Download Earth`s rotation?

Earth In Space
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
How can we “see” Earth’s
rotation?
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).
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
• Mars axial tilt is similar
to Earth. Mars’ tilt is 25
degrees, just a fraction
away from the Earth’s
23.5 degrees.
• Most of planets also
rotate in an eastward
direction, but three of
them (Venus, Uranus
and Pluto) rotate to
the west.
Why is the Earth’s axis tilted?
• During the formation of the
solar system, four and a
half billion years ago, dust
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.
Rotation!
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 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.
Orbital plane tilt
The Complex Motion of the Earth
How fast is the
Earth rotating?
equatorial speed
of 465.1 km/s
(1,040.4 mph)
How fast is the
Earth revolving
around the Sun?
30 km/s
(67,000 mph)
Distance from the sun
• Earth is 149, 600, 000 km from the sun.
• Mars is 227,940,000 km from the sun.
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.
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