  A perceived problem with the standard flat-lambda model is that in the far
future spacetime becomes an exponentially expanding de Sitter space, filled
with Gibbons-Hawking thermal radiation, and given infinite time there will
appear an infinite number of Boltzmann Brains (BB's) per finite co-moving
volume today. If BB's outnumber ordinary observers by an infinite factor, why
am I not one? This Gibbons-Hawking thermal radiation is observer dependent--due
to observer dependent event horizons. Different observers moving relative to
each other will see different photons, and different BB's. I will argue that
the only particles that are real are the particles dredged out of the quantum
vacuum state by particular real material detectors. (In much the same way,
accelerated detectors dredge thermal Unruh radiation out of the Minkowski
vacuum due to their observer dependent event horizons.) Thus, I may see a
thermal BB, but cannot be one. Observer independent BB's can be created by
quantum tunneling events, but the rate at which ordinary observers are being
added to the universe by tunneling events to inflating regions exceeds the rate
for producing BB's by tunneling by an infinite factor. I also argue that BB's
do not really pass the Turing test for intelligent observers. Thus, the
standard flat-lambda model is safe.
