There is a long standing tradition among physicists to search for the cosmos in a coffee cup. I don’t know if this tradition arises from the quiet contemplation that coffee produces or from generations of boring physics seminars where you have nothing else to do but look for galaxies in a swirl of cream. I had a colleague years ago, who would finish his coffee and then slowly knead the cup inside out until it looked like a sombrero. But even that speaks to the mathematics of topology that so dominate the theory of General Relativity, and it is that which ultimately governs the universe. And, of course, there is the appealing science fiction possibility that our universe is merely a vortex in the coffee cup of some titan race.
Anyway, this past Sunday I departed from my usual espresso and chose instead a more standard cafe’ Americano and as a result I spotted this little bubble on the surface of my brew and marveled at the reflections that it created. These include two images of the IPhone that I used to capture it. The double image almost certainly results from reflections off two surfaces – the convex top and concave bottom of the bubble.