Transcript Earth in Space

Earth’s Motions in Space
Topics that are covered:
1.
2.
3.
4.
5.
Geocentric Model
Heliocentric Model
Rotation
Revolution
Precession
Mrs. Degl
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Geocentric Model
Ptolemy (85-165) came up with this model.
This model of the solar system suggests that Earth is in the center
and it is stationary while the other planets, and the Sun, revolve
around it.
Is this correct?
Mrs. Degl
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Heliocentric Model
Nicolai Copernicus (1473-1543) came up with this.
Inner Planets ORRERY - NOT draw n to scale: Mercury, Venus, Earth, Mars
This model says that the Earth, and each of the other planets,
rotate on their own axis, while they revolve around the Sun.
This is the correct model of our solar system.
Mrs. Degl
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Mrs. Degl
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Rotation
The Earth rotates 15º of longitude every hour, from West to East.
There are a few proofs that the Earth rotates.
Mrs. Degl
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Proofs that the Earth rotates:
1. Sunrise/Sunset or Day/Night
2. Star Trails (the stars appear to move across the sky during the
night)
3. Coriolis Effect (objects in the air seem to curve before they land)
Cannons and arrows miss their targets when aimed straight
on.
Winds and ocean currents are also curved because of rotation.
http://daphne.palomar.edu/pdeen/Animations/34_Coriolis.swf
4. Foucault Pendulum/Free Swinging Pendulum
Mrs. Degl
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Can you find Polaris?
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Revolution
The Earth revolves around the Sun once every year.
How many days is that?
Mrs. Degl
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Proofs that the Earth revolves around the
1. Star shift
Constellations that are visible in one part of the sky during
one season are not going to be in the same part of the sky during
the following season. This is because the Earth is revolving
around the Sun and facing different parts of the night sky during
different seasons. Since there is 360 º in a circle, it takes about
360 days (@ 1 year) for the Earth to be facing the same part of
the sky again. That means that the positions of constellations in
the sky change by about 1º per night.
Mrs. Degl
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2. Doppler Effect
This is the distortion of a wave (light or sound) caused by
objects moving closer together or further apart from each other.
As the Earth moves towards stars, the light waves are compressed.
This is called a Blue shift. Blue is one of the shortest wavelengths.
As the Earth moves away from stars, light waves are stretched out.
This is called a Red Shift. Red is one of the longest wavelengths.
Mrs. Degl
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Precession
Polaris is not going to be the North Star forever.
Every 26,000 years, the Earth tips the other way, just like a
spinning top.
Scientists call this earth motion “Precession” or wobble.
Mrs. Degl
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