Earth’s relative motion
1.
2.
3.
4.
5.
Kepler’s 1st law states that planetary orbits
are _________________ shapes?
Kepler’s 2nd law states that 2 equal intervals
of time an imaginary line connecting a planet
and the sun will sweep an equal amount of
___________?
Kepler’s third law states that the innermost
planets orbit ______________________ than
the outermost planets.
Rotation is the earth spinning on it’s
_________________.
One trip around the ______________ is called
a revolution.
 EEn.1.1
Explain the Earth’s role as a body
in space.

EEn.1.1.1 Explain the Earth’s motion through
space, including precession, nutation, the
barycenter, and its path about the galaxy.
 Explain relative motion of the Earth in the solar
system, the solar system in the galaxy, and the
galaxy in the universe—including the expanding
nature of the universe; Orbital motion (Earth
around the Sun- once/year, seasons depend upon
an approximate 23.5 degree tilt); Rotation around
our axis (day/night,)
 How
do galaxies and planets move in the
universe?
 Rotation

Turning or spinning of a body on its axis
 Revolution

Motion of a body along a path around some point
in space
 Precession

Slight movement of Earth’s axis

26,000 years
Prove Earth is Rotating? OK!
 Results


in day and night
24 hours
1,667 km/hr (1,036 mi/hr)
 Earth
moves around the sun in an elliptical
orbit


Speeds around 107,000 km/hr (66,500 mph)
Average distance is 150 million kilometers
 Perihelion
is the point where earth is closest
to the sun
 Aphelion is the point where earth is farthest
from the sun
Earth's Seasons
 Earth’s


axis is tilted about 23.5º on its axis
This tilt brings the sun 23.5º south of the equator
on the winter solstace
This tilt bring the sun 23.5º north of the equator
on the summer solstace
Precession and polar shift
 Direction
which earth’s axis points changes
very slowly over time without a change in tilt

Takes about 26,000 years to complete one period
 Currently
the axis points toward Polaris
making it the North Star, in 14,000 years
Vega will be the North Star.
Earth's not orbiting the sun?!
 Earth
accompanies the sun as the entire solar
system speeds toward a distant star, Vega
 The sun revolves around the galaxy


Over 230 million years
At 250 km/sec
 Now
Earth is approaching our nearest
galactic neighbor, Andromeda
 Earth’s





only natural satellite
Orbit’s Earth in one month
When viewed from the North Pole, the orbit is
counterclockwise
Average distance is 384,401 kilometers
Point close to the Earth is Perigee
Point farthest from Earth is Apogee
Moon Phases
supermoon
 Phases
are the
amount of moon that
appears lit
 Half of the moon is
always illuminated
 Phases result from
the motion of the
moon and the
sunlight reflected
from its surface
 Every 29.5 days
tidal mystery
bay of fundy
Daily elevation
changes of the ocean
surface.
 Rhythmic
 Caused by
gravitational pull of
the moon



Atmosphere and
ocean are fluids and
free to move due to
this force.
The sun is further
away resulting in less
tug
gyroscope demo
 The
moon pulls on Earth and Earth pulls on
the moon
 This pull causes the Earth to wobble on its
axis by about ½ a degree.

Changing in the tilt of the Earth’s axis
 How
does this differ from precession?
barycenter animation
barycenter
 Point
between 2 or more objects where they
balance each other

Point where 2 celestial bodies orbit each other
 When
a moon orbits a planet or a planet
orbits a star, both are actually orbiting a
point outside the center of the larger body.

The moon and earth actually orbit a spot about
1,710 km below earth’s surface.
 Not
a true sphere
 Called an oblate spheroid, geoid, or ellipsoid
 Not
equal throughout
 Poles are squished making a bulge at the
equator
 Diameter and circumference are greater at
the equator than at the poles.
 Earth’s
rotation and gravity
 Gravity pulls on the mass causing it to
contract
 Rotation causes earth to flatten due to
centrifugal force

The force that causes objects to move outward,
away from the center of gravity
 We
call this the coriolis effect
coriolis effect
Topography- study of
surface shape and
feature
 On a global scale this
difference is very
small
 Mt. Everest is about
8,850 m above sea
level
 The Mariana Trench is
about 10,900 m below
sea level
 The difference is only
about 19,000 m or 12
mi
