Dark energy — the mysterious substance responsible for the accelerated expansion of the universe — may not be a constant factor but a variable force. Recent data from the DESI survey (Dark Energy Spectroscopic Instrument) pointed to an unexpected burst of acceleration in the relatively recent cosmic past, as if the 'push' of dark energy suddenly surged for a moment.

Scientists have proposed an explanation that avoids exotic physics. Picture a kettle with limescale: if heated unevenly, steam escapes not smoothly but in spurts. In the cosmological analogy, massive galaxy clusters play the role of limescale. Their gravity locally 'cools' and condenses dark energy, temporarily raising its density and pressure. Such gravitational condensation of particles produces a brief 'phantom' phase — a state where energy density exceeds the critical value, making the universe accelerate beyond its usual rate for an instant.

The model describing these oscillations agrees with observational data on type Ia supernovae — stellar explosions that serve as 'standard candles' for measuring cosmic distances. It reminds us that sometimes simple mechanisms, not just exotic fields, operate in space. An unexpected fact from the calculations: if this acceleration jump had lasted a bit longer, our sky today would look different, with scattered constellations and disrupted familiar gravitational bonds.