rational and irrational numbers

ancient Greek mathematics: http://www.historyforkids.org/learn/greeks/science/math/

rationality in ancient Greek thought: http://www.historyforkids.org/learn/greeks/philosophy/rationality.htm

math lair on irrational numbers http://www.stormloader.com/ajy/irrational.html

square root of 2 proof: http://www.stormloader.com/ajy/root2.html

basic idea:

numbers are "natural" - they are used for counting or for measuring lengths.

rational numbers work rationally and make sense; they are either natural numbers or they are ratios of natural numbers.

don't tell me the world is not rational. that would be chaos, and scary

Wikepeida entry: http://en.wikipedia.org/wiki/Irrational_number

Bookrags entry: http://www.bookrags.com/sciences/mathematics/irrational-numbers-wom.html

Calssification of numbers: http://numbers.computation.free.fr/Constants/Miscellaneous/classification.html