short SF: a vaster void

No one could really have imagined that Star Trek would prove to be this accurate.
First, the solar system was broken up in a wave of exponential expansion. By the twenty-fifth century, a Dyson Cloud of space stations was beginning to replace the planets. An endless paradise of super diverse environments. Even in a small space cylinder, there could be storms and forests.

All humans were immortal, but they kept humanoid bodies as anthropic anchors. Particle amplification effects meant that the complexity of their bodies multiplied their perception into the multiverse, stabilizing reality and preventing absurd things from happening.
At night they split into numerous software persons, whose memories were combined and refined before being reinjected. Quantum versions of everyone could think much faster. They formed great cartels and hypergroups.
It was almost as if they were more like cartoons now.

The first human hypership was called The Empty. It was more like an office building than a craft, as if IBM had gone to space.
Faster-than-light ships could only travel at infinite speed and sample a vast sea of potential. The blackness of outer space through a viewport remained shocking. Distance didn't change the color of nothingness.
They discovered too many things that seemed impossible:

Two planets beginning to merge. Their surfaces collided almost gently in the weightless zone, floating rocks slowly rolling between horizons.

A planet with immense rings, far wider than Saturn's; but they were not in one plane. A series of rigidly separated hoops, tilted at progressively different angles. Something strange had happened here.

A nova planet, an ocean world where liquid hydrogen mixed perfectly with oxygen.

Almost a trillion lightyears wide, a black hole that had become so large that it was expanding at the speed of light, simply from the infalling cosmic background radiation.

It took a bit longer to find the first aliens.
The first floating islands on a lava ocean molten to the core. A crushing SiO2 atmosphere, inevitably blown away by asteroid impacts. Early life on surface pools, evolved to perpetually stay on top.
The same planet six billion years later had become a totally bureaucratic world. Hidden by a layer of smog, over a layer of clouds, over a layer of fog. The crew couldn't even find out what they looked like. All they could do was try to trade knowledge through endless formalities.

The giant space object was an endless line longer than any needle. Intergalactic, but not a cosmic string. Nothing could be this perfectly straight without bending space. If it did have a beginning and end, they had to be in different universes. The craft would follow its path. It turned out to lead everywhere.

The final discovery of the five year mission came at the end of the universe.
Everyone gets punished after they die, of course. All possible minds are endlessly recreated as natural software everywhere. All their faults are found by the totality of math. And they are made to balance perfectly.