georgmi: (Gurren_Lagann_Kamina)
( Jul. 19th, 2012 05:22 pm)
In the car on the way to day camp at his school, teh_boy was thinking about the rain cycle and speculated that there might be, somewhere on Earth, some water that had never been vapor. I said that, given that the Earth congealed out of molten rock, I thought it was pretty unlikely. He then asked me how the water got to the planet in the first place.

By the time I dropped him off, I'd gotten as far as the current estimate of the age of the Universe (~13.5 billion years), and how that age was determined, which involved a digression into Doppler shifting, from water waves through sound to light. When I picked him up this afternoon, I walked him through the stellar life cycle, fusion from hydrogen up to iron, and supernovae, and brought him home to the giant cloud-with-rocks-in that collapsed into our solar system complete with oxygen, iron and all those other elements that go into our everyday experience and started out inside stars.

Then I dug out a little battery-powered airplane I've had for like seven years but never had enough space to play with, and we flew that off the deck for a while.