Whether we upload our consciousnesses into computers, grow clones or change out our squishy, organic bits for shiny, new cybernetics, chances are we'll retain a soft spot in our cold, metal hearts for what becomes of our remains.
That hasn't stopped sci-fi authors from contemplating gray areas that would make disposing of our bodies trickier and more nuanced than we imagine. "Star Trek" popularized the idea of transport via matter-energy-matter conversion, in which bodies are literally destroyed and reconstituted across thousands of miles, forcing us to contemplate whether our bodies hold intrinsic value, or are merely assemblages of matter to be sloughed off like a snakeskin. After all, with a few exceptions such as our eyes, cerebral cortex neurons and possibly heart muscle, some researchers have theorized that the bulk of our body's cells might get replaced, on average, every seven to 10 years [source: Wade].
Are those few remaining bits of us significant? Are we more than the sum of our parts?
Science fiction doesn't stop there, however. Philip K. Dick, for example, posited a consciousness that was kept alive after physical death within its body's brain, in conjunction with machinery and cryonic suspension.
Of course, it's conceivable that science might one day conquer death altogether, but we're interested in burial, so let's assume we're still mortal by the time humans set out for the nearest stars. How might we deal with our departed in this new space age?
Whatever our preferences, it's likely that certain practical realities, such as velocity, health and the shortage of materials, would limit our options.
Let's consider velocity first. Barring some advanced, warplike technology that we can't yet conceive of, a ship traveling between stars will need to ramp up to some percentage of light speed, or c. Depending on available technology and velocity achieved, this could take months, years or generations -- meaning our imaginary ship could not afford to waste precious braking time or fuel to release a body or ashes into space, and anything it released while zooming along would retain its velocity and pose a serious threat to anything struck by it.
Alastair Reynolds took the idea of high-velocity burial to an extreme in his Revelation Space series, when a dying man requested that his remains be released as the ship crested light speed, thereby achieving "burial at c."
Of course, from a scarcity standpoint, this begs the question of whether we would dispose of human remains at all. During interplanetary travel -- aboard a generation ship, for example, in which people live entire lifetimes en route to distant star systems -- human remains might prove too valuable not to reuse. By mass, the human body consists mostly of oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus -- all essential elements to sustaining life. Looked at another way, our component cells contain 65-90 percent water, arguably the most valuable substance in the universe, especially to people alone in the black desert of interstellar space.
Such concerns could be ameliorated if humanity has mastered matter-energy relationships or the ability to build matter efficiently from raw materials, such as interstellar hydrogen. Even so, keeping a body around would be difficult in a closed environment, unless the air recycling system were capable of removing the harmful gases released by a decaying body. Alternatives might include embalming, freezing or mummification, assuming available space could be found.
These are all practical concerns, however. How might cultural and religious traditions cope with the realities of space burial now and in the future?