From Eternity to Here: The Quest for the Ultimate Theory of Time

by Sean M. Carroll

Hardcover, 2010




New York : Dutton, 2010.


A rising star in theoretical physics offers his awesome vision of our universe and beyond, all beginning with a simple question: Why does time move forward?

User reviews

LibraryThing member jeroenvandorp
I don't like a quest. I like scientific research, creativity, non-conformist ideas. Luckily it's only the subtitle of the book that I hold a grudge against. In the book itself you'll find scientific research, creativity and non-conformist thinking. And a scientist who tells us that some of his
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ideas aren't science but speculation. (Well, 'predictions' my ass). All too often scientists use misplaced authority in popular science books when it comes to defending their own theories. Sean Carroll, theoretical physicist at CalTech, isn't one of them, and that is laudable.

From Eternity to Here (2010) is a book about the arrow of time. What is time? The answer in a nutshell: experiencing the tendency of the universe to increase its entropy, a measure of "disorder". There we have them again. Scrambled eggs won't unscramble (although quantum mechanics tell us there's a small chance it will happen. And if you wait long enough it inevitably will happen). The milk in your coffee that won't get unmixed.
Entropy tends to stay the same or increase on a large scale. That's because there are more possible combinations of chaos than of order. If an earthquake hits your pile of books, it tends to fall over. If the books are on the ground and the second wave of earthquakes come, generally they won't pile on top of each other.
That seems to be what we perceive as time: the direction from low entropy to higher entropy. It will eventually end with everything - all matter, all fields, all of spacetime - in equilibrium, which means time will stop as well. No change, no time, ma'am.

Carroll speculates however that it won't stop there. In an equilibrium universe entropy will continue to grow by creating bubbles that are new universes. These universes start out low in entropy, and the unlimited increase can continue.
Why does Sean Carroll come up with the need for eternal increase of entropy, to the cost of a yet unfalsifiable multiverse theory? Reason is that our own universe started out in a strange, very low entropy state. And that poses problems. Not only for the development of our universe, but for the current state of our universe as well. After all, the highest chance for us is to find ourselves in such a De Sitter space. In such a space there's equilibrium without an arrow of time. Weak anthropic principle, but with a twist.

The book fills up with explanations about the usual suspects. That is: entropy, general relativity, quantum physics, string theory, black holes and event horizons, AdS/CFT . The whole cast of characters you'll find in most current books about cosmology. In that regard the book won't teach you much extra. But it is a good overview structured from another perspective: the perspective of time. As a bonus it takes you on a mind-boggling tour of possibilities. From the dimensions of infinite space to the multiverse in its many variations. A well written book with an interesting conclusion. Worth your time.

For those missing the most basic of mathematics you should read the 'math' section at the end of the book first. For those with a few years of high school math: dive right in. Follow the arrow From Eternity to Here.

In the right direction, that is.
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LibraryThing member rondoctor
Good explanations and examples of entropy. A little repetitive, but that may be necessary to get complex concepts across to the educated lay reader.
LibraryThing member steve.clason
Something about the tone of the first few chapters put me off at first and it took me a long time to get back to this book. Once I did get back to it, though, I read it through quickly and eagerly. Carroll's lighthearted and "geekish" style (which may have been what put me off at first) makes
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pleasant reading of his voluminous background information so that a casual, non-physicist, reader can get up to some kind of speed, at least, on recent (and not-so-recent) developments in cosmology that pertain to our understanding of time.

Most of the book--maybe 95%--is background information. He reserves explication of his own theory for the last chapter, although it's forwshadowed throughout. I would have preferred a longer explication, mainly because it's pretty mind-warping to me, but it could be that there's just not that much to say about new universes bubbling up out of vacuum energy.

I'm a sucker for popular books on difficult scientific/mathematical subjects so might have this overrated, but I liked it a lot and recommend it.
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LibraryThing member michaelbartley
a very thoughtful book, at times very readable for non sciencfic at other times very hard, not a lot of math but very detialed
LibraryThing member jefware
Eternity. There is a big idea. Introduced me to the wonders of gravitation and entropy. Were the number of microstates fewer in the early universe? He comes down on the side of no but the mechanics of it would say yes. If that were true (fewer micro-states) where did the new information come from?
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So much for LaPlace's Demon.
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LibraryThing member GlennBell
The book starts out with an understandable discussion. Toward the end I started to get lost and disinterested. Note: I have a PhD in engineering and taught physics. I appreciate that Sean is an expert in theoretical physics and has written an interesting book.
LibraryThing member HumbleOpinion
This is more of a layperson's book than I expected. The first 3/4 of the book rehashes your high school and college physics, and then it proposes some speculative ideas to explain the low entropy of the early universe. However, the speculative ideas (I'm trying avoid spoilers) are not new. That
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would be fine, if there were some evidence to support them, but there was none. I was disappointed.

It's a quick read though.
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LibraryThing member gopfolk
A good read...please take the time to grasp what is being said...this is not for a first timer in my opinion. You need at least a base understanding of the concepts of space-time and relativity (it would help to understand basic cosmology too). Now I'm not saying that this is meant for a PhD
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candidate by any means it just would help to understand it a little.
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LibraryThing member DLMorrese
Ostensibly this book is about time and why it goes only one way. Mostly, it's about entropy, and it's a bit repetitive, and not as elucidating as one might hope. I think it may be intended primarily for those working or studying in the areas of cosmology or quantum field theory rather than laymen
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such as myself.
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LibraryThing member pgSundling
I read this as research for an upcoming book that I probably won't write for another 5 years from now. I'll have to reread the book again and will leave a more detailed review then.
LibraryThing member bookomaniac
I’ll be honest: this was a tough job. Sean Carroll really does his best to explain the basic issues of theoretical physics in a comprehensible and pleasant way. Certainly in the beginning he uses a lot of humour (lots of cats!), nice literary references and a very patient style to successfully
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present the basics on classical mechanics (from Newton to Einstein) and quantum mechanics.

But somewhere halfway through, he starts with what is the logical main part when it comes to time as a physical phenomenon: entropy. And from then on this book becomes a difficult read. From as many as 20 different perspectives, Carroll tries to answer the question why that entropy exists, how it defines the one-directional arrow of time, and why in our universe it runs from past to future (yep, apparently that is not an obvious question).

Everything seems to come down to the initial state of our universe, namely in low entropy. But why was it actually that low back then? Carroll jumps from one issue to another, from one scenario or theory to another, and new aspects constantly appear that make the proposed hypotheses unlikely. It has been cited in some reviews: this book looks like an infinite set of Russian dolls that are put together. But he has to conclude: we know to little (especially on quantum gravity) to give clear answers.

At the end of the book, Carroll ventures into his own hypothesis (he calls it a prediction), which is inspired by multiverse theory. He admits that he is very speculative, but he also defends that approach, because that is simply the way in which science advances. This was a very interesting book, which ultimately does not provide a satisfactory answer to the question why time exists as it exists, but it does provide an honest insight into how science works.
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LibraryThing member Devil_llama
A lucid, reasonably understandable look at relatively, quantum mechanics, and time. The author seeks to understand and explain time's arrow, and trace time back to the Big Bang...or before, if possible. There are some points where it appears the author does not understand biology (nothing unusual
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for a physicist; most don't), but otherwise the work is interesting, comprehensible, and thorough. His solution to the problems posed by the current state of physical knowledge is interesting, and he almost convinces me it could be possible. I am at least leaving an open mind. There are a couple of chapters in which the explanations get a bit tedious, but most of the book reads well, though for some inexplicable reason, it took me a longer time than usual. Perhaps some sort of cosmic irony, considering the topic.
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