Transcript Earth’s Motions - Lumio's Science World

Earth’s Motions
ROTATION
PRECESSION
REVOLUTION
ROTATION

Earth spinning on its axis is called rotation.

The “AXIS” is an imaginary line
passing through Earth’s center
through the N. and S. Pole.

The N. Pole points toward
the star Polaris

The axis is tilted 23.5°
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DAY AND NIGHT

Counterclockwise rotation (In N.
Hemisphere)!
 Sun
(Celestial Sphere; stars) rise in the East and
set in the West.
 Time of Complete Rotation = ~24 hours
 Speed at Equator = ~1 mile every 3 seconds
= 1,038 miles per hour
{Ch.1}
Oblate Spheroid

Earth’s shape is considered to be the
shape of an ellipsoid.
 Earth
is wider than it is tall.
 Bulges at equator
 Flattened at Poles.
Evidence of Rotation
Foucault Pendulum
 The
pendulum is suspended
above Earth’s Surface.
 The Earth spins underneath pendulum.
 Pendulum
rotation.
seems to change direction because
(ch.8)
Solar vs. Sidereal

Solar Day (SYNODIC)
 The
time it takes Earth to rotate once with respect
to the sun. (Suns Highest point in sky to the next
highest point in sky).
 Time = 24 hours (mean time)

Sidereal Day
 The
time it takes the Earth to
rotate once with respect to a
reference star.
 One 360° Rotation
1-2: Globe rotates 360° - sidereal
 Time = 23 hr. 56 min.
1-3: Globe re-points to sun - synodic
1-2: Globe rotates 360° - sidereal
1-3: Globe re-points to sun - synodic
Precession

The slow gyration of a spinning body.
 Movement
 The
around a point or axis.
top does not fall over as long as it stays
spinning.
Earth’s Precession

The Earth “WOBBLES” on its axis once every
26,000 years.

Earths precession
moves opposite to its
rotation.

Earth’s axis will not straighten
due to its constant
rotation.
Moving Toward VEGA
Revolution

The movement of one object around another is
called revolution.

Earth revolves around the sun in a path called its
orbit (Counterclockwise direction).


1 revolution = 365.25 Days (LEAP YEAR?)
Rate of Revolution = 66,000 mph