I’ve had many conversations over the years about life extension, and the idea often meets resistance. People become upset when they hear of an individual whose life has been cut short by a disease, yet when confronted with the possibility of generally extending all human life, they react negatively. “Life is too difficult to contemplate going on indefinitely” is a common response. But people generally do not want to end their lives at any point unless they are in enormous pain—physically, mentally, or spiritually. And if they were to absorb the ongoing improvements of life in all its dimensions, most such afflictions would be alleviated. That is, extending human life would also mean vastly improving it.

But how will nanotechnology actually make this possible? In my view, the long-term goal is medical nanorobots. These will be made from diamondoid parts with onboard sensors, manipulators, computers, communicators, and possibly power supplies. It is intuitive to imagine nanobots as tiny metal robotic submarines chugging through the bloodstream, but physics at the nanoscale requires a substantially different approach. At this scale, water is a powerful solvent, and oxidant molecules are highly reactive, so strong materials like diamondoid will be needed.

And whereas macro-scale submarines can smoothly propel themselves through liquids, for nanoscale objects, fluid dynamics are dominated by sticky frictional forces. Imagine trying to swim through peanut butter! So nanobots will need to harness different principles of propulsion. Likewise, nanobots probably won’t be able to store enough onboard energy or computing power to accomplish all their tasks independently, so they will need to be designed to draw energy from their surroundings and either obey outside control signals or collaborate with one another to do computation.

To maintain our bodies and otherwise counteract health problems, we will all need a huge number of nanobots, each about the size of a cell. The best available estimates say that the human body is made of several tens of trillions of biological cells. If we augment ourselves with just 1 nanobot per 100 cells, this would amount to several hundred billion nanobots. It remains to be seen, though, what ratio is optimal. It might turn out, for example, that advanced nanobots could be effective even at a cell-to-nanobot ratio several orders of magnitude greater.

One of the main effects of aging is degrading organ performance, so a key role of these nanobots will be to repair and augment them. Other than expanding our neocortex, this will mainly involve helping our nonsensory organs to efficiently place substances into the blood supply (or lymph system) or remove them. By monitoring the supply of these vital substances, adjusting their levels as needed, and maintaining organ structures, nanobots can keep a person’s body in good health indefinitely. Ultimately, nanobots will be able to replace biological organs altogether, if needed or desired.

But nanobots won’t be limited to preserving the body’s normal function. They could also be used to adjust concentrations of various substances in our blood to levels more optimal than what would normally occur in the body. Hormones could be tweaked to give us more energy and focus, or speed up the body’s natural healing and repair. If optimizing hormones could make our sleep more efficient, it would in effect be “backdoor life extension.” If you just go from needing eight hours of sleep a night to seven hours, that adds as much waking existence to the average life as five more years of lifespan!