Hydro Power

Do you know??

Simple machines - less effort more work

Science, like life, feeds on its own decay. New facts burst old rules; then newly divined conceptions bind old and new together into a reconciling law. ~William James, The Will to Believe and Other Essays in Popular Philosophy, 1910

magnetic field of the earth

http://www.viewzone.com

Behaviour of magnetic poles

http://www.physics.sjsu.edu

Forest succession: From simple to complex

source:

http://www.physicalgeography.net/fundamentals/9i.html