Chapter Nineteen

Earth, Moon, and Sun

19-1 Earth in Space

• The study of the moon, stars, and all objects in space is called astronomy.

• The imaginary line that passes through Earth’s center and North-South poles is called Earth’s axis.

• Earth’s rotation on its axis causes day and night. It takes Earth 24 hours to rotate once on its axis.

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• Earth completes one revolution, around the sun once every year. It takes 365 ½ days and 12 moon cycles.

• Sunlight hits Earth’s surface at an angle – this is why it is warmer by equator than at the poles.

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• Earth has seasons because its axis is tilted as it moves around the sun.

• When the north end of Earth’s axis is tilted toward the sun, the Northern Hemisphere has summer and the Southern Hemisphere has winter. The hemisphere tilted toward the sun has more daylight hours.

19-2 Tides, Eclipses and Phases

• The positions of the moon, Earth, and the sun causes the phases of the moon, eclipses, and tides.

• The moon revolves around Earth every 27.3 days. The moon rotates on its own axis every 27.3 days. The same side of the moon always faces Earth.

• The different shapes of the moon are called phases. The phases of the moon you see depends on the sunlit side of the moon facing Earth.

The Dark Side of the Moon

Phases of the Moon

19-2 Eclipses

• When the moon’s shadow hits Earth or Earth’s shadow hits the moon, an eclipse occurs.

• A solar eclipse occurs when the moon passes between Earth and the sun, blocking the sunlight from hitting Earth.

• A lunar eclipse occurs at full moon, when Earth is directly between the moon and sun.

Solar Eclipse

Lunar Eclipse

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• The darkest part of the moon’s shadow is called umbra – the moon completely blocks light from the sun. (Solar eclipse).

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• Lighter and larger is Penumbra – this is a partial eclipse because the sun is still visible.

• 1998 September 6 Penumbral Lunar Eclipse Images and Animation http://www.netspeed.com.au/minnah/U3A1998/Penumbral.html

The Moon’s Shadow

19-2 Tides

• The rise and fall of the ocean’s water every 12.5 hours or so is called a tide.

• The force of gravity pulls the moon and Earth toward each other.

• Tides mainly occur because of differences in how much the moon pulls on different parts of the Earth.

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• As Earth rotates, the moon’s gravity pulls water toward the point on Earth’s surface closest to the moon.

19-3 Rockets and Satellites

• A rocket moves forward when gases expelled from the rear of the rocket push it in the opposite direction.

• Fueling a rocket: – Multi-stage rocket – at each stage, or section,

the rocket uses up its fuel, and the empty fuel container drops off and the next stage ignites. This helps to send rockets further into space.

Multi-Stage Rocket

19-3 Satellites

• A satellite is any natural or artificial object that revolves around an object in space.– The Soviet Union launched the first satellite to orbit

Earth – “Sputnik 1” – 1957.– In 1961, Yuri Gagarin, from the Soviet Union, was the

first person in space – he orbited the Earth.– Satellites are used for:

• Communication• Navigation• Weather data• Research

Satellite

Satellite Dish

19-3 Satellites

• Satellite dish: some satellites move in geo synchronous orbits, they revolve around Earth at the same rate that Earth does. These satellites broadcast and relay television signals. Satellites are used for communication for cell phones.

• NASA: National Aeronautics Space Administration:– Developed reusable space shuttles. These are called

shuttles because they move back and forth or shuttle between Earth and space.

19-4 Earth’s Moon

• The Collision Theory: About 4.5 billion years ago, an object about as large Mars hit Earth.

• Material from the object and from Earth’s outer layers was thrown into orbit around Earth, eventually, that material formed the moon.

19-4 The Moon’s Features

• Galileo made his own telescope by putting two lenses in a wooden tube. He saw the moon in more detail than anyone. Features include:

– Craters – covers much of the moon’s surface. Craters are round pits formed by impacts from rock from space.

– Maria – dark, flat parts on the moon’s surface. Maria = “seas”, these occurred from flooding molten rocks.

– Highlands.

– Surveyor was the first space craft to land on the moon.

– The Eagle, carried Neil Armstrong and Buzz Aldrin, to a flat region called the Sea of Tranquility.

– Neil Armstrong was the first person to step on the moon. He said, “ One small step for man, one giant leap for mankind”.

The Moon’s Craters

Images made from the Maria of the Moon

• The Man on the Moon

Images made from the Maria of the Moon

• The Toad

Images made from the Maria of the Moon

• The Crab

Rotating Moon Animation

• http://www.solarviews.com/raw/moon/vmoon3.mpg

Apollo 11

• The crew of Apollo 11: Commander Neil A. Armstrong, Command Module pilot Michael Collins, Lunar Module pilot Edwin E. Aldrin, Jr. May 1, 1969.

Apollo 11

• This photo of Earthrise over the lunar horizon taken from the orbiting Command Module

"That's one small step for man, one giant leap for mankind."

Apollo 11

• The footprints left by the astronauts in the Sea of Tranquility

US Flag on the Moon