You read everything about the heart that you can find. You learn about coronary and circumflex arteries, preload and afterload, the difference between the mitral and tricuspid valves (one has three leaves, one has two; both hold back the tides of your blood, keep everything in order).
You learn how a heartbeat is constructed, the electrical pulses that keep you moving. AV node, SA node, bundle branches, Purkinje fibers, wetwiring laced through myocardium. Cardiac cells use calcium instead of the normal sodium-potassium pump, choosing a harder process in order to ensure a steady rhythm and optimum results. Nothing but the best, won't settle for less. Your heart will strip your bones dry to keep beating if it has to.
The average human heart beats 2.21 billion times over a lifespan. You think that between all the splintered versions of you, you've hit that number already. Your heart beats more slowly due to your constant training, however, so maybe you have a bit more time. You take your pulse over and over again to confirm.
You read EKG strips, counting tiny boxes, 0.04 seconds per box, thirty boxes to every six-second strip. It only takes six seconds to learn everything you need to know about a person's heart rhythm. Multifocal preventricular contractions, bundle branch blocks. You learn about dopamine. You learn about amiodarone. You learn that adrenaline can revive dead hearts, or cause your pulse to spike when he messages you. You learn methods of repair.
Atrial flutter manifests as a bumpy sawtooth pattern on the EKG, caused primarily by valve disease. You count the number of small boxes between each tooth and divide by 1500, admire the perfect regularity, how even when malfunctioning the heart is a precision machine. A square-wave defibrillator can save lives, reset the heart to adjust the tempo—beat one, beat two.
(Music, too, has sawteeth and squarewaves. In a future devoid of pharmaceuticals and surgery, music is the only medication you have. You self-administer heavily.)
You're up to your elbows in robot viscera, staring down at your creation through the blueprints projected across the inside of your shades. Metal gleams in the predawn light that creeps through your window—steel ribs cracked open, slabs of green silicon stamped with circuitry more convoluted than a Golgi complex. The spinal column took you months to make, each vertebra filled with ball bearings and color-coded wire. Brobot is your finest work. You're sending it to Jake so he can tear it apart.
You move Brobot to the specialized container you've created and load the whole thing onto your narrow boat. The early morning chill makes you shiver as you slip out across the ocean. Your arms stretch and pull at the oars, setting up an easy rhythm, until you reach the place where your uranium supplies are stored. A few lever systems later, Brobot's container is counterweighted against your uranium storage unit and suspended several feet beneath you, its clean metal lines blurring as the sun slants through the water. Better living through physics.
You strip your shirt and pants off, folding them neatly beside you, and pull rubber gloves onto your hands. After a moment of hesitation you remove your shades and set them on top of your clothing. Then, you dive.
The uranium you have isn't particularly potent before you irradiate it. You pull out a silvery chunk and compare it against your fist. It's about the same size, roughly heart-shaped. It'll do. You tuck it close to your chest as you swim around to the other side of the storage unit.
This is the tricky part. You insert the uranium piece into the waiting compartment, press the neon green button marked with a radiation symbol, and then kick for your life towards the surface. You have fifteen seconds to get clear before the reactor powers on, or you'll be fried. The need for oxygen burns through your chest.
You breach the surface with a rough gasp and a shake of your head, throwing your arms over the side of your boat to anchor you. You look down between your feet and see green light unfurling through the sea below. Water is the best insulator you have, a valuable and limitless resource, so you're safe enough.
You pull yourself back onto the boat and affix your glasses to the bridge of your nose, not yet bothering with the rest of your clothing. You pick up the remote control you've brought with you. With a flick of your fingers a robotic arm extends from the underside of Brobot's container to pluck the glowing uranium from the reactor. It brings it inside the case and you switch your shades to the internal camera feed. From there, it's all laparoscopy. Your touch is as delicate as a surgeon's as you navigate the uranium heart into the shielded casing in Brobot's thoracic cavity, install the heat sink and secure it with thermal paste, and finally connect the wiring to the motherboard.
There's a green spasm of light as the power levels stabilize, and Brobot's shades come alive with an orange-red glow. You switch your camera feed again and look out through Brobot's eyes, but there isn't much to see—just gray walls illuminated by blinding LED light.
You imagine watching Jake's hands scrabbling for purchase on the metal skin, his green eyes pinching with a smile that takes up his whole face. You imagine hearing his laugh crackle through your speakers and pretending that you're only separated from him by a brittle plastic pane.
You shake your head, clearing it. There's still work to be done, and first up is towing Brobot back to shore. You dress yourself before hauling the box back up through the water, giving it a friendly pat when you've got it secured, and begin the journey back to your apartment. By the time you get home the sun is high in the sky and your whole body is drenched in sweat. You can't wait to take a shower.
Later, Brobot stands beside your desk as you install the necessary software. You made him taller than you so that when Jake finishes growing, Brobot will still be equally matched. Maybe he'll think you're that tall now; maybe he'll think that's impressive. Maybe your calculations are meaningless when Jake English is involved, what does it even matter how tall you are. But. Still.
You hold the tip of your tongue between your teeth and watch lines of code fly up your computer screen, trying not to daydream too much. Your apartment is quiet for once, and in the silence you hear a faint beating sound. When you trace the source, you realize it's coming from Brobot's chest.
You frown, thinking you installed something wrong, you'll have to run diagnostics, take the whole thing apart. Then you remember the way the lump of uranium looked in your hand—ventricles smoothing towards the apex, a bump to shape the aorta. Too easy, you think. No. Maybe?
You run your diagnostics and you don't find a thing wrong with the build. Somehow, you're not surprised.
What English doesn't understand won't hurt him, anyway.
Sometimes your love feels like a sucking chest wound, raw and open, a one-way valve to your lungs that won't let air escape. You can't live without it—you have to breathe—you inhale—and your chest tightens, your trachea dislocates. You choke on oxygen.
One day, you'll explode.