MOVEMENT IN THE SOLAR SYSTEM

The sun is a huge ball of glowing gases at the center of the solar system. This star supplies light energy for the earth and for the other planets that move around it. Without this light energy, the earth would be a cold, dark planet.

Many years ago, people watched the sun rise, move across the sky, and then set. They believed that the earth was still and that the sun was moving around the earth. We now know that the sun only appears to rise and set. It is the turning of the earth that causes sunrise and sunset.

The earth is like a ball that is spinning on someone’s finger. The earth spins on an imaginary line called an axis. Each time the earth goes around it is called a rotation. The rotation makes day and night. As the earth turns, the part that faces the sun has day and the part away from the sun has night. The length of time for the earth to rotate is one full day. It takes 24 hours for the earth to rotate. T

REVOLVING AROUND THE SUN As it spins, the earth also moves around the sun. This movement is called revolving. The path that the earth takes around the sun is called the orbit. When the earth completes one complete path around the sun it is called one revolution. It takes the earth one year to complete this trip. So a revolution takes about 365 days.

If the earth was straight up and down on its axis, sunlight would always hit the earth at the same angle. However, the earth is tilted and as it makes its revolution around the sun different parts of the earth get more sunlight than others.

WHAT DOES THE MOON’S MOVEMENT CAUSE? You have seen the brightness of a full moon on a dark night. However, the moon does not make its own light. Moonlight is actually sunlight reflected from the moon.

Even though the moon is shaped like a ball, its shape seems to change from day to day. Those different shapes are the moon’s phases. Sometimes it appears that the moon is a full circle. This is a full moon.

As the moon revolves around the earth, a part of the dark side of the moon faces the earth. As the days pass, people see more of the dark side and less of the moon. The moon slowly changes to a half circle. When the moon is a half circle, half of the moon is lit, and half is dark. This is called a half moon. As time passes, only the dark side of the moon faces the earth. The moon does not appear in the sky. This is called a new moon, though it is really not new. The moon is beginning a new set of phases or stages. The new moon takes place a little more than two weeks after a full moon.

The moon slowly changes from the new moon back to a full moon. The changes from a full moon, to a new moon, and back to a full moon take 29 1/3 days. The moon takes this long to revolve around the earth once. June 12 June 15 June 18 June 21 June 24 June 27 June 30 July 2 July 5 July 7 July 8

ECLIPSES OF THE MOON : As the moon revolves around the earth, the earth usually does not come between the sun and the moon. When the earth does come between the sun and moon the moon will pass through the earth’s shadow, which causes a lunar eclipse.

The moon usually does not come between the earth and The moon usually does not come between the earth and the sun. When it does, the moon blocks some sunlight from the earth, and a solar eclipse takes place. The moon makes a small shadow on the earth. From this shadow, the sun appears to get covered slowly.

HOW DO THE PLANETS OF THE SOLAR SYSTEM MOVE ? For thousands of years, people have watched the stars at night. The stars appear to rise and set slowly as the night goes on. The stars and sun make their own light. From night to night, some points of light seem to move among the stars. These are the planets. Planets, like the earth and moon do not make light. They get light from the sun. It has been known for more than 500 years that planets are satellites of the sun. That means that they go around the sun.

This model represents the scale size of the nine planets as they are in orbit around the sun.

THE PLANETS Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto

MERCURY This picture represents the hills on Mercury. Time for orbit - 88 days Time for rotation-176 days Moons - 0

Mercury Mercury is covered with large holes called craters. These craters were formed when Mercury was hit by huge rocks from space. Because Mercury is closest to the sun, it is very hot. The temperature on Mercury can reach 425 degrees Celsius. Mercury is less than half the size of Earth and has no moons.

VENUS Gula Mons - a volcano Eistla - A Rift Valley Time for orbit - 8 months Time for rotation days Moons - 0

This is a picture of the Arachnoids, one of the most interesting things about Venus. Notice how the land is spiral-shaped. This picture was taken using special equipment so that the different elevations of Venus would show up. Venus is about the same size as Earth. It is always covered with clouds. These clouds are made from drops of acid. The air is mostly carbon dioxide. Venus has giant volcanoes.

EARTH Time for orbit - 1 year Time for rotation - 1 day Moons - 1

MARS Time for orbit years Time for rotation-25 hours Moons - 2 As you look at the pictures you will notice that Mars is much like Earth.

Mars Mars is covered in reddish dust and rocks. Winds blow the dust into the air and make the sky pink. Mars has giant volcanoes. It also has a giant canyon much larger than the Grand Canyon on Earth. The temperature on Mars is usually lower than on Earth.

JUPITER Time for 1 orbit - 12 years Time for rotation -10 hours Moons - 16 Notice the large red spot on Jupiter. It is a large storm that is larger than Earth.

Jupiter Jupiter is the largest planet. Some of its moons are bigger than some of the planets. One of its moons even has volcanoes. Unlike the other planets, Jupiter gives off energy that heats the gas above it. These are the rings of Jupiter. This is the Giant Red Spot on Jupiter. It is a storm that is larger than the Earth.

SATURN Time for 1 orbit hours Time for rotation - 10 hours Moons - 17 Saturn is the 2nd largest planet. It has many moons. Saturn has storms and gives off energy that heats the air above it. Saturn has bands that are harder to see than Jupiter’s bands. It has beautiful rings that are made of thousands of thinner rings. Here is a close up of the rings.

URANUS Time for 1 orbit - 84 years Time for 1 rotation - 17 hours Moons -15 Uranus is 4 times larger than Earth. It is so far away that it is very cold. Uranus is a blue-green color because of a gas that is around it. Uranus has at least 10 narrow rings.

NEPTUNE Time for 1 orbit years Time for rotation - 18 hours Moons -2 Not much is known about Neptune and Pluto. Neptune is a large planet that looks greenish. Scientists hope to learn more about Neptune in the future.

PLUTO Time for 1 orbit years Time for 1 rotation -6 days Moons -1 Pluto is the smallest planet. It is about the size of Earth’s moon.

Meteors and Asteroids A meteor is a piece of rock or dust from space that burns up in the earth’s air. People see meteors as flashes of light crossing the sky. Some people call them shooting stars, but they aren’t stars at all. Meteorites are any part of the meteor that reaches the Earth. Asteroids are rocky objects that orbit the sun between the planets. The largest asteroid is about the same size as the state of Texas.

Comets Large chunks of ice and dust orbit the sun. These are called comets. Comets have orbits that are much longer and flatter than the planets. Comets can not be seen from the earth when they are far away in their orbit. When comets are far away from the sun, they do not get much heat. As comets move closer to the sun, the sun’s energy begins to heat them. Some of the ice becomes a gas. The sun pushes the gas and dust into a long tail. The tail goes from the bright part of the comet known as the head. A comet’s tail can be millions of kilometers long.