New studies indicate that the universe may be decaying or expanding faster than current cosmological models predict, which raises questions about the accuracy of the standard Lambda-CDM model. This unexpected acceleration intensifies the ongoing debate surrounding the Hubble tension, which concerns discrepancies in measurements of the universe’s expansion rate. This article discusses the evidence challenging current cosmological models, considers the scientific implications of a decaying universe, and examines the broader implications of this rapid expansion for dark energy, vacuum stability, and the future of cosmology.
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The Expanding Universe: A Background
In 1929, Edwin Hubble discovered that distant galaxies are moving away from us, implying that the universe is expanding. This observation laid the foundation for the Big Bang theory, which states that the universe started from a hot, dense state about 13.8 billion years ago and has been expanding ever since. Shortly after the Big Bang, a rapid inflationary period caused the universe to expand faster than the speed of light, smoothing out its structure. Over time, the expansion slowed but never reversed. 1
Modern cosmology is dominated by the Lambda-CDM model, which incorporates dark energy. It is an unknown form of energy that permeates space and drives the accelerated expansion of the universe. Dark energy currently accounts for about 70% of the universe’s total mass-energy content and is modeled as a cosmological constant. This framework has successfully explained a wide range of observations, like the cosmic microwave background (CMB), and the large-scale structure of galaxies. 2
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New Data, New Questions
Recent observations have shown some inconsistencies despite the success of the Lambda-CDM model. Two primary methods to measure the universe’s expansion rate, quantified by the Hubble constant (H₀), yield conflicting results. Local measurements using standard candles such as Cepheid variable stars and Type Ia supernovae indicate a higher expansion rate (~73 km/s/Mpc), while measurements based on the CMB radiation from the early universe suggest a lower rate (~67 km/s/Mpc). This discrepancy, known as the Hubble tension, has reached a statistical significance that suggests it is unlikely to be due to chance. 3
Recent data from NASA’s James Webb Space Telescope (JWST) have added nuance to this debate. A study led by Wendy Freedman analyzed ten nearby galaxies and found a Hubble constant value of about 70 km/s/Mpc, which aligns more closely with the CMB-based measurements. 4, 5, 6 However, other analyses, including new methods proposed by researchers at the University of Waterloo, continue to highlight the inconsistency, suggesting that our understanding of cosmic expansion may still be incomplete. 7
Moreover, new theoretical work indicates that the universe might be decaying faster than previously thought. Dutch scientists have recalculated the timescale for the evaporation of stellar remnants like white dwarfs via Hawking-like radiation, finding that the universe’s ultimate decay could occur around 1078 years (a much shorter timescale than the previously estimated 101100 years). This suggests that processes contributing to the universe’s long-term evolution might be more dynamic than assumed. 8
What Does "Decaying Universe" Mean?
When scientists refer to a decaying universe, they don’t necessarily mean it's falling apart in a literal sense. Instead, decay can refer to several phenomena in cosmology. For instance, the thermodynamic decay, or the increase of entropy, suggests that the universe is moving toward a state of maximum disorder. Vacuum decay postulates that our universe exists in a false vacuum, a temporarily stable energy state that could, in principle, collapse to a lower-energy to a true vacuum, altering the laws of physics in the process. Similarly, another theory named Big Rip proposes that dark energy’s repulsive force could grow without bound, eventually tearing apart galaxies, stars, planets, and atomic structures.
Implications for Physics and Cosmology
If the universe's expansion is indeed faster than Lambda-CDM predicts, physicists may have to rethink the nature of dark energy: whether it is truly a cosmological constant or whether it evolves over time. If the latter, we might be looking at a dynamical dark energy model, such as quintessence or phantom energy, which could alter our predictions about the universe’s future. Moreover, the discrepancy could stem from unaccounted-for matter distributions or the presence of unknown particles influencing cosmic evolution. 9
Methodologies Behind the Findings
Scientists utilize various sophisticated instruments and techniques to study cosmic expansion and decay. For instance, redshift measurements of distant galaxies help determine how fast the universe is expanding by observing how light stretches as space itself grows. Standard candles like Cepheid variables and Type Ia supernovae provide reliable distance markers as well. 1, 3
The cosmic microwave background radiation is analyzed to infer early universe conditions and the expansion rate. Instruments like the Planck satellite have provided high-precision CMB data. 5
Similarly, new telescopes such as JWST provide high resolution and sensitivity, and enable more accurate measurements of galaxy distances and expansion rates. 3 Theoretical calculations involving Hawking radiation and quantum field theory simulations complement observational data and provide a better understanding of the universe’s long-term decay processes. 8
Future Directions in Cosmology
Upcoming missions and observatories would further clarify these cosmic phenomena. For instance, the Rubin Observatory will conduct wide-field surveys to map billions of galaxies, improving measurements of cosmic expansion and dark energy’s behavior. 10 The Roman Space Telescope will complement these with deep infrared observations, targeting supernovae and galaxy clusters.
Continued data from JWST, along with cosmic microwave background experiments, will refine the understanding of the early universe and the Hubble constant. Advances in quantum simulations and theoretical physics will also probe vacuum decay and scalar field dynamics more deeply. 11
All these efforts may confirm or refute current decay hypotheses, resolve the Hubble tension, and potentially reveal new phenomenon that redefines our understanding of the cosmos.
References and Further Reading
- Bahcall, N. A. (2015). Hubble’s Law and the expanding universe. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.1424299112
- Lahav, O. (2020). Dark energy: is it ‘just’Einstein's Cosmological Constant Λ?. Contemporary Physics. https://doi.org/10.1080/00107514.2020.1837456
- Freedman, W. L. (2021). Measurements of the Hubble constant: tensions in perspective. The Astrophysical Journal. http://doi.org/10.3847/1538-4357/ac0e95
- Louise Lerner (2024) University of Chicago News. New Webb telescope data suggests our model of the universe may hold after all. https://news.uchicago.edu/story/new-webb-telescope-data-suggests-our-model-universe-may-hold-after-all
- Freedman, W. L., Madore, B. F., Hoyt, T. J., Jang, I. S., Lee, A. J., & Owens, K. A. (2025). Status Report on the Chicago-Carnegie Hubble Program (CCHP): Measurement of the Hubble Constant Using the Hubble and James Webb Space Telescopes. The Astrophysical Journal. http://doi.org/10.3847/1538-4357/adce78
- NASA. (2019). New Hubble constant measurement adds to mystery of universe’s expansion rate. https://science.nasa.gov/missions/hubble/new-hubble-constant-measurement-adds-to-mystery-of-universes-expansion-rate/
- Krolewski, A., Percival, W. J., & Woodfinden, A. (2025). New Method to Determine the Hubble Parameter from Cosmological Energy-Density Measurements. Physical Review Letters. https://doi.org/10.1103/PhysRevLett.134.101002
- Netherlands Research School for Astronomy. (2025). Universe expected to decay in 10⁷⁸ years, much sooner than previously thought. Phys.org. Retrieved June 30, 2025, from https://phys.org/news/2025-05-universe-decay-years-sooner-previously.html
- Fay, S. (2020). ΛCDM periodic cosmology. Monthly Notices of the Royal Astronomical Society. https://doi.org/10.1093/mnras/staa940
- Rubin Observatory. (2023). Rubin Observatory will help unravel mysteries of dark matter and dark energy. Retrieved from https://rubinobservatory.org/news/unravel-mysteries-dark-universe
- Freedman, W. L., & Madore, B. F. (2023). Progress in direct measurements of the Hubble constant. Journal of Cosmology and Astroparticle Physics. https://doi.org/10.1088/1475-7516/2023/11/050
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