James Webb telescope confirms Universe expands at contradictory speeds

Universe expands at 67 km/s/Mpc via Planck, but Cepheids show 74 km/s/Mpc—a 10% gap.

Key Takeaways

The James Webb and Hubble telescopes confirm a major flaw in cosmology theories.
The “Hubble Tension” shows the universe expands at conflicting rates, defying current models.

Dual observations ruled out measurement errors as the source of the expansion discrepancy.
Two leading methods for calculating expansion—the CMB and Cepheid stars—yield incompatible results.
Combining data from both telescopes solidifies the mystery and supports the reality of the tension.

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The Hubble Tension: A Crisis in Cosmology

Astronomers using the James Webb Space Telescope (JWST) and Hubble Space Telescope have confirmed a persistent and troubling discrepancy in the universe’s expansion rate, a phenomenon called the Hubble Tension. Published in Astrophysical Journal Letters, this study definitively rules out measurement errors, leaving scientists to question fundamental cosmological principles.

The problem arises from two methods used to calculate the Hubble constant, a value that describes the speed of the universe’s expansion. The first method examines the cosmic microwave background (CMB)—a faint afterglow from the Big Bang. Between 2009 and 2013, ESA’s Planck satellite inferred a value of approximately 67 km/s/Mpc. The second method uses Cepheid variable stars, which pulsate predictably and act as “cosmic yardsticks” to measure distances. Observations by Nobel laureate Adam Riess and his team yielded a higher value of 74 km/s/Mpc. The 10% gap between these results cannot be reconciled by current cosmological models.

Illustration of the expansion of the Universe. (Image credit: Mark Garlick/Science Photo Library via Getty Images)

A Triple-Check with Advanced Telescopes

Initially, some scientists speculated that Hubble Telescope measurements were flawed due to blending Cepheid stars with other stars. However, JWST’s sharper resolution eliminated this concern, confirming Hubble’s accuracy for nearby galaxies. To solidify their findings, Riess and his colleagues analyzed 1,000 more Cepheid stars across five host galaxies up to 130 million light-years away. The results upheld their previous measurements, ruling out measurement errors entirely.

“This is no longer a question of technique or tools. The tension is here to stay,” Riess stated. With the combined power of Hubble and JWST, astronomers confirmed that the discrepancies in expansion rates are real and significant.

JWST’s infrared cameras allow it to look at the universe in more precise detail than any telescope before it. (Image credit: NASA, ESA, CSA, J. Diego (Instituto de Física de Cantabria), B. Frye (University of Arizona), P. Kamieneski (Arizona State University), T. Carleton (Arizona State University), and R. Windhorst (University of Arizona), A. Pagan (STScI), J. Summers (Arizona State University), J. D’Silva (University of Western Australia), A. Koekemoer (STScI), A. Robotham (University of Western Australia), and R. Windhorst (University of Arizona))

Implications for Our Understanding of the Universe

The Hubble Tension represents more than a scientific puzzle; it challenges our foundational understanding of cosmology. As Nobel laureate David Gross described it, this isn’t merely a problem but a full-blown crisis. It suggests that new physics may be required to bridge the gap between these conflicting measurements.

The tension highlights potential limitations in current theories, including the role of dark energy in the accelerating expansion of the universe. Whether this leads to a paradigm shift or refinement of existing models, the Hubble Tension underscores how much we have yet to learn about the cosmos.