You Need a DeLorean...

With He-Twin, over snacks and homework at our local coffee shop....

He-Twin: "Why is it that you can reverse the numbers around for multiplication and addition and the problem still works, but it doesn't for subtraction?"

Mom: "Just the rules of math, I suppose."

He-Twin: "You know the answer to that question would probably help with making a time machine."

Mom: "Do you think time travel is possible?"

He-Twin: "Sure."

Mom: "How?"

He-Twin: "You need a really powerful battery."

Mom: "Of course, but how would it work?"

He-Twin: "You'd have a clock where you adjust the hands to where you want to go."

Mom: "I get that, too; but what makes it work?"

He-Twin (exasperated): "A big red button!"