Overview: This theoretical paper explores whether the universe could eventually stop expanding and collapse in a Big Crunch. The authors model dark energy as an ultralight axion field plus a negative cosmological constant: as the axion’s energy fades, expansion gives way to contraction. Their best-fit benchmark predicts expansion ending roughly 11 billion years from now and a total cosmic lifespan of about 33.3 billion years, roughly 20 billion years remaining. This is a model-dependent scenario, not an established countdown: the paper acknowledges substantial parameter uncertainty, gives a different lifespan using mean parameters, and stresses that both the observational hints of changing dark energy and the proposed model require further testing (Sections 4.2, 5, and 7).
Further Reading & Explanatory Resources
- Start here — dark energy basics: What Is Dark Energy? — NASA. An accessible introduction to accelerating expansion, the cosmological constant, and alternative explanations for dark energy.
- Understand the observations: DESI DR2 Results: March 19 Guide — DESI Collaboration. Explains the 2025 measurements, how researchers reconstruct the universe’s expansion history, and the evidence for evolving dark energy. These observations are context for the paper, not a direct measurement of a Big Crunch date.
- Watch an explanation: DESI’s YouTube channel . The collaboration’s results guide points to this channel for videos covering the DR2 findings.
- Original paper (technical): The Lifespan of our Universe — Luu, Qiu & Tye, version 2 — The version matching the embedded PDF. Section 4.2 derives the benchmark lifespan; Section 5 discusses parameter sensitivity; Section 7 summarizes the conditional conclusion.