Sci-Fi Ghosts

How do you do non-supernatural ghosts in a science fiction setting?

non-baryonic lifeforms that can phase through most matter

Nanomachines

Johnny Depp.

For the record, psychic stuff is supernatural for these purposes, right?

Depending on how theoretical you want to go: a race that survived the previous Big Crunch by embedding their minds into space-time. They'd subsist off of quantum probability creating miniscule amounts of heat differences across lightyears and millenia.

>non-supernatural ghosts
Isn't that like saying "non-projectile bullets"?

Sometimes, users with brain-machine interfaces who die while plugged in to the internet... they flatline, but they don't go offline.

>non-supernatural ghosts
Oh boy

Infomorphs.

Paracausal echoes of quantum data.

AI holograms of someone who died, but can continue to learn and shit

AI copies, including streamed memory of death

A guy with a bedsheet over the head.

Artificial intelligence and pattern-recognition software designed to help people move around throughout their daily lives.

Patterns of people are noted, copied, and updated constantly with information, analyzed so that a computer knows what a person wants just a fraction of a second after they've started doing it, or sometimes much longer beforehand. This, of course, only applies to actions taken that are very routine and normal, with hundreds or thousands of datapoints that lead to this calculation.

Individual profiles are scrubbed from the systems on their deaths, or at least the issuing of their Death Certificate, but the data if often stored and analyzed so that they can be used to further learn people's patterns of behavior. Sometimes these routines aren't properly scrubbed, and analysis can lead to certain devices actually carrying out actions that are simulated, much like sleepwalking. The computer has no memory of this happening, since it though it was a simulation rather than a carried out action.

This can lead to poltergeist actions where there's a lot of technology present, and where someone spend a good deal of time it's most likely that those systems would be looking over that data in order to learn, and there would be a higher probability of glitches. And, of course, most of this would be happening when you aren't paying attention or actively looking for it, since the computers would be defaulting to watching your own routines and analyzing their old profiles to help. If you were to stop and pay attention, they'd have no frame of reference for that behavior and would cease analyzing past data in order to watch you more closely.

Two routes I know of:

A: Echoes of memories imprinted genetically through recycled stem cells used in genetic augmentation drugs a la Bioshock

B: Near-perfect computer simulations of a person's mind down to memories, personalities, quirks, ect that are self-aware and either trapped jumping from mechanical body to mechanical body(leaving exact copies lf themselves behind) a la Soma.

>jumping from mechanical body to mechanical body(leaving exact copies lf themselves behind) a la Soma.
They don't jump to a new body and leave a copy behind. They make a copy, put that copy into a new body, and are themselves left behind.

Ah but if the copy is exact, then can one really say the original is left behind?

Yes. The game's own ending shows that.

This is a lot easier than the thread is making it out to be.

Best way to do it would be that the person had an AI copy their personality/memories/mannerisms or whatever you like most for your ghostliness and then the AI projects the data in holograms that appear and act as people would. If you then want spooky shenanigans do this WITH the addition of malfuctioning software/hardware that makes what should normally be a pleasant experience into a nightmarish one.

I'd imagine that the intent of this technology is to make it so that people can preserve wisdom or ease their passings or even create memorials to their own memories, but the unintended consequences would be fun to explore.

Some kind of crossover from a parallel universe.

Some kind of quantum physics fuckery - superposition gone bad or somesuch

Echoes of a person's self trapped in cyberspace, taking over machines, personality imprints on cyberware, etc.?

ghosts dont really have a set definition though. Bullets do.

The best definition of a ghost is the spirit of a dead person who seems to continue to live.

A ghost could be emails from someone who turn out to have died years ago...