Download Movements of Earth

Movements of Earth
Chapter 26 section 2
Objectives
• Describe several lines of evidence for Earth’s
___________________.
• Explain how the change in the apparent positions of constellations
provides evidence of Earth’s
_______________________________.
• Summarize how Earth’s rotation and revolution provide a basis for
______________________.
• Explain how the ________________________
_________________________ cause seasons.
The Rotating Earth
• ______________- the spinning of Earth on its axis
• How do we know?
Evidence of Earth’s Rotation
• Day & Night
• Foucault Pendulum
• Coriolis Effect
The Revolving Earth
• ________________- the motion of a body that travels
around another body in space
• The Earth travels around the sun at an average speed of
29.8 km/s. One complete revolution takes ____________
days.
Definitions
• ___________- the path that a body follows as it travels
around another body in space
• __________- a closed curve whose shape is determined
by 2 points (foci) within the ellipse
(__________________________)
• _____________________- the point in an orbit where the
planet is closest to the sun
• _________________- the point in an orbit where the
planet is farthest from the sun
Constellations
• _________________- a group of stars that are organized into a
recognizable pattern
• Evidence of rotation- constellations appear to change position over
several _____________
• Evidence of revolution- constellations appear to change positions
over several _____________
Constellations’ Motion
Measuring Time
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Earth’s motion is the basis for measuring time.
___ rotation = ___ day = ____ hours
___ revolution = ___ year = _______ days
___ month used to be the time between successive full
moons = _______ days, BUT the number of full moons in a
year is not a whole number. A month is approximately
__________of a year.
Woops!
• If 1 revolution = 365¼ days, where does the ¼ day go?
• _____________- the year that contains 1 extra day every
___ years to account for the ¼ day. Created by Julius
Caesar. The extra day was added to the shortest month
(__________) by Augustus Caesar.
The Modern Calendar
• Developed by Pope Gregory XIII
• Century years (1700, 1800, 1900, 2000, etc.) are NOT
leap years unless they are evenly divisible by _________.
Time Zones
• _____________- the time when the sun is at its highest
point in the sky BUT
• Because of Earth’s rotation, the sun is at its highest point
in different places at different times. SO
• Earth’s surface is divided into ______ standard time zones
Time Zones
• Why 24?
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The Earth is basically spherical.
The circumference of a sphere = ______°.
_____° ÷ ____ = ____° per time zone.
Earth rotates at ____° per hour.
The time in each zone is one hour earlier than in the zone
to its east.
International Date Line
• ___________________________- line that runs from
north to south through the Pacific Ocean where the date
changes.
• When it is ____________ west of the IDL, it is
__________________ east of the IDL.
Daylight Savings Time
• ________________________________ - system where clocks are
set 1 hour ahead of standard time during the summer months
• Due to Earth’s tilt on its axis, ________ days are shorter than
__________ days, DST gives us an extra hour of useable daylight
and saves energy.
• Equatorial countries do not use DST because they have ≈
_________________ all year round.
The Seasons
• Earth’s axis is tilted at _______°. The axis always point
toward the north star. So, during revolution, the North Pole
sometimes tilts _____________________ and sometimes
tilts ____________.
• Seasons are not determined by
_________________________________. In fact, we are
___________ from the sun during our summer!
Seasonal Weather
• When the North Pole tilts _____________, the sun’s rays
strike the Northern Hemisphere directly—what season is
this?
• When it is summer in the Northern Hemisphere, what
season is it in the Southern Hemisphere? WHY?
Equinoxes
• During an equinox, the sun’s rays strike at a 90° angle
along the equator. _________
________________________________.
• ___________________ - Sept. 22/23, marks the beginning
of fall in the NH.
• ______________________ - March 22/23, marks the
beginning of spring in the NH.
Summer Solstice
• _______________- June 21/22, the North Pole is at its
greatest tilt toward the sun.
• It marks the beginning of _____________ in the NH.
• Longest day of the year in the NH.
• All areas of the globe above the Arctic Circle have
_________________ daylight.
Winter Solstice
• _____________________ - Dec. 21/22, the North Pole is
at its greatest tilt away from the sun.
• Marks the beginning of ______________ in the NH.
• Shortest day of the year in the NH.
• All areas of the globe above the Arctic Circle have
________________ darkness.
Objectives revisited
• Describe several lines of evidence for Earth’s rotation.
• Explain how the change in the apparent positions of constellations
provides evidence of Earth’s rotation and revolution.
• Summarize how Earth’s rotation and revolution provide a basis for
measuring time.
• Explain how the tilt of Earth’s axis and Earth’s movements cause
seasons.