Download Earth takes 365.24 days.

How does Earth move?
• Earth moves through space in two major
ways: rotation and revolution.
What is rotation?
• Spinning of Earth on its axis
(imaginary line that passes
through Earth’s center).
ROTATION
X
I
S
http://www.singularvortex.com/pictures/earth_axis.jpg
Car Lights at Night
Stars’ Light at Night
Earth’s rotation as seen in the stars.
http://jennifersaylor.files.wordpress.com/2006/09/startrails11h_hambsch_c90.jpg
How long does it take to rotate?
• Earth takes 23 hours and 56 minutes
(day).
• Mars takes 24 hours and 37 minutes (sol).
Our Body Clock!
Earth Axial Tilt
• Earth's axial tilt is
currently about
23.4°.
• The Earth rotates
from the west
towards east. As
viewed from North
Star or polestar
Polaris, the Earth
turns counterclockwise.
Martian Axial Tilt
• Of all the features of
Mars, its axial tilt is
most similar to Earth.
Mars’ tilt is 25 degrees,
just a fraction away
from the Earth’s 23.5
degrees.
• Most of them also
rotate in an eastward
direction, but three of
them (Venus, Uranus
and Pluto) rotate to
the west.
Rotation!
Why is the Earth’s axis tilted?
• During the formation of the
• EXT: (your experience,
solar system, four and a
new question, WU
half billion years ago, dust
answered)
and rocks were floating
around and crashing into
each other. That debris
eventually came together
to form the planets.
• This process was a little
messy, and the Earth
probably experienced
some big impacts that
eventually tilted the axis.
What is revolution?
• One object moving around
another.
• Follows a path or orbit.
REVOLUTION
R
B
I
T
http://gb.fotolibra.com/images/previews/31408earths-orbit-around-the-sun-illustration.jpeg
What shape is the Earth’s orbit?
• The Earth’s orbit around the
sun is shaped like an ellipse.
• An ellipse is a slightly flattened
circle.
• Mars also has a very elliptical
orbit. Because of this, the
difference between its closest
and most distant point along
its orbit vary by 19%. This
extreme difference makes the
planet’s southern winters long
and extreme. The northern
winters aren’t as long or cold.
Revolution!
• All of the planets move around the Sun
in the same eastward direction.
• Earth takes 365.24 days.
• Mars takes 687 earth days.
Distance from the sun
• Earth is 149, 600, 000 km from the sun.
• Mars is 227,940,000 km from the sun.
Average Temperature
• The average temperature on Earth is about
16 C (61 degrees F). But temperatures vary
greatly around the world depending on the
time of year, ocean and wind currents and
weather conditions. Summers tend to be
warmer and winters colder.
• On average, the temperature on Mars is
about -80 degrees F (-60 degrees C). In
winter, near the poles temperatures can get
down to -195 degrees F (-125 degrees C).
Orbital plane tilt
“Dance, Dance, Revolution”
• Everybody up!
http://picture-book.com/files/userimages/1896u/ballerina-new-lines.jpg
How does sunlight strike the Earth’s surface?
• Near the equator, sunlight strikes Earth’s
surface more directly and is less spread out
than near the poles.
• Please draw
this picture
in your notes.
EXT:
What causes the seasons?
• Earth has seasons because Earth is tilted on it’s axis
as it revolves around the sun – not because it’s orbit
brings it closer to or farther from the sun!
Seasons of Mars
Because of this tilt, Mars has seasons, just like the Earth. Of course,
since Mars takes twice as long as Earth to orbit the Sun, the seasons
are twice as long.
What is equinox and solstice?
• Solstice = North
or south end is
tilted toward the
sun.
• Equinox = neither
end of Earth’s
axis is tilted
toward the sun.
Earth’s equinox and
solstice
Mars equinox and solstice
Climate
• Climate is the average, year-after-year
conditions of temperature, precipitation,
winds, and clouds in an area.