Transcript Precession, Nutation and Tides

Lesson 4
The Man in the Moon
Precession and Nutation
Think About It…
How would Earth be different
if it did not have a moon?
The Moon’s orbit is tilted 5°…
http://earthsky.org/astronomy-essentials/what-is-the-ecliptic
Precession
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Precession is…
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One full cycle of
precession takes…
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the wobble in Earth’s
rotational axis.
26,000 years!
The force that causes
precession is…

the sideways pull from the
Moon’s gravitational force
on Earth.
Precession…
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Our current north star
is…
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Polaris
In about 12,000 years,
our new north star will
be…

Vega
http://www.wwu.edu/skywise/a101_precession.html
A New North Star and Our
Seasons…
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Winters in the N. hemisphere will be…
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colder (Earth will be farthest from the Sun in
July – our new winter!)
Summers in the N. hemisphere will be…
warmer (Earth will be closest to the Sun in
January – our new summer!)
 Next slide…

A New North Star and Our
Seasons…
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter16/precession.html
Nutation
Small wobble in the precession of
Earth’s axis.
It is caused by the 5 degree tilt of the
moon’s orbit from the plane of earth’s
orbit around the Sun.
Tides
Lesson 5
Tides…
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Tides are…
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High tide…
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the periodic rise and fall of sea level.
Highest level to which the water rises
Low tide…
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lowest level of the water
http://www.amusingplanet.com/2012/03/tides-at-bay-of-fundy.html
Tides: Bay of Fundy…
Low
Tide
High
Tide
http://www.srh.noaa.gov/jetstream/ocean/fundy_max.htm
The Cause of Tides…

Tides are caused by…
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The Moon and the Earth experience unbalanced
gravitational and centrifugal forces due to the
fact that they…
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orbit around their barycenter (Remember that word?!)
These forces generate…
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the gravitational attraction among Earth, the Moon,
and the Sun.
tidal bulges on opposite sides of Earth.
See next slide…
Tides…
http://mail.colonial.net/~hkaiter/Moon_Phases_Tides.html
Tide Simulation:
http://astro.unl.edu/classaction/animations/lunarcycles/tidesim.html

The Moon and the Earth experience
unbalanced gravitational and centrifugal
forces due to the fact that they…

orbit around their barycenter (Remember that
word?!)