Unit 5: The Solar SystemLesson 3: What holds the

moon and planets in place?

Vocabulary #1

Orbit: › The path that one body takes in space

as it revolves around another body

Vocabulary #2

Elliptical:› Oval shaped

Vocabulary #3

Inertia:› The property of matter that keeps an object at rest or moving in a straight line

Vocabulary #4 Gravity:

› The attraction that pulls objects toward Earth.

The Path of a Planet Around the Sun

The Earth revolves around the Sun in an elliptical orbit.

The moon revolves around the Earth in an elliptical orbit.

2 Properties that hold the Moon and Planets in Orbit Inertia:

Keeps objects moving in a straight line unless it is pushed or pulled by some force.

Gravity: the attraction that pulls objects toward Earth.

FACTS ABOUT THE MOON

Both Earth & the moon rotate as they revolve. The same side of the moon always faces Earth. The side we can’t see is called the far side of the

moon. The moon only reflects light from the Sun.

PHASES OF THE MOON

Gravity in Space When inertia and gravity are balanced (as

they would be in space), we see things as “floating”.

The shuttle is actually “falling” around Earth at a constant speed which causes a weightless environment.

Online Resources

http://www.youtube.com/watch?v=h0hmnX91SD0 phases of the moon rap (3:43)

http://www.youtube.com/watch?v=dOy5T6hRhpk&feature=related phases of the moon (3:42)

http://www.youtube.com/watch?v=exIpL0Uhr_k&feature=related moon rotation (1:00)

http://www.youtube.com/watch?v=XHL1opjFR7Y astronauts weightless in space (2:34)