Earth’s Motions Guided notes
Earth’s Motions
______, ______, and ______
Rotation - Earth turning or ______on an ______
· The Earth rotates on its axis from W to E or ______!
Effects of Earth’s rotation…
· We experience______as our location on Earth turns to the sun and night as it turns ______from the sun
· When we look south, the Sun, stars, planets, & constellations appear to rise in the ______and set in the ______
· Star trails look different in the northern sky than they do in the southern sky because:______
______
______
Effects of Earth’s Rotation: Coriolis effect
· Because the Earth is ______at the equator, Earth rotates ______at the equator than it does at the poles
· In the Northern Hemisphere winds, currents, airplanes, etc. appear to deflect to the right because ______.
· Plane flights - pilots and navigators must compensate for objects veering to the ______
· Space flights - Creates special problems for astronauts in space
· Winds- Uneven ______of the atmosphere causes winds to blow from areas of ______pressure to areas of ______pressure
· Distribution of ______ - If not for the ______caused by the rotating Earth, the equator would get constant rain and north & south would be deserts
Evidence that Earth Rotates: the Foucault Pendulum
· A ball swinging back and forth on a string is called a ______.
· In 1851, French scientist Léon Foucault observed that his pendulum seemed to ______.
· Forces acting on a pendulum:
o ______causes it to swing straight out (Newton’s______Law of Motion)
o ______pulls it back ______(Newton’s Law of Gravity)
o Air resistance makes it swing in ______arcs (Friction is a force that acts against inertia)
Pendulum as Evidence that Earth rotates:
· There is ______acting on the pendulum to make its plane of oscillation rotate
· The pendulum seems to change its path during the day, but actually it is the ______ beneath it that changes, being twisted around by the daily ______of earth.
· At the north pole the apparent rotation would be a full ______of 360 degrees each day, or about ______degrees per hour
Other evidence of Earth’s rotation:
· Astronauts have observed Earth’s rotation from space!
Periods of Rotation of other Planets
· Which two planets have the longest periods of rotation?
· Which planet has the shortest?
· Which planet’s period of rotation is almost the same as Earth’s?
Revolution
· Earth revolves around the ______at an average speed of about 107,000 km/hr or 30 km/sec
Earth’s Orbit
· We are closer to the Sun at ______(147 million kilometers) on about January 3rd and a little further from the Sun (152 million kilometers) at ______on July 4th
Evidence of Earth’s Revolution: Changing ______
· As Earth moves along its orbital path, we face the sun from a different ______and we view different areas of space at ______
· Most of the constellations we see in the summer are ______in the night sky during the winter.
· This is evidence that Earth has ______locations in space!
Other Planets revolve on the same ______as Earth
Revolutions of other Planets
· According to Kepler’s 3rd law, what is the correlation between a planet’s distance from the sun and its period of revolution?
______
Understanding Orbital Motion: The universal law of gravity allows us to understand orbital motion of planets and moons:
· Earth and moon attract each other through ______.
· Since Earth is much more ______than the moon, the moon’s effect on Earth is ______.
· The moon’s ______would cause it to move in a ______line, but…
· Earth’s gravitational force constantly ______the moon ______Earth
· Gravity is constantly ______the moon’s direction of motion, holding it on its almost circular ______.
Precession
· Earth’s “______” on its axis
· Takes ~26,000 years to complete one wobble
What causes Precession?
· The Earth is slightly ______
o it bulges in the middle
o ~0.34% larger at equator due to its ______and the fact that it is not completely rigid.
· The Sun and Moon exert ______gravitational forces on the Earth, pulling harder on the ______side of the bulge than on the far side. (gravity weakens with ______)
Consequences of Precession
· What happens as one consequence of precession?
______
______
______
Earth’s Motions and Time
· There are various ways to define units of time like a day or a year…
o Sidereal (or star) day:
o It takes the earth 23 hours and 56 minutes to rotate once with respect to the ______
o Solar day
o During this time, the earth has ______a bit along its ______around the Sun. So…
· It takes about 4 minutes longer for the ______to return to the same position in the sky
· Because we use the ______day, the stars rise and set 4 minutes ______each day.
Focus Questions:
How do the motions of the Earth affect our observations?
How are Earth’s motions related to our definition of time?