Space and the Solar System Stars are enormous balls of superheated gases.Stars are enormous balls of superheated gases. The sun is a star. It is the major source of energy for the EarthThe sun is a star. It is the major source of energy for the Earth The solar system consists of the sun and eight planets—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and NeptuneThe solar system consists of the sun and eight planets—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune

Major Ideas Continued The Earth spins or rotates on its axis. This spinning causes us to have day and night.The Earth spins or rotates on its axis. This spinning causes us to have day and night. The Earth is tilted on its axis as it revolves around the sun. This explains why the seasons of the year change from spring and summer to fall and winter.The Earth is tilted on its axis as it revolves around the sun. This explains why the seasons of the year change from spring and summer to fall and winter. The moon orbits the Earth. The sun’s light reflects off the moon, causing us to see the moon at night.The moon orbits the Earth. The sun’s light reflects off the moon, causing us to see the moon at night.

Stars Stars are enormous balls of superheated gases. The nearest star to Earth, after the sun, is 40 trillion kilometers away.Stars are enormous balls of superheated gases. The nearest star to Earth, after the sun, is 40 trillion kilometers away. Stars are formed by clouds of gases and dust in space.Stars are formed by clouds of gases and dust in space. These gases and dust come together and begin to spin. This action eventually forms a star.These gases and dust come together and begin to spin. This action eventually forms a star.

The Sun The sun is one of millions of stars in the galaxy known as the Milky Way.The sun is one of millions of stars in the galaxy known as the Milky Way. The sun is the source of most of our energy on Earth and the rest of the solar system.The sun is the source of most of our energy on Earth and the rest of the solar system. The sun is the source of our heat and allows living things on our planet to survive.The sun is the source of our heat and allows living things on our planet to survive. The sun’s energy id the main influence on Earth’s climate and weather.The sun’s energy id the main influence on Earth’s climate and weather. The sun is the largest object in our solar system.The sun is the largest object in our solar system. Cooler areas on the sun’s surface are known as sunspots.Cooler areas on the sun’s surface are known as sunspots.

The Planets Planets are objects of rock, metal, ice and gas that circle the sun.Planets are objects of rock, metal, ice and gas that circle the sun. The largest planet is Jupiter— ten times the width of Earth.The largest planet is Jupiter— ten times the width of Earth. In general, the farther away a planet is from the sun, the cooler it is.In general, the farther away a planet is from the sun, the cooler it is.

Diagrams of the Solar System Diagrams and models of the solar system are not usually made to scale.Diagrams and models of the solar system are not usually made to scale. Scale diagrams showing how far apart the planets are from each other would not fit on a page in a book.Scale diagrams showing how far apart the planets are from each other would not fit on a page in a book. The same is true of the size of the planets. The sun’s width is 10 times that of Jupiter. If drawings were to scale, the entire solar system would not fit on one page.The same is true of the size of the planets. The sun’s width is 10 times that of Jupiter. If drawings were to scale, the entire solar system would not fit on one page.

The Movement of the Earth and Moon Earth moves in two different ways at the same time: it rotates and it revolves.Earth moves in two different ways at the same time: it rotates and it revolves.

Earth’s Rotation The Earth rotates, or spins, on its axis.The Earth rotates, or spins, on its axis. This rotation takes 24 hours, causing day and night on Earth.This rotation takes 24 hours, causing day and night on Earth.

Earth’s Revolution The Earth revolves,or circles, around the sun in just over 365 days or one year.The Earth revolves,or circles, around the sun in just over 365 days or one year. The Earth tilts on its axis as it revolves.The Earth tilts on its axis as it revolves. This tilt causes the sun’s rays to hit the Earth more directly or indirectly in the different hemispheres at different times of the year, causing our seasons.This tilt causes the sun’s rays to hit the Earth more directly or indirectly in the different hemispheres at different times of the year, causing our seasons.

Movement of the Moon The moon is a satellite of the Earth.The moon is a satellite of the Earth. The moon takes 29¼ days to orbit the Earth.The moon takes 29¼ days to orbit the Earth. The moon is about one fourth the size of EarthThe moon is about one fourth the size of Earth Because the moon is smaller than Earth, its gravitational pull is weaker.Because the moon is smaller than Earth, its gravitational pull is weaker. Something with the same mass will weigh less on the moon than on Earth.Something with the same mass will weigh less on the moon than on Earth.

More on the Movement of the Moon The pull of the moon’s gravity is the main cause of the rising and fall of ocean tides.The pull of the moon’s gravity is the main cause of the rising and fall of ocean tides. The moon does not produce its own light. It appears bright because it reflects light from the sun.The moon does not produce its own light. It appears bright because it reflects light from the sun. The amount of the moon that is reflected each night changes every 29¼ daysThe amount of the moon that is reflected each night changes every 29¼ days

Moon Phases The moon changes that we see on Earth are known as the moon’s phases.The moon changes that we see on Earth are known as the moon’s phases. The moon appears to change as the moon orbits Earth. When both the Earth and sun are on the same side of the moon, the moon is lit up. When the moon is between the Earth and the sun, the moon appears totally dark.The moon appears to change as the moon orbits Earth. When both the Earth and sun are on the same side of the moon, the moon is lit up. When the moon is between the Earth and the sun, the moon appears totally dark. Look on page 134 at the principal phases of the moon.Look on page 134 at the principal phases of the moon.

Characteristics of the Moon The moon is made of hard rock with craters.The moon is made of hard rock with craters. There is no water, air, soil or living things.There is no water, air, soil or living things. There is no wind.There is no wind. There is no atmosphere and no weather like we have on Earth.There is no atmosphere and no weather like we have on Earth. Meteors hit the moon without slowing down due to the absence of any atmosphere.Meteors hit the moon without slowing down due to the absence of any atmosphere. Temperatures on the moon range from 100° C to -173°C.Temperatures on the moon range from 100° C to -173°C.