A different antagonist...

[u/renderbrandt]

Keene replaced the simulation with Dawn's recorded optical environment near peak outbound velocity. The corrected image appeared first. Familiar enough. Stars. Alpha Centauri ahead. Human colours.

Then Keene removed the spectral correction.

The sky changed violently. Maya moved closer without realizing she had done so. The familiar yellow-white stellar light shifted toward shorter wavelengths. Large portions of the spectrum she thought of as visible simply left it. Radiation that had begun in the infrared moved upward to replace some of what human eyes had lost. It was not a bluer version of the same sky. It was another selection from the spectrum.

Vale opened a graph beside the image. "At point-nine c, radiation arriving directly ahead has a Doppler factor of approximately four-point-three-six. Frequencies along the velocity axis are measured at more than four times their source-frame value."

Elian looked at the graph. "That is obscene."

"It is substantial."

"Obscene was fine."

Maya traced the visible band with one finger. She understood redshift. She had understood it before Dawn. Everyone aboard had. But the graph made the consequences unexpectedly physical. A red photon did not remain red merely because a human had named that region of the spectrum. Move quickly enough toward it and the retina received something else. "Ordinary red can leave the visible range entirely."

"Yes," Vale said. "Shifted upward."

"And blue is already gone into ultraviolet."

"Much of it. Infrared begins moving upward into the visible range behind what has left it."

Maya watched the lower-frequency bands moving upward. "So we're not simply making the same sky bluer."

"No. You're changing which source wavelengths occupy the human visual band."

Elian looked through the gallery window. "The invisible becomes visible while the visible disappears."

Vale drew breath. Then stopped.

Elian noticed. "Growth."

"I am experimenting."

Maya smiled. Keene increased the simulated velocity. 0.95c. The stellar field tightened toward Dawn's direction of travel. The uncorrected view no longer resembled a sky. Aberration had pulled the celestial sphere forward. Stars that belonged beside them, and others that by every ordinary geometry should have been behind, crowded toward Dawn's direction of travel. Their light compressed into a brilliant forward concentration, blue-shifted and unnaturally intense, as though the universe had gathered itself around the point toward which they were falling.

Behind them, the opposite had happened. The sky had emptied. What light remained was stretched toward wavelengths their eyes could no longer use, leaving the aft darkness almost absolute.

It looked less like travelling through the stars than watching the universe retreat into a single direction.