With the debris some of Earth's atmosphere was taken with it and Earth's gravity forced everything into one and kept it in orbit around the Earth.