Astronomers on earth inferred a hospitable, earth-like planet in a parallel universe. So they mounted an expedition through the wormhole to explore the planet.
The planet turned out to be a natural wilderness with settlements of Stone Age humanoids. At first, everything seemed normal. But on closer inspection, something was off. Take the cherry trees. When the astronauts landed, the trees had ripe cherries. But after a few weeks the cherries became cherry blossoms, then buds.
When an astronaut accidentally cut himself, the wound healed up in a matter of minutes. And their hair began growing shorter rather than longer. When an astronaut dropped a glass, the shattered glass reassembled in moments.
It's as if time's arrow was reversed. The next day was the day before. They went from March 15 to March 14. They remembered March 15 but had no recollection of March 14 because they hadn't experienced it yet. They remembered the future but not the past.
Then they befriended the natives. The natives were highly intelligent but initially cautious about the astronauts. Yet the astronauts were eventually able to question the natives. Didn't they find it disconcerting to be living backwards?
But the natives has no other basis of comparison. For them, it was natural for dead things to come back to life. Indeed, for them, life began as adults, when their aging corpses came to life. That's when they became conscious. That's when their experience began. That's when their memories began.
For them it was natural to see a melted snowman reconstitute. That was their only frame of reference.
So they didn't view themselves as living backwards. It felt like they were living forwards. They couldn't tell the difference between moving from the past into the future or moving from the future into the past. For them there was a day behind and a day ahead. There was a certain predictability, even uniformity to nature, as things aged down.
They found the descriptions of time's passage by the astronauts puzzling. It would be very disorienting to live in a world where dead things stayed dead. Where a campfire burned out, reducing the wood to ashes. In their experience, the wood was not consumed. The fire died out when the embers recombined as branches. At the end of the process was a pile of fresh firewood. It took a lot of imagination on their part to conceive the kind of world the astronauts came from. A world where meteors were falling stars. The natives were used to watching meteor showers rain upwards. So there didn't seem to be one right way to experience time's passage. Each world had its own now and then.
When the astronauts tried to return to their home planet, they were unable to. In a sense, they'd done it already, but that lay in the past. At present, their "future" was in the parallel world–because that's where they were. So they couldn't get back. They had been back, but yesterday was like March 15 while today was like March 14 and tomorrow was like March 13. They could make plans and carry out their plans, but that was always a thing of the past, over and done with. The only way forward was backward.
