Archiv vom Juli 11th, 2009

Amongst by books, there are several that have been waiting for quite some time to be read. There are one or two I have started, but did not make much progress with.

But Brian Greene's Fabric of the Cosmos was among those I did not really look forward to in the first place. By now, I have finished it, and I have to admit there was no reason to hesitate all the time.

In his book, Greene tackles the question of what time and space really are -- are they things, a something; or are they only a mathematical construct that enables us to talk about the relationship between things (whether they are subatomic particles whole galaxies)? This is not a philosopical treatise (for the most part), but quite down-to-earth physics. The author is very successful at relating this physics: the book is quite accessible to non-experts, without being shallow; physicists may be able to learn something new as well.

Starting with classical mechanics' notion of space and time, Greene explains relativistic spacetime and proceeds to string and M-theory, teasing out along the way how physics treats the texture of reality. I was surprised to learn that for instance the origin of the arrow of time[1] is much more complex than I had thought: the second law of thermodynamics is not sufficient to explain it.

In looking at the different theories, the author is also delineating a history of physics  -- much like Singh did for mathematics. This history, in turn, is very well suited to get an overview of physics.

[1] The question is: What is the difference between tomorrow and yesterday? Almost all physical laws are symmetric with respect to past and future, so that phenomena may take place forward as well as backwards. Nevertheless, we can easily tell whether any of a number of macroscopic phenomena is running in reverse: a glass may break, but shards to not spontaneously combine to form a glass; we remember the past, but not the future.

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