MOVEMENT IN THE SOLAR SYSTEM

The sun is a huge ball of glowing gasesat the center of the solar system. This starsupplies light energy for the earth and forthe other planets that move around it.Without this light energy, the earth wouldbe a cold, dark planet.

Many years ago, people watched the sun rise, move across the sky, and then set. They believedthat the earth was still and that the sun wasmoving around the earth. We now know thatthe sun only appears to rise and set. It is theturning 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 theearth goes around it is called a rotation. The rotation makes day and night. As the earth turns, the partthat 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 24hours for the earth to rotate.

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REVOLVING AROUND THE SUN

As it spins, the earth also moves around the sun. This movementis 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 oneyear to complete this trip. So a revolution takes about 365 days.

If the earth was straight up and down on its axis, sunlight wouldalways hit the earth at the same angle. However, the earth is tiltedand as it makes its revolution around the sun different parts of theearth 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 isactually 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 ofthe dark side and less of the moon. The moon slowly changes to ahalf 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 ofphases 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 usuallyAs the moon revolves around the earth, the earth usuallydoes not come between the sun and the moon. When the does not come between the sun and the moon. When the earth does come between the sun and moon the moon will passearth does come between the sun and moon the moon will passthrough the earth’s shadow, which causes a through the earth’s shadow, which causes a lunar eclipselunar eclipse..

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

HOW DO THE PLANETS OF THE SOLAR SYSTEM MOVE ?HOW DO THE PLANETS OF THE SOLAR SYSTEM MOVE ?

For thousands of years, people have watched the stars atnight. The stars appear to rise and set slowly as the nightgoes 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 earthand moon do not make light. They get light from the sun.

It has been known for more than 500 years that planets aresatellites 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 PLANETSMercury

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. Thesecraters were formed when Mercury was hit by huge rocks fromspace.

Because Mercury is closest to the sun, it is very hot. Thetemperature 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 ValleyTime for orbit - 8 months

Time for rotation - 127 days

Moons - 0

This is a picture of the Arachnoids, oneof the most interesting things about Venus.Notice how the land is spiral-shaped.

This picture was taken usingspecial equipment so that thedifferent elevations of Venuswould show up.

Venus is about the same size as Earth. It is always coveredwith clouds. These clouds are made from drops of acid. Theair 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 - 1.9 years

Time for rotation-25 hours

Moons - 2

As you look at the pictures you will notice that Mars ismuch like Earth.

Mars

Mars is covered in reddish dust and rocks. Winds blow thedust into the air and make the sky pink.

Mars has giant volcanoes. It also has a giant canyon muchlarger 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 biggerthan some of the planets. One of its moons even has volcanoes.

Unlike the other planets, Jupiter gives off energy that heats thegas above it.

These are the rings ofJupiter.

This is the Giant Red Spot onJupiter. It is a storm that islarger than the Earth.

SATURN

Time for 1 orbit - 29.5 hours

Time for rotation - 10 hours

Moons - 17Saturn is the 2nd largestplanet. It has many moons.Saturn has storms andgives off energy that heatsthe air above it. Saturn hasbands that are harder to seethan Jupiter’s bands. It hasbeautiful rings that are madeof 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 becauseof a gas that is around it. Uranus hasat least 10 narrow rings.

NEPTUNE

Time for 1 orbit - 165 years

Time for rotation - 18 hours

Moons -2

Not much is known about Neptune and Pluto. Neptuneis a large planet that looks greenish. Scientists hope to learnmore about Neptune in the future.

PLUTO

Time for 1 orbit - 250 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 upin the earth’s air. People see meteors as flashes of light crossing thesky. Some people call them shooting stars, but they aren’t stars atall.

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. Theseare called comets. Comets have orbits that are much longerand flatter than the planets. Comets can not be seen from theearth when they are far away in their orbit.

When comets are far away from the sun, they do not getmuch heat. As comets move closer to the sun, the sun’senergy begins to heat them. Some of the ice becomes a gas.The sun pushes the gas and dust into a long tail. The tail goesfrom the bright part of the comet known as the head. Acomet’s tail can be millions of kilometers long.