Section 1: Earth in Space

1
Section 1Earth in Space

• How does Earth move in space?
• What causes the cycle of seasons on Earth?

2
How Earth Moves

• Earth moves through space in two major ways
  rotation and revolution.
• A revolution is the movement of one object around
  another. How long does one complete revolution
  of Earth around the sun take?
• Answer
• 365.25 days
• (1 year)
• Is the Earths orbit circular?
• No, it is an ellipse.

3
How Earth Moves

• The spinning of Earth on its axis is called
  rotation. As the Earth spins eastward, only half
  of the planet is facing the sun (day) while the
  other half is not (night).
• How long does it take the
• Earth to rotate once?
• Answer 24 hours (1 day)

4
Origin of Calendars

• A calendar is a system of organizing time that
  defines the beginning, length, and divisions of a
  year.
• Over the last 4000 years, they have been based on
  moon and star cycles, season changes, and sun
  position.

Egyptian calendar
What is a leap year?
An extra day added every 4 years.
Mayan Calendar
Stonehenge 1500 B.C.
5
Sunlight Striking Earths Surface

• Near the equator, sunlight strikes Earths
  surface more directly and is less spread out than
  near the poles.

6
Seasons on Earth

• Earth has seasons because its axis is tilted as
  it revolvesaround the sun. The axis is always
  tilted at what angle?

23.5 degrees
7
Common Misconception Alert!

• Although the Earth can be at different distances
  from the sun due to its ellipsoid orbit, this
  DOES NOT cause the changes in season. In fact,
  the Earth is farthest from the sun during our
  summer!

8
Seasons on Earth

• The height of the sun above the horizon varies
  with the season. It is at its lowest angle in
  winter and highest angle (more direct) in summer.

9
Section 2Gravity and Motion

• What determines the strength of the force of
  gravity between two objects?
• What two factors combine to keep the moon and
  Earth in orbit?

10
Gravity, Mass, and Distance

• The strength of the force of gravity between two
  objects depends on two factors the masses of the
  objects and the distance between them.

11
Gravity Versus Distance

• Reading Graphs
• What is the force of gravity on the rocket at the
  planets surface?

• Four million newtons

12
Gravity Versus Distance

• Reading Graphs
• What is the force of gravity on the rocket at a
  distance of two units (twice the planets radius
  from its center)?

• One million newtons

13
Gravity Versus Distance

• Drawing Conclusions
• In general, how does the force of gravity pulling
  on the rocket change as the distance between it
  and the planet increases?

• It decreases.

14
Gravity and Inertia

• Newton concluded that two factorsinertia and
  gravitycombine to keep Earth in orbit around the
  sun and the moon in orbit around Earth.

15
Section 3Phases, Eclipses,and Tides

• What causes the phases of the moon?
• What are solar and lunar eclipses?
• What causes the tides?

16
Motions of the Moon

• The changing relative positions of the moon,
  Earth, and sun cause the phases of the moon,
  eclipses, and tides.

How long does it take the moon to orbit the Earth?
29.5 days
17
Phases of the Moon

• The phase of the moon you see depends on how much
  of the sunlit side of the moon faces Earth.

18
The Moons Orbit

• The moons orbit is tilted about 5 degrees
  relative to Earths orbit around the sun.

19
Solar Eclipse

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

20
Lunar Eclipse

• During a lunar eclipse, Earth blocks sunlight
  fromreaching the moons surface.

21
Tides

• Tides occur mainly because of differences in the
  force of gravity between the moon and different
  parts of Earth.

22
Spring and Neap Tides

• When Earth, the sun, and the moon are in a
  straight line, a spring tide occurs (twice a
  month at new full moons).
• When the moon is at a right angle to the sun, a
  neap tide occurs (at 1st and 3rd quarter moons).

23
Section 4Earths Moon

• What features are found on the moons surface?
• What are some characteristics of the moon?
• How did the moon form?

24
The Moons Surface

• Features on the moons surface include maria,
  craters, and highlands.

25
The Moons Surface

• Maria (Latin for seas) Dark, flat areas first
  thought to be oceans, but actually huge ancient
  lava flows.
• Craters Large round pits caused by the impacts
  of meteoroids (NOT volcanoes).
• Highlands These are the mountains and crater
  rims that cover most of the moons surface.

Why do the maria have fewer craters than the
rest of the moon?
Most of the impacts occurred before the maria
formed.
26
The Moons Size

• The moon is 3,476 km in diameter, a little less
  than the distance across the contiguous Untied
  States. Its about ¼ the Earths diameter.

27
Characteristics of the Moon

• The moon is very dry and airless. Since it has
  no atmosphere, it has large variations in its
  surface temperature (from 130 degrees Celsius in
  direct sunlight to -180 degrees at night).
• The moon is made out of much of the same elements
  that make up the Earth such as oxygen, silicon,
  magnesium, potassium, nickel, sulfur among many
  others.
• Though its ¼ the diameter of Earth, it only has
  1/80th of the mass. This causes its gravity to
  be about 1/6 of what it is here on Earth.
• What would you weigh on Earth? Divide your weight
  by six.

28
The Origin of the Moon

• Scientists theorize that a planet-sized object
  collided with earth to form the moon.

29
The Origin of The Moon

• Moon Mysteries Part One