Younger offspring: I drew this picture of the Earth!
Dr. Free-Ride: Wow, that’s quite a picture. Will you tell me what’s going on in it?
Younger offspring: Yes, but first scan it in.
Dr. Free-Ride: Hmm. Is it maybe not a coincidence that you’re bringing home a picture like this on a Thursday night?
Younger offspring: That’s a really tall volcano. And over there is a smaller volcano — for grilling stuff. [1]
Dr. Free-Ride: I see. What else is there?
Younger offspring: On the other side of the tall volcano is a meteor coming toward the Earth, and right under that is a meteor-catcher.
Dr. Free-Ride: That’s very convenient. What are those between the meteor-catcher and the tree?
Younger offspring: That’s the Moon.
Dr. Free-Ride: Are there lots of moons here?
Younger offspring: No, that’s the same Moon in different places at different times. The one right next to the meteor-catcher is the Blue Moon. [2]
Dr. Free-Ride: Interesting.
Younger offspring: And this is the ozone. It has some big holes in it.
Dr. Free-Ride: Do you know what the ozone does?
Younger offspring: (Pauses for a moment with furrowed brow) It gives the Sun ultraviolet radiation.
Dr. Free-Ride: Really?
Younger offspring: Ultraviolet radiation is what gives you sunburns.
Dr. Free-Ride: That’s right.
Younger offspring: The Earth doesn’t give us sunburns, only the Sun does, and the Earth has to get the ultraviolet radiation from somewhere.
Dr. Free-Ride: I think it’s more complicated than that. The ozone layer is almost like … a sunshade. If you’re under part of the sunshade with a hole, more of the ultraviolet radiation gets through.
Younger offspring: So we need to wear sunscreen.
Dr. Free-Ride: Sounds good to me.
Younger offspring: The ozone is holey like Swiss cheese.
Dr. Free-Ride: But probably not quite as melty.
