“Imagine a sphere,” he explained, “large enough to hold two people and their luggage. It will be made of steel lined with thick glass; it will contain a proper store of solidified air, concentrated food, water-distilling apparatus, and so forth. And enamelled, as it were, on the outer steel⁠—”

“Cavorite?”

“Yes.”

“But how will you get inside?”

“There was a similar problem about a dumpling.”

“Yes, I know. But how?”

“That’s perfectly easy. An airtight manhole is all that is needed. That, of course, will have to be a little complicated; there will have to be a valve, so that things may be thrown out, if necessary, without much loss of air.”

“Like Jules Verne’s thing in A Trip to the Moon ?”

But Cavor was not a reader of fiction.

“I begin to see,” I said slowly. “And you could get in and screw yourself up while the Cavorite was warm, and as soon as it cooled it would become impervious to gravitation, and off you would fly⁠—”

“At a tangent.”

“You would go off in a straight line⁠—” I stopped abruptly. “What is to prevent the thing travelling in a straight line into space forever?” I asked. “You’re not safe to get anywhere, and if you do⁠—how will you get back?”