I have been playing and singing that song for many years now, since my father-in-law, Abraham Chertoff, who has Alzheimer's, still responds to classical music and spirituals, which he loves, and sang in his better days. But I could never figure out the "swing low" part, in concrete terms - even when I learned some navigational astronomy.

Some people might have said, "Oh, yes, this is like the chariot that swung down to earth to pick up Elijah, and bring him to heaven." That's nice, but it's metaphor without flesh and bones. And I suppose, like most other people, I thought it was about passing from this vale of sorrows, to heaven on the other side. And the slave master was to think the same thing.

But then, the second verse, as I sang it, said "If you get there before I do, Coming for to carry me home, Tell all my friends I'm a-coming too." Well, I suppose if you get to heaven, you might see your old friends there - but I had never thought of heaven in those terms, having been brought up a fairly strict Protestant.

Then when I learned some rudimentary astronomy, I found out that the "Big Dipper" was also called "the Wain" or Wagon around the time of Chaucer; still today "il Carro" in Italian. OK, but since the Wagon, or Dipper, or Chariot goes around the north star every 24 hours, it swings low every day, — so what's crucial about its swinging low? And when does it do so?

At this point, stymied, I brought in another slave song, "Follow the Drinking Gourd," which is clearly about slaves escaping to the north, following the Big Dipper, the Drinking Gourd. The first verse goes: