Hi, When we talk about neutrino oscillations, the discussion is always about the phase that a particular flavour eigenstate picks up with time. The phase is usually partly geometric and partly dynamic. I have a question about this. How do we measure the phase experimentally? What is the basic idea behind the setup that allows us to compare on beam of neutrinos which have evolved with a geometric and dynamic phase with a beam of "unevolved" neutrinos? This really puzzles me since most experiments involve straight paths i.e. nowhere does the neutrino beam travel in a circle or something to come back and recombine or something like that. I can see that if we bring them together, then of course, we will get an interference pattern but how do we do this? Thank you.