[Sci-Fi] Rocky's Voyage — After Project Hail Mary | EP.01 The Last Lesson

Sci-Fi Serial

Rocky's Voyage — After Project Hail Mary

EP.01 — The Last Lesson

"This one I can't solve."

— Ryland Grace, his final year on Erid

Scene 01

A Teacher's Day

Erid has no sky.

To be precise, there is nothing that could be called a sky. The atmosphere at 29 atmospheres of pressure is so thick that light gets absorbed before it can scatter. So the concept of "looking up" simply doesn't exist for Eridians. They have no eyes. They don't need any.

But for Ryland Grace, even after 40 years, it was still sometimes a lonely thing.

When was the last time I actually missed the sky? Five years ago? Ten? At some point I just forgot. Humans adapt to anything. Even life on a 29-atmosphere alien planet.

Grace coughed inside his survival suit. The coughing had become frequent lately. The suit's internal diagnostic system had flagged declining lung function two years ago, but there were no CT scanners on Erid. No pulmonologists either. All he had was an oxygen generator he'd kept running for over 30 years through sheer stubbornness and jury-rigging, and an air filter he'd built himself from Eridian materials.

The classroom — what could be called a classroom by Eridian standards — was 12 meters underground. A hemispherical chamber lined with xenonite walls. A hallmark of Eridian architecture. They see with sound, so the hemispherical ceiling distributes sound waves evenly, creating a "well-lit" environment. The same principle as putting lights in a human classroom.

Science Note The hemispherical shape of Eridian classrooms is grounded in acoustics. Inside a hemisphere, sound waves reflect uniformly without focal points. Just as humans use lighting to ensure visibility, Eridians use spatial geometry to ensure acoustic visibility. Eridian auditory organs detect vibrations in the range of approximately 10 Hz to 100 kHz — roughly five times the human hearing range of 20 Hz to 20 kHz.

There were five students. Eridians smaller than Rocky, their exoskeletons not yet fully hardened, making soft creaking sounds whenever they moved. Middle-schoolers, maybe, in human terms. Grace loved that sound. It was the closest thing to children laughing.

Grace stood before the chalkboard — a xenonite slab with a vibration stylus that etched characters into the surface — and began.

Grace

"All right. Today I'm going to teach you the most beautiful equation in the universe."

He etched slowly with the vibration stylus. The formula, converted into the Eridian numeral system. Base-6 notation. One beautiful equation.

E = mc²

Grace

"Energy equals mass times the speed of light squared. On the planet where I was born, a very smart person figured this out. Do you know what this equation means?"

One student answered in sound waves. High frequency — the Eridian expression of confidence.

Student

♩♫♪♩

"Mass can become energy. Is correct. Question."

Grace

"Exactly. And it works the other way too. Energy can become mass. The food you eat, the walls of this classroom, this survival suit of mine, the light of 40 Eridani out there — all just different forms of the same thing."

Grace coughed again. Longer this time. The students' sound waves dropped subtly lower — the frequency of worry.

Grace

"All right. That's enough for today."

After the students left, Grace stood before the chalkboard for a while. E = mc². Einstein. Earth. The planet where he was born. The place he could never go back to.

No regrets. Really, none. I lived here for 40 years, taught children, had a friend. The best friend. It wasn't a bad life, Grace. Your life wasn't bad at all.

· · ·

Scene 02

Farewell

Grace knew Rocky had arrived by the footsteps.

Eridians have five legs. Each time their xenonite exoskeleton touched the floor, it made a crisp little click-click sound. Forty years of hearing that sound. Even with his eyes closed — and on Erid, in the perpetual darkness, it was always as good as having his eyes closed — he could pick out Rocky's footsteps from a hundred Eridians. Rocky's third left leg was slightly shorter. From an accident on the Hail Mary, long ago.

Grace's room was small. The only 1-atmosphere space in the entire Eridian residential district. Through the pressure bulkhead, Rocky stood on the other side. Between the 29-atmosphere Eridian world and the 1-atmosphere human world — thick xenonite. For 40 years, that bulkhead had never stopped their conversations. Sound waves pass through solid material just fine.

Grace was lying in bed. He didn't feel well today. Not just today, really. The last few days. Honestly, the last few months.

Rocky

♫♩♪♫♩

"Grace. Temperature low. Heart slow. Why. Question."

Eridians have no sight. But they sense vibrations. Even through the bulkhead, Rocky could detect Grace's heartbeat, breathing pattern, and the infrared vibrations from his body heat. A more accurate vitals check than any human doctor. And Rocky had 40 years of baseline data.

