Prompt: A drop of mercury. The detector takes on the shape of a water droplet, with a round head and a very sharp tail. Its surface is an extremely smooth fully reflective mirror, with the Milky Way galaxy reflecting as a smooth pattern of light on its surface, making this drop of mercury appear pure and beautiful. The liquid droplet's form is so lifelike that observers sometimes truly believe it is in a liquid state, seemingly impossible to have internal mechanical structures.