THE multiverse is dead, long live the multiverse. A radical new way of looking at quantum mechanics suggests that even the multiverse will come to an end.
A popular view of the multiverse says that our universe is just one of an ever-inflating multitude of discrete “bubble” universes. These bubbles are eternally budding off new universes even as individual universes age and die.
But a new view of quantum effects – the brainchild of Sean Carroll at the California Institute of Technology and his colleagues – challenges this picture. It is also potentially very useful to quantum theorists, as it does away with some thorny issues that currently dog cosmology, including a particularly baffling paradox involving disembodied consciousnesses known as “Boltzmann brains”.
Boltzmann brains are an interesting, and somewhat disturbing concept. Basically, as I understand it, the idea is that in a universe of infinite space and time, matter would at times randomly coalesce into a temporary functional brain. This brain might have memories (false ones) of an entire life and have what it thinks are ongoing sensory inputs. The brain might only hold together for a few seconds, but during that time, it might believe it lifetime of experience behind it, that it lived in a world, and that it had a future.
The kicker is that in this infinite universe, Boltzmann brains are believed to outnumber brains in evolved creatures. (I think the reason is that the portion of time that will allow the evolution of intelligent life is a literally infinitesimal portion of the time line of an infinite universe.) In other words, there is a higher probability right now that you are a Boltzmann brain, that your memories are all false, and that you will momentarily dissolve after a brief flash of consciousness.
Still here? Okay, you might be good then. Unless of course your memory of reading the above is itself false and you still will dissolve in a few seconds. Obviously this line of reasoning borders on solipsism. Still, if we do live in an infinite universe, this is a logical possibility.
Apparently, Sean Carroll has found a way to banish infinity and as a result, Boltzmann brains. I’m sympathetic, but I don’t think that’s sufficient reason to justify a scientific theory. Of course, I doubt it’s Carroll’s only reason, and it does have some interesting consequences for multiverse theories. Like all multiverse theories, this is playing with mathematics and logical concepts but remains well outside of observational testing, at least for now. (Must…resist…urge…to mention philosophy 🙂 )