Earth, Moon, and Sun

By: John Palmer

The moon may not affect us on Earth besides the tides and having us see it phase, but why does it phase?

Earth in Space

     First to understand how the moon moves and phases, we need to understand how the Earth moves. The Earth moves due to its revolution around the sun. We also get day and night from rotation on the Earths axis. As it spins the suns rays hit half of the Earth, while the other is dark and repeats every 24 hours that we know as a day. Revolution occurs on an orbital path around the sun. The orbit takes 365 1/4 days to go around the Sun, known as a year. Every four years a leap-year occurs for the 1/4 a day, so dates can remain similar.    

     Seasons occur in our world due to the position of the Earth in its orbital path. We see changes in temperature because the sun's rays hit the side of the Earth facing the sun more directly than another side of the Earth. Because the Earth is always on the same axis that a different hemisphere is facing the sun at a certain time. The equator almost always has the Sun's rays hitting it directly all year, making it warmer than other places. How we decide where the sun is, is by equinoxes and solstices. the Summer solstice happens around June 21 every year and on December 21. They mark the longest and shortest days of the year for the Northern hemisphere and the opposite for the Southern hemisphere. Equinoxes are the halfway points between solstices. Both hemispheres are receiving the same amount of sunlight.

Gravity and Motion

     If our planet and the moon are constantly orbiting, what is keeping the orbit in place? The force keeping the orbital path together is gravity. Gravity is a force that attracts all objects toward each other. The greater the mass of an object, or the closer an object the more pull. Weight does not affect gravitational pull unlike mass and distance. If the moon was much closer to Earth, there would be many changes but most of all gravity between the two would  

     How does a planet continue moving in space? Inertia is the tendency of an object to resist a change in motion. When a planet is pushed into an orbital path, the speed that the object was going at will always stay the same. This is also known as the law of universal gravitation.

     Why does the Earth never get pushed out of its orbit? The combined factors of inertia and gravity keep the moon pulled in while still being able to orbit due to inertia. If gravity did not exist than Earth would travel in a straight line forever, but because gravity does it keeps us from straying to far from the sun.

Moon Phases, Eclipses, and Tides

     The moon phases due to its rotation around the Earth, and the rotation of the Earth around the Sun. About Every 29.53 days a full moon occurs. The axis the Earth spins on does not decide full moons, the side of the moon facing the us does. Really the moon is always like Earth, has a day and night that just takes much longer because it takes 27 days for one full rotation. This makes us not be able to see parts of the moon because they are blocked by the bright side of the moon making the other side unseen, and that unseen side we see as often as a full moon, however, it is completely unseen and is referred to as a new moon. Every stage inbetween are classified by their own name. First the New Moon, which is invisible in space to the human eye, the second is the waxing crescent, third the first quarter moon (1/4 through the cycle, also know as a half moon,) fourth is the waxing gibbous, fifth is the full moon, 6 is the waning Gibbous, then the third quarter moon, finally, the Waning crescent is the final phase before another New moon.

     Eclipses occur whenever the moon or the Earth is blocking light from reaching the other. Solar Eclipses happens when the Moon passes in front of the Sun, blocking off sunlight from Earth. Lunar Eclipses happen when the Earth blocks off Sunlight to the moon. There are 2 types of eclipses besides lunar and solar, they are partial and total. Partial is where only part of the Moon or Earth is blocked out from light, while full means that the moon is blocking light from the earth or vice versa. Eclipses don't occur every month because the Moon doesn't directly move into the shadow or in front of the Sun, making it only happen rarely.

     Tides occur due to the Moon's gravity. Wherever the moon is it pulls water towards it, so when the moon is at a position in front of or behind the shore it pulls on the water, dragging it closer to land or pulling it away from land. Most coastal regions have two high tides and low rides a day because the earth spins daily the water masses move and get pulled by the moon on Earth. Spring tides and neap tides also occur during the month. Spring tides occur whenever the Sun, Earth, and Moon line up. Neap tides occur whenever the Moon, Earth, and Sun line up to make a right angle. Both of these tides occur twice a month.

Earth's Moon

     Before any tools to study the Moon were invented, many people would guess what the Moon was like. When Galileo Galilei invented the telescope, people started to learn more about the Moon and even our Solar System. The moons surface is not flat or smooth, it is actually covered with craters, maria, and highlands. Craters are large dents in the surface from meteoroids or other chunks of rock from space. Earth has had its fair share of meteorites when it was a new planet, but over time our atmosphere created weather which washed away and remains of those meteorites, because the moon doesn't have an atmosphere it has more craters because they can not be eroded. Maria, at Galileo's time, were thought to be oceans, but it was later discovered maria was not a sea, but a large area of rock formed from lava millions of years ago. finally, highlands are just like mountains we have on Earth and cover much of the Moons surface.

     Although when young we dream of going to the Moon, how different would it be from Earth? The moon is very different than the Earth, rather it is the temperature or size they are always going to be different. First of, size. The size of the moon is much smaller than Earth. its diameter is only 3,476 kilometers, nearly enough to fit the United States on it. Also, its gravity is much weaker than ours because of how much less mass it has. Second is temperature. The moon is either hot, or cold. The moon does not have an atmosphere meaning it can not keep itself warm when one side isn't facing the sun, unlike Earth which can.

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