From Eternity to Here

by Sean Carroll

The arrow of time, therefore, is not a feature of the underlying laws of physics, at least as far as we know. Rather, like the up/down orientation space picked out by the Earth, the preferred direction of time is also a consequence of features of our environment. In the case of time, it’s not that we live in the spatial vicinity of an influential object; it’s that we live in the temporal vicinity of an influential event: the birth of the universe.

indistinguishable from a macroscopic perspective.

but who defines or how do we define indistiguishable?

So either closed timelike curves can’t exist, or big macroscopic things can’t travel on truly closed paths through spacetime—or everything we think we know about thermodynamics is wrong.

There are several different answers to these questions, none of which is found satisfactory by everyone working in the field of statistical mechanics.

What Is Life? written by none other than Erwin Schrödinger.

According to quantum mechanics, what we can observe about the world is only a tiny subset of what actually exists.

Stephen Hawking has been able to accomplish remarkable things while working under extraordinary handicaps, and the reason is basically straightforward: He refuses to compromise in any way.

We don’t have a full picture of the space of microstates in quantum gravity, and correspondingly lack a rigorous understanding of

It is a curious feature of general relativity that the total energy of a closed, compact universe is exactly zero, once

See Schacter, Addis, and Buckner (2007)

recent overviews, see Morange (2008) or Regis (2009).