Astronomers use Type Ia supernovae as candles. Their brightness was thought to be unchanging. The discovery of the Universe’s acceleration using them brought a Nobel Prize to Riess, Perlmutter, and Schmidt. But measurements of the parent stars’ ages revealed: the older, the dimmer the explosion (5.5 sigma). The farther we look, the brighter supernovae appear — this distorts the picture of the Universe’s expansion. It’s like old candles giving off less light, and we misjudge distances.

Adding to the analysis the ‘echoes’ of the early Universe (baryon acoustic oscillations) and the cosmic microwave background, the contradiction with a constant dark energy intensifies to a staggering 9 sigma. The most unexpected outcome: the Universe’s acceleration may have already stopped.