Earth, Moon, and Sun
by Caden Musser
The Earth in Space
How does Earth Move through Space?
Earth moves through space in two major ways: rotation and revolution
The imaginary line that passes through Earth's center and the North and South poles is Earth's axis. The spinning of Earth on its axis is called rotation. Earth's rotation causes day and night.
In addition to rotating on its axis, Earth travels around the sun. Revolution is the movement of one object around another. One complete revolution of Earth around the sun is called a year. One revolution of Earth around the sun is a year. The path that Earth follows around the sun is it's orbit.
What causes the seasons on Earth?
The seasons are caused by how the sun hits the Earth and the tilt of Earth's axis. The seasons occur because the Earth's axis is tilted as it revolves around the sun.
Most places outside the tropics and polar regions have four distinct seasons: winter, spring, summer, and fall. It is always warmer near the equator than near the poles. This is because the sun hits directly at the equator and at a steep angle towards the poles.
Summer and Winter are caused by Earth's tilt as it revolves around the sun. The change in seasons is not caused by changes in Earth's distance from the sun. In fact, Earth is farthest from the sun when it is summer in the Northern Hemisphere.
Gravity and Motion
What is Gravity
Gravity is the attractive force between objects. Its strength depends on their masses and the distance between them. The force of gravity is measured in units called newtons, named after Isaac Newton.
According to the law of universal gravitation, all of the objects around you, including Earth, are pulling on you, just as you are pulling on them. The strength of gravity depends on the mass and on the distance between the two objects.
The force of gravity decreases rapidly as distance increases. An example is that if the distance between two objects was doubled, the force of gravity between them would decrease to one-fourth of it's original value.
What is Inertia and Orbital Motion?
Inertia is the tendency of an object to resist a change in motion. An example of inertia is when you are riding in a car and it stops suddenly and you keep on moving forward. The more mass an object has, the greater its inertia.
Orbital Motion is the path followed by an object revolving around another object. An example of this is the Earth revolving around the sun. Isaac Newton concluded that inertia and gravity keep Earth in orbit around the sun and the moon in orbit around Earth.
Phases, Eclipses, and Tides
What are the Motions of the Moon?
Like Earth, the moon moves through space in two ways: revolution and rotation. The moon revolves around Earth and rotates on its axis. The changing relative positions of the moon, Earth, and sun cause the phases of the moon, eclipses, and tides.
What are the phases of the Moon?
The moon doesn't give off it's own light, the sun reflects light off of the moon. The phases of the moon are the different ways that we see the sun hitting the moon. The types of phases include New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Third Quarter, Waning Crescent.
During the new moon, the side of the moon facing Earth is not lit because the sun is behind the moon. As the moon revolves around Earth, you see more and more of the lighted side of the moon everyday, until the side of the moon you see is fully lit. As the moon continues its orbit, you see less and less of the lighted side. The cycle of moon phases occurs for about 29.5 days and restarts with a new moon.
What are Eclipses?
When an object in space comes between the sun and a third object, it casts a shadow on that object, causing an eclipse. In other words, when the moon's shadow hits Earth or Earth's shadow hits the moon, an eclipse occurs.
There are two types of eclipses: solar eclipses and lunar eclipses. The words solar and lunar come from the Latin words for "sun" and "moon" A solar eclipse is when the moon passes directly between Earth and the sun, blocking sunlight from Earth. A lunar eclipse is when Earth blocks sunlight from reaching the moon.
What are Tides?
Tides are the rise or fall of ocean water that occurs every 12.5 hours or so. The water rises for about six hours, then falls for about six hours, in a regular cycle. Tides are caused by differences in how much the moon's gravity pulls on different parts of Earth.
What is on the Moon's surface?
The features on the moon include maria, craters, and highlands. Maria is the dark, flat areas of the moon. Maria is the word for "seas" in Latin. Craters are large round pits on the moon that can sometimes be hundreds of kilometers across. They are caused by meteoroids hitting the moon. Highlands on the moon cover much of the moon's surface. The peaks of the lunar highlands and the rims of the craters cast dark shadows on the moon.
What are the Characteristics of the Moon
The moon is very different than the Earth. The moon is dry and airless. Compared to Earth, the moon is small and has large variations in its surface temperature. If you visited the moon, you would have to wear a special outfit to live suitably, as on Earth you wouldn't need anything because of the atmosphere protecting us. A difference between the moon and Earth is that the moon is about 3476 kilometers in diameter. That is about the distance across the United States. The temperatures of the moon can vary from 130 degrees Celsius (266 degrees Fahrenheit) to -180 degrees Celsius (-292 degrees Fahrenheit)
What is the Origin of the Moon?
About 4.5 billion years ago, when Earth was very young, the solar system was full of rocky debris. Some of this debris was the size of small planets. Scientists theorize that a planet-sized object collided with Earth to form the moon. Material from the object and Earth's outer layers was ejected into orbit around Earth, where it formed a ring. Gravity caused this material to form the moon.