"Ah! Karl," I said, seeing my crazy science friend as I walked into the coffee shop. "How's the research going?"
"Very nicely, Brian. Why don't you sit and join me."
I got a cup of coffee and sat down at his table.
"Time, isn't it? That's what you're researching. Right?"
"Right. Movement through time, to be more precise."
"You mean like time travel?," I said with a laugh. "Ha! I could sure use that!"
"Yeah. Last night I got in a big fight with my wife. Silly topic, but oh, what I said! I wish I could just go back and not say it."
"Well, why don't you?"
"Ha ha! If I could I would."
"You think it can't be done?"
"Of course I think it can't be done, Karl. Are you saying you've found a way to travel through time?"
"What are you sounding all surprised for? You've been traveling through time all your life."
"I've been travelling forward in time all my life, Karl."
"And it's pretty effortless, isn't it?"
"Of course, but I was talking about going back in time and this time not insultng my wife."
"Going backward is just about as easy as going forward; people do it all the time, but I'm not at all sure you would correct your mistake when you get there."
"Karl, this is ridiculous, but you have me interested. So why wouldn't I correct my mistake and make everything right with my wife?"
"Because if you go back to before the mistake then the mistake has not yet happened, so you will have no knowledge of it. You do not bring your future knowledge back with you."
"So you're saying I wouldn't know that I made a mistake and I'm likely to repeat the mistake?"
"Well, roughly. Yeah."
"So, under your theory there's not much point in going back because the same thing will just happen. Right?"
"It is very likely the same thing will happen again, but you have a free will so there is a small chance you will make a different decision."
"Okay, Okay," I smiled, "when are you going to show me your wayback machine so I can give it a try?"
"There's no machine. Just decide to do it."
"Like right now?"
"Okay," I said, "easy enough to test. I'm right now deciding to go back to last night before I offended my wife."
I sat there feeling foolish.
"I'm still here," I said.
"Of course you're still here! You went back in time and then lived your life forward from then to now."
"Karl, this is ridiculous. Nothing happened. I wrecked my car last week and my car is still a wreck. Nothing at all has changed!"