[imagesource: NASA, ESA, CSA]

NASA’s James Webb Telescope has made a groundbreaking discovery that could shake up our understanding of the universe.

The latest finding, from analysing data collected by both the James Webb and Hubble space telescopes, reveals a puzzling observation in all of physics.

Depending on where we look, the universe appears to be expanding at bafflingly different speeds.

Live Science reports that this conundrum, known as the Hubble Tension, has the potential to alter or even upend cosmology altogether. The study, published February 6 in the Astrophysical Journal Letters, suggests that there may be something seriously wrong with our understanding of the universe.

In 2019, measurements by Hubble confirmed the puzzle was real and then in 2023, even more precise measurements from the JWST solidified the discrepancy. This triple-check by both telescopes working together might just have put the possibility of any measurement error to bed for good.

“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.)

This might be the only time that a mistake in understanding is considered exciting.

Scientists typically use two “gold-standard” methods to measure the universe’s expansion (called the Hubble constant), that is studying the cosmic microwave background and observing pulsating stars called Cepheid variables.

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. 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 other approach involves using pulsating stars known as Cepheid variables, which are essentially dying stars with outer layers of helium gas that 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.

However, these two methods have produced conflicting results, with one suggesting a slower rate of expansion and the other indicating a faster one. 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.

This challenged the researchers to reconcile the discrepancy. Thanks to the James Webb Telescope’s advanced capabilities, scientists have been able to gather more precise data, providing further evidence for the Hubble Tension.

“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.

[source:livescience]