Author's Note

On the Mutability of Science

Technically speaking, science fiction need not have any real science in it at all, and quite a bit of it does not. I do feel, however, that some of the best kinds of science fiction rest on exploring the wonders of actual scientific theories or observations, especially when they are first advanced and not yet dogmatic. I use things of that sort often. When I do I try to get them right.

Unfortunately, what is "right" at one point in time isn't necessarily still right a couple of decades, or even a couple of years later.

For example, black holes.

When I wrote Gateway, the first of the Heechee books, in 1978, black holes were quite a novelty. Most scientists were willing to believe that such objects did exist. However, not one of the things had ever been unambiguously detected, and speculations about their precise nature were both plentiful and diverse. For the novel, I placed my bets on a couple of the most interesting of the scientists' speculations. One, that there was a great black hole at the center of our galaxy. And, two, that whenever a sufficiently densely packed amount of matter or energy existed anywhere a black hole would automatically form around it. Therefore within such a black hole a number of stars and planets might exist.

For the record, I got it half right. No reputable scientist known to me still thinks organized matter of any kind can exist inside a black hole, so that is a definite miss. On the other hand, it turns out that there really is at our galaxy's core an object known as Sgr A*, pronounced "Sagittarius (or, for short, simply Sajj) A Star." And it is pretty definitely an authentic black hole.

However, when we look at the fine print we find that Sgr A* isn't much like the black hole I was describing. I never specifically identified the mass of the Heechee's Core, but it would have had to have been some thousands of solar masses. It seemed to me that this would be massive enough for any normal purpose. I was wrong, though. Actually Sgr A* weighs in at some 3.7 million solar masses, which, as you can see, is a very great deal bigger.

What's more, a couple of other variorum kinds of black holes, including the kugelblitz that the Foe lived in, are also pretty much out of favor these days. Still, I did not feel that I could omit them where indicated, and so they are still part of the background referred to in the present novel.

I should add, however, that I am unregenerate enough so that I won't let any of this keep me from continuing to try to pick up some of the hairiest of scientists' speculations and do my best to work them into science-fiction stories. So you are warned.

Frederik Pohl

Palatine, Illinois

2004