Scientists have used the most powerful space telescopes available to confirm a truly confusing fact about our vast universe.
The James Webb