Friday Sprog Blogging: warmth underground.

Why is it that on hot days, the Free-Ride offspring take up the question of how animals stay warm on cold days? Does this kind of consideration make the heat seem more desirable?
Younger offspring: During the winter, why do some animals go underground to get warm?
Dr. Free-Ride: Why do you think?

Younger offspring: Their holes underground are warmer because they’re closer to the center of the earth, and the center of the earth is made of magma, which is hot.
Dr. Free-Ride: Hmm. When I lie down on the ground, I’m closer to the center of the earth when I’m standing up, but I don’t feel any warmer.
Elder offspring: I think the holes would need to be really, really deep for the animals to be able to feel the heat from the magma.
Younger offspring: Well, why do you think they’re warmer in their holes?
Elder offspring: They’re out of the wind or rain or snow or whatever cold weather is happening above the holes.
Dr. Free-Ride: That’s true. The ground can get pretty cold, though.
Elder offspring: Hmm. Maybe the holes warm up from the animals being in them.
Younger offspring: But if the animals are warm, why can’t they stay warm out of the holes, too?
Dr. Free-Ride: Well, when the animals are warming up the holes, what are the really warming up?
Elder offspring: The air that’s in the holes?
Dr. Free-Ride: That sounds right to me. And what’s the difference between the air that’s in the holes with them and the air that’s around them when they’re not in the holes but out and about?
Younger offspring: There’s less air in the holes?
Dr. Free-Ride: Yeah, which means …
Elder offspring: It’s easier to warm up the air in the holes, ’cause there’s less up it, than to warm up all the air outside.
Dr. Free-Ride: You got it. And wind would make it even worse.
Younger offspring: How?
Dr. Free-Ride: Well, your body manages to warm up the layer of air that’s right around you, and then the wind can blow that warm air away from you.
Elder offspring: And then your body has more cold air it needs to warm up!
Younger offspring: That’s not fair!
Dr. Free-Ride: Eh, it’s thermodynamics.
Elder offspring: It’s enough to make you want to crawl into a hole.