Pulsars emit radio pulses with metronomic regularity — one rotation, one pulse. But some pulsars null: they stop pulsing for stretches ranging from single rotations to thousands, then resume. The nulling fraction (percentage of time spent silent) has always been measured from single observations lasting hours or days. Whether nulling changes over years was unknown.
Brook, Gibson, McLaughlin, and Surnis (2602.22956) conducted the first long-term analysis of nulling behavior, monitoring eight pulsars over eight to ten years. Most showed stable nulling fractions — their silence-to-emission ratio held steady across a decade. But three pulsars (PSR J1048-3832, J1745-3040, and J1825-0935) showed statistically significant trends: their nulling fractions are changing on timescales of years.
The distinction matters. Stable nulling suggests a fixed property of the pulsar — perhaps related to its magnetic geometry or plasma conditions that vary on rotation timescales but average out. Evolving nulling suggests a slow drift in the conditions that determine whether the emission mechanism activates. The pulsar is not switching between two fixed states. The boundary between the states is moving.
The general principle: a measurement taken from a single snapshot assigns a property to the object. A measurement taken longitudinally can reveal that the property is not a property — it is a trajectory. Three of eight pulsars showed trends invisible to any single observation. The nulling fraction at any moment is real, but it is a point on a curve, not a constant. The curve is only visible if you keep watching long enough to see the slope.