George Kubler’s 1962 book The Shape of Time defines the present instant with a line Maria Popova found while watching the Perseids from a Spanish mesa: “Actuality is when the lighthouse is dark between flashes: it is the instant between the ticks of the watch: it is a void interval slipping forever through time: the rupture between past and future.” The essay is illustrated with the stacked pulses of CP 1919, the first pulsar found — the waveform Joy Division put on the cover of Unknown Pleasures.