Yep. Energy is one of the more difficult things to explain, because it's really more of a mathematical property that results from a conservation law about symm

Yep. Energy is one of the more difficult things to explain, because it's really more of a mathematical property that results from a conservation law about symmetric transformations (Noether's theorem). Luboš Motl has a great explanation here: http://physics.stackexchange.com/questions/3014/what-is-energy-where-did-it-come-from http://physics.stackexchange.com/questions/3014/what-is-ener... Feynman's explanation is pretty amazing as well. I can't find the one where he gives an analogy to blocks (or something) but here is one definition he gives: http://www.phy.davidson.edu/fachome/swp/courses/PHY110/Feynman.html http://www.phy.davidson.edu/fachome/swp/courses/PHY110/Feynm...