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[Eckhart Aurelius Hughes]

Please use this topic to discuss Quasiclassical Realms by Jim Hartle, which is chapter 2 of the July book of the month Many Worlds?: Everett, Quantum Theory, & Reality edited by Saunders, Barrett, Kent, Wallace. We are discussing this book chapter-by-chapter, including a discussion for the introduction and the transcript at the end. Please do not post in this topic until you have read chapter 2.

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What do you think of this chapter? What do you think of Hartle's ideas and arguments? If you chose mostly disagree or utterly disagree for the poll, then on what specifically do you disagree with Hartle?

For a memory refresher, here is the abstract:

The most striking observable feature of our indeterministic quantum universe is the wide range of time, place, and scale on which the deterministic laws of classical physics hold to an excellent approximation. This essay describes how this domain of classical predictability of everyday experience emerges from a quantum theory of the universe’s state and dynamics.

Overall, I like this chapter. I wish the equations and mathematics were explained in more detail, but I agree with most of the arguments in this chapter particularly the main premise of the emergence of classical physics in everyday practical life. I also seems to me that Hartle does a good job admitting the weaknesses of certain ideas, theories or candidates thereof. At the same time, he writes in an interesting and positive manner, marked most by what I feel is well-written conclusion that simultaneously speaks to the wonder of both what we know and what we do not yet know.

I found an acronym referring in part to humans in this chapter that I never saw before which I love: IGUSes - "information gathering and utilizing systems"

The Copenhagen interpretation might be seen as the number 1 enemy of those advocating instead for MWI. But I think Hartle provides an interesting and strong method of argument in that regard by, as I read it, existentially treating it like we might treat Newtons laws, as something true within its own context as an emergent approximation. He may say it better in his own words:

Copenhagen quantum mechanics is thus not an alternative to decoherent histories, but rather contained within it as an approximation appropriate for idealized measurement situations.

I also like Hartle's description of the significance of gravity, part of which is thus:

It is the gravitationally driven expansion of the universe that ensures the separation of the energy scales of matter from those of quantum gravity. It is the attractive and universal character of gravity which allows isolated systems to form by the growth and collapse of fluctuations., And it is the relative weakness of the gravitational interaction which allows the universe to remain out of total equilibrium on the timescale of its present age.

Of course, this comes when Hartle is describing some of the aspects of quantum mechanics still not understood, in this case particularly the lack of a quantum theory of gravity.

How might the recent discovery of the Higgs Boson relate to this point?

Anyway, what do you all think?