Communion Of Dreams

*Apologies to both John Lennon and Philip K. Dick.

Last Saturday, my sister and her husband came to town, and we celebrated Thanksgiving.  Yes, about six months late.

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About two weeks ago Sean Carroll of Cosmic Variance had a teaser post up about a new article of his in Scientific American.  Carroll has long been one of my favorite reads in cosmology, and his discussion of the cosmological basis for time’s arrow was delightful.  From the opening of the article:

Among the unnatural aspects of the universe, one stands out: time asymmetry. The microscopic laws of physics that underlie the behavior of the universe do not distinguish between past and future, yet the early universe—hot, dense, homogeneous—is completely different from today’s—cool, dilute, lumpy. The universe started off orderly and has been getting increasingly disorderly ever since. The asymmetry of time, the arrow that points from past to future, plays an unmistakable role in our everyday lives: it accounts for why we cannot turn an omelet into an egg, why ice cubes never spontaneously unmelt in a glass of water, and why we remember the past but not the future. And the origin of the asymmetry we experience can be traced all the way back to the orderliness of the universe near the big bang. Every time you break an egg, you are doing observational cosmology.

The arrow of time is arguably the most blatant feature of the universe that cosmologists are currently at an utter loss to explain. Increasingly, however, this puzzle about the universe we observe hints at the existence of a much larger spacetime we do not observe. It adds support to the notion that we are part of a multiverse whose dynamics help to explain the seemingly unnatural features of our local vicinity.

Carroll goes on to explore what those hints (and the implications of same) are in some detail, though all of it is suitable for a non-scientist.  The basic idea of how to reconcile the evident asymmetry is to consider our universe, as vast and ancient as it is, as only one small part of a greater whole.  We are living, as it were, in a quantum flux of the froth of spacetime of a larger multiverse:

Emit fo Worra
This scenario, proposed in 2004 by Jennifer Chen of the University of Chicago and me, provides a provocative solution to the origin of time asymmetry in our observable universe: we see only a tiny patch of the big picture, and this larger arena is fully time-symmetric. Entropy can increase without limit through the creation of new baby universes.

Best of all, this story can be told backward and forward in time. Imagine that we start with empty space at some particular moment and watch it evolve into the future and into the past. (It goes both ways because we are not presuming a unidirectional arrow of time.) Baby universes fluctuate into existence in both directions of time, eventually emptying out and giving birth to babies of their own. On ultralarge scales, such a multiverse would look statistically symmetric with respect to time—both the past and the future would feature new universes fluctuating into life and proliferating without bound. Each of them would experience an arrow of time, but half would have an arrow that was reversed with respect to that in the others.

A tantalizing hint of a larger picture, indeed.

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Philip K. Dick, tormented mad genius that he was, said something that has become something of a touchstone for me:  “Reality is that which, when you stop believing in it, doesn’t go away.”

It is, in fact, a large part of the basis for my skeptical attitude towards life.  But it also leaves open the idea of examining and incorporating new information which might be contrary to my beliefs.  It is this idea which I explored over the 132,000 words of Communion of Dreams, though not everyone realizes this at first reading.

But what if reality only exists if you believe in it?

That’s a question discussed in another longish piece of science writing in the current issue of Seed Magazine, titled The Reality Tests:

Most of us would agree that there exists a world outside our minds. At the classical level of our perceptions, this belief is almost certainly correct. If your couch is blue, you will observe it as such whether drunk, in high spirits, or depressed; the color is surely independent of the majority of your mental states. If you discovered your couch were suddenly red, you could be sure there was a cause. The classical world is real, and not only in your head. Solipsism hasn’t really been a viable philosophical doctrine for decades, if not centuries.

But that reality goes right up against one of the basic notions of quantum mechanics: the Heisenberg Uncertainty Principle.  Or does it?  For decades, the understanding of quantum effects was that it was applicable at the atomic-and-smaller level.  Only in such rare phenomenon as a Bose-Einstein Condensate (which in Communion is the basis for some of the long-range sensors being used to search for habitable planets outside our solar system) were quantum effects seen at a macroscopic scale.  But in theory, maybe our whole reality operates at a quantum level, regardless of scale:

Brukner and Kofler had a simple idea. They wanted to find out what would happen if they assumed that a reality similar to the one we experience is true—every large object has only one value for each measurable property that does not change. In other words, you know your couch is blue, and you don’t expect to be able to alter it just by looking. This form of realism, “macrorealism,” was first posited by Leggett in the 1980s.

Late last year Brukner and Kofler showed that it does not matter how many particles are around, or how large an object is, quantum mechanics always holds true. The reason we see our world as we do is because of what we use to observe it. The human body is a just barely adequate measuring device. Quantum mechanics does not always wash itself out, but to observe its effects for larger and larger objects we would need more and more accurate measurement devices. We just do not have the sensitivity to observe the quantum effects around us. In essence we do create the classical world we perceive, and as Brukner said, “There could be other classical worlds completely different from ours.”

Indeed.

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Last Saturday, my sister and her husband came to town, and we celebrated Thanksgiving.  Yes, about six months late.   Because last year, going in to the usual Thanksgiving holiday, we had our hands full caring for Martha Sr and didn’t want to subject her to the disconcerting effect of having ‘strangers’ in the house.  Following Martha Sr’s death in February, other aspects of life had kept either my sister or us busy and unable to schedule a time to get together.

Until last weekend.  And that’s OK.  Because life is what we make of it.  Whether that applies to cosmology or not I’ll leave up to the scientists and philosophers for now (though I have weighed in on the matter as mentioned above and reserve the right to do so again in other books).  This I can tell you – it was good to see my sister and her husband, and the turkey dinner we ate was delicious.

Jim Downey