Station Time-Earth Motions:
The Motion What It Is What It Causes Picture / Diagram
Rotation (Ro-tay-shun)
Tilt of the Earth
Revolution (Rev-o-lew-shun)
Precession (Pre-cess-shun)
Nutation (New-tay-shun)
Rotation
Rotation •Rotation means an object spins on it’s axis (like a basketball on someone’s finger)
•Takes about 24 hours for 1 rotation, and we call that a “day”
•Rotation causes day and night
The earth rotates on its axis.
• Rotates = spins.
• The earth makes 1 full rotation every 24 hours.
•We have day and night because of the Earth’s rotation.
Why does the Earth spin?
http://www.youtube.com/watch?v=TQxeutcYP6I
Tilt of the Earth
Tilt of the Earth • The Earth is tilted at
23.5⁰
• The tilt of the Earth causes our seasons
• When tilted towards the Sun it’s summer, when tilted away from the Sun it’s winter
-When you tilt/ lean towards the Sun, you get more light = Summer -When you tilt/ lean away from the Sun, you get less light = Winter
Fast Fact: Right now (in the winter) we’re closer to the Sun
than during the summer!
Distance from the Sun makes no difference to the seasons
Revolution
Revolution •The Earth’s orbit around the Sun is an oval/ ellipse shape, and that trip around the sun is revolution.
•Each revolution takes about 365 1/4 days (rotations), and we call this a “year”
•Every 4 years we have a leap year to combine all ¼ days
Revolution and distance from the Sun HAS NO IMPACT ON THE SEASONS!!!
The Earth also revolves around the sun in an elliptical orbit.
The earth makes one full revolution
around the sun every 365.25 days.
365 days = 1 year
You get one birthday each revolution
Precession
Precession Precession – A 26,000 year cycle where the
direction the North Pole Points changes ( a change in the direction of Earth’s
axis)
It looks like a top spinning on it’s axis
Precession • Precession is the circular
movement of where the north pole points.
• Causes a change in what we see as the North Star
• Imagine a top wobbling as it slows down, that is similar to the Earth’s precession
Precession The direction this axis of a planet is
pointing in will change, but the tilt will
not change.
This will change the stars near the
pole but will not change the seasons
(as long as the angle of the tilt, 23.5 in
the case of Earth, stays the same)
Precession Videos:
What does precession look like?
https://www.youtube.com/watch?v=Dw4Xhw4q4ec&index=10&list=PLF6MBJeQzCk3udD
ZYRye0bxtUEH2Q4UAI
http://www.youtube.com/watch?v=0qHjtp4cdCA
Nutation
Nutation • Nutation is a
wobbling motion the Earth makes while rotating and orbiting the sun, it is caused by gravity from the moon.
• Changes the tilt by a degree
• 19 year cycle
• “The Wobble”
Nutation • An 18.6 year cycle
• Causes a wobble in precession
• Helps increase the strength of tides on Earth
Nutation
Nutation happens when the axis of a
planet starts to wobble (do the wobble!)
The angle of the axis will change during
nutation ½ degree one direction or the
other
Nutation happens over the course of 18
years
Nutation is a direct result of the moon (or
moons) of a planet
