Transcript Ch. 19 Earth, Moon, and Sun

Astronomy
Ch. 19 Earth, Moon,
and Sun
This amazing
Earthrise above
the moon's
horizon was seen
by astronaut
Michael Collins in
the Apollo 11
moon orbiter
Columbia.
Objectives
Identify the effects of Earth’s
rotation and revolution.
Explain the causes of the
seasons on Earth.
19.1 Earth in Space
Discover
Activity - p.
636
Why Does
Earth Have
Day and Night?
Introduction
 Egyptian farmers planted
their crops after the floods
every year. They noticed
that the star Sirius
became visible before the
floods. That’s when they
could start predicting the
floods.
 The Egyptians were the
first people to study the
stars.
Days and Years
Astronomy is the
study of the moon,
stars, and other
objects in space.
Rotation
 Axis - the
imaginary line
that passes
through Earth’s
center and the
North and South
poles.
 Rotation - the
spinning of Earth
on its axis.
 A point on the
equator rotates at
about 1,600 km
per hour.
Rotation
Earth’s rotation on its axis
causes day and night.
Earth rotates eastward.
It takes 24 hours to rotate
once on its axis. This is called
a day.
Revolution
Earth also travels around the
sun.
Revolution - the movement of
one object around another
object.
Earth’s orbit is a oval shape.
Calendars
The Egyptians counted the number of
days between Sirius stars which was
about 365.
Earth’s orbit around the sun is about
365 1/4 days.
Four years of 365 1/4 days each can be
approx. by taking 3 years of 365 days
and a fourth year of 366 days. This is
known as leap year.
On a leap year, one extra day in
February is added for 29 days.
Calendars
Dividing the year into smaller parts
(months) was difficult.
Early people used the moon cycle
which is 29 1/2 days but this only
added up to 354.
The Egyptians had a plan to have 12
months of 30 days and 5 extra days.
The Romans borrowed the calendar
and devised the one that we have
today with 11 months of 30 to 31
days and February with 28 or 29
days.
Seasons on Earth
Most places
have four
seasons:
winter, spring,
summer, and
autumn.
Earth’s Tilted Axis
Earth has
seasons
because its
axis is tilted as
it move around
the sun.
Earth in June
 The north end of
Earth’s axis is
tilted toward the
sun. It is
summer in the
Northern
Hemisphere and
winter in the
Southern
Hemisphere.
Earth in December
The south end
of Earth’s axis
is tilted toward
the sun. It is
summer in the
Southern
Hemisphere
and winter in
the Northern
Hemisphere.
Both in June and
December
Summer solstice - longest day
of the year (June 21).
Winter solstice - shortest day
of the year (December 21).
Both of the these are in the
Northern Hemisphere and the
opposite in the Southern
Hemisphere.
Earth in March &
September
Neither
hemisphere is
tilted toward or
away from the
sun. So the days
and nights are in
a equinox which is
equal.
Earth in March and
September
Vernal equinox, or spring
equinox, occurs around March
21 and is the first day of
spring.
Autumnal equinox, or fall
equinox, occurs around
September 23 and is the first
day of fall.
Plants and Animals
Plants and animals are effected by
the amount of day light hours.
In the spring and summer, plants
grow, animals feed on the plants,
insects and animals get more food.
In the winter, animals go dormant
and birds travel to warmer climates
to find food.
Reasons for the
Seasons
Lab
Books, Styrofoam balls
and flashlights.
Phases, Eclipses, and
Tides
Objectives
Describe the causes of the
moon’s phases.
Explain what causes solar and
lunar eclipses.
Identify the cause of the tides.
Engage/Explore
When does the moon appear?
 Moon Rise and Set
Discover Activity
How Does the
Moon Move?
Quarter &
penny
P. 646
Motions of the Moon
The moon revolves around
Earth and rotates on its own
axis.
It takes 27.3 days to revolve
around Earth.
The same side of the moon
always faces the Earth.
Phases of the Moon
Phases of the moon are seen by
the reflection of the sun on the
moon’s surface.
The different shapes of the moon
you see from Earth are called
phases. The moon goes through
its whole set of phases each time it
revolves around the Earth, about
once a month.
What Causes Phases?
Phases are caused by changes
in the relative positions of the
moon, Earth, and the sun.
P. 648
The Cycle of the Phases
of the Moon
Eclipses
When the moon’s shadow hits
Earth or Earth’s shadow hits
the moon, an eclipse occurs.
Two types of eclipses:
solar and lunar
Solar Eclipse
Solar Eclipses
During a new moon, most of the
time the moon is a little above or
below the sun in the sky.
A solar eclipse occurs when the
moon passes between Earth and
the sun, blocking the sunlight from
reaching Earth.
It is really a new moon that blocks
your view of the sun.
Solar Eclipses
Total Solar Eclipses
Umbra - the
darkest pat of
the moon’s
shadow that is
cone-shaped.
The point of
the cone can
reach a small
part of Earth’s
surface.
Partial Solar Eclipses
 Penumbra - larger
part of the
shadow which is
more visible on
Earth. During a
partial eclipse,
part of the sun is
visible.
 It is not safe to
look at a partial
eclipse.
Solar Eclipse
August 11, 1999
Lunar Eclipses
A lunar eclipse
occurs at a full
moon when
Earth is
between the
moon and the
sun. Earth
blocks sunlight
from reaching
the moon.
Total Lunar Eclipse
 When the moon
is in Earth’s
umbra, you see a
total lunar
eclipse. You are
more likely to see
a total lunar
eclipse than a
total solar eclipse.
Partial Lunar Eclipses
 Occurs when the
moon passes
partly into the
umbra of Earth’s
shadow. The
edge of the
shadow appears
blurry and you
can watch it pass
across the moon
for up to two or
three hours.
Tides
Two high tides and two low
tides occur daily, over 24
hours.
19. 3 Rockets and
Satellites
19.4 Earth’s Moon
The End of Ch. 19