Think of a light bulb. Part of the energy you give to the light bulb is used for illumination. This part is the “useful” part of the energy. Another part of the given energy dissipates to the light bulb’s environment and is lost. This second part is the “useless” part of the energy. The fact that this second part is lost in every light bulb and every system is indicated by the word “entropy”.
Unless we invent a perfect light bulb that does not dissipate any heat, there will always be a cost for the illumination that the light bulb provides. So the use of the “useful” part of the energy will require the loss of its “useless” part. This means that it’s not right to call the lost energy “useless”. The lost part is sacrificed for the other part to be gained. Thus entropy is sacrifice.
The second law of thermodynamics says that the entropy always increases. This means that sacrifice and cost are inevitable in gaining any utility. Thus it’s very important to know and understand the measure of sacrifice and cost.
An important issue about the technology that has designed the light bulb is the calculation of the necessary sacrifice of energy for the desired utility and the minimization of this loss. The technology that intends to calculate and find the minimum necessary loss should rely on scientific theories and equations. But however scientific, however advanced its theories, the best it can do is prediction, estimation.
The determination of the real loss is possible only with experience and this is done by scientific-technological experiments. One must switch on the light bulb to see and measure what will happen. Just like the light bulb, it’s also important to determine the necessary loss and sacrifice in one’s life experience. Psychoanalysis refers to the manifestations of this entropic dimension of life by the word “trauma”.
This brings us to Freud’s concept of “afterwardsness” (retroactive realization, Nachträglichkeit, après-coup). Afterwardsness is the retroactive burdening of a memory from the past with a traumatic valence due to the events that were experienced afterwards. Maybe this is the basis of the human mechanism of knowing and learning: (1) Learning is always about the entropic-traumatic dimension of life; (2) Learning takes place “always afterwards”, like Ahmet Kaya’s song, “Always afterwards I come to my senses, always afterwards, afterwards” .
If we call the minimization of entropic sacrifice “rationality”, we can say that humans are not rational in this sense. Humans are not living beings that minimize the entropy in their lives. This reality finds its expression in Freud’s concept of “death drive”.
If we define the continuation of the human species in evolution as the “basic utility”, we can relate sexuality and death to this “basic utility”. People reproduce via sexuality, thus sexuality is the pathway that the “basic utility” must follow. Individual deaths of people are the entropic sacrifice of the “basic utility”, individuals are sacrificed for the continuation of the species. Lacan defined this as the “real lack” :
The real lack is what the living being loses, that part of himself qua living being, in reproducing himself through the way of sex. This lack is real because it relates to something real, namely, that the living being, by being subject to sex, has fallen under the blow of individual death. (Seminar XI)
The entropic dimension that Freud designates in humans as the “death drive” was designated by Lacan with the term “enjoyment” (jouissance) :
it is only through this effect of entropy, through this wasting, that jouissance acquires a status and shows itself … at its origin, knowledge is reduced to an articulation of signifiers. This knowledge is a means of jouissance. And, I repeat, when it is at work, what it produces is entropy. … This is where work begins. It is with knowledge as a means of jouissance that work that has a meaning, an obscure meaning, is produced. This obscure meaning is the meaning of truth. (Seminar 17)
The dimension that we designate with the word “work” in daily life surely includes the calculation of the entropic sacrifice for producing “utility”, but this cost calculation is not a rational calculation, because the knowledge-at-work is a means of enjoyment. The meaning it produces is called the truth.
 For the extended quote, see “Separation of Authorization from Embodiment”
 For the extended quote, see “Entropy: Deleuze’s Symptom, Lacan’s Key”