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