From Eternity to Here
From Eternity to Here: The Quest for the Ultimate Theory of Time by Sean Carroll
My rating: 2 of 5 stars
This book is a through and frequently tedious exploration for a theory of time. Pay close attention to the word "Quest" in the subtitle. This books poses many questions that don't have answers yet and instead focuses on the various theories that currently exist. The book starts with an introduction to possible definitions of what time is, the role of entropy, and the Second Law of Thermodynamics. With that foundation it dives into microscopic constituents, macroscopic systems, and quantum mechanics before finishing off with inflation, the reversibility of time, and multiverses. I found as I went along the tractability became further removed from everyday life and ended up almost entirely in the realm of theoretical physics and dare I say philosophy. If you are interested in understanding the current state of thinking about what time is, the origins of the universe, and similar topics the author's writing is excellent and the copious footnotes helpful. It just felt like it took an eternity to read.
A few of the notes I took while reading:
* Time labels moments in the universe [10]
* Time measures the duration elapsed between events [10]
* Time is a medium through which we move [10]
* An event is x, y, z and time [14]
* Spacetime = every point in space at every moment of time [14]
* The duration elapsed along two trajectories connecting two events in spacetime need not be the same [20]
* A straight trajectory between two events in spacetime describes the longest elapsed duration [21]
* Time has a direction, space doesn't [21]
* Take milk and mix it into a cup of black coffee; never take coffee with milk and separate the two liquids = irreversible processes [28]
* There are many different arrangements of particular atoms that are indistinguishable from our macroscopic perspective [36]
* Being - existence in the world, Becoming - a dynamical process of change, bringing reality into existence [42]
* Extraneous motion decreases the time elapsed between two events in spacetime, whereas it increases the distance traveled between two points in space [76]
* Thermodynamic arrow of time (defined by entropy and the Second Law), cosmological arrow of time (the universe is expanding), psychological arrow of time (we remember the past and not the future), radiation arrow of time (electromagnetic waves flow away from moving charges, not toward them), ... [171]
* There are more ways to be high entropy than low entropy, so most microstates in a low-entropy macrostate will evolve toward higher-entropy macrostates [176]
* The information content of a message goes up as the probability of a given message taking that form goes down [190]
* Essence of life: staving off the natural tendency toward equilibration with one's surroundings [195]