I’m reading Old Man’s War by John Scalzi, and while it’s entertaining, I was irritated early on by technical errors in it. In the discussion about the “beanstalk” (which I can only infer is a space elevator), the supposed physics professor explains that it’s used so that that it’s not necessary to “reach escape velocity” with a rocket to get to earth orbit. Of course, it’s not necessary to reach escape velocity to get into orbit–in fact, it’s not possible to do so. Escape velocity is the velocity necessary to leave orbit, and depart from the gravitational pull of the body you’re orbiting altogether.

This one is forgiveable, though, and a common error. What really boggled my mind was the next one, in which he explained that the earth physicists didn’t understand what “held it up.”

Either Scalzi is appallingly ignorant of physics himself, or this is some future in which the people of earth have forgotten basic physics (though if that’s the case, this is the only hint of it that I’ve seen in the book so far). The physics of space elevators is well understood. A space elevator is “held up” in exactly the same way that water is held inside a bucket being swung in circles on a rope–through inertia which appears as a centrifugal “force” in the rotating reference frame. The intergrated mass of the elevator times its centripital acceleration exceeds its weight if it extends sufficiently far beyond its natural orbital altitude (in this case, geostationary orbit, since it rotates with the earth once every twenty-four hours).

Scalzi has been compared to early Heinlein by many reviewers, but Heinlein always worked pretty hard to get his basic science right (which is one of the reasons that I liked to read him–it was entertainingly educational). It’s disappointing that Scalzi doesn’t seem to take the same care in his exposition, particularly since many may take his descriptions at face value.

[Update a few minutes later]

I discussed this topic more extensively last fall.

[Sunday night update]

When I was a kid, if I had a question about one of Bob Heinlein’s books, it would remain a question. There was no place to discuss it, except with my (few) friends who’d also read the book. But now, I can read a book, I can make a comment on it, and the author himself shows up to clarify the issue in my comments section. Just how cool is that?

And I’ve no idea how he knew that I was whining about the book. I’d be both flattered and amazed to learn that he reads this blog daily, so I’m guessing that one of my other readers emailed him to tell him.

Of course, if you visit his bio section, and read the comments (including his), in addition to being a very imaginative and entertaining writer, Mr. Scalzi seems to be a genuinely good guy.

Anyway, don’t consider this post a book review. It’s just a comment that occurred to me shortly after beginning reading it. Other than what I wrote above (which may be just a consequence of misreading on my part, as noted in comments), I expect to enjoy it quite a bit.