Here we see high-speed video of air bubbles rising through sesame oil. The flow rate of air is just right for one bubble to catch up to and merge with the previous bubble. As it the trailing bubble pinches off from the valve, it shoots a small jet through itself and into the prior bubble. For information on how to recreate this and related experiments, check out this article. (Image credit: C. Kalelkar and S. Paul, source; see also C. Kalelkar)
Celebrating the physics of all that flows