Wednesday, 10 September 2008

Information, causation and energy

In a comment on an earlier post, Robin Faichney said
Personally, in the most general terms, I see causation, information flow and energy flow as three different aspects of one phenomenon.
I think the relationship between the three (and matter, though that's the same thing as energy by E = mc2) warrants a lot more thought. I'm uneasy with Dretske's separation of causality and information. Shannon's equation:

C = B log(1+S/N)

links energy to information flow, since C is information capacity and S is signal energy (B is bandwidth and N noise power). However, C here is average information flow, and Dretske makes the point that engineers are always concerned with averages, whereas he is also addressing specifics. In a specific case, information can be communicated without any energy flow. "If I don't call I'll meet you at the station". The absence of a call communicates the fact that I'll meet you at the station - and causes you to go to the station to meet me.

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