On Friday, October 31, 2003, at 10:55 AM, Hal Finney wrote:
David Kwinter writes:The concept of what makes a real quantum branch irks me. Surely a man standing beside a nuclear explosion will never survive.
Not necessarily. What exactly kills a man standing by a nuclear explosion? Well, probably a lot of things, but let's think about the radiant heat energy released by the blast. This heat is carried by photons, each of which is emitted by some atom in the nuclear device. When an atom emits a photon, the direction of its emission is random. With the large numbers of atoms and photons involved, the emission is, on average, uniform in all directions, which is what we expect.
But each individual emission is a quantum effect, and there is a chance that all of the atoms in the nuclear device could happen to emit their photons in a different direction than towards the man. In that case he would not experience the heat energy from the device and would not be killed by it.
I think similar arguments are possible for the radiation and all other sources of destruction coming from the nuclear explosion. So a man standing beside such an explosion could in fact survive.
It's also possible that the photons and other radiation from the device
might happen to pass through the man's body without being absorbed.
Each photon has a certain probability of being absorbed, per unit distance
that it travels through biological tissue. And each absorption event is
governed by quantum randomness. Therefore there is a nonzero chance that
a photon could pass entirely through the man's body, and in fact that
all of the photons could do so. In effect the man might just happen to
become transparent at the precise instant necessary to survive the blast.
Probably there are other bizarre quantum coincidences which could occur to let him survive as well.