Ah, July, when a young man’s fancy turns to… thermodynamics. Seriously, it is just broiling up here on the second floor. My plan tonight was to post the final “Category IV Bad Movie” entry, but that’s going to be a long one, and it’s just way too hot to even try that tonight.
Instead, I’ll riff off a post by physicist Chad Orzel, who discusses how “common sense” can apply to physics. Orzel makes a distinction between one kind of common sense, our natural human intuition about how the universe works, and the second kind of common sense, the logic of the scientific process. I’ll focus on the first kind, though.
Most people who have taken physics classes at some point in their lives will tell you that quantum mechanics (or alternatively, special relativity) is weird and counter-intuitive. And these people are absolutely right about when they say this. However, whenever I hear this complaint/observation, I think of two counterpoints.
First, our minds evolved in a world that operates at a particular scale and energy. Here’s what would be really weird: if we were born with an intuitive understanding of the physics of extremely hot things or extremely large things or extremely small things. Why would evolution have provided us with that functionality? And why would we think that our realm of “tables and chairs” would be anything like the realm of galaxies or particles?
Second, all realms of physics are weird, even boring old Newtonian mechanics. All objects instantaneously exert an invisible attractive force on each other? Really? How? Who’s crazy enough to believe that? (Certainly not physicists.) And for that matter, even if you ignore all the conceptual and philosophical issues, it’s still hard to work out Newtonian problems. Aristotlean physics might be commonsensical, but Newtonian physics clashes with common sense all the time.[1] There are all sorts of fun Newtonian thought-experiments out there that not only trip up all “regular people”, but also most physics undergrads, many grad students, and even the occasional young and unwary professor. For examples of what I mean, go read Lewis Epstein’s outstanding Thinking Physics. If you think you know Newtonian mechanics, this book will blow your mind. Ditto for fluid mechanics, electromagnetism, and other less sexy realms of physics.
Hmmm. I really sold that one, didn’t I?
1. I remember that as a little kid, my science fair project one year was to prove that objects of equal mass fall at the same rate. Despite what Galileo had to say about the matter, I was sure that the heavier rocks were hitting the ground first. Dropping rocks off a 6′ step ladder was insufficient; we had to go to the park and drop the rocks off a 20′ climbing structure before I was convinced. This experiment would be impossible to reproduce today, since such climbing structures have long been litigated out of existence.