One of my favorite aspects of dinner with my sons is the conversation. It rarely touches on how everyone’s day was. That information is simply not forthcoming. But the talk does cover the gamut of substantive topics: science, religion, politics – all the good stuff. Last night was no different.

Somehow the idea of absolute zero came up. For some reason my younger son was speculating on the temperature of his chicken as measured in Kelvins. He then went on to explain absolute zero pretty accurately as the point at which all motion within atoms stop. This apparently lead him to think about places in the universe that are at absolute zero and how things roaming through space might cope with that.

I assured him that absolute zero existed nowhere in the universe. Quantum physics actually prohibited anything from getting below its zero-point energy, which non-intuitively, is not equal to zero. It was a limit which we could approach asymptotically, but not actually get to in nature.

So apparently a thought experiment was in order. He posits, “Suppose there is a place where the temperature is absolute zero. And gravity is also zero, and while were at it, let’s make it a perfect vacuum as well. “

“Okay,” I agree.

“Now,” he says. “Lets push a rock into this space. Will it come out the other side?”

“Well the rock is warmer and would transfer heat into the space, so yes.”

“Wait,” he says. “Let’s make the rock at absolute zero. Will it still go through?”

“Hmmmm…” I say as I ponder and stall for time. The atomic or quantum motion in the rock will have stopped, but the Newtonian momentum shouldn’t be effected by temperature. It’s not a factor in any of the motion equations. So I think it will still pass through – probably without slowing down at all.

“But you’re not sure,” he presses.

“No, I’m not sure,” I confess.

“HAH!”, he exclaims, pumping his fist. “I stumped him! Can I be excused?”

Which leads me to believe that perhaps I’ve missed the point of these conversations all along.