Astronomy
Ch. 19 Earth, Moon, and Sun
Name_______________________
Objectives
Identify the effects of Earth’s rotation and revolution.
Explain the causes of the seasons on Earth.
Days and Years
Astronomy is the study of the _________, ___________and other objects in space.
Rotation
Axis - the imaginary __________ that passes through Earth’s _________ and the North
and South __________.
Rotation - the spinning of __________ on its axis.
A point on the equator rotates at about _____________ km per hour.
Earth’s rotation on its axis causes ______________________________.
Earth rotates _____________.
It takes ____ hours to rotate once on its axis. This is called a day.
Revolution
Earth also travels around the ________.
Revolution - the movement of one ____________ around another object.
Earth’s orbit is an ________ shape.
Calendars
The Egyptians counted the number of days between Sirius ________, which was about
365.
Earth’s orbit around the sun is about __________ days.
Four years of 365 1/4 days each can be approx. by taking 3 years of 365 days and a
__________ year of 366 days. This is known as _________year.
On a leap year, one extra day in February is added for _____ days.
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 _____.
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
____months of 30 to 31 days and February with 28 or 29 days.
Seasons on Earth
Most places have four seasons: ________, spring, _______________, and autumn.
Earth’s Tilted Axis
Earth has seasons because its axis is _____________ as it move around the sun.
Earth in June
The _________ end of Earth’s axis is tilted toward the sun. It is summer in the
______________ Hemisphere and winter in the Southern Hemisphere.
Earth in December
The __________ 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 (______________).
Winter solstice - shortest day of the year (_______________).
Both of these are in the Northern Hemisphere and the opposite in the Southern
Hemisphere.
Earth in March & September
Neither hemisphere is ___________ toward or away from the sun. So the days and
nights are in an ___________________ which is equal.
Earth in March and September
Vernal equinox, or ____________ equinox, occurs around ______________ and is the
first day of spring.
Autumnal equinox, or ________ equinox, occurs around _______________ and is the
first day of fall.
19.2 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.
Motions of the Moon
The moon revolves around _____________ and rotates on its own axis.
It takes __________ days to revolve around Earth.
The same side of the moon always _____________ the Earth.
Phases of the Moon
Phases of the moon are seen by the _____________ of the sun on the moon’s surface.
The different shapes of the moon you see from Earth are called ___________. The
moon goes through its whole set of phases each time it revolves around the Earth, about
once a ___________.
What Causes Phases?
Phases are caused by changes in the relative ____________of the moon, Earth, and the
sun.
The Cycle of the Phases of the Moon
Eclipses
When the moon’s __________ hits Earth or Earth’s shadow hits the moon, an eclipse
occurs.
Two types of eclipses:
_____________ and_______________
Solar Eclipses
During a ________ 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 _________and the _______,
blocking the sunlight from reaching Earth.
It is really a new moon that blocks your view of the sun.
Total Solar Eclipses
Umbra - the ______________ 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 _________ is visible.
It is not safe to look at a partial _____________.
Lunar Eclipses
A lunar eclipse occurs at a _________ moon when Earth is between the moon and the
sun. Earth blocks sunlight from reaching the ______________.
Total Lunar Eclipse
When the moon is in Earth’s ___________, you see a total lunar eclipse. You are more
likely to see a total lunar eclipse than a total ___________ eclipse.
Partial Lunar Eclipses
Occurs when the moon passes partly into the ___________ 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 _______ tides and two _______ tides occur daily, over 24 hours.