EARTHSpace Unit
The Earth is not a true circle, it is a:Oblate Spheroid
Bulges in the middle
Earth’s Shape
1. Right distance from the Sun2. Right amount of water3. Right amount of atmosphere
Why Does Earth Have Life?
The rotation of the Earth lasts for 24 hours.A rotation is the Earth turning around itself.http://eoimages.gsfc.nasa.gov/images/imagerecords/57000/57760/rotate_320.mpg
Earth’s Rotation
The revolution of the Earth around the Sun takes 365.25 days.(which is why we have a leap year every 4 years)
Earth’s Revolution
A revolution is the path the Earth takes in the solar system around the Sun.http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page01.cfm
Earth’s Revolution
The Earth is NOT perfectly vertical.It’s tilted!
Earth’s Tilt
Not only is the Earth tilted but it wobbles!!http://en.wikipedia.org/wiki/Precession The wobble changes which star is our North Star (Polaris to Vega)This takes 26,000 years
Earth’s Tilt
The Earth’s tilt is 23.5 degrees.The tilt of the Earth is the reason our planet has seasons.
Earth’s Tilt
The seasons are a result of two things:1. The tilt of the Earth2. Earth’s location in its
revolution around the Sun
Seasons
Seasons
Vernal Equinox (equinox=equal)March 21st Equally 12 hrs of light and 12 hrs of night.
Seasons - Spring
Summer SolsticeJune 21st 16hrs of light and 8 hrs of night.
Seasons- Summer
Autumnal EquinoxSeptember 21st 12 hrs of light and 12 hrs of night.
Seasons-Fall
Winter SolsticeDecember 21st 8 hrs of light and 16 hrs of dark
Seasons- Winter
If we did not have a tilt in the Earth we would not have seasons. What would that be like?http://www.nasa.gov/multimedia/videogallery/index.html?media_id=161642931
Seasons
http://astro.unl.edu/naap/motion1/animations/seasons_ecliptic.swf