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Tuesday, March 21, 2017

Review: Now - The Physics of Time

I'd previously audited Mysteries of Modern Physics - Time and found it interesting. Then I watched Arrival and it sparked a discussion about time with my wife. Then I saw Richard Muller's Tachyon Murder quora answer and that got me to check out Now - The Physics of Time.

I sort of expected it to cover the same material as Sean Carroll's lecture series, but this book has several advantages over Sean Carroll's lecture series, not least of which is that it's fairly recent (2015) and has more up to date information. Muller also has a completely different perspective than Carroll, and approaches things very differently from Carroll.

For instance, Carroll's lecture series spends a lot of time covering entropy, and basically comes to the conclusion that the arrow of time occurs because of entropy. Muller disagrees with this theory or approach. His primary objection is that this explanation doesn't provide any falsifiable ways of proving the theory. And of course, local entropy on Earth (powered by the sun as an energy source) doesn't always increase.

Muller makes 2 key points: the first is that the physics approach to describing the universe is necessarily incomplete, not just because we have incomplete knowledge, but also because of Godel's Incompleteness Theorem. In a world where we can't even predict when the decay of an atom could occur, determinism seems out of the question and the existence of free will is a strong possibility. The implication is that this means that there's no perspective in which all moments of time are equal: the now is a special time because if you have free will you can then change what will happen in the future.

The second point is that space is constantly being created by the expansion of the universe. His conjecture is that time is also continuously being created by that very expansion. He provides several approaches to falsifying this theory, though sadly he doesn't state whether there are experiments that aim to falsify it in the future.

The book's journey is quite fun, and an interesting read. There are a few places where Muller gets repetitive (especially in the philosophical section where he discusses determinism vs free will), but overall, I particularly enjoyed his descriptions of the experiments that were used to confirm both relativity and quantum mechanics. These are particularly good ways to illustrate how science works and made for great reading.


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