Today and every day I'm thankful for that time I visited the University of Chicago as a prospective student and went to that talk about the Core.
I could go on and on about the Core, and how much it means that a member of the faculty took time to speak to prospective students about it, but for the purpose of today's moment of thankfulness, I'll just recount what the professor said.
He said that physics is not the study of nature. Physics is a mathematical model of nature.
And he said that history is not the study of the past. The past is gone; you can't study it. You can only study evidence that the past has left behind. And so history is a model of the past that we build based on this evidence.
That has stuck with me, and now, more than fifteen years later, I am thankful.