Coffee Cup Science

A collection of anecdotes and experiments that relate the physics of coffee to the physics of the universe as a whole. Please click the links below to explore, or visit the Daily Grind to read more.

Tears of Wine

Coffee and Wine

We may drink one during the morning and then turn to the other as the day progresses, but what happens when we bring them together? All liquids have surface tension but the surface tension of alcohol is weaker than that of coffee. In this experiment, which you can do in your kitchen or watch online, we investigate how to create a hole in coffee using wine and look at the reasons behind the wine ‘legs’.

Milk Ring

From coffee to exploding stars

Smoke rings are found throughout nature, not just in smoke.  This section shows how you can make ‘smoke rings’ by adding drops of milk (or coffee) to water and then explores where else in nature ‘smoke rings’ are observed, from volcanoes to supernovae.

Blue sky, light scattering, Tyndall blue

Blue sky in your coffee

What makes the sky blue? And why does the world look very different to a bumble bee?

A chance to explore why the sky is blue (and sunsets red) with equipment you can find in your kitchen.


Why coffee is a bad idea for your smart phone

Coffee rings can be irritating, but have you ever stopped to wonder why these stains form the way that they do? Amazingly no one had asked this question until 1997 and yet the physics behind the coffee ring can be explored with some experiments that you can do at home, while the consequences of the mechanism behind coffee ring formation extend to the manufacture of your smart phone.

pigeon, sun, sunbathing, age of the earth

Kelvin, Darwin and cooling coffee

The physics determining how objects cool is the same whether those objects are cups of coffee or stars like the Sun. The theory of evolution was proposed by Charles Darwin in 1859. But was it possible that the Earth was actually old enough for evolution to have occurred? The understanding based on the physics of the day suggested that it could not be. Find out the reason behind this apparent conflict between physics and biology, how it was eventually resolved, and how coffee comes into it.


Coffee Physics Reviews

Wherever you look there are connections to be made and physics to be explored. Take some time to enjoy a coffee in a favourite cafe and then slow down and look around. The cafes featured here are places where good coffee and some interesting physics combined. It’s always good to know about good new cafes elsewhere. If you think that a cafe has great coffee and could offer a bit of thought provoking physics, please let me know by emailing me here.

More stories can be found in the Bean thinking blog “The Daily Grind“.  If you have a suggestion for a topic to include in “Coffee cup science” or you have any comments on the articles above please contact me.