a gauge of water that writes itself. five harmonic constituents — m2, s2, n2, k1, o1 — sum into a bright record drawing across the dark; the faint lines behind it are earlier cycles of the same sea, and they never quite match, because the weather is never quite the same. hold the pointer to make it rain.
a real tide is a sum of cosine curves: 37 harmonic constituents are used to predict tidal conditions for a location, each with its own amplitude and phase [1]. the two largest are m2, the lunar constituent that gives 2 peaks every 24 hours and 50 minutes [1], and s2, the solar constituent that gives 2 peaks every 24 hours [1]. this instrument sums five of them — m2, s2, n2, k1, o1 — into one line of water, drawing from left to right across 44 simulated hours. the ghosts behind it are the same water one and two lunar days earlier. hold the pointer (or a finger) over the gauge to make it rain: the surge lifts the record, then settles. space pauses, r finds the next port, s saves a png.