Crisis in Cosmology Intensifies as Debate Over Whether the Universe Is Really Accelerating is Reignited

A controversy over one of modern cosmology’s foundational ideas has been renewed, with new research that points to critical issues in a recent analysis defending the view that our universe is expanding. The Yonsei University research team claimed that Type Ia supernovae are affected by their age, leading to biases in past cosmological measurements. After correcting for this, the team’s new results suggested that the cosmic expansion may have already transitioned from acceleration to deceleration. The findings challenge the standard Lambda-CDM model, which assumes dark energy remains constant.

• Yonsei University team: 2023
• New analysis: Type Ia supernovae
• Correction: Age bias
• Implication: Cosmic expansion may have transitioned from acceleration to deceleration

A pushback from proponents of the standard model was issued in June by an international team led by University of Southampton researchers. They argued that the relationship between the ages of supernovae and their luminosity is far weaker than previously thought, suggesting that the proposed age correction was too small to upend current evidence.

• Southampton team: 2023
• Argument: No significant age bias
• Implication: Current evidence supports an accelerating universe

The original Yonsei research team has responded in Monthly Notices of the Royal Astronomical Society with an additional study, pointing to methodological problems in the Southampton team’s rebuttal. The Yonsei team claims that the new analysis combined supernovae across too broad a range of redshifts, weakening apparent correlations.

• Yonsei team: 2023
• Argument: Redshift range too broad
• Implication: May have weakened the observed correlations

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