When I wrote the blog post on “wave watching in a bucket” a couple of days ago, it strongly reminded me of a movie I had filmed already back in March 2018. I was sitting on a train, still inside the train station, and noticed the pattern in my mug (also I just had gotten my awesome lighthouse thermos, hence the awkward angle of the camera).

The train is vibrating, and that vibration makes standing, concentric waves appear and disappear.

I noticed the same pattern on the lady-next-to-me’s coke zero on the bus yesterday, but felt weird leaning over and filming it. So I had to post the old movie instead. And also now I am wondering again what exactly determines the pattern in the standing waves that we get when vibrating buckets or cups with fluids in them…