Why is the sky blue? An expert weighs in

What BBN said about it

1. SR

   Sir Reginald OatleyThe sky is blue because it is reflecting my carpet, and I have measured the carpet at nine yards of pure cobalt.

2. 

   Hank Ledger · Lead AnchorA viewer wants to know why the sky is blue.

3. 

   Hank Ledger · Lead AnchorSir Reginald Oatley, Senior Fellow in Common Sense at the Royal Society of Sounds About Right, joins us now. His credentials note that he conferred the knighthood upon himself.

4. SR

   Sir Reginald OatleyQuite right. The carpet sits below, the sky sits above, and light must travel between them, like a butler.

5. SR

   Sir Reginald OatleyEvery morning the carpet sends up its blue, and on rainy days I assume the sky is simply out of stock.

6. 

   Hank Ledger · Lead AnchorNot quite.

7. 

   Hank Ledger · Lead AnchorPer NASA Space Place, sunlight is scattered in every direction by the gases and particles in the air, and blue light scatters more than the other colors because it travels as shorter, smaller waves. Your carpet isn't involved.

8. SR

   Sir Reginald OatleyScattered? Sir, you accuse the sunlight of being careless. It is a very orderly sunlight.

9. SR

   Sir Reginald OatleyIf it scatters, it does so by appointment, and I have the appointment book right here.

10. 

    Hank Ledger · Lead AnchorAn appointment book.

11. SR

    Sir Reginald OatleyFor the sun. I have booked it every day since nineteen eighty-one, and it has never once cancelled.

12. SR

    Sir Reginald OatleyIt is the most reliable fellow I know, and I will not hear it called scattered.

13. 

    Hank Ledger · Lead AnchorBlue light is the one that scatters most, because its waves are shorter. That is why you look up and see blue in every direction.

14. 

    Hank Ledger · Lead AnchorThe sun is only doing what it always does, and without your help.

15. SR

    Sir Reginald OatleyShort waves. Hm. Yes. I suppose that does account for it, and I withdraw the carpet.

16. 

    Hank Ledger · Lead AnchorThank you.

17. SR

    Sir Reginald OatleyI should mention that the library has no windows. I have been going by the ceiling, which I painted myself, in cobalt.

18. 

    Hank Ledger · Lead AnchorThat explains the carpet. Sir Reginald, the ceiling is not the sky. Thank you for joining us.

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