The professor relaxed in his chair. “You are a clever man. You will have your little joke.
“But we must be serious. I will tell you how long a second is. It is exactly one-thirty-one millionth, five hundred and fifty-eight thousandth, one hundred and forty-ninth part of a year.”
“Oh,” said Tubby.
“Do you know what a year is?”
“Three hundred and sixty-five days,” said Tubby promptly.
The professor smiled again. “A year is the time it takes the Earth to revolve once around the Sun. Thus you see there are 31,558,149 seconds in a year—which is a little more than 365¼ days.”
“Yes,” said Tubby. “I see.”
“Now to find out how far light travels in a year we simply take its speed per second and multiply it by sixty. That is its speed per minute. Multiply that by sixty gives it speed per hour and so on up to a day or a year. Do you understand?”
“Yes,” said Tubby. “How—how far does it go in a year?”
The professor raised his hand.