Earth’s Movement
Rotation
Earth rotates on its axis once every 23 hours
and 56 minutes.
 What is another term we might use for
rotating?
 spinning
 Rotation on its axis causes what?
Day and night

How fast are we spinning?


467 m/s counterclockwise when viewed from above
the north pole
An animation of earth’s rotation and revolution.
Foucault's Pendulum Explained
 Foucault's Pendulum Chicago

Earth’s Shape
Earth is not a perfect sphere.
 Rotation of the planet has slightly flattened it
out, so it has a larger diameter at the equator
than at the poles.
 The equatorial diameter of Earth is 12,756 km,
its polar diameter is 12,713 km.

Revolution
Our revolution around the sun is also called
our orbit.
 The earth’s orbit is shaped like an ellipse.
 We revolve around the sun once every 365.24
days.
 What do we call that period of time?
 A year

Kepler’s Laws

1st law: each planet orbits the Sun in a shape
called an ellipse.

2nd law: An imaginary line sweeps equal
amounts of area in equal amounts of time
hence planets move fastest when they are
closest to the Sun
3rd Law: P (orbital period) squared equals a
(semimajor axis of the orbital ellipse) cubed.
Or P2 = a3

Mercury’s Orbit/Rotation

Compare Mercury’s orbit to Earth’s
Mercury's Orbit
Revolution Continued

The sun is not directly in the center of Earth’s
elliptical orbit.
perihelion/aphelion
Seasons
The perihelion and aphelion are not
responsible for the seasons but rather the tilt of
Earth’s axis.
http://astro.unl.edu/naap/motion1/animations
/seasons_ecliptic.swf

Seasons
Seasons



Summer solstice: the Sun is directly overhead at the
Tropic of Cancer.
Winter solstice: the Sun is directly overhead at the
Tropic of Capricorn
Equinox: “equal nights”; the axis is not pointed at the
Sun


Autumnal – the northern hemisphere is beginning to tilt
away from the Sun
Vernal – the northern hemisphere is beginning to tilt
toward the Sun
Precession
The wobble in Earth’s rotational axis.
 Currently the axis points toward Polaris – by
14,000 the axis will point toward Vega

In this alignment winter will occur in the northern
hemisphere when we are at aphelion so winters
will be very cold and summer will occur when we
are at perihelion so summers will be very hot.
 precession animation

Nutation

A small oscillation in the precession of earth’s rotation.
Barycenter

The point between two objects where they balance
each other.

Earth-Moon Barycenter video

Earth's Movement video
Tides
Periodic rise and fall of sea level
 Caused by the moon’s and to a lesser extent
the sun’s gravitational pull on the earth

Spring Tide
the largest tidal
ranges – differences
in high and low tide
 Occur when the
moon, sun and earth
are aligned or at the
full moon or new
moon phases

Neap tide
Lowest tidal range
 Occurs when the
moon is
perpendicular to the
earth sun alignment

http://www.youtube.com/watch?feature=play
er_detailpage&v=17jymDn0W6U
Earth
Solar System
Galaxy
Local Group
Local Supercluster
Universe
Formation of our Solar System
Nebula – a cloud of dust and gas
Nebular theory: the sun and planets formed from
a rotating disk of dust and gases.
 As the speed of rotation increased the disk
would flatten and matter became more
concentrated in the center which formed the
sun
 The growth of planets began as solid bits of
matter began to clump together
The Milky Way

http://www.youtube.com/watch?v=58fs5yI
8K9I&feature=fvwrel
Big Bang Theory
 Steady State Theory
 Inflation Theory




The most widely accepted theory for the
formation of our universe is the Big Bang Theory
first proposed in the 1930s.
Time began 12 -15 billion years ago when all the
matter in the universe exploded from a singularity
a dense point with a infinitely small volume.
As matter and energy began to move outward
gravity caused the matter to condense and form
galaxies.
The universe appears to be expanding.
 The Big Bang predicts that the composition
of the universe should be 75% hydrogen
and 25% helium which it is.
 The Big Bang explosion should have left
behind radiation. The Cosmic Background
Radiation was first detected in 1965.

Proposes that the universe looks the same
and has always looked that way
 Proposes that new matter is created and
added to the universe as it expands


proposes a period of extremely rapid
(exponential) expansion of the universe
prior to the more gradual Big Bang
expansion