Miss Rogers taught physics in a New York school. Last month she was explaining to one of her classes about sound, and then decided to test them to see how successful she had been in her explanation. She said to them, “Now, I have a brother in Los Angeles. If I was calling him on the phone, and at the same time you were 75 feet away, listening to me from across the street, which of you would hear what I said earlier, my brother or you-and for what reason?”
The smartest student at once answered, “Your brother, Miss Rogers, because electricity travels faster than sound waves.”
“That´s very good”, Miss Rogers answered, but then one of the girls raised her hand, and Miss Rogers said, “Yes, Debbie?” “ I disagree”, Debbie said. “Your brother would hear you earlier because when it´s eleven o´clock here it´s only eight o´clock in Los Angeles”.
Hill, L.A. Intermediate Anecdotes in American English. Oxford University Press, 1980.