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33 Cards in this Set

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Why does the moon orbit the Earth?
.
Why is the Earth always half dark?
The Earth is always half dark because ...

Sun light travels away from the sun in straigh line paths.

- Half of the earth is in light where the sun rays strike and
- the other half is in darkness because the light can not reach it.
Draw a model of the sun, Earth, and moon system including their orbits.
.
What is gravity?
Gravity is the force of attraction between two objects.
What is an orbit?
An orbit is the path an object takes when it revolves around another object.
Name four systems that the Earth belongs to.
Four systems that the Earth belongs to are:

- sun and Earth,
- moon and Earth,
- sun, moon, and Earth, and
- the Solar System.
How does sunlight travel in space?
Sunlight travels in rays away from the sun in space.
What is weight?
Weight is the pull of gravity between objects.

Weight changes.
What two actors affect gravitational pull?
Two factors that affect gravitational pull are ...

- mass and
- distance.
Why doesn't Earth orbit the moon?
The moon orbits the Earth because ...

the Earth has more mass and the moon can move more freely.
Does sunlight light up space?
No, sunlight does not light up space.

Sun rays light up solid objects that they hit
as they travel away from the sun.
What is mass?
Mass is the amount of matter an object contains.

Mass remains constant.
What is a revolution?
A revolution is one full orbit around another object.
Why does the moon orbit the Earth?
The moon orbits the Earth because...

when two objects attract each other, the object with less mass will move more easily. The moon has much less mass than Earth. Therefore, the moon orbits around Earth instead of Earth orbiting around the moon.
Draw a model of a lunar eclipse.
.
What is a system?
A system is a set of parts that affect each other.
What is an ellipse?
An ellipse is an oval shaped orbit.

Orbits around planets are not circles. Orbits are ellipses or oval shaped.
What determines how much of the moon is visible to us here on Earth?
The position of the moon in its orbit around Earth

determines how much of the moon is visible to us here on Earth.
What causes the seasons on Earth?
Seasons are caused by two things... the Earth's

- tilt on its axis, and its
- revolution around the sun.
What happens to the force of gravity between to objects moving farther apart?
The force of gravity between to objects depends on how far apart those objects are. The greater the distance between two objects, the weaker the force of gravity is between them.

(see note.)
How long does it takes to make one full rotation of Earth on its axis?
It takes...

- 24 hours for Earth to make
- one full rotation on its axis.
What path would the moon take if it were not pulled by the Earth's gravity?
The moon would take a straight path instead of an orbit.

The gravitational pull between the Earth and the moon causes the moon to orbit the Earth.
Draw a model of a solar eclipse.
.
What causes Polar climates?
Polar climates are cold because the tilt of the Earth on its axis point polar areas away from the sun.

In winter, some polar areas receive no sun rays at all.

In summer, they receive indirect sun rays.
How many days does is take moon to travel around the Earth?
It takes 29 1/3 days for the moon to travel around the Earth.
Where are the Temperate climate zones on Earth?
The Temperate climate zones lie between the Polar and Tropical zones.

Earth has two Temperate climate zones ... one in the Northern and one in the Southern hemisphere.

What is a solar eclipse?
A solar eclipse occurs when...

- the moon moves directly between the sun and the Earth.

All three planets are lined up in a straight line.
Note.
Gravity is not affected by the distance between objects. Gravity is affected by mass.

The larger the object,
the greater the mass,
the greater the gravitational pull.
What is a rotation?
A rotation is one full spin around an axis.
What is a lunar eclipse?
A lunar eclipse occurs when the Earth passes between the sun and the moon.

The Earth casts a shadow on the moon.
How many days does is take Earth to travel around the sun?
It takes 365 days for the Earth to travel around the sun.

365 days = 1 year
What causes Tropical climates on Earth?
The tilt of Earth on its axis , as it revolves, and rotates, around the sun creates the Tropical climate.
The Tropical climate receives the sun's full rays over a smaller area of Earth creating a hotter (tropical)area.
How many degrees is the tilt of Earth on its axis?
Earth tilts on its axis 23 degrees.

Earth's 23 tilt never changes.