Ethan started keeping a notebook.
Not digital. The Engine somehow corrupted files—text documents developed strange character substitutions, spreadsheets recalculated themselves according to geometries that made his head ache. So he went analog: a Moleskine from the drugstore, mechanical pencil, entries dated by Earth time and Substrate time both.
The first page read simply: *Twelve percent of everything vanishes.*
The second page: *Not random. Not decay. Deliberate.*
He'd tested it across every measurable transaction. Chemical bonds forming in the primordial soup—twelve percent of the energy released just disappeared. Lightning strikes heating the atmosphere—twelve percent gone between flash and thunder. Even gravity seemed affected, though the math there made his temples pulse. Objects fell fractionally slower than they should, as if something skimmed a tithe from potential energy's conversion to kinetic.
Maya called while he was measuring tidal forces that didn't quite match the moons' masses.
"You haven't answered in three days," she said. No preamble.
"I've been working."
"On what? Your thesis defense was last month. You're supposed to be job hunting, not—" She paused. He heard traffic behind her, the doppler whine of passing cars. "Are you eating?"
Ethan glanced at the kitchen. Cereal boxes on the counter, protein bars, a banana turning brown. "Define eating."
"Ethan."
"I'm fine. I found something interesting."
"Interesting like 'publishable physics' or interesting like 'hasn't slept in forty hours'?"
He looked at the Engine on his desk, its surface swimming with symbols he almost recognized. "I need to go."
"Wait—"
He hung up. Felt the weight of it—another small cruelty, another relationship degraded by degrees. But the Substrate demanded attention the way his ALS would eventually demand attention: absolutely, without negotiation.
---
In the Substrate, the algae mats had begun to differentiate.
Three hundred years had passed there since he'd first observed them. Evolution worked quickly in the warm shallows, selection pressure intense in an ecosystem with limited niches. The original blue-green sheets had fragmented into distinct species: some that grew dense and matted, others that sent up frond-like structures to catch light above their competitors, a third variant that had somehow developed motility—drifting on currents, following chemical gradients toward nutrients.
Ethan watched a mat of the frond-builders sway in tidal current. Measured the energy they captured from starlight, tracked how they stored it in primitive molecular batteries.
Twelve percent vanished. Always twelve percent.
He leaned back from the Engine, rubbed his eyes. The observation was free, but focus had a cost—his neck ached, his hands tingled with the particular numbness that preceded his body's daily rebellion. He'd learned to recognize his limits. Two hours watching the Substrate, then rest. Four hours reading in bed, then protein and water. A rhythm dictated by deterioration.
But tonight the pattern nagged at him differently.
Twelve percent wasn't arbitrary. It couldn't be. In physics, specific numbers meant something—the fine structure constant, the ratio of electron to proton mass, the cosmological constant. Values that if changed even slightly would preclude chemistry, stars, life itself.
He pulled up his notes on conservation violations, cross-referenced them with the Engine's other oddities. The non-rotating planet. The fusion-less star. The moons in perfect orbital resonance. The gravity that worked but didn't quite work, light that traveled but seemed to take shortcuts through space.
A pattern emerged.
The Substrate didn't run on physics. It ran on *something that approximated physics*, but cut corners wherever the difference wouldn't matter. Stellar fusion was expensive to simulate—skip it, just produce light. Tidal locking took billions of years—skip it, lock the rotation from the start. Conservation of energy was ironclad in the real universe, but here?
Here it leaked. Twelve percent, always twelve percent, as if—
As if something was taking a cut.
Ethan's hands stilled on the notebook.
The Engine drew power from his observation, his intention, his intervention. Small costs for looking, larger costs for speaking, catastrophic costs for acting directly. But those were *his* costs, measured in vitality, in years shaved from a already-truncated life.
Where did that energy go?
He'd assumed it simply fueled the Engine's operations—observation required processing power, speech required bandwidth, intervention required the brute force of rewriting reality. But the Engine never grew warm. Never hummed with exertion. Never showed any sign of working at all except the slow parade of symbols across its surface.
And the Substrate itself... it leaked twelve percent of every transaction.
Into what?
Ethan placed his palm on the Engine's surface. Felt its warmth, constant and sourceless. In his notebook, he wrote a new line:
*The Engine feeds on something. The Substrate feeds it.*
And below that, in smaller script:
*What feeds the Engine?*
Outside his window, Boston slept. Inside his chest, his heart beat its measured rhythm—seventy-two times per minute, four thousand three hundred twenty times per hour, roughly one hundred million times per year. He had perhaps three years left. Four if he was lucky.
The Engine pulsed once beneath his palm.
Ethan counted the seconds until it pulsed again.
Exactly twelve.