The big bodies orbiting the Sun are called planets. The planets have moons of various sizes orbiting them. The above picture shows the planets of our solar system with relative sizes. The Earth, the planet on which we live, is a sphere shaped like a ball that is part of our solar system. This can be seen from pictures taken from space vehicles. Also, a ship can sail in one direction and sail all the way around the world before returning to the place it set out form. Ancient Greeks observed that islands appeared to rise from the sea when approached by sailors. This supported the beliefs of some ancient philosophers that the Earth was round. There are eight other planets in our solar system and smaller objects such as satellites, asteroids (dense objects orbiting the Sun) meteroids, and comets.
Earth
 The Earth is sometimes referred to as the "watery planet." Water covers about 70 percent of the Earth's surface and part of the atmosphere. The Earth has a single satellite---the moon." Most scientist believe life originated on the Earth about 3.5 billion years ago. The view of Earth from outer space should remind us that we must good stewards of our planet. The Earth is the only planet home we have. Many of the planets and their satellites are named after Roman gods. For example, Mars was the Roman war god, Diana, or Luna, was the Roman goddess of the Moon. The study of planets celestial bodies beyond the earth is part of the science of Astronomy. See if you can use the dictionary and find out what planet was named for a goddess of love and beauty. What do these planets names mean: Neptune, Jupiter, and Pluto?
The Sun brings heat and light to the Earth. The heat and light travel from the Sun to the Earth. The sunlight is made up of photons. Trillions of photons make up the sunlight we see. Even though the Sun is of average size star, it dwarfs our Earth. More than a million Earths could fit inside the Sun.
 The Sun is boiling and is always changing. It shapes our lives on Earth through climate, weather, and other ways. Our seasons result from the way the sun's energy strikes the Earth's surface, due to the tilt of the Earth's rotation.
Activities
Can you build a scale model of the solar system? If you use Earth's diameter as a unit of measure (Earth diameter = 1 ), figure out how big the other planets are compared to Earth. Hint: divide each planet's diameter by Earth's diameter. What objects might you use to depict the sizes of the Sun and planets? How far away would the planets be from each other? Map out a scale model of the solar system.
References These web sites contain additional information that may be researched. Physical
Science Earth Link Additional mini-quiz A good reference book is the"National Geographic Picture Atlas of Our Universe," by Roy A. Gallant, 1996, National Geographic Society, Washington, D. C.
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