Earth, Moon, and Sun
By: Valentino Carriero
Section 1- Earth in Space
How does the Earth move in space?
The Earth moves through space in two major ways: rotation and revolution.
Rotation- The Earth has an imaginary line that passes through the center of it called the axis. The spinning of this axis is called rotation. The Earth's rotation causes day and night, it also shows how the sun moves westward across the sky. It takes about 24 hours for all this to occur, this cycle is also called a day.
Revolution- As Earth rotates on it's axis it also travels around the sun. Revolution is the movement of one object around another, the Earth moving around the sun. One revolution takes one year to complete. Earth follows a path or its orbit as it revolves around the sun. Earths orbit is not quite circular, oval or slightly long circle.
What causes the cycle of seasons
The Earth's axis causes the seasons.
As the Earth revolves around the sun it's axis is on a tilt this causing the seasons on Earth. The Earth's axis is on an angle of 23.5 degrees from vertical. As Earth revolves around the sun the southern end of the Earth is tilted towards the sun for part of the year then away from the sun for the rest of the year. Summer and winter are caused by the tilt not how far Earth is away from the sun. In summer in the Northern hemisphere, Earth is the farthest from the sun.
Section 2- Gravity and Motion
What determines the strength of the force of gravity between two objects?
The strength of the force of gravity on two objects depends on two factors: the mass of the objects and distance between those two objects at a certain time.
The pull of the object may not seem that strong but it all depends on the amount of mass the object has. Mass is the amount of matter in an object. Therefore since Earth is so huge it has a greater pull on us attracting us to the ground so that we don't float away into space. The object also has weight, this is the force of gravity on the object. Weight can differ from mass, weight can change but mass cant change. Like when you go the moon you could weigh much less than on Earth, but you will still have the same amount of mass.
What two factors combine to keep the moon and Earth in orbit?
Inertia and gravity keep the Earth in orbit around the sun and the moon in orbit around Earth.
To take an example, the Earth's gravity is always pulling on the moon, preventing the moon to move in a straight line out into space. At the same though the moon keeps moving ahead around Earth because of it's inertia. Inertia being, the tendency of an object to resist a change in motion. Without Earth's gravity the moon would just drift out into to space slowing moving in a straight line. The same thing happens to the Earth and the sun.
Section 3- Phases, Eclipses, and Tides
What causes the phases of the moon?
The changing of the positions of the moon, Earth, and sun causes the phases of the moon.
The moon rotates and revolves the same as the Earth meaning that a day and a year on the moon are equal to the Earth's, this is why the same side of the moon always faces the Earth.The moon reflects light from the sun, the shapes you see in the night are the phases. For example, a full circle where you can see the whole moon is called a full moon and a crescent is when there is a sliver of the moon the appears. The moon goes through a whole set of phases as it completes one revolution around the Earth. Since the moon reflects the sun half of the moon is always lit but since its also revolving around the sun that's why we see different shapes.
What are solar and lunar eclipses?
An eclipse is when an object in space comes between the sun and a third object, it casts a shadow on that object.
Solar- A solar eclipse occurs when the moon passes directly between the Earth and the sun, blocking sun from the Earth. It occurs only when a new moon blocks the sun. The darkest part of the moons shadow is called the umbra, this is cone shaped with the smallest part of the cone touching the Earth where there is absolutely no light. The larger part of the shadow is called the penumbra. This is where you can only part of the sun and there is still light its just not pitch black like the umbra. Both these make it dark during the middle of the day.
Lunar- A lunar eclipse occurs when the moon is at a full moon. During the lunar eclipse Earth blocks sunlight from reaching the moon. The moon is then in Earth's shadow and looks very dim. These only occur with a full moon because the moon is closest to the Earth's shadow. Earth's shadow has an umbra and penumbra but the shadow is so big that just the umbra covers the moon making this a total lunar eclipse. Unlike solar eclipses you can see a lunar eclipse from anywhere on Earth and it will be the same.
What causes the tides?
The moon's and sun's gravity mainly affects the Earth's tides.
The Earth's tides also have cycles on Earth. High tides occur when the moon is closest to the Earth, low tides occur when the moon is farthest from the Earth. The sun's gravity also pulls on the Earth's tides. The gravity of the sun and the moon combine to form a tide with the greatest difference between consecutive low and high tides, called a spring tide. Spring tides only occur during a full moon and a new moon. During the moons first and third quarter the moon and sun are at a 90 degree angle between the Earth, the suns pull is at a right angle to the moon's this creating a neap tide. A neap tide is a tide with the least difference between consecutive low and high tides, they occur twice a month.
Section 4- Earth's Moon
What features are found on the moons surface?
The moon's surface includes maria, craters, and highlands.
Maria- Maria are hardened rock formed from huge lava flows that occurred between 3 and 4 billion years ago. They are usually dark and flat ares. Galileo thought that these areas were oceans hence the word maria which is Latin for seas.
Craters- These are large round pits located on the moon. Some of these craters can be huge, sometimes hundreds of kilometers wide. Scientists mistakenly thought these craters had been created by volcanoes, until later they figured that they are caused by impact of meteoroids, chunks of or dust from space, on the moons surface leaving behind huge pits or craters. Most craters formed in the early stages of the moon rather then today, on Earth these have worn away by water, wind, and other forces and since the moon has no water or wind it still has craters left behind.
Highlands- These are are raised levels on the moons surface like mountains and as seen they appear brighter then other parts of the moon. The highlands cast shadows everywhere around the moon. Highlands also form around the edges of craters making them dark casting shadows into craters making them dark. The lunar highlands cover most of the moon's surface.
What are some characteristics of the moon?
Some characteristics of the moon is that it's dry and airless, the moon is small compared to other planets, and it has large variations of temperatures on it's surface.
Size and density- The moon is 3,476 kilometers in diameter, this is a little less then across the United States. The moon is about one-fourth the Earth's diameter, and the moon has about one-eighth as much mass as the Earth. The moon's density is similar to the density of the Earth's outer layers.
Temperature and atmosphere- Temperatures can range from 130 degrees Celsius to -180 degrees Celsius at night. Temperatures vary so much that's why the moon has no atmosphere. The moons gravity is so weak any gases can escape it.
Water- The moon has no liquid form of water, yet some scientists believe that there could be large patches of ice near the poles. Locations shielded by crater walls are so cold in temperature that its possible that maybe ice could be located there.
How did the moon form?
Scientists believe that a small planet-sized object collided with the Earth to form the moon.
As this planet like object collided with Earth, material or rock from Earth's outer layers was pushed out into orbit around Earth where it formed a ring. Gravity caused these materials to combine to form the moon. There were also many other theories like that the moon just drifted into the Earth's orbit or gravity and that the moon was formed near the Earth when as there Earth was getting formed.