The planet earth and its motionPresentation Transcript
The Planet Earth: Its Motions and Seasons Chapter 1
Everything in Earth's system can be placed into one of four major subsystems: land, water, living things, or air.
These four subsystems are called "spheres."
Specifically, they are the "lithosphere" (land), "hydrosphere" (water), "biosphere" (living things), and "atmosphere" (air).
Each of these four spheres can be further divided into sub-spheres.
The lithosphere contains all of the cold, hard solid land of the planet's crust (surface), the semi-solid land underneath the crust, and the liquid land near the center of the planet.
*The surface of the lithosphere is very uneven.
There are high mountain ranges like the Rockies and Andes, huge plains or flat areas like those in Texas, Iowa, and Brazil, and deep valleys along the ocean floor.
The hydrosphere contains all the solid, liquid, and gaseous water of the planet.
**It ranges from 10 to 20 kilometers in thickness.
The hydrosphere extends from Earth's surface downward several kilometers into the lithosphere and upward about 12 kilometers into the atmosphere.
The atmosphere contains all the air in Earth's system.
****It extends from less than 1 m below the planet's surface to more than 10,000 km above the planet's surface.
The upper portion of the atmosphere protects the organisms of the biosphere from the sun's ultraviolet radiation.
It also absorbs and emits heat.
The biosphere contains all the planet's living things.
***This sphere includes all of the microorganisms, plants, and animals of Earth.
FACTS ABOUT THE EARTH Average Distance from the Sun 92,955,820 miles Equatorial Circumference 24,901 miles Sidereal Rotation Period (Length of Day) 23.934 hours Sidereal Orbit Period (Length of Year) 365.24 Earth days Mean Orbit Velocity 66,629 mph Equatorial Inclination to Orbit 23.45 degrees Volume 259,900,000 mi3 Mass 5.9737 x 1024 kg Density 5.515 g/cm3
MOTIONS of the EARTH
REVOLUTION The movement of the earth in its orbit.
ROTATION The spinning of an object on its axis.
The spin axis of the Earth undergoes a motion
This changing of direction of the spin axis is called precession .
Seasons of the Earth
Earth at Winter Solstice
Earth at Summer Solstice
Why do we have seasons?
The Winter & Summer Sun
Seasons in the Northern & Southern Hemisphere
The solstices are days when the Sun reaches its farthest northern and southern declinations.
The winter solstice occurs on December 21 or 22 and marks the beginning of winter (this is the shortest day of the year).
The summer solstice occurs on June 21 and marks the beginning of summer (this is the longest day of the year).
Equinoxes are days in which day and night are of equal duration. The two yearly equinoxes occur when the Sun crosses the celestial equator.
The vernal equinox occurs in late March (this is the beginning of spring in the Northern Hemisphere and the beginning of fall in the Southern Hemisphere); the autumnal equinox occurs in late September (this is the beginning of fall in the Northern Hemisphere and the beginning of spring in the Southern Hemisphere).