I was working in a scrap yard during summer vacation at an engineering university.
I worked repairing construction equipment.
One afternoon, I was taking apart a piling hammer that had some very large bolts holding it together.
One of the nuts had corroded on to the bolt, so to free it I started heating the nut with an oxyacetylene torch.
As I was doing this, one of the dimmest apprentices I have ever known came along.
He asked me what I was doing.
I patiently explained that if I heated the nut, it would grow larger and release its grip on the bolt, so I could then remove it.
“So, things get larger when they get hot, do they?” he asked.
“Yes,” I said. “That’s why days are longer in summer and shorter in winter.”
There was a long pause, then his face cleared.
“You know, I always wondered about that,” he said.