“Sensei Omuzaki!” said the little boy. “I have discovered that time travel is impossible.”
“And how did you do that?” asked Omuzaki.
“I now make the solemn promise to dedicate my life to discovering time travel. Also, if I do invent it, I promise to appear right here in front of us in five seconds.”
After five seconds, the boy said: “You see? It’s impossible!”
“You’re a very clever boy. Why don’t you go play with your friends now?”
The boy darted away.
“You’re a very clever boy, Ikazumo,” said the sensei with a grin. “A very clever boy indeed.”
Author’s Note: This would be a great way to prove or disprove time travel, but no one bothers to dedicate his life to it.