A new study challenges one of modern cosmology’s core pillars: the idea that universe expansion accelerates due to dark energy. Led by Professor Young-Wook Lee of Yonsei University in South Korea, the research argues the universe may have entered a deceleration phase, reopening debate on its ultimate fate.​

A Blow to the Nobel-Winning Theory

Since the late 1990s, scientists have held that the universe not only expands but does so ever faster. This discovery, based on type Ia supernovae observations, earned the 2011 Nobel Prize in Physics.

Type Ia supernovae were deemed “standard candles“—stellar explosions with uniform brightness for measuring cosmic distances. Observing distant supernovae as dimmer than expected in a decelerating universe led astronomers to conclude expansion was accelerating.

However, the new study suggests that conclusion rested on a flawed assumption. Analyzing 300 host galaxy ages via an alternative method, the team found early universe stars had distinct properties. This implies ancient supernovae were intrinsically dimmer, not necessarily farther than calculated.

Correcting this potential systematic bias shows continued expansion but at a decreasing rate. Plus, dark energy—the hypothetical acceleration force—may weaken over time.

A “Big Crunch” Future in the universe?

The implications are profound. If dark energy keeps declining and turns negative, expansion could reverse. The universe would stop expanding and contract into a “Big Crunch,” a reverse Big Bang.​

The work sparks skepticism. Many cosmologists view acceleration evidence—backed by independent observations—as solid. Yet DESI consortium’s recent similar results have reignited debate.

Professor Carlos Frenk of Durham University, not involved, called findings “provocative and worth attention,” though possibly incorrect.

If future observations confirm deceleration, cosmology faces its biggest paradigm shift since dark energy’s discovery 27 years ago. The universe’s fate is once again wide open.

Referencia:
Monthly Notices of the Royal Astronomical Society/Strong progenitor age bias in supernova cosmology – II. Alignment with DESI BAO and signs of a non-accelerating universe. Link

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