(fragment)
That night, much midnight oil was burned at the main camp. Barton was frankly skeptical, but Davis had already built up an elaborate superstructure of
theory around their visitor’s remarks.
“It would explain so many things,” he said. “First of all, their presence in this place, which otherwise doesn’t make sense at all. We know the ground
level here to within an inch for the last hundred million years, and we can date any event with an accuracy of better than one per cent. There’s not a
spot on Earth that’s had its past worked out in such detail — it’s the obvious place for an experiment like this!”
“But do you think it’s even theoretically possible to build a machine that can see into the past?”
“I can’t imagine how it could be done. But I daren’t say it’s impossible—especially to men like Henderson and Barnes.”
“Hmmm. Not a very convincing argument. Is there any way we can hope to test it? What about those letters to Nature?”
“I’ve sent to the College Library; we should have them by the end of the week. There’s always some continuity in a scientist’s work, and they may give
us some valuable clues.”
But at first they were disappointed; indeed, Henderson’s letters only increased the confusion: As Davis had remembered, most of them had been about the
extraordinary properties of Helium II.
“It’s really fantastic stuff,” said Davis. “If a liquid behaved like this at normal temperatures, everyone would go mad. In the first place, it hasn’t
any viscosity at all. Sir George Darwin once said that if you had an ocean of Helium II, ships could sail in it without any engines. You’d give them a
push at the beginning of their voyage and let them run into buffers on the other side. There’d be one snag, though; long before that happened the stuff
would have climbed straight up the hull and the whole outfit would have sunk—gurgle, gurgle, gurgle... “
“Very amusing,” said Barton, “but what the heck has this to do with your precious theory?”
“Not much,” admitted Davis. “However, there’s more to come. It’s possible to have two streams of Helium II flowing in opposite directions in the same tube — one stream going through the other, as it were.”
“That must take a bit of explaining; it’s almost as bad as an object moving in two directions at once. I suppose there is an explanation,
something to do with Relativity, I bet.”
Davis was reading carefully. “The explanation,” he said slowly, “is very complicated and I don’t pretend to understand it fully. But it depends on the
fact that liquid helium can have negative entropy under certain conditions.”
“As I never understood what positive entropy is, I’m not much wiser.”
“Entropy is a measure of the heat distribution of the Universe. At the beginning of time, when all energy was concentrated in the suns, entropy was a
minimum. It will reach its maximum when everything’s at a uniform temperature and the Universe is dead. There will still be plenty of heat around, but
it won’t be usable.”
“Whyever not?”
“Well, all the water in a perfectly flat ocean won’t run a hydro-electric plant — but quite a little lake up in the hills will do the trick. You must
have a difference in level.”
“I get the idea. Now I come to think of it, didn’t someone once call entropy ‘Time’s Arrow’?”
“Yes — Eddington, I believe. Any kind of clock you care to mention — a pendulum, for instance — might just as easily run forward as backward. But
entropy is a strictly one-way affair — it’s always increasing with the passage of time. Hence the expression, ‘Time’s Arrow.’ ”
“Then negative entropy—my gosh!”
For a moment the two men looked at each other. Then Barton asked in a rather subdued voice: “What does Henderson say about it?”
“I’ll quote from his last letter: ‘The discovery of negative entropy introduces quite new and revolutionary conceptions into our picture of the
physical world. Some of these will be examined in a further communication.’ ”
“And are they?”
“That’s the snag: there’s no ‘further communication.’ From that you can guess two alternatives. First, the Editor of Nature may have declined to
publish the letter. I think we can rule that one out. Second, the consequences may have been so revolutionary that Henderson never did write a
further report.”
“Negative entropy — negative time,” mused Barton. “It seems fantastic; yet it might be theoretically possible to build some sort of device that could see
into the past....”
“I know what we’ll do,” said Davis suddenly. “We’ll tackle the Professor about it and watch his reactions. Now I’m going to bed before I get brain
fever.”
That night Davis did not sleep well. He dreamed that he was walking along a road that stretched in both directions as far as the eye could see. He had
been walking for miles before he came to the signpost, and when he reached it he found that it was broken and the two arms were revolving idly in the
wind. As they turned, he could read the words they carried. One said simply: To the Future; the other: To the Past.
