Webb telescope confirms the universe is expanding at an unexpected rate

Two years of data from NASA’s James Webb Space Telescope have now validated the Hubble Space Telescope’s earlier finding that the rate of the universe’s expansion is faster - by about 8% - than would be expected based on what astrophysicists know of the initial conditions in the cosmos.

Fresh corroboration of the perplexing observation that the universe is expanding more rapidly than expected has scientists pondering the cause - perhaps some unknown factor involving the mysterious cosmic components dark energy and dark matter.

Two years of data from NASA's James Webb Space Telescope have now validated the Hubble Space Telescope's earlier finding that the rate of the universe's expansion is faster - by about 8% - than would be expected based on what astrophysicists know of the initial conditions in the cosmos and its evolution over billions of years. The discrepancy is called the Hubble Tension.

The observations by Webb, the most capable space telescope ever deployed, appear to rule out the notion that the data from its forerunner Hubble was somehow flawed due to instrument error.

"This is the largest sample of Webb Telescope data - its first two years in space - and it confirms the puzzling finding from the Hubble Space Telescope that we have been wrestling with for a decade - the universe is now expanding faster than our best theories can explain," said astrophysicist Adam Riess of Johns Hopkins University in Maryland, lead author of the study published on Monday (December 9, 2024) in the Astrophysical Journal.

"Yes, it appears there is something missing in our understanding of the universe," added Riess, a 2011 Nobel laureate in physics for the co-discovery of the universe's accelerating expansion. "Our understanding of the universe contains a lot of ignorance about two elements - dark matter and dark energy - and these make up 96% of the universe, so this is no small matter."

"The Webb results can be interpreted to suggest there may be a need to revise our model of the universe, although it is very difficult to pinpoint what this is at the moment," said Siyang Li, a Johns Hopkins doctoral student in astronomy and astrophysics and a study co-author.

Dark matter, thought to comprise about 27% of the universe, is a hypothesised form of matter that is invisible but is inferred to exist based on its gravitational effects on ordinary matter - stars, planets, moons, all the stuff on Earth - which accounts for roughly 5% of the universe.