Exotic states of matter known as time crystals are largely considered a quantum phenomenon. Now, a team from New York University (NYU) has shown that a classical time crystal can emerge in a far simpler way – using nothing but speakers and styrofoam. This system might not just be an extraordinarily clean example of a classical time crystal, but a really neat laboratory for studying non-reciprocal interactions on a macroscopic scale, where particles interact through scattered sound waves rather