His Dark Materials

I recently read a fantasy book, His Dark Materials, by Philip Pullman. I enjoyed it, and I recommend it for a light reading. I’m not fan of spoilers, but I need to comment something to make my point in this entry. Sorry… 

So, in his Universe, the Dark Matter is something like particles that give consciousness to intelligent beings. They cluster around our early ancestors, when we discovered how to make tools and all that. Well, it is a fantasy book. Don’t expect it to be accurate. Or not? 

I always find interesting the selection of articles in The Physics arXiv Blog. The article that recently interested me was the one related to the relation between Cosmology and Information Theory (See here). In it, they comment the work by Fields, who proposes a hypothesis of what the discrepancy in the energy density when calculating it from physical principle and when measuring it. 

In his approach, he argues that objects such as stars and planets act in a classical way, that is, they have a specific location in space. This location is measured with respect to the cosmic microwave background. But this knowledge comes with a cost: the cost of information. 

A quantum object such as a photon or an electron are in a superposition of states, and it state is defined only when we measure it. A quantum object has a small amount of information associated to its position. However, if we know the position of an object, the information is much higher. And the point is that information costs energy. 

Fields argues that the discrepancy between theory and measurement for the energy density could be that amount of information. The mechanism for an object to become classical is known as decoherence. The quantum nature of the system (the stars, the planets), “leaks” into the environment. Decoherence means entanglement with the environment, an irreversible process from the system’s point of view. 

As I already mentioned in another post, irreversibility, time, is the arrow of increasing correlations. Decoherence is at the system’s level. The Universe might be in a pure state, but what individual pieces of it see, is something defined with respect to the environment. 

To experience time is to entangle with the other parts of the Universe, to create information. And information is knowledge. We know ourselves by experiencing time, by interacting, by defining ourselves with respect to the others. 

Is dark mater consciousness, knowledge? Sometimes fantasy is not so far from science. Just a little step further.