December 2019 American Journal of PhysicsDecember 2019 Issue,

Volume 87, No. 12


When dipping toast into a cup of tea leads to a scientific investigation

This article recounts a scientific investigation that started from the observation of an ordinary everyday phenomenon. In a cup of tea, dipping buttered toast produces on the surface of the tea beautifully evolving lenses, which are pierced repeatedly by moving holes. To unravel this dynamic observation, we show here how we simplified the system into its basic ingredients, and how we excluded several hypotheses such as thermal convection. We reproduce the phenomenon with an inverse emulsion of surfactant-laden water droplets. Depending on the spreading of the lens, we also observe and explain the formation of an oil lacework and “swimming” lenses.



Family or faculty? by Richelle Teeling-Smith. DOI: 10.1119/10.0000187


When dipping toast into a cup of tea leads to a scientific investigation by Philippe Marmottant, Florian Orthion and Salima Rafaï. DOI: 10.1119/10.0000025

A sundial with hour lines portraying the Earth by Joachim Heierli. DOI: 10.1119/10.0000033

Equilibrium and stability of thin spherical shells in Newtonian and relativistic gravity by Philip LeMaitre and Eric Poisson. DOI: 10.1119/10.0000026

An alternative formulation of the magnetostatic boundary value problem by L. Nasser and Z. Chacko. DOI: 10.1119/10.0000004

Low-cost Fourier ghost imaging using a light-dependent resistor by Ritz Ann Aguilar, Nathaniel Hermosa and Maricor N. Soriano. DOI: 10.1119/10.0000163

Particle sliding down an arbitrary concave curve in the Lagrangian formalism by Leonardo Balart and Sebastián Belmar-Herrera. DOI: 10.1119/10.0000037

A simple mechanical apparatus for measuring the surface tension of soap bubbles by Martin Specht, Tom Frömbgen, Hannah Wessely and Moritz Sokolowski. DOI: 10.1119/10.0000003


Scaling exponents by Sanjoy Mahajan. DOI: 10.1119/10.0000188


Molecular dynamics simulation of a two-dimensional dusty plasma by István Donkó, Peter Hartmann and Zoltán Donkó. DOI: 10.1119/10.0000045


Estimating the size of Earth's umbral shadow using sky brightness light curves during a lunar eclipse by Jennifer J. Birriel and J. Kevin Adkins. DOI: 10.1119/10.0000134


Energy-resolved coincidence counting using an FPGA for nuclear lifetime experiments by Mario Vretenar, Nataša Erceg and Marin Karuza. DOI: 10.1119/1.5122744

Audio encryption through synchronization of chaotic oscillator circuits: Teaching non-linear dynamics through simple electrical circuits by Keyur Mistry, Sudeshna Dash and Siddharth Tallur. DOI: 10.1119/10.0000024


American Journal of Physics 87, 1020 (2019);

About AJP

General Information, Resources for Authors, Reviewers, and Readers

Additional Resources