AstronomyName______
Ch. 19 Earth, Moon, and Sun
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.