The Earth in Space

THE EARTH IN SPACEHOW WE DETERMINE TIME

USING THE SUN AND EARTH

Objectives1. What is rotation and how does it affect Earth2. What is revolution and how does it affect

Earth3. Be able to compare and contrast rotation

and revolution4. How day and night are determined5. How a year is determined

Determining Day and Night • Axis – an imaginary line that

goes through a planet, moon or other space object. The space objects “spins” on that line like a wheel on an axle.

• Rotate -Determining night and day

To turn around an axis

Courtesy of The Freeman Institute

• Determining night and day

• Period of rotation/rotationThe time it takes an object to

turn on its axis

• Earth’s period of rotation is– about 24 hours

• This determines– 1 DAY ON EARTH

• http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.html

Revolution

• Determining a planetary year

Revolution – one object moving around another

Period of Revolution - the time it takes one object to move around another

• It takes the Earth 365 ¼ rotations to make 1 revolution around the sun

• so we have 365 ¼ days pr year – These are counted for 3 years and on

the 4th year we add the quarters up for 366 days and add that day in February – LEAP YEAR

• Orbit – the path an object takes to move around another object

In your science notes create a double bubble thinking map to compareAnd contrast Rotation and Revolution - remember you may have more bubblesthan what is represented in the diagram above

Period ofrotation

Period of revolution