Chapter 12 Earth, Moon, and Sun
Section 1:
Earth in Space
How does Earth move in space?
What causes the cycle of seasons on Earth?
Chapter 12 Earth, Moon, and Sun
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 Earth’s orbit circular?
No, it is an ellipse.
Chapter 12 Earth, Moon, and Sun
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)
Chapter 12 Earth, Moon, and Sun
Origin of Calendars
A calendar is a system of
organizing time that defines the
beginning, length, and divisions of a
year.
Egyptian calendar
Over the last 4000 years, they have
been based on moon and star
cycles, season changes, and sun
position.
What is a leap year?
An extra day added
every 4 years.
Stonehenge 1500 B.C.
Mayan Calendar
Chapter 12 Earth, Moon, and Sun
Sunlight Striking Earth’s Surface
Near the equator, sunlight strikes Earth’s surface more
directly and is less spread out than near the poles.
Chapter 12 Earth, Moon, and Sun
Seasons on Earth
Earth has seasons because its axis is tilted as it revolves
around the sun. The axis is always tilted at what angle?
23.5 degrees
Chapter 12 Earth, Moon, and Sun
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!
Chapter 12 Earth, Moon, and Sun
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.
Chapter 12 Earth, Moon, and Sun
Section 2:
Gravity 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?
Chapter 12 Earth, Moon, and Sun
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.
Chapter 12 Earth, Moon, and Sun
Gravity Versus Distance
Reading Graphs:
What is the force of gravity on
the rocket at the planet’s
surface?
Four million newtons
Chapter 12 Earth, Moon, and Sun
Gravity Versus Distance
Reading Graphs:
What is the force of gravity on
the rocket at a distance of two
units (twice the planet’s
radius from its center)?
One million newtons
Chapter 12 Earth, Moon, and Sun
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.
Chapter 12 Earth, Moon, and Sun
Gravity and Inertia
Newton concluded that two factors–inertia and gravity–
combine to keep Earth in orbit around the sun and the moon
in orbit around Earth.
Chapter 12 Earth, Moon, and Sun
Section 3:
Phases, Eclipses,
and Tides
What causes the phases of the moon?
What are solar and lunar eclipses?
What causes the tides?
Chapter 12 Earth, Moon, and Sun
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
Chapter 12 Earth, Moon, and Sun
Phases of the Moon
The phase of the moon you see depends on how much of
the sunlit side of the moon faces Earth.
Chapter 12 Earth, Moon, and Sun
The Moon’s Orbit
The moon’s orbit is tilted about 5 degrees relative to Earth’s
orbit around the sun.
Chapter 12 Earth, Moon, and Sun
Solar Eclipse
A solar eclipse occurs when the moon passes directly between
Earth and the sun, blocking sunlight from Earth.
Chapter 12 Earth, Moon, and Sun
Lunar Eclipse
During a lunar eclipse, Earth blocks sunlight from
reaching the moon’s surface.
Chapter 12 Earth, Moon, and Sun
Tides
Tides occur mainly because of differences in the force of
gravity between the moon and different parts of Earth.
Chapter 12 Earth, Moon, and Sun
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).
Chapter 12 Earth, Moon, and Sun
Section 4:
Earth’s Moon
What features are found on the moon’s
surface?
What are some characteristics of the moon?
How did the moon form?
Chapter 12 Earth, Moon, and Sun
The Moon’s Surface
Features on the moon’s surface include maria, craters, and
highlands.
Chapter 12 Earth, Moon, and Sun
The Moon’s 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
moon’s surface.
Why do the maria have fewer craters
than the rest of the moon?
Most of the impacts occurred before the maria formed.
Chapter 12 Earth, Moon, and Sun
The Moon’s Size
The moon is 3,476 km in diameter, a little less than the
distance across the contiguous Untied States. It’s about ¼
the Earth’s diameter.
Chapter 12 Earth, Moon, and Sun
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 it’s 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.
Chapter 12 Earth, Moon, and Sun
The Origin of the Moon
Scientists theorize that a planet-sized object collided with
earth to form the moon.
Chapter 12 Earth, Moon, and Sun
The Origin of The Moon
Moon Mysteries Part One