Definition of Entropy
The term entropy is often avoided because it contains a certain complexity. The phenomenon entropy, however, is constitutive for everything that is going on in our lives. A closer look is worth the effort.
Entropy is a measure of information and it is defined as:
Entropy is the information
– known at micro,
– but unknown at macro level.
The challenge of this definition is:
- to understand what is meant by the micro and macro states and
- to understand why entropy is a difference.
What is Meant by Micro and Macro Level?
The micro level contains the details (i.e. a lot of information), the macro level contains the overview (i.e. less, but more targeted information). The distance between the two levels can be very small (as with the bit, where the microlevel knows just two pieces of information: on or off) or huge, as with the temperature (macrolevel) of the coffee in a coffee cup, where the kinetic energies of the many molecules (microlevel) determine the temperature of the coffee. The number of molecules in the cup is really large (in the order of Avogadro’s number 1023) and the entropy of the coffee in the cup is correspondingly high.
Entropy is thus defined by the two states and their difference. However, states and difference are neither constant nor absolute, but a question of observation, therefore relative.
Let’s take a closer look at what this relativity means for the macro level.
What is the Relevant Macro Level?
In many fields like biology, psychology, sociology, etc. and in art, it is obious to me as a layman, that the notion of the two levels is applicable to these fields, too. They are, of course, more complex than a coffee cup, so that the simple thermodynamic relationship between micro and macro becomes more complex.
In particular, it is conceivable to have a mixture of several macro-states occurring simultaneously. For example, an individual (micro level), may belong to the macro groups of the Swiss, the computer scientists, the older men, the contemporaries of 2024, etc – all at the same time. Therefore, applying entropy reasoning to sociology is not as straightforward as the simple examples like Boltzmann’s coffee cup, Salm’s lost key, or a basic bit might suggest.
Entropy as a Difference
Micro and macro level of an object both have their own entropy. But what really matters ist the difference of the two entropies. The bigger the difference, the more is unknown on the macro level about the micro level.
The difference between micro and macro level says a lot about the way we perceive information. In simple words: when we learn something new, information is moved from micro to macro state.
The conventional definition of entropy states that it represents the information present in the micro but absent in the macro state. This definition of entropy via the two states means that the much more detailed microstate is not primarily visible to the macrostate. This is exactly what Niklas Luhmann meant when he spoke of intransparency1.
When an observer interprets the incoming signals (micro level) at his macro level, he attempts to gain order or transparency from an intransparent multiplicity. How he does this is an exciting story. Order – a clear and simple macro state – is the aim in many places: In my home, when I tidy up the kitchen or the office. In every biological body, when it tries to maintain constant form and chemical ratios. In society, when unrest and tensions are a threat, in the brain, when the countless signals from the sensory organs have to be integrated in order to recognise the environment in a meaningful interpretation, and so on. Interpretation is always a simplification, a reduction of information = entropy reduction.
Entropy and the Observer
An essential point is that the information reduction from micro to macro state is always carried out by an active interpreter and guided by his interest.
The human body, e.g., controls the activity of the thyroid hormones via several control stages, which guarantee that the resulting state (macro state) of the activity of body and mind remains within an adequate range even in case of external disturbances.
The game of building up a macro state (order) out of the many details of a micro state is to be found everywhere in biology, sociology and in our everyday live.
There is – in all these examples – an active control system that steers the reduction of entropy in terms of the bigger picture. This control in the interpretation of the microstate is a remarkable phenomenon. Always when transparency is wanted, an information rich micro state must be simplified to a macro state with less details.
Entropy can then be measured as the difference in information from the micro to the macro level. When the observer interprets signals from the micro level, he creates transparency from intransparency.
Entropy, Re-Entry and Oscillation
We can now have a look at the entropy relations in the re-entry phenomenon as described by Spencer-Brown2. Because the re-entry ‘re-enters’ the same distinction that it has just identified, there is hardly any information difference between before and after the re-entry and therefore hardly any difference between its micro and macro state. After all, it is the same distinction.
However, there is a before and an after, which may oscillate, whereby its value becomes imaginary (this is precisely described in chapter 11 of Spencer-Browns book ‘Laws of Form’)2. Re-entries are very common in thinking and in complex fields like biology or sociology when actions and their consequences meet their own causes. These loops or re-entries are exciting, both in thought processes and in societal analysis.
The re-entries lead to loops in the interpretation process and in many situations these loops can have puzzling logical effects (see paradoxes1 sand paradoxes2 ). In chapter 11 of ‘Laws of Form’2, Spencer-Brown describes the mathematical and logical effects around the re-entry in details. In particular, he develops how logical oscillations occur due to the re-entry.
Entropy comes into play whenever descriptions of the same object occur simultaneously at different levels of detail, i.e. whenever an actor (e.g. a brain or the kitchen cleaner) wants to create order by organising an information-rich and intransparent microstate in such a way that a much simpler and easier to read macrostate develops.
We could say that the observer actively creates a new macro state from the micro state. However, the micro-state remains and still has the same amount of entropy as before. Only the macro state has less. When I comb my hair, all the hairs are still there, even if they are arranged differently. A macro state is created, but the information can still be described at the detailed micro level of all the hairs, albeit slightly altered in the arrangement on the macro level.
Re-entry – on the other hand – is a powerful logical pattern. For me, both re-entry and entropy complement each other in the description of reality. Distinction and re-entry are very elementary. Entropy, on the other hand, always arises when several things come together and their arrangement is altered or differentely interpreted.
See also: Five preconceptions about entropy
Translation: Juan Utzinger
1 Niklas Luhmann, Die Kontrolle von Intransparenz, hrsg. von Dirk Baecker, Berlin: Suhrkamp 2017, S. 96-120
2 Georg Spencer Brown , Laws of Form, London 1969, (Bohmmeier, Leipzig, 2011)