Will messages to the future (or from the past) be at the nano-scale?
Ripe Premise Series
Storage decays. Paper rots, fades, crumbles. Optical storage like CDs can become unreadable in a decade or two -- much sooner if exposed to sunlight or other stresses. Magnetic storage fades. None of these media are the stuff of a fossil record.
As a result, any project that hopes to communicate complex thoughts to the distant future may need to invent its own mass-density, long-lived archival media. For the Rosetta Project, as initiated by the Long Now Foundation, that media is a laser-etched nickel plate. But such plates still only have an expected usable life of 2,000 years.
Might molecular-level memories -- such as IBM's recently-announced "Millipede" -- be even more robust? If they could be mass-produced, and stored away from the rampant chemical and nuclear processes (life and sunlight) that lead to decay, might they have a chance to persist for millions of years?
Sure, only advanced technology could read these tiny, molecular digital messages. But if tiny molecular digital messages are the only media that endure, then tiny molecular digital messages will be all we can consider sending to the distant future.
Or all we might expect to get from the distant past.
Perhaps the search for extra-terrestrial intelligence (SETI) should be using microscopes as much as radio telescopes -- microscopes pointed at hard material scooped from places unlikely to have been disturbed for millions of years. Some terrestrial geologic formations might qualify, but nearby regions of outer space seem a better bet.
The closest thing to a 2001-like obelisk that humanity ever discovers might be a pockmarked speck of dirt. Rosetta dust.
Biovariant: If you can't guarantee that a storage medium will be undisturbed, you could make it self-replenishing, with the ability to copy and rebuild itself in reaction to external stresses. Hmm, do we know of any information-dense molecular entities that behave that way? Say, DNA? Might the Earth's genome have begun as a consciously-designed storage mechanism and/or intentional communication-to-the-future? Might any part of the original message still be recoverable at this point? (This idea also appeared in a 1993 Star Trek:TNG episode called The Chase, and a short story called We'll Return, After This Message, by AutoDesk founder John Walker, written in 1989 and published in 1993.)