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.

Actually the book is a pretty fair read, comparable to Heinlein, facts not withstanding. It's obviously not one that I will keep in my collection though.

Rich

"The physics of space elevators is well understood."

Indeed it is. I was saying the physics of the specific space elevator *in the book* were not understood because its specific construction appeared to violate basic physics (i.e., as it is constructed in the book, this particular beanstalk should have fallen out of the sky). That this *particular* beanstalk can apparently ignore basic physics and yet still stay up suggests that the folks who own it (the Colonial Union, an organization independent of the Earth) have access to compensating technology people on Earth do not -- and indeed that access to advanced tech is a recurring theme in the book.

At the very least, that's what I had *intended* to suggest in the book. It's entirely possible I wrote this in such a way that might not have been immediately clear. In which case, my apologies.

Well, John, thanks for dropping by. I'm honored that you thought my comments worth responding to, and so quickly.

Yes, I guess it wasn't clear (at leat to me) that it was this particular elevator that was problematic. You didn't provide (or at least I didn't discern) any explanation of just what it was about it that was defiant of physical laws, or why its being "held up" was a mystery. Was it too thick, or in compression?

I remember this from when I read "Old Man's War" a few months ago. As I recall, the problem was that the elevator's construction was such that it should have required a substantial counterweight beyond GEO in order to generate the apparent "centrifugal force" needed to hold it up, but had none. This, according to the main character, is essentially a demonstration of the Colonial forces' superior technology to Earth, hanging in a place where they can't forget about it.

OK, I'll have to go back an reread that part, but it wasn't clear to me from my first reading that it didn't extend beyond GEO.

But then, maybe my reading comprehension wasn't up to snuff.

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

I have a set of queries with icerocket.com packaged as RSS feeds and delivered to my reader. Search terms include company name, key technologies and so on.

A curious writer might do the same for his name or his book.

I enjoyed the book immensely and am looking forward to the sequel, which is coming out soon. The plot, of course, tracks Starship Troopers in many ways, but there is more to the Heinlein resemblance than that. The tough mindedness necessary to struggle against the universe is vintage Heinlein. Loved it.
Laura

Ditto Mr. Scalzi's comments. I read the book several months ago after favorable reviews at Vox Popoli. That is one of the sub-plots in the book is that Earth was able to get ahold of some alien technology to get an edge on the enemy.

You'll recall the one on one battle to the death, where the winner may request something of the other race. In this case whether that race had given technology to the enemy whereby they could know in advance where a ship would appear from hyperspace, setting up the ultimate ambush.

I'm looking forward to the sequel.

I've read The Fountains of Paradise a number of times, and recall that the method of construction of that elevator was to start with a station in geostationary orbit, and then "grow" the elevator in both directions -- "down" and "up" -- carefully maintaining the center of gravity the whole time.

That background probably helped me understand why, as Scalzi mentioned, the Earth physicists couldn't explain the stability of the tower, despite not extending beyond geosynchronous orbit. (Because the center of mass of such a tower would be below geosynchronous orbit, and so that whole mass would tend to orbit faster....)