Here’s a hellishly simple joke:
A man claims he has solved the grandfather paradox. He says he killed his grandfather, and yet he himself did not disappear.
Someone tells him the grandfather paradox has a prerequisite.
He asks, confused: what prerequisite?
And then there’s another joke, sadder than funny.
In all sorts of "time-travel games," people are asked what they would say if they could return to the moment when their parents first met. A surprising number of answers are the same: they would tell them not to fall in love—partly for their parents’ sake, partly because they themselves would rather never be born.
When I was a student, I once wrote an essay built around the idea of going back to the past and speaking to your former self. At the time I was deep into science fiction, and I had just come across the Novikov self-consistency principle. So my angle was that even if we could return to the past, we still wouldn’t be able to interfere with the present or the future in any meaningful way, and fantasies like that only tempt people into dodging their responsibilities in the here and now.
It was moralizing in exactly the self-important way I was prone to back then. It also happened to align perfectly with what the teacher liked, so it got a high score. Some classmates, though, rolled their eyes and said I was just showing off by dropping a term nobody understood.
Not long after that, the school debate competition picked a related topic: should humanity invent a time machine? This time I ended up on the affirmative side. So I split myself neatly in two and began waving the flag for changing fate with a machine, making impassioned speeches about how people ought to seize their own destiny.
As luck would have it, the classmate who had mocked my essay was on the opposing side. He brought that essay up as evidence, pointing out that I clearly had not always thought this way.
My response was immediate: you don’t know this, but I went back in time and wrote that essay precisely so you would use it against me now.
I’ve always loved stories that use units of time the way a caliper measures distance. Passengers is one example. The voyage is supposed to require 120 years of hibernation, but the protagonist wakes up 90 years too early. When death is translated into something less direct, less dramatic, and more brutally numerical, the despair becomes slower and deeper.
What lingers most for me is the ending. After the two leads decide to give up returning to hibernation and instead spend their entire lives aboard the ship in the solitude of deep space, they fill the vessel with plants. Ninety years later, when everyone else finally wakes, vines and greenery have spread across the cabin. Trees have quietly recorded time according to their own laws, laying down rings that point, in silence, to when they were first planted.
As a form of life older than humanity, plants would eventually overrun the totems humans leave behind at the end of the world—skyscrapers, monuments, all those symbols meant to prove that man can conquer nature. Then, in their own way, they would dissolve those symbols until some new civilization appeared and turned the remnants into signs inside its own mythology. It’s like those recent photos of the Martian surface, where geometric traces invite wild speculation; perhaps they really are the worn-down ruins of some previous civilization’s emblems.
♾️Mobius Ring World♾️
In films about reversing time, what viewers really want is not the miracle itself. It is not enough to watch time run backward and fix everything. What matters is that after passing through those enviable miracles, the protagonist finally understands that living in the present was what their life had been asking for all along.
In Goodbye Mr. Loser, the most moving moment is not when Xia Luo becomes successful and rich. It is when he returns to reality and clings to Dongmei’s sleeve like a lost dog, refusing to let go. No matter how many times life could rewind, all that reversal would really be for is this realization: the present moment is the true body of eternity.
After all, nobody really wants time to reverse—at least not if only other people get that privilege.
When I was a kid, I used to play Contra with my uncle. I could never keep up with him, so I was always getting forced off the screen and losing lives at the edge. There was one stage in particular, full of mechanical traps and jets of fire, that I simply couldn’t handle. He often had to clear it for me.
He would move his own character forward first and wait in a safe area, then go back to control my character and bring me over to meet him. At that age I thought he was incredible.
Years later, when I played that level again, I could get through it in one uninterrupted run, almost without thinking, just by muscle memory. And in doing so I arrived again at the game’s ultimate commandment: keep moving forward, until the mission ends.
Within the rules of that timeline, I can only move ahead. Even if I already know every enemy that will appear in each stage, even if I remember every pattern in every boss fight, the rule of that world is still the same: from left to right, onward, escaping the dangerous island.
Because forward is the only direction, the present is the only place to live.