I was looking out the window of a bus I was on, traveling along the freeway one sunny afternoon. There were two birds flying alongside the bus. I noticed that both birds stopped flapping their wings at around the same time. Their altitude dropped, slowly, then faster.

You flying imbeciles! I thought, you had better get your flap on soon, or you're going to crash-land into the cement!

They continued their perilous descent as if by mutual engine failure. It got dark for a moment. The bus had gone under an overpass. The birds, now low enough to make it through, made it through, and right before the overpass came to its end, they resumed flapping, and up they went on their merry way.

Wow, birds, I thought, you get gravity more than I do.