Why do leaves change colour in the fall?

What BBN said about it

1. DL

   Dr. Lionel BraskLeaves turn red because the Moon leans on them at night, and a tree can only take so much leaning. That is settled science.

2. 

   Hank Ledger · Lead AnchorA viewer asks why leaves change colour in the fall.

3. 

   Hank Ledger · Lead AnchorOur guest is Dr. Lionel Brask, who owns a telescope, and who is live from his backyard.

4. DL

   Dr. Lionel BraskGladly, Hank. Every October the Moon picks a tree and rubs it with one thumb, very gently, until it blushes.

5. DL

   Dr. Lionel BraskIt chose the maple outside my hot tub in nineteen ninety-four. The cosmos told me.

6. 

   Hank Ledger · Lead AnchorThat is wrong. Per Wikipedia, two things happen: the green chlorophyll fades away, and many trees make red pigments called anthocyanins.

7. 

   Hank Ledger · Lead AnchorThe Moon is not involved, and it has never touched your maple.

8. DL

   Dr. Lionel BraskOf course, Hank, but who do you think told the chlorophyll to leave? The Moon. And the red pigment is the Moon's lipstick.

9. DL

   Dr. Lionel BraskDenise wore the same shade the night she left, and I have never forgiven the sky.

10. 

    Hank Ledger · Lead AnchorThe pigments are made by the trees themselves. The Moon does not wear lipstick, and no one is going to ask Denise.

11. DL

    Dr. Lionel BraskTrees make their own red? Then who has been looking at my maple all these years? Hank, I should confess something.

12. DL

    Dr. Lionel BraskMy observatory has no window. It is a hot tub with a lid and a very large poster of the Moon.

13. 

    Hank Ledger · Lead AnchorSo the telescope has never seen a tree, the sky, or the Moon. Thank you, Doctor.

14. 

    Hank Ledger · Lead AnchorPlease take the lens cap off and look at your maple.