The Boltzman brain problem suggests that, over eons of time, there is an infinite possibility atoms colliding in outer space to create recognizable things, from the mundane (the unscrambling of an egg) to the grandiose (a parallel universe). There could also be another you out there, just floating in space. Or, according to the Boltzman brain problem, an exact replica of your brain.
In fact, it is more likely that
just your brain is out there than your whole body. Nature tends to do thing as simply and with as little energy as possible, and the creation of your brain is statistically "cheaper."
So it's entirely likely that your brain is floating somewhere out in space, fully aware, with your memories and the illusion of your world around it. Lots of your brains, in fact.
And because the creation of our universe the way it is was
such an improbable occurrence (ie there's only one "real" you, compared to many floating brains), it is statistically more likely that you are one of these brains in space, and not yourself in this universe.
Kind if disturbing, right?
The thing is that most cosmologists don't really believe this is true - but
they can't figure out how to disprove it. And this flaw in the use of probability to predict the universe creates all sorts of issues in other parts of cosmology, which is in itself disturbing.
Or maybe it is true, in which case - wooooaaaahhh.
Check out the
NYTimes article for a much longer and more detailed description of the whole phenomenon.
