There’s a new universal law that explains why hot coffee can actually cool down faster than lukewarm coffee.
March 23, 2026
Original Paper
Macroscopic Mpemba Effect from Cumulative-Heat-Enhanced Relaxation
arXiv · 2603.19887
The Takeaway
This phenomenon, known as the Mpemba effect, has puzzled thinkers since Aristotle. The new theory shows that a system's 'memory' of its starting state can force it to take a structural shortcut, allowing a hotter object to skip past the cooling stages of a colder one.
From the abstract
The counterintuitive Mpemba effect, wherein a hotter system cools faster, critically lacks a universal macroscopic theory. Here, starting from linear irreversible thermodynamics, we formulate a generalized Newton's cooling law for the system-reservoir temperature difference $\Delta T$, given by $\mathrm{d}\Delta T/\mathrm{d}t = -[\gamma_0 + \mathcal{M}Q(t)][\Delta T - \mathcal{I}Q(t)]$, where $\gamma_0$ is the bare relaxation rate, and the cumulative heat exchange $Q(t)$ explicitly encodes initi