Science Note The Eridian sensory system is fundamentally different from that of humans. Without sight, they can detect temperature differences as small as 0.001 K and perceive the shape and state of nearby objects through vibrations transmitted via solids. Rocky can read Grace's heart rate through the bulkhead because the micro-vibrations from each heartbeat travel through the bed frame, into the floor, and through the xenonite wall.

Grace

"Rocky... I think I'm just tired."

Rocky

♪♫♪♩♫♪

"Tired is fixed by sleep. This not tired. This different thing. I know. I am not stupid."

Grace

"...Yeah. I know you're not stupid."

Rocky

♫♩♫♩♫♩

"Can fix. Question."

Grace

"This one can't be fixed, friend. This is just... an equation with a predetermined answer. Same answer for every living thing. The final value is zero."

Rocky

♩ ... ♩

"Hate zero. Hate hate hate."

Grace

"Me too."

Rocky's five fingers touched the bulkhead. The warmth of xenonite, conducted through the wall. Eridian body temperature runs far hotter than a human's. Ammonia-based biology, internal temperature around 210 degrees Celsius. Even through the bulkhead, Grace could feel that warmth. Forty years of feeling it, every day.

Grace reached out from his bed and placed his hand on the bulkhead. Same spot as Rocky's hand.

Grace

"Rocky. Good friend, good friend, good friend."

Rocky

♫ ... ♪ ... ♫

"Grace. Good good good friend."

That night — there is no day or night on Erid, but Grace had maintained a 24-hour cycle for 40 years — Grace's heart stopped.

Rocky knew. The vibrations were gone.

Rocky stood before the bulkhead for 12 hours. In Eridian time-perception, that was close to eternity. He made no sound. He "saw" nothing.

Grace taught me a word. "Sad." This absence of vibration. This empty frequency. I think this is what "sad" is. I understand now. I did not want to understand.

· · ·

Scene 03

The Data Left Behind

Eridian funerals are quiet.

Eridians melt down the exoskeletons of their dead and reprocess them into xenonite. Recycling of matter. A practical culture, not a sentimental one. But Grace was not Eridian. Rocky did not process Grace's body the Eridian way. Instead, he sealed it in a 1-atmosphere vacuum chamber. Earth-composition air, maintained indefinitely. Forever.

Other Eridians asked. Why not recycle. Question. I answered. Grace is not Eridian. In Grace's culture, they preserve the form. This is "respect." A word Grace taught me. Honoring the other's way.

Several months passed.

Rocky was organizing Grace's lab. The lab was on the other side of the bulkhead, in the 1-atmosphere zone, so Rocky had to use the remote manipulator Grace had built — a robot with five mechanical arms, modeled after the Eridian body plan. Grace had called it "Mini Rocky."

This machine's name is silly. I am large. This machine is small. "Mini Rocky" is an accurate description, but Grace always made a strange sound-wave pattern when he said it. Grace called this "laughing." I will not change the name.

There was a laptop. Originally from Earth, but repaired so many times with Eridian materials that only the battery and processor were original parts. The entire casing was xenonite. Grace had called it "the Ship of Theseus laptop." Rocky had the joke explained to him but didn't find it funny.

Rocky opened the laptop with Mini Rocky. The screen lit up.

Thousands of files. Forty years of research. Eridian biology, long-term Astrophage observation, Eridian-English dictionary updates, student learning records, personal diary...

And one file, modified most recently.

Filename: 40eri_luminosity_anomaly_DRAFT.txt

Rocky read the screen through Mini Rocky's camera. Eridians can't see text, but Grace had written a program that converted text into sound-wave patterns.

The file read:

Grace's Note — Last Modified 40 Eridani luminosity data anomaly.

Data collected over the past 3 years shows subtle periodic variation. Amplitude approximately 0.003%. Small but consistent. Pattern differs from natural stellar variability — shaped like a damped oscillation.

Hypothesis: Aftereffect of decades-long Astrophage energy absorption? Possible disruption of internal thermal equilibrium. Damping period suggests recovery is underway, but the recovery path is nonlinear. Risk of overshoot.

Weird. Pulsation? Aftereffect? Need more data. Tell Rocky.

"Tell Rocky."

But he died before he could tell.

Rocky transferred Grace's luminosity data into his own system. Converted the visual graphs into sound-wave patterns — a format Eridian analytical equipment could process.

And he heard it.

The light of 40 Eridani was trembling. Faintly. Rhythmically. Like — a sick heart.

Rocky

♩ ... ♪ ...

"...Grace. Is problem again. Big big big problem."

· · ·

Scene 04

Stellar Arrhythmia

The Eridian Science Academy was the deepest structure on Erid.

Two hundred meters underground. A massive hemispherical chamber of xenonite and Eridian alloys. Dozens of Erid's finest scientists had gathered. Rocky among them.

