uh oh, we forgot something

[eub]

Vampires don't appear in mirrors. Light is lost at some point in the path from source to vampire to mirror to eye. We don't know where in that path it is lost. If vampire-reflected light reflects from mirrors, and merely is imperceptible to the human eye, then the cell succeeds, though it cannot be used directly in a zero-fuel lighthouse built for isolated locales, but we should consider the more troublesome case. If vampire-reflected light is absorbed by mirrors, the mirrored vampire power cell is in trouble. (Experiment: see if a heated mirror radiates strongly in the pallid band reflected by vampires.)

At first thought, one is tempted to insert a vampire into a loop of fiber-optic cable. However, total internal reflection presumably constitutes a mirror. A graded-index fiber, though?

(My mail informs me that thatmathchick has already called us on this whole mirrors problem.)

If all else fails, vampiric light amplification may be left to more-advanced civilizations, ones capable of assembling a mass concentration approaching a black hole. For simplicity, take a black hole, and consider dipping a vampire into the photon sphere, at R_* = 3/2 R_s, where light travels in a circle. (No vampire report I am aware of suggests that this could act as a mirror.) The useful photons for public-utility purposes are those just outside R_*, which will receive repeated vampiric gain and then escape.

Huh. Dropping a vampire into a black hole would be very, very bad.

No, well, in some sense it may eat the universe, but I think not within finite time in an external observer's timeline. I think. What do you think?

Comments

[eub.livejournal.com]

I was concerned that photon trajectories within the black hole would be constrained to intersect the vampire infinitely many times within a bounded interval, causing the the black hole to gain mass at a corresponding rate. On second thought, I think this need not happen before both vampire and photons hit the singularity, and then all bets are off.

In any case, this is only from the black hole's point of view. An external observer never sees the infalling vampire (or anything else) penetrate the event horizon; it redshifts to invisibility as it asymptoticall approaches the horizon. No worries.