The time machine

I love our conversations~ Every day at the lunch break we laugh normal and also abnormal things.
"Isn't it Dumbledore? Right there-" And I see my friend pointing to the 16.y.o. boy who queue.
"Yeah," I nod and look at my other friend. She loves secretly this guy. His name is... Thomas but we've promised we never say his true name. So... no better option than give him a nickname?
"Shut up," she mumbles and looks down at her plate with UBS (=universal brown sauce). Do her cheeks get a red colour or not?
Well, then starts the conversation. Not only about Dumbledore and other boys. I don't know how but...
Last week we were talking about the time machine. About way how it works etc.
"Imagine that you have used the time machine. You cannot prove its existence because during using the time machine you changed the past and now the things you changed are changed. And you think the things were always same, but they weren't.
Example: Your napkin is here. But in the past it had been there, you used the time machine to change his location and now the napkin is here instead of there."
"Difficult..." frowned both my friends.
I smiled and shrugged.
Normal day with normal people. :)