But these complications do not change the key issue.) (To account for some very rare events discovered by particle physicists, the movie is only guaranteed to be valid if it is also reflected in a mirror and has every particle relabeled as the corresponding antiparticle.
This one-way behavior of matter in bulk is called the "arrow of time." Nonetheless, the microscopic laws that describe collisions of molecules are time-symmetric, making no distinction between past and future.Īny movie of a collision could be played backwards, and it would also show a valid picture of a collision. The gas makes a huge distinction between the past and the future, always evolving toward larger entropy in the future. This behavior seems very natural, but it is hard to reconcile with our understanding of the underlying laws of physics. But it never goes the other way: if the gas molecules fill the box, we will never see them spontaneously collect into one corner. The gas molecules will fill the box, increasing the entropy to the maximum. If we start with all the gas molecules in a corner of the box, we can imagine watching what happens next. The classic example is a gas in a closed box. In terms of the underlying quantum description, entropy is a measure of the number of quantum states that correspond to a given description in terms of macroscopic variables, such as temperature, volume, and density. Even though entropy will play a crucial role in this discussion, it will suffice to use a fairly crude definition: entropy is a measure of the "disorder" of the physical system. Isolated systems tend to evolve toward the state of maximum entropy, the state of thermodynamic equilibrium. This idea is now known as the second law of thermodynamics, which is most often described by saying that the entropy of an isolated system always increases or stays constant, but never decreases. The roots of this issue go back at least to 1865, when Rudolf Clausius coined the term "entropy" and stated that the entropy of the universe tends to a maximum.
0 kommentar(er)
