Earth Patterns, Cycles, Changes

SOL 4.7

Science Notes

Earth Patterns, Cycles, Changes

The Earth-Moon-Sun System

1  The sun is a star that is about 110 times the diameter of the Earth. (It is so large, that over 1 million Earths could fit inside it).

1  The sun is a ball of hot gases (hydrogen and helium) that gives off heat and light.

1  Temperatures on the sun’s surface can reach 5,500°C or 9,900° F.

1  Nine planets revolve around the sun.

1  A planet is a large body that doesn’t give off light and orbits (or circles) around a star.

1  Earth is one of the small, rocky planets in our solar system and is the third planet from the sun. It is covered by land and water, with an oxygen rich atmosphere.

1  Scientists believe that Earth is the only planet that is home to living organisms.

1  The moon is a gray, rocky satellite that revolves around the Earth.

1  The moon is one-quarter the diameter of the Earth. This means if the Earth were the size of a basketball, the moon would be the size of a tennis ball.

1  Like the Earth, the moon does not produce its own light.

1  Unlike the Earth, the moon does not have water.

1  The moon has no atmosphere. During the day, the temperatures can become very hot (220° F) and at night, they can drop to -279°.

1  With no air or water, and extreme temperatures, the moon is unable to support life.

1  The United States Apollo Space Program run by NASA, has added a great deal to our understanding of the moon.

1  Samples brought back by NASA astronauts have revealed the composition of the moon’s surface is made of soil and rock.

Phases of the Moon

1  The moon is 239,000 miles away from the Earth.

1  One of the most important similarities between the Earth and Moon is the way in which they move throughout the heavens.

1  The Earth revolves around Sun and rotates on its own axis.

1  The Moon revolves around the Earth and rotates on its own axis.

1  Another similarity between the Earth and Moon is that neither of them produces their own light.

1  The moon does not shine; it only shines because it is illuminated by the sun.

1  As the sun’s light hits the moon, it bounces, or reflects off the moon’s surface and into our eyes. This reflection makes it appear that the light is coming from the Moon itself and very visible at night.

1  The changing shapes of the Moon that is viewed each month are known as the phases of the Moon. Sometimes in the nighttime sky we see a full circle; at other times we see a thin slice of the full circle called a crescent; and sometimes we see no moon at all. These different shapes or phases occur because, like the Earth, the Moon has day and night.

1  As the Moon revolves around the Earth, we see different amounts of the illuminated half of the Moon.

1  Scientists have identified eight (8) phases of the Moon:

New Moon (no moon visible)

Waxing Crescent (small sliver visible)

First Quarter (half of Moon visible)

Waxing Gibbous (over half of Moon visible)

Full (full circle visible)

Waning Gibbous (over half of Moon visible)

Last Quarter (half of Moon visible)

Waning Crescent (small sliver visible)

1  As the Moon moves from new to full, it appears to grow larger. This is called waxing.

1  As the Moon moves from full back to new, it appears to grow smaller. This is called waning.

Earth’s Season

1  On Earth, a year lasts for 365 days. This is the time it takes the Earth to complete one orbit, or circle, around the sun.

1  This movement of the Earth around the sun is called a revolution.

1  The Earth does more than revolve around the Sun. It also rotates or spins on its axis.

1  The Earth takes 24 hours, or one day, to spin around once on its axis.

1  Earth’s axis is an imaginary line through the center of the planet, which is tilted to one side.

1  It is the tilted axis of the Earth and its yearly revolution around the Sun that cause the changing seasons we enjoy.

1  As the Earth revolves around the Sun, we experience winter when the northern half (northern hemisphere) of the Earth is tilted away from the Sun. When we are tilted away, the rays of the sun hit us at an angle which makes them weaker. These weaker rays are not able to add much warmth to our atmosphere.

1  Summer arrives when the northern hemisphere of the Earth is tilted toward the Sun. When we are tilted toward the sun, the rays hit us almost straight on, which heats up the air and land more quickly.

Historical Understandings of Our Solar System

1  Throughout Earth’s history, man has tried to understand the Earth and the heavens.

1  Ancient people believed the Earth was the center of the universe and the Sun, stars, and planets revolved around it. This is known as the Earth-centered model. Aristotle, a Greek astronomer, and Ptolemy, an Egyptian astronomer, both believed this theory.

1  Copernicus, a Polish astronomer, challenged the Earth-centered model, believing the Sun was the center of the solar system and the Earth, stars, and other planets revolved around it. This was the beginning of the Sun-centered model and modern space science.

1  Galileo, and Italian astronomer, believed in the Earth-centered model until he began to make improvements to his telescope. With the help of his new and improved version of the telescope, Galileo was able to study the heavens and see, for the first time, clear evidence that Copernicus’ Sun-centered model was correct. Modern astronomer was born!