THE EARTH, GRAVITY,
TIDES, AND ECLIPSES
CHAPTER 19
SECTION 1 THE EARTH IN SPACE
What causes night and day? – The spin of the earth on its axis.
The Earth moves through space in 2 major ways:
An imaginary line that passes through Earth’s center and North
and South poles is called an axis.
Rotation- the spinning of a planet on its axis. (causes day and
night)
Revolution- The movement of one object around another. (the
earth around the sun-its orbit)
SEASONS
 Summer, Fall, Winter, Spring - seasons
 What causes them?
 How the sunlight hits the Earth’s surface
 http://www.brainpop.com/science/weather/seasons /
 Earth has seasons because it is tilted as it revolves
around the sun.
http://ww
w.youtube
.com/wat
ch?v=Dui
QvPLWziQ
Section 2 Gravity and Motion
https://www.youtube.com/watch?v=mezkHBPLZ4A (what is gravity?
4. Gravity is the force of attraction between two objects. The
two factors that determine the strength of gravity are mass and
distance.
https://www.youtu
be.com/watch?v=
p_o4aY7xkXg
(gravity in 1min)
5. What keeps the earth and other objects in orbit? –
the combination of inertia and gravity.
6. What is inertia? –
the resistance to change in motion. (Newton’s 1st law of motionan object will stay at rest and an object will stay in motion until
acted on by another force) https://www.youtube.com/watch?v=u6rbrFgudLg
(inertia)
7. What is the difference between weight and mass? –
Mass is the amount of matter in an object. Weight is the
force of gravity on an object.
https://www.youtube.com/watch?v=SegMt7sa42E
What is the difference between weight and mass?
Section 3 Phases, eclipses, and tides
8. What causes the phases of the moon? –
the changing relative positions the moon, Earth and sun.
9. What factor determines what phase of the moon you will see? How
much of the sunlit side of the moon faces Earth.
https://www.youtube.co
m/watch?v=79M2lSVZiY
4 (moon phases rap)
Eclipses
10. Describe an eclipse- When the moon’s shadow hits earth or
earth's shadow hits the moon, an eclipse occurs.
11. Name the two types of eclipses- Solar and Lunar
12. Describe in detail a solar eclipse: When the moon passes directly
between E and Sun blocking light and casting a shadow.
13. Umbra- the darkest part of the moons shadow
14. Penumbra- the area of the shadow that is less dark than the
umbra.
15. Describe a lunar eclipse: What the E passes
between the sun and moon
Tides
16. What are tides and how are the caused? The rise and fall of
water due to gravity. Caused by the gravity of the sun and
especially the moon.
17. Why do you think it is important for people to know the
tide cycles?
Bay of Fundy Canada
Highest tidal range in the world. (Extreme high and low)
Oceanographers attribute it to tidal resonance. The time it takes a
large wave to go from the mouth of the bay to the inner shore and
back is practically the same as the time from one high tide to the
next.