Analysis indicates that the universe’s expansion is not accelerating

Timing and Meaning of “Now”

• Commenters clarify “now” refers to our current evidence, not a sudden recent change.
• Based on the paper’s figure, the deceleration would have started ~2.5 billion years ago, not in human timescales.
• Some tie this to earlier 2025 results (e.g., DESI BAO) that already hinted the standard ΛCDM model might be off.

Cosmic Expansion vs Local Structures and Travel

• Expansion is between galaxies; gravity dominates within galaxies and bound groups, so stars don’t drift apart due to expansion.
• The Local Group (Milky Way, Andromeda, many dwarfs) remains gravitationally bound; expansion doesn’t affect travel inside it.
• Interstellar vs intergalactic: several argue that once you can go to stars 10–100 ly away, Andromeda is “just” a longer wait; others counter that very long mission durations, engineering reliability, and the rocket equation are fundamental hurdles.
• Time dilation allows crossing huge distances in short ship-time, but at the cost of extreme energies and huge elapsed external time.

Standard Candles, Supernovae, and the Core Claim

• Central claim: Type Ia supernovae, previously treated as “standard candles,” show a strong correlation between standardized brightness and progenitor age, causing a redshift-dependent bias.
• Correcting for this age bias reportedly makes SN data align with a dark-energy–free CDM model and, when combined with BAO+CMB, strongly disfavors constant-Λ ΛCDM in favor of time-varying dark energy.
• Some are excited this dovetails with independent BAO and galaxy clustering analyses; others stress that SN distance ladders already include many cross-checks and that one paper overturning all of that is unlikely without very strong confirmation.
• There is concern about possible overfitting and sample biases; the team itself, via secondhand reports, acknowledges limitations and expects better tests with future survey data.

Dark Energy, Fate of the Universe, and “Big Bounce”

• Users ask if deceleration implies eventual recollapse or a cyclic/bouncing universe. Multiple replies: deceleration alone does not guarantee recollapse; expansion can slow forever without reversing.
• Some note evidence still favors dark energy, but perhaps dynamic rather than a fixed cosmological constant.
• Others raise thermodynamic objections to infinitely oscillating universes and cite work arguing bounces conflict with the second law, unless that law is incomplete.

Conservation Laws and Cosmology

• One commenter claims expansion must eventually be balanced by contraction to preserve conservation; others invoke Noether’s theorem: in a dynamic spacetime without global time-translation symmetry, global energy conservation need not hold, and “missing energy” is not automatically a contradiction.

Methodological Skepticism and Philosophy

• Several highlight that cosmology rests on long assumption chains (distance ladders, model choices), making “credibility” hard to assess without deep domain knowledge.
• Others emphasize error bars, multiple independent probes, and the inherently provisional nature of science: models are updated as new data arrive, unlike the certainty offered by religion or pseudoscience.
• A long side-thread debates whether “existence” must exist, whether “nothingness” is coherent, and how this relates to infinite or cyclic cosmologies—conceded to be more metaphysical than empirical.