Jan 24, 2015 08:40 PM
Who's looking at you?
http://plus.maths.org/content/whos-looking-you
EXCERPT: [...] The observer has once again returned to a central role in physics with cosmology, says Hartle. This is because many cosmologists today work with the assumption in their models that the Universe is very large, and could contain many possible observers. And the future we will observe will be very different depending on what kind of observer we are.
"In these large universes where, in principle, systems could be replicated, [the physical situation of the observer] comes back again to affect the observations," says Hartle. Since we are physical systems, like any other, we have only a certain probability of existing in the Universe. There's a probability we are as we appear to be, a population of human beings existing together on a small blue-green planet. But in these very large Universes it's also possible we are merely a Boltzmann brain — a random fluctuation in the Universe that has coalesced momentarily into a conscious brain who's memories and knowledge, a random fluctuation of data, matches our own.
It's slightly alarming but according to the maths it's far more likely we are one of these Boltzmann brains, these deluded observers who are just imagining they have all the data and experience that we have. "It's much rarer to have multiple individual human beings, of course, but, in the large universes that are contemplated by today's theorists, that would occur." And the future we will observe will be very different depending on which of these possible "copies" we are. So not only do we need theory that describes the evolution of the Universe, making predictions for what each of these copies will observe. But in order to make first-person predictions about what we will observe we also need to know which copy we are, or have a probability distribution for which copy we are most likely to be. Hartle and his colleague Mark Srednicki call this distribution the xerographic distribution, and it is this combination of theory and xerographic distribution that is testable by observations....
http://plus.maths.org/content/whos-looking-you
EXCERPT: [...] The observer has once again returned to a central role in physics with cosmology, says Hartle. This is because many cosmologists today work with the assumption in their models that the Universe is very large, and could contain many possible observers. And the future we will observe will be very different depending on what kind of observer we are.
"In these large universes where, in principle, systems could be replicated, [the physical situation of the observer] comes back again to affect the observations," says Hartle. Since we are physical systems, like any other, we have only a certain probability of existing in the Universe. There's a probability we are as we appear to be, a population of human beings existing together on a small blue-green planet. But in these very large Universes it's also possible we are merely a Boltzmann brain — a random fluctuation in the Universe that has coalesced momentarily into a conscious brain who's memories and knowledge, a random fluctuation of data, matches our own.
It's slightly alarming but according to the maths it's far more likely we are one of these Boltzmann brains, these deluded observers who are just imagining they have all the data and experience that we have. "It's much rarer to have multiple individual human beings, of course, but, in the large universes that are contemplated by today's theorists, that would occur." And the future we will observe will be very different depending on which of these possible "copies" we are. So not only do we need theory that describes the evolution of the Universe, making predictions for what each of these copies will observe. But in order to make first-person predictions about what we will observe we also need to know which copy we are, or have a probability distribution for which copy we are most likely to be. Hartle and his colleague Mark Srednicki call this distribution the xerographic distribution, and it is this combination of theory and xerographic distribution that is testable by observations....