Insulated by an outer crust, the surface of the earth acquires nearly all of its heat from the sun. The only exit for this heat to take is through a door marked "Radiation." And therein lies a tale... Recently, I chanced upon an Atmospheric Science Educator Guide [PDF] published by NASA. Aimed at students in grades 5 through 8, it helps teachers explain how so-called "greenhouse gases" warm our planet Earth.These guides are interesting on a number of levels, so I recommend that you look them over. But what caught my eye was this:Question: Do all of the gases in our atmosphere absorb heat? Answer: (Allow students to discuss their ideas. Don't provide the answer at this time.)Indeed, that's a good one to think over yourself. Almost all of what we're breathing is nitrogen and oxygen -- do these gases absorb heat? Lakes and rocks absorb heat, after all, and thereby reach a higher...(Read Full Article)