Early example of he idea that if you were in a room falling freely, you could not detect the force of gravity, while if the room were pulled downward faster than free fall, this would seem like negative gravity.

From Lewis Carroll, Sylvie and Bruno (1889), Chapter 8 (pp.294-295 in The Complete Illustrated Works of Lewis Carroll, Chancellor Press, 1982).

"How convenient it would be", Lady Muriel laughingly remarked, a propos of my having insisted on saving her the trouble of carrying a cup of tea across the room to the Earl, "if cups of tea had no weight at all!  Then perhaps ladies would sometimes be permitted to carry them for short distances."

"One can easily imagine a situation", said Arthur, "where things would necessarily have no weight, relatively to each other, though each would have its own weight, looked at by itself."

"Some desperate paradox!" said the Earl.  "Tell us how it could be.  We shall never guess it."

"Well, suppose this house, just as it is, placed a few billion miles above a planet, and with nothing else near enough to disturb it: of course it falls to the planet?"

The Earl nodded.  "Of course -- though it might take some centuries to do it."

" ... But now as to the relative weight of things.  Nothing can be heavy, you know, except by trying to fall, and being prevented from doing so.  You all grant that?"

We all granted that.

"Well, now, if I take this book, and hold it out at arm's length, of course I feel its weight.  ... But, if we were all falling together, it couldn't be trying to fall any quicker, you know: so, if I let go, what more could it do than fall? ..."

. . .

"There is a more curious idea yet," I ventured to say. "Suppose a cord fastened to the house, from below, and pulled down by someone on the planet.  Then of course the house goes faster than its natural rate of falling: but the furniture -- with our noble selves -- would go on falling at their old pace, and would therefore be left behind."

"Practically, we should rise to the ceiling," said the Earl.  "The inevitable result of which would be concussion of the brain."

Everyone has read Lewis Carroll's Alice in Wonderland and Through the Looking Glass, and many have also read The Hunting of the Snark; but his Sylvie and Bruno and Sylvie and Bruno Concluded (1893) are almost unknown.  I enjoyed them greatly.  The stories alternate between the "real world" and fairyland, with characters moving back and forth between them. The above passage is in the "real world".  The book begins in fairyland, in mid-sentence:

-- And then all the people cheered again, and one man, who was more excited than the rest, flung his hat high into the air, and shouted (as well as I could make out) "Who roar for the Sub-Warden?"  Everybody roared, but whether it was for the Sub-Warden, or not, did not clearly appear: ...

(It wasn't till about 50 years after reading this, and a couple of years after putting this page on the web, that I realized that the phrase "as well as I could make out" was there for a reason.)

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