This morning was interesting. I poured my 7 1/2 year old son a bowl of cereal for breakfast while I was finishing making lunches. He sat and ate for a few minutes and then he asked, “Dad, if someone from the future takes someone from the past on a time machine to the future, are they the same age or is one really old?” Yea, ponder that for a minute.
I sat there for a minute or two and finally said “Yes, to both questions.” Needless to say he was confused. So here I am trying to figure out how to explain relativity and time travel to a 7 year old so he can understand it. Yea, his brain is unique.
I started with a bit of relativity, glossing over the theoretical science and math and got to “If you are on an airplane you don’t notice you are moving unless to look out at the ground, but if you are standing on the corner watching the plane it is going fast. It is all how you are looking at the same thing.” Confused look for a minute and then, “Oh, so it is like watching a car go by on the road.” Bah, bested by a 7 year old.
“Yes,” I said, “it is like that.” And then we get into what happens with time travel and people. I hold 2 fingers up, one on each hand. “OK, these are people and they are both 10 years old and they were born 100 years apart. In normal time they would move at the same rate.” As i move my fingers at the same time, “each gets older the same but they will never meet. When the guy in the future goes to the past, he is getting older to himself, but hasn’t even been born yet to the past guy!” Eyes began to glaze a bit but he stuck with it.
“Ok, if they both jump back to the future, the future guy is still 10 to himself and 10 in his world. the past guy is 10 in his body, but 110 by his birthday? Make sense?” He looked for a minute and said, “So if they guy from the past goes to the future he is still 10. Got it.”
Yea sure Tristan, you got it. I am still waiting for a call from the school, either from his teacher, “What are you teaching this kid?” or from the principal, “Your son got in a fight about time travel and how old he will be in 103 years.” We will see what happens.