Lesson 3 The Third Rock from the Sun! (Continued)

Lesson 3Lesson 3

The Third Rock from the Sun! The Third Rock from the Sun! (Continued)(Continued)

Think About It…Think About It…

How would Earth be different How would Earth be different if it did not rotate on its if it did not rotate on its

axis?axis?

Earth’s Rotation…Earth’s Rotation…

Day and night are caused by…Day and night are caused by…The rotation of the Earth on its axisThe rotation of the Earth on its axis

Earth spins…Earth spins…15 degrees each hour15 degrees each hour

There are There are 360360 degrees in a circle (the degrees in a circle (the circumference of Earth).circumference of Earth).

360 divided by 15 is 360 divided by 15 is 2424 so there are so there are 2424 hours in a day!hours in a day!


The exact amount of time it takes Earth to The exact amount of time it takes Earth to spin one time on its axis is…spin one time on its axis is…23.9345 hours23.9345 hours

If an Earth day was 5832.5 hours long (like If an Earth day was 5832.5 hours long (like that of Venus!) then…that of Venus!) then… It would take 243 days for Earth to spin one It would take 243 days for Earth to spin one

time on its axis!time on its axis!Our day and night would be much longer! Our day and night would be much longer!

(It’d get really hot and really cold!)(It’d get really hot and really cold!)


The exact amount of time it takes Earth to The exact amount of time it takes Earth to spin one time on its axis is…spin one time on its axis is…23.9345 hours23.9345 hours

If an Earth day was 5832.5 hours long (like If an Earth day was 5832.5 hours long (like that of Venus!) then…that of Venus!) then… It would take 243 days for Earth to spin one It would take 243 days for Earth to spin one

time on its axis!time on its axis!Our day and night would be much longer! Our day and night would be much longer!

(It’d get really hot and really cold!)(It’d get really hot and really cold!)

Earth’s Rotation and Its Shape…Earth’s Rotation and Its Shape…

Earth’s rotation causes it to take the shape Earth’s rotation causes it to take the shape of an of an oblate spheroidoblate spheroid..

As Earth rotates on its axis, As Earth rotates on its axis, centrifugal centrifugal force causes the Earth’s mass to move force causes the Earth’s mass to move away from its center at the equator where away from its center at the equator where this force is greatest.this force is greatest.

There is a slight bulging at the There is a slight bulging at the equatorequator and and a slight squishing at the a slight squishing at the polespoles..

See next slide!See next slide!


Simulation: http://www.cleonis.nl/physics/phys256/equatorial_bulge.php


http://www.cleonis.nl/physics/phys256/equatorial_bulge.php

Earth’s Orbit and Seasons…Earth’s Orbit and Seasons…

The ecliptic The ecliptic is…is…the plane in the plane in

which Earth which Earth orbits around orbits around the Sunthe Sun

http://en.wikipedia.org/wiki/Ecliptic

Earth’s Orbit and Seasons…Earth’s Orbit and Seasons… Remember, Earth’s axis is…Remember, Earth’s axis is…

the imaginary line that cuts through the north and the imaginary line that cuts through the north and south poles. south poles.

The tilt of Earth’s axis relative to the ecliptic is 23.5 The tilt of Earth’s axis relative to the ecliptic is 23.5 degrees. degrees.

http://republicanredefined.com/2010/03/02/chile-quake-shifted-earths-axis-and-made-days-shorter/

The Seasons!The Seasons!

http://www.exploratorium.edu/ancientobs/chaco/HTML/TG-shadows.html


What causes summer in the northern What causes summer in the northern hemisphere? hemisphere? when it is tilted toward the Sun during Earth’s when it is tilted toward the Sun during Earth’s

orbitorbitWhat causes winter in the northern What causes winter in the northern

hemisphere?hemisphere?when it is tilted away from the Sun during when it is tilted away from the Sun during

Earth’s orbitEarth’s orbit


The seasons in the northern and southern The seasons in the northern and southern hemispheres are…hemispheres are…opposites!opposites!

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Lesson 3 The Third Rock from the Sun! (Continued)