A heavy dew overnight leaves thousands of droplets on the hot-tub cover. After years of science classes I can say that I know where that water comes from, although I’d be hard pressed to convert that vague intuition into a clear explanation. Much of what I think I know is like that: not wrong, but not detailed enough to be helpful.
A small pond hosts at least 40 turtles, counting only the ones out sunning themselves on the rocks and the concrete edging of a pond in the middle of an urban neighbourhood in the middle of a desert. After years of casual observation I can say that I know where those turtles *must* have come from–from someone seeding that artificial pond with baby turtles–but I’d be hard pressed to convert that assumption into a conviction (I’ve seen a lot of artificial ponds with turtles in them). Much of what I think I know is like that, too: not unreasonable, but not confirmed.
If pressed hard, I would say that I’m pretty sure that neither the droplets nor the turtles fell from the sky. So that’s something.