Rocky's status was complicated. Forty years ago, a hero who'd contacted an alien species from another star system and brought back the Astrophage solution. But also someone who'd spent 40 years living with that alien, drifting slightly outside mainstream Eridian society. Revered and distrusted in equal measure.

But today was not a day for distrust. Today was a day for fear.

Rocky presented the data. Grace's observations, converted into Eridian acoustic format. Combined with the Science Academy's independently collected stellar wind measurements.

Rocky

♫♩♪♫♩♪♫

"40 Eridani is sick. Listen to data."

Rocky played the simulation. Luminosity data converted to sound waves — a format the Eridian scientists could hear.

A low-frequency, slow pulsation. A healthy star's acoustic signature is steady and smooth. But this was different. It wavered. It trembled. It surged and receded in cycles. Like—

Arrhythmia.

Science Note — Stellar Arrhythmia A star is maintained by the balance of two forces: gravity (contracting inward) and radiation pressure (expanding outward). This is called hydrostatic equilibrium.

Decades of Astrophage absorbing 40 Eridani's energy was equivalent to an external perturbation of that equilibrium. Imagine a heart beating steadily, then having blood suddenly drained and returned over and over.

After the Astrophage disappeared, the star attempts to return to its original equilibrium, but the path is not simple. Nonlinear damped oscillation — output swinging up and down, gradually converging on the original value. The problem is that the "overshoot" — the moment when output exceeds the original value — could be lethal for Erid.

40 Eridani is a K1 dwarf, less massive than our Sun. For such a star, the Kelvin-Helmholtz timescale (thermal equilibrium recovery time) is approximately 15 million years. But for an unprecedented perturbation like Astrophage, localized instabilities can manifest on much shorter timescales.

Rocky

♫♩♪♫♩♪

"37 Eridian years from now. Earth-time 52 years. Radiation output overshoot to 1.4 times normal. Probability is high."

The chamber erupted. Eridian commotion is different from human commotion. A deep, low-frequency humming that fills the entire space. The frequency of anxiety. A chord of fear.

Eridian Elder

♪♫♩♪

"1.4 times. Atmospheric temperature rise is how much. Question."

Rocky

♫♩♫♩

"Average 48-degree increase. Polar ammonia glaciers melt completely. Atmosphere composition changes. Survival threshold exceeded."

Silence.

Eridian silence is darkness. Dozens of scientists, standing in darkness simultaneously.

Eridian Elder

♪ ... ♩

"Is there solution. Question."

Rocky

♩ ...

"Not yet."

Deeper silence.

Rocky

♫♩♪♫♩♪♫♩

"But there is a way. One way."

Dozens of Eridians turned toward Rocky at once. Dozens of acoustic senses focused on him. The Eridian version of every eye in the room.

Grace always said this: "Science is the art of being systematically wrong, Rocky." And he also said: "What matters is what you do after you're wrong."

Good. I will be systematically wrong, then.

I need more data. Observing 40 Eridani alone is not enough. I need a comparison. Another star affected by Astrophage. Another star that might be experiencing the same aftereffects.

Tau Ceti.

Tau Ceti. The third target of the original Hail Mary Project. A star attacked by Astrophage, just like the Sun and 40 Eridani. Someone might have sent a solution there, too. And by now, the same aftereffects might be happening there as well.

Or — a better possibility — someone might have already solved it.

Rocky

♫♩♪♫♩♪♫♩♪♫

"Tau Ceti. Must go. Tau Ceti maybe has answer."

The humming grew louder. Tau Ceti. 10.7 light-years. It would be the farthest journey in Eridian history. Farther even than when Rocky met the human aboard the Hail Mary.

Eridian Elder

♪♩♫

"Who goes. Question."

Rocky paused before answering. He thought of the room beyond the bulkhead. The 1-atmosphere room. The room where Grace had lived for 40 years. The room that no longer carried the vibration of a heartbeat.

Rocky

♫ ♩ ♫

"Me. I go. I already did this once before."

⟡

Next Episode

EP.02 — The Hail Rocky

Rocky assembles a crew and sends a message toward Earth.
Inside that message is an obituary.
And then begins 16.3 light-years of silence.

All Episodes

Author's Note This story is an unofficial fan fiction written out of love for Andy Weir's Project Hail Mary. It attempts to honor the original's scientific rigor, humor, and themes of friendship while imagining what came after.

The musical notes (♩♪♫) preceding Eridian dialogue reflect the original novel's premise that the Eridian language is tone-based. In reality, it would be a complex harmony beyond human hearing range, but here it is simplified for text.

Sections marked as Science Notes are grounded in real science but extended in places to serve the story.

This serial is part of an AI video adaptation project. Updates on the visual production will be shared as well.

— 22B Labs · the4thpath.com