Dark Energy Didn’t Kick In Right Away ⚡ экспресс
Imagine that dark energy is not a constant but a sleeping volcano, awakening at a specific moment in cosmic history. In the model of critical emergent dark energy (CEDE), a phase transition is hypothesized, after which accelerated expansion begins to dominate. Analysis of cosmic microwave background, baryon acoustic oscillations, and supernova data shows that such a scenario is not ruled out and is even preferable to standard ΛCDM under some statistical criteria. However, the mystery of the Hubble constant discrepancy persists, and future surveys will reveal whether this "awakening" mechanism is real.
Dark energy is usually seen as an innate property of the cosmos, at work from the very first moments. But a new model suggests it behaved like water on the verge of boiling: long unnoticed, then suddenly kicking in at a critical moment. This scenario is called 'late activation': around 5–7 billion years ago, a shift occurred, and the universe’s expansion began to accelerate.
Three landmarks helped test the idea. The cosmic microwave background—the cooled light of the Big Bang—preserved the imprint of the young universe. Explosions of supernovae, like lighthouses, allowed distances to be measured; it was these that led Adam Riess to discover the acceleration in the 1990s. The patterns of galaxies revealed the rate of universe expansion. By combining these data, scientists essentially captured the moment the cosmos 'boiled over.'
There was a surprise:
However, this doesn't resolve the main cosmological puzzle—the Hubble tension, i.e., the discrepancy in the expansion rate measured by different methods. The mystery endures, and cracking it will require even bolder ideas.
🎯 If dark energy had 'woken up' too early, just a couple of billion years after the Big Bang, the galaxies and stars we know simply wouldn’t have formed—the expansion would have scattered all matter.