Space and the Solar Space and the Solar SystemSystem

• Stars are enormous balls of Stars are enormous balls of superheated gases.superheated gases.

• The sun is a star. It is the major The sun is a star. It is the major source of energy for the Earthsource of energy for the Earth

• The solar system consists of the The solar system consists of the sun and eight planets—Mercury, sun and eight planets—Mercury, Venus, Earth, Mars, Jupiter, Saturn, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and NeptuneUranus, and Neptune

Major Ideas ContinuedMajor Ideas Continued

• The Earth spins or rotates on its axis. This The Earth spins or rotates on its axis. This spinning causes us to have day and night.spinning causes us to have day and night.

• The Earth is tilted on its axis as it revolves The Earth is tilted on its axis as it revolves around the sun. This explains why the around the sun. This explains why the seasons of the year change from spring seasons of the year change from spring and summer to fall and winter.and summer to fall and winter.

• The moon orbits the Earth. The sun’s light The moon orbits the Earth. The sun’s light reflects off the moon, causing us to see reflects off the moon, causing us to see the moon at night.the moon at night.

StarsStars

• Stars are enormous balls of superheated Stars are enormous balls of superheated gases. The nearest star to Earth, after gases. The nearest star to Earth, after the sun, is 40 trillion kilometers away. the sun, is 40 trillion kilometers away.

• Stars are formed by clouds of gases and Stars are formed by clouds of gases and dust in space. dust in space.

• These gases and dust come together These gases and dust come together and begin to spin. This action eventually and begin to spin. This action eventually forms a star.forms a star.

The SunThe Sun

• The sun is one of millions of stars in the galaxy The sun is one of millions of stars in the galaxy known as the Milky Way.known as the Milky Way.

• The sun is the source of most of our energy on The sun is the source of most of our energy on Earth and the rest of the solar system.Earth and the rest of the solar system.

• The sun is the source of our heat and allows The sun is the source of our heat and allows living things on our planet to survive.living things on our planet to survive.

• The sun’s energy id the main influence on The sun’s energy id the main influence on Earth’s climate and weather.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 Cooler areas on the sun’s surface are known as

sunspots.sunspots.

The PlanetsThe Planets

• Planets are objects of rock, metal, Planets are objects of rock, metal, ice and gas that circle the sun.ice and gas that circle the sun.

• The largest planet is Jupiter—ten The largest planet is Jupiter—ten times the width of Earth.times the width of Earth.

• In general, the farther away a In general, the farther away a planet is from the sun, the cooler it planet is from the sun, the cooler it is.is.

Diagrams of the Solar Diagrams of the Solar SystemSystem

• Diagrams and models of the solar Diagrams and models of the solar system are not usually made to scale.system are not usually made to scale.

• Scale diagrams showing how far apart Scale diagrams showing how far apart the planets are from each other would the planets are from each other would not fit on a page in a book.not fit on a page in a book.

• The same is true of the size of the The same is true of the size of the planets. The sun’s width is 10 times that planets. The sun’s width is 10 times that of Jupiter. If drawings were to scale, the of Jupiter. If drawings were to scale, the entire solar system would not fit on one entire solar system would not fit on one page.page.

The Movement of the The Movement of the Earth and MoonEarth and Moon

• Earth moves in two different ways Earth moves in two different ways at the same time: it rotates and it at the same time: it rotates and it revolves.revolves.

Earth’s RotationEarth’s Rotation

• The Earth rotates, or spins, on its The Earth rotates, or spins, on its axis.axis.

• This rotation takes 24 hours, This rotation takes 24 hours, causing day and night on Earth.causing day and night on Earth.

Earth’s RevolutionEarth’s Revolution

• The Earth revolves,or circles, around the The Earth revolves,or circles, around the sun in just over 365 days or one year.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 This tilt causes the sun’s rays to hit the

Earth more directly or indirectly in the Earth more directly or indirectly in the different hemispheres at different times different hemispheres at different times of the year, causing our seasons.of the year, causing our seasons.

Movement of the MoonMovement 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 The moon takes 29¼ days to orbit the

Earth. Earth. • The moon is about one fourth the size of The moon is about one fourth the size of

EarthEarth• Because the moon is smaller than Earth, Because the moon is smaller than Earth,

its gravitational pull is weaker.its gravitational pull is weaker.• Something with the same mass will Something with the same mass will

weigh less on the moon than on Earth.weigh less on the moon than on Earth.

More on the Movement of More on the Movement of the Moonthe Moon

• The pull of the moon’s gravity is the The pull of the moon’s gravity is the main cause of the rising and fall of main cause of the rising and fall of ocean tides.ocean tides.

• The moon does not produce its own The moon does not produce its own light. It appears bright because it light. It appears bright because it reflects light from the sun.reflects light from the sun.

• The amount of the moon that is The amount of the moon that is reflected each night changes every 29¼ reflected each night changes every 29¼ daysdays

Moon PhasesMoon Phases

• The moon changes that we see on Earth The moon changes that we see on Earth are known as the moon’s phases.are known as the moon’s phases.

• The moon appears to change as the The moon appears to change as the moon orbits Earth. When both the Earth moon orbits Earth. When both the Earth and sun are on the same side of the and sun are on the same side of the moon, the moon is lit up. When the moon, the moon is lit up. When the moon is between the Earth and the sun, moon is between the Earth and the sun, the moon appears totally dark.the moon appears totally dark.

• Look on page 134 at the principal Look on page 134 at the principal phases of the moon.phases of the moon.

Characteristics of the Characteristics of the MoonMoon

• 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 There is no atmosphere and no weather like we

have on Earth.have on Earth.• Meteors hit the moon without slowing down Meteors hit the moon without slowing down

due to the absence of any atmosphere.due to the absence of any atmosphere.• Temperatures on the moon range from 100° C Temperatures on the moon range from 100° C

to -173°C.to -173°C.