Gravity Alters the Dynamics of a Phase Transition
An experiment uncovers the role played by gravity in Ostwald ripening, a spontaneous thermodynamic process responsible for many effects such as the recrystallization of ice cream. [...] What do magnets and decaf coffee have in common? Both involve physical systems that belong to the same “universality class.” Ferromagnetic materials are used to make magnets, and supercritical carbon dioxide extracts caffeine from coffee beans. At the critical point, when ferromagnetic and liquid–gas phase transitions occur, these two systems are described by the same critical exponents [1]. By identifying a system’s universality class, one can quantitatively characterize its behavior at the critical point without prior knowledge of microscopic details. Observing macroscopic properties suffices. However, taking that shortcut is often experimentally challenging, not least because many interesting systems are opaque to light. Now Raphael Saiseau of the University of Bordeaux in France and his collaborators have devised an ingenious experiment that enabled them not only to follow a phase transition but also to uncover the subtle and surprising effect of gravity on its dynamics [2].
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