New Metric Fables, wavelength, dervishes

The Emperor Is Visited by Dervishes

The Emperor was standing on the wall of the Forbidden City overlooking the square outside the Lion Gate. Three dervishes were dancing in the square. They had tall white hats and long white robes. They turned slowly and they formed a triangle which turned slowly.

The Emperor sent someone to ask about the dervishes but no one knew anything. They had recently arrived at the capital but no one could say whether they came from nearby or far away or how they were traveling. Some said they walked across fields without bending the grass and others said they arrived riding on donkeys. Each dervish stirred up a small dustcloud as he danced in the square below. The Emperor sent a messanger to invite the dervishes to visit him in the palace.

When the messager spoke to them, the dervishes bowed solemnly and did not open their mouths. They did not appear to understand anything he said. However they followed the messager in through the Lion Gate and to the throne where the Emperor was waiting.

The dervishes danced before the throne in the sight of the Son of Heaven and when they were finished they opened their mouths. From the first one's mouth came red light, from the second came green, and from the third came blue. It was a deep violet shade of blue.

Then the Emperor did the strangers an honor. To show his respect for the dervishes he motioned for his scribes to bring a diffraction grating and to record the wavelengths of the dervishes' light. A diffraction grating is a finely-lined window which bends any beam of light passing through it by an angle proportional to the light's wavelength. By noting the angle the scribes could reckon the three dervishes' wavelengths. The wavelength of the red light was 7 millionths of a fingerwidth, that of the green light was 5 millionths, and that of the blue was 4 millionths. A fingerwidth is the thickness at the first knuckle of the little finger on Emperor's right hand. The barbarians speak of the fingerwidth as 1.616 centimeters but this is bad manners and when foreigners talk this way a polite person pretends not to notice.