The Sun
The sun is shaped like a ball and it is huge in size. More than a hundred earths could fit across it, side by side. It would take the fastest rocket a year to travel to the sun. The sun is very bright and very hot. The sun glows, like a light bulb wire, and does not burn like wood. The sun glows hotter and brighter than a million H-bombs all shooting off at once. Nothing can be solid on the sun because it is so hot, not even iron. The great heat on the sun makes iron float around like a cloud of steam. The sun turns like the other planets and it takes nearly a month to make a full turn. Sometimes there are dark spots on the sun and they are called sun patches. All around the sun there is a silvery fog which is called the corona. The corona cannot be seen by us on earth because the sky around the sun is so bright. The sun is billions of years old, sending heat and light out into space. The earth gets only a tiny part of this light and heat, but it is enough to make plants grow and to give us life.
Mercury
Mercury is the planet closest to the sun. It is less than half as wide as the earth. In less than 3 months Mercury travels around the sun. The sunny side of Mercury is hotter than an oven. The side away from Mercury is cooler than we can imagine. Nothing can live on the planet Mercury.
Venus
Venus is the brightest planet in the sky. It is earth’s nearest planet neighbor. It takes Venus 7 months to go around the sun. This planet is always covered with clouds and it is very hot on Venus, much hotter than it ever gets on earth.
Earth
The size of the earth is the largest of the four planets comprising the inner group (Mercury, Venus, Earth, and Mars), and it is the third closest to the sun. The earth is shaped like an oblate spheroid, which means it is almost ball-shaped, or spherical, except for a slight flattening at the poles. This flattening, and an accompanying bulge at the equator, are produced by the centrifugal force of rotation. As we know, the earth has 1 moon. The earth has a polar diameter of about 7900 miles (the equatorial diameter is approximately 27 miles greater because of the bulge described above). The circumference of the earth is about 24,874 miles, and the surface area comprises roughly 197 million square miles, of which about 51 million square miles (29 per cent) are surface lands. The remaining 71 per cent of the earth’s surface is covered by water. Like all planets, the earth rotates around the sun in its own orbit and period of revolution. In addition to its trip around the sun, the earth also rotates. The earth turns on its axis (the shortest diameter connecting the poles), and this turning motion is called rotation. The earth rotates from west to east and makes one complete rotation each day. It is this rotating motion that gives us the alternating periods of daylight and darkness which we know as day and night. It takes the sun 365 ¼ days to orbit (in slightly elliptical orbit) around the sun.
The Earth’s Moon
The size of earth’s moon is more than 2000 miles wide. It takes a fast rocket more than 2 days to get to the moon. Everything on the moon is covered with dust--dry, with dust. There is no air. There is no water. In the sunshine, it is as hot as the inside of a baking oven. But in the shade, it is colder than dry ice.
The moon has high, sharp peaks. There are huge, round holes everywhere, and these holes are called craters. Some of these craters are so big that it would take a whole day to drive around one crater in a fast moving car.
The moon has no light of its own and can only catch some light from the faraway sun and throw it down to the earth which is called reflected light. The moon is shaped like a ball, and depending on how much sunlight the moon gets, that determines if it is a full, half, or quarter moon. The gravity of the earth pulls the moon and keeps it from going into space.
Mars
Mars is a little more than half as wide as the earth. This planet takes nearly 2 years to go around the sun. On Mars it gets never warmer than one of our summer days. At night it gets very, very cold there---almost as cold as dry ice. Mars is the only planet that might have a little air and water. Perhaps some plants could live there, but nobody really knows for sure. Mars shines with a reddish color. It has 2 tiny moons of its own.
Jupiter
Jupiter is the giant of the solar system and it is 11 times as wide as the earth. It is so big that more than a thousand earths could be packed into it. Jupiter takes almost 12 years to make a trip around the sun. It is always very, very cold on Jupiter. This planet has 12 moons.
Saturn
Saturn is nearly 10 times as wide as the earth. It takes almost 30 years to go once around the sun. This is the only planet that has a ring around it. The ring is made up of swarms of small stones. Besides the ring, there are 9 moons going around Saturn. Noting at all could live on Saturn. It is even colder than Jupiter.
Uranus
Uranus is 4 times as wide as the earth and has 5 moons of its own. It takes Uranus 84 years to go around the sun. Nothing could live on Uranus. It is far, far too cold there.
Neptune
Neptune is nearly 4 times as wide as the earth and it has 2 moons. It takes Neptune 165 years to go around the sun. This planet is also way too cold for anything to be able to live there.
Pluto
Pluto is smaller than the earth and it has 2 moons. It takes Pluto 250 years to travel around the sun. Pluto gets almost no light or heat from the sun because it is so very far away. From Pluto, the sun would look as tiny as a star.
How gravity works:
Make a hole through the middle of a potato. Put a long string through the hole, and tie it tightly. Hold the other end of the string, and swing the potato around in circles. You will feel the strong pull of the string.
You are the earth, and the potato is the moon. The pull of the string is the pull of gravity. The pull makes the moon stay in its path as it goes around and around the earth.
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