“No,” I said. “It was a flight of birds.”
“What?”
I had to laugh at the expression on her face. I said, “Placet is a crazy place. A minute ago, you said you felt as though you were walking on air. Well, in a way, you are doing just exactly that. Placet is one of the rare objects in the universe that is composed of both ordinary and heavy matter. Matter with a collapsed molecular structure, so heavy you couldn’t lift a pebble of it. Placet has a core of that stuff; that’s why this tiny planet, which has an area about twice the size of Manhattan Island, has a gravity three-quarters that of Earth. There is life—animal life, not intelligent—living on the core. There are birds, whose molecular structure is like that of the planet’s core, so dense that ordinary matter is as tenuous to them as air is to us. They actually fly through it, as birds on Earth fly through the air. From their standpoint, we’re walking on top of Placer’s atmosphere.”
“And the vibration of their flight under the surface makes the houses collapse?”
“Yes, and worse—they fly right through the foundations, no matter what we make them of. Any matter we can work with is just so much gas to them. They fly through iron or steel as easily as through sand or loam. I’ve just got a shipment of some specially tough stuff from Earth—the special alloy steel you heard me ask Reagan about—but I haven’t much hope of it doing any good.”
“But aren’t those birds dangerous? I mean, aside from making the buildings fall down. Couldn’t one get up enough momentum flying to carry it out of the ground and into the air a little way? And wouldn’t it go right through anyone who happened to be there?”
“It would,” I said, “but it doesn’t. I mean, they never fly closer to the surface than a few feet. Some sense seems to tell them when they’re nearing the top of their ‘atmosphere’. Something analogous to the supersonics a bat uses. You know, of course, how a bat can fly in utter darkness and never fly into a solid object.”
“Like radar, yes.”
“Like radar, yes, except a bat uses sound waves instead of radio waves. And the widgie birds must use something that works on the same principle, in reverse; turns them back a few feet before they approach what to them would be the equivalent of a vacuum. Being heavy matter, they could no more exist or fly in air than a bird could exist or fly in a vacuum.”
While we were having a cocktail apiece in the village, Michaelina mentioned her brother again. She said “Ike doesn’t like teaching at all Phil. Is there any chance at all that you could get him a job here on Placer?”