Which is the correct answer to the Mpemba puzzle?

In my editorial in the last issue of Temperature, I included a riddle that was suggested to me by Gerald Pollack (University of Washington, Seattle, Washington, USA). Here is the original text of the riddle: "In 1963, Erasto Mpemba, a precocious middle school student in Tanganyika (now Tanzania) was taking a cooking course. The subject was: making ice cream. The participants would dump a premixed "ice cream" powder into water, stir the mixture, and stick it into a freezer. Soon they could enjoy their dessert. Mpemba noticed something odd. When he mixed the powder with warm water instead of cold water, the ice cream froze sooner. Since then, many have confirmed the Mpemba paradox: warm water freezes more quickly than cold water. Why?" In the editorial, I gave the readers a hint, stating that the puzzle was based on Pollack’s latest book, which I disclose now: see reference 2. However, neither of the 2 answers we received used this hint. One answer came from Chang Quing Sun (Nanyang Technological University, Singapore). His explanation of the Mpemba paradox is focused on the microstructure of water and, specifically, on the hydrogen bond. A relatively short description of what Sun calls the abnormal relaxation of the hydrogen bond, and how this relaxation accelerates water freezing, can be found in this issue of Temperature. Sun views the Mpemba paradox as a fundamental effect, which is insensitive to convection, evaporation, water impurity, and many other processes and factors. The present text is my Reply to the second answer, which is a Letter to the Editor written by Marek Bal a zovi c (Constantine the Philosopher University, Nitra, Slovakia) and Boris Tom a sik (Matej Bel University, Bansk a Bystrica, Slovakia). Interestingly, the Mpemba paradox was the topic of Bal a zovi c’s thesis, on which Tom a sik acted as the supervisor. In contrast to Sun, Bal a zovi c and Tom a sik consider the Mpemba phenomenon multi-causal. They also emphasize that, in real life, the outcome of experiments aimed at reproducing the Mpemba effect is highly sensitive to experimental conditions, e.g., water purity. Depending on the conditions, heating water may lower, raise, or not change the original freezing temperature. Is this an example of what Thomas Huxley called the great tragedy of Science—the slaying of a beautiful hypothesis by an ugly fact? The authors list 8 factors, which, under different experimental conditions, may contribute to various extents to the faster freezing of warm water—when it occurs. These factors range from ice coating in the freezer (remember, student Erasto was making ice cream in a freezer) to the microstructure of water (Sun’s fundamental mechanism). In their Letter, Bal a zovi c and Tom a sik mentioned that 2 years ago, the Royal Society of Chemistry offered a £1,000 prize for the best explanation of the Mpemba phenomenon. However, the