# Old science fiction story with an alien creature tapping Planck's constant

About 50 years ago, I read a science fiction story in a "year's best" anthology.

As I remember it, a guy was visiting a small moon and ran into a scary giant spider-like creature. He fired a shot, but missed. They somehow get trapped together. At some point, one or the other starts rapping out numbers on the (wall?) between them.

Just as the guy realizes that the creature is tapping out Planck's constant and is an intelligent being, the shot he fired, which has circled the tiny moonlet they are on, hits and kills the creature.

• Huh. That would be one heck of a shot. Jan 13, 2019 at 23:28

Possibly "Moon Duel" (1965) by Fritz Leiber, which appeared in 11th Annual Edition: The Year's Best S-F (1967). The story is available at the Internet Archive.

A guy was visiting a small moon and ran into a scary giant spider-like creature.

At the same time I was thinking how if the biped humanoid shape is a good one for medium-size creatures on any planet, why so the spider shape is a good one for tiny creatures and apt to turn up anywhere and be copied in robots too.

The top hole in the sixth bubble showed me the stars, while one half of its rim shone white with sunlight.

The guy realizes that the creature is tapping out Planck's constant and is an intelligent being.

Then the number came to me. With the butt of my Swift I rapped out five. No answer. No scratching either. I rapped out five again.

Then the answer came, ever so faintly. Five knocked back at me.

Six five five—Planck’s Constant, the invariant quantum of energy. Oh, it should be to the minus 29th power, of course, but I couldn’t think how to rap that and, besides, the basic integers were all that mattered. [...]

We each knew the other had a suit and a gun (and a lonely hole?) and so we knew we were both intelligent and knew math. So why was our rapping so precious?

He raised his gun—I think to rap out one, to start off pi.

The shot he fired, which has circled the tiny moonlet they are on, hits and kills the creature.

But I’ll never be sure, for just then there were two violet bursts, close together, against the fissure wall, quite close to him.

He started to swing the muzzle of his gun toward me. At least I think he did. He must know violet was the color of my explosions. I know I thought someone on my side was shooting. And I must have thought he was going to shoot me—because a violet dagger leaped from my Swift’s muzzle and I felt its sharp recoil and then there was a violet globe where he was standing and moments later some fragment twinged lightly against my chest—a playful ironic tap.

He was blown apart pretty thoroughly, all his constants scattered, including—I’m sure—Planck’s.

Found with the Google query `"year's best" "planck's constant" "science fiction"`.

• Not just an intelligent creature - smart enough to know human units for the Planck constant. Jan 13, 2019 at 21:36
• @Adamant And to use base-10 rather than octal, which would be more natural for a spider-like being, assuming it has eight legs ;) Jan 13, 2019 at 21:38
• Also, he's lucky it didn't know the up-to-date value, which starts 6.626 (or 6.582 if he meant the reduced Planck constant in eV*s) Jan 13, 2019 at 21:40
• Microjoule.decaseconds of course Jan 13, 2019 at 21:50
• @Neo Darwin: There is nothing to remember, because measurement inaccuracies do not allow us to determine more than a handful of digits. Pi on the other hand is a mathematical construct, which can be calculated to arbitrary precision. Jan 14, 2019 at 13:10