James Webb telescope confirms there is something seriously wrong with our understanding of the universe

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

Astronomers have used the James Webb and Hubble space telescopes to confirm one of the most troubling conundrums in all of physics — that the universe appears to be expanding at bafflingly different speeds depending on where we look.

This problem, known as the Hubble Tension, has the potential to alter or even upend cosmology altogether. In 2019, measurements by the Hubble Space Telescope confirmed the puzzle was real; in 2023, even more precise measurements from the James Webb Space Telescope (JWST) cemented the discrepancy.

Now, a triple-check by both telescopes working together appears to have put the possibility of any measurement error to bed for good. The study, published February 6 in the Astrophysical Journal Letters, suggests that there may be something seriously wrong with our understanding of the universe.

Related: After 2 years in space, the James Webb telescope has broken cosmology. Can it be fixed?

"With measurement errors negated, what remains is the real and exciting possibility we have misunderstood the universe," lead study author Adam Riess, professor of physics and astronomy at Johns Hopkins University, said in a statement.

Reiss, Saul Perlmutter and Brian P. Schmidt won the 2011 Nobel Prize in physics for their 1998 discovery of dark energy, the mysterious force behind the universe's accelerating expansion.

Currently, there are two "gold-standard" methods for figuring out the Hubble constant, a value that describes the expansion rate of the universe. The first involves poring over tiny fluctuations in the cosmic microwave background (CMB) — an ancient relic of the universe's first light produced just 380,000 years after the Big Bang.

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))

Between 2009 and 2013, astronomers mapped out this microwave fuzz using the European Space Agency's Planck satellite to infer a Hubble constant of roughly 46,200 mph per million light-years, or roughly 67 kilometers per second per megaparsec (km/s/Mpc).

The second method uses pulsating stars called Cepheid variables. Cepheid stars are dying, and their outer layers of helium gas grow and shrink as they absorb and release the star's radiation, making them periodically flicker like distant signal lamps.

As Cepheids get brighter, they pulsate more slowly, giving astronomers a means to measure their absolute brightness. By comparing this brightness to their observed brightness, astronomers can chain Cepheids into a "cosmic distance ladder" to peer ever deeper into the universe's past. With this ladder in place, astronomers can find a precise number for its expansion from how the Cepheids' light has been stretched out, or red-shifted.

Related: Mysterious 'unparticles' may be pushing the universe apart, new theoretical study suggests

But this is where the mystery begins. According to Cepheid variable measurements taken by Riess and his colleagues, the universe's expansion rate is around 74 km/s/Mpc: an impossibly high value when compared to Planck's measurements. Cosmology had been hurled into uncharted territory.

"We wouldn't call it a tension or problem, but rather a crisis," David Gross, a Nobel Prize-winning astronomer, said at a 2019 conference at the Kavli Institute for Theoretical Physics (KITP) in California.

Initially, some scientists thought that the disparity could be a result of a measurement error caused by the blending of Cepheids with other stars in Hubble's aperture. But in 2023, the researchers used the more accurate JWST to confirm that, for the first few "rungs" of the cosmic ladder, their Hubble measurements were right. Nevertheless, the possibility of crowding further back in the universe's past remained.

To resolve this issue, Riess and his colleagues built on their previous measurements, observing 1,000 more Cepheid stars in five host galaxies as remote as 130 million light-years from Earth. After comparing their data to Hubble's, the astronomers confirmed their past measurements of the Hubble constant.

"We've now spanned the whole range of what Hubble observed, and we can rule out a measurement error as the cause of the Hubble Tension with very high confidence," Riess said. "Combining Webb and Hubble gives us the best of both worlds. We find that the Hubble measurements remain reliable as we climb farther along the cosmic distance ladder."

In other words: the tension at the heart of cosmology is here to stay.

Ben Turner
Staff Writer

Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.

  • A Duck
    Ok, so maybe the universe expands at different rates. There's no reason to believe the universe is round or consistent, it could be amoeba-shaped. What if the amount of dark energy isn't consistent throughout the universe? That would mean expansion in inconsistent rates, potentially explaining the "dark spots" we see. Those could just be "fingers" of the amoeba extended out further from the main body.
  • jnawf
    The obvious problem in my mind is the Big Bang. It seems like everyday I read another article about how observations made by the JWST challenge our understanding of so many different things. The speed at which galaxies formed after the Big Bang, the speed at which galaxies began to die after the big bang, etc. And now we confirm that the universe is inconsistently expanding.

    Remove the Big Bang from the equation and suddenly it all makes more sense. There was no beginning. There is no end. It's the same in mathematics. Why do we need a beginning and end so badly. Energy has no beginning, matter has no beginning. It just transfers and changes. So does the universe.
  • Sharkbyte
    Mmaybe the simulation only draws in the direction you are looking like minecraft. It would appear that the universe is expanding at different rates when really its just limited by the processor speed and available memory of the system running the simulation...
  • gardendude67
    Could it be that mathematics is a man made construct? Numbers can solve human problems. The expansion of the universe may be beyond our understanding. We limit ourselves by assigning limits and numbers to the behavior of the Cosmos. All the same- it’s fascinating.
  • sgtcook1
    I’m not a scientist, but why would we expect that the universe would expand in some sort of order? If we believe in the Big Bang, then we are only seeing one face and one plane of the expansion and surely the energy of the bang was not uniformly distributed. The expansion coming directly in our view does not necessarily have to equal that of 5 degrees on either side of our direct line of sight.
  • fingers
    No scientists but the weird observations seems to make sense as to 2 bubbles of light hitting each other.

    If the big bang was bigger then you originally thinking vast sections of space would begin emmiting light around the same time but be in massively separate areas of space.

    All light in our light bubble is visible but, we see what our light and connected light permiates. But other more further out bubbles wont be visible or seen as expanding until light from those and our bubbles light meet godether. It would look like it's expanding way faster but in reality has been then the same amount of time and instead of expanding its just sort of becoming visible.

    The same method would stand true to any other means of testing the universe, like using radiation since it would be connected in multiple directions also representing expansion but actually its just like 2 laser running into one and other.
  • Bruins
    A Duck said:
    Ok, so maybe the universe expands at different rates. There's no reason to believe the universe is round or consistent, it could be amoeba-shaped. What if the amount of dark energy isn't consistent throughout the universe? That would mean expansion in inconsistent rates, potentially explaining the "dark spots" we see. Those could just be "fingers" of the amoeba extended out further from the main body.
    Yes, I like this train of thought. It would also fit into the idea that there could be multiple universes. Could it be that other universes are pulling or pushing our universe, like balloons would do if you would try to inflate a hundred balloons together inside a box?
  • CaptainGoose
    We live in a super massive black hole. The big bang was the formation of the black hole, expansion is the hole constantly getting larger.
  • Jamesapeterson
    Also not a scientist here … just wondering if there could be multiple bangs. Could it be possible that after the initial big bang, there were others in various areas of the universe resulting in faster expansion in those areas? Is it possible to have the biggest bang and then subsequential bangs that lead to a universe which doesn’t come from just one immense detonation?
  • David B
    As far as I understand, the measurements are made just based on optical information. This means that expansion is measured independently of galaxies, which could pose a fundamental problem, if my understanding is correct in general. My understanding is that the expansion is happening usually between galaxies. Gravitational dependencies between stars and planets aren't considered, and I'm not sure if galaxies can be clearly defined, I think the border areas are probably only very approximate.
    So assumed that expansion happens at different speed, it has to be considered if that happens under the same conditions, or if there is just one or several galaxies between which pose completely a different condition.