From Eternity to Here, Sean Carroll

From Eternity to Here:  The quest for the ultimate theory of time by Sean Carroll is a quest to understand the meaning of time.  Perhaps in more detail, why time seems to move in one direction when conventional physics allows it to move in either direction.

Started: 5/3/2014
Completed: 8/15/2014
Recommendation: Good read, but you have to like physics
Recommended By:  I read a review of this book in Science News and decided to put it on my reading list.

Words I researched:

heterodox -- Not conforming with orthodox standards or beliefs

Review:

What an excellent discussion of time (and black holes).  I learned a ton about de Sitter space and spent way too much time trying to figure out what it must be like inside and near a black hole (just a side effect of considering entropy and information loss).  So, if you don't find physics and cosmology concepts daunting, this book presents a pretty good series of arguments for why time currently moves in one direction associated with entropy.

Unfortunately, thinking about black holes left me with these questions:

1)      I know that a black hole has an Event Horizon.  I understand that the Event Horizon marks where the escape speed exceeds the speed of light in a vacuum, “c,” but I’m wondering about the force of gravity inside the black hole approaching the singularity.  It strikes me that there might also be a limit as to how fast things can fall into the singularity that would also approach the speed of light.  What happens when the force of gravity would accelerate a given mass above the speed of light as the mass approaches the singularity of a sufficiently large black hole?

a.       My guess is that the mass being accelerated would start converting to energy as it approaches the speed of light which would reduce the speed at which the mass was being accelerated (the acceleration due to gravity depends on the mass of the object being so accelerated, correct?).  The impact, to my way of thinking is that a black hole of sufficient size would convert all the mass coming into it into energy.  Does that sound right or have I lost track of something important?  If so, does that mean something for the force of gravity at the black hole?  Would incoming mass being reduced to energy mean that the black hole would no longer accumulate mass (since incoming mass was converted to energy)?  Would it be possible to see the a fluctuation in the Event Horizon as the mass becomes energy?

2)      If a black hole reduces to a singularity, then it seems to me that the singularity itself would be smaller than a Plank length (or at a minimum small enough to fall within the dimensions of a virtual particle).  If so, I’m thinking that would make the singularity subject to a time-energy uncertainty relation constantly.  If so, wouldn’t that cause constant gravitational shock waves inside the black hole which would be observable externally as fluctuations in the Event Horizon (as the singularity undergoes a state change)?

a.       My guess is that it would, but that these shock waves would either be so small or happen so quickly that they would not be detectible (maybe the fluctuations would, by definition be within some application of the Heisenberg Uncertainty principal?) outside or at the Event Horizon.  If they were discernable, then the black hole would “leak” information in an unpredictable way that would effectively generate entropy.  Or, have I assumed too much and there is a glaring error in one of the “if so” extensions above?

b.      A corollary to this would be that momentum would not necessarily be conserved (since the black hole is within the Heisenberg Uncertainty Space), so if momentum of the black hole was randomly changing, a black hole might have a certain “bounce” to it.  Again, however, I think that would create some kind of gravitational shock waves that would propagate through to the Event Horizon.

3)      Finally, when thinking about black holes in general, I stumbled across anti-de Sitter space.  In the book, Sean Carroll points out that the Maldecena correspondence suggests that actions in our universe can be explained by a 5-dimensional anti-de Sitter space.  Has someone suggested that the fifth dimension in that space could be gravity itself?  It seems to me that if a 5-dimensional space can map into a 4-dimensional space that doesn’t include gravity, then the missing dimension is gravity.  I have to assume that I’m not the first to posit that.  Do you know of anywhere I could read more about that possibility?