Although the laws of thermodynamics are one of the physical principles best known by the general public, entropy usually causes some doubts in its understanding, as it is related to time.
Thermodynamics is probably one of the branches of the physical what has caused researchers the most curiosity over time; This is the one in charge, neither more nor less, of studying the interaction between heat and different manifestations of energy, describing the states of thermodynamic equilibrium at macro levels.
In the Second law of thermodynamics –The one of interest for this article– it is stated that the entropy of the universe always tends to increase. Now, what does entropy mean and what does it refer to when it is claimed that it “tends to increase”?
In a recent article by Computer Today, a very didactic review is made through the history of this curious concept, entropy. According to the most basic physical definitions offered by the physicist Rudolf clausius, could be defined as a transformation that implies that entropy never decreases, but increases until an equilibrium in which it is maximum.
Besides, entropy is directly related to time, unlike other laws of thermodynamics that studied the temperature, volume, mass or pressure of elements such as gases and liquids, in a purely experimental way. For this reason, the entropy is almost unique, since, in the past, this was low, while when moving towards the future, it increases. This is known as the “arrow of time.”
Entropy and rooms that fill with smoke
Clausius explained at the time that there are no spontaneous processes related only to the transfer of heat from a cold body to a warm one. For example, the fact that an ice cube melts is not reversible, unless this process is forced through freezers, of course.
Thus, a metaphor to explain entropy in a relatively simple way would be that of the rooms that fill with smoke. On the one hand, there is a room without smoke; on the other, one that is completely filled with smoke, and in the middle, a closed door that connects them.
Not surprisingly, the most probable state – known in physics as macrostate– is that, when you open the door, the smoke floods all the rooms. However, considering separate smoke particles, they will all be equally likely –microstates-. Thus, the definition of entropy does not refer to disorder or chaos, but to the probability that these particles adopt any of the many configurations established by macrostates.
Therefore, the most accurate conceptualization of entropy would be the magnitude that is responsible for measuring the number of probable microstates in the same macrostate, within an isolated system. Still, what does entropy have to do with time?
More accurate clocks, higher entropy
In a recent study, published in Physical Review X, a team of physicists has used a simplified clock, composed of a membrane 50 nanometers thick and 1.5 millimeters long, stretched between 2 poles, and vibrating with pulses of electricity.
Each movement up or down referred to a tick of the clock. Thus, more powerful electrical signals caused the watch to tick more regularly and accurately; however, with this, more heat was added and, therefore, more entropy (remember the cube of yarn). In this way, increasing the precision of a clock of such size causes the entropy to increase, a cost that must be paid.
“If you want your watch to be more accurate, you have to pay for it. (…) Every time we measure time, we are increasing the entropy of the universe”, Has assured Natalia Ares, physicist at the University of Oxford (England) and co-author of the study, Live Science.
In other words, as the researchers have explained, there is a linear relationship between precision and entropy, always within the orders of magnitude of the theoretical limits. For all these reasons, entropy continues to fascinate physics, although it is increasingly possible to understand in more detail why this phenomenon occurs in the universe.
“We don’t know for sure yet, but what we have found, for both our clock and quantum clocks, is that there is a proportional relationship between precision and entropy.“Ares added.”It may not always be a linear relationship for other clocks, but it seems that the precision is limited by the laws of thermodynamics“.
This article was published in Business Insider Spain by Abraham Andreu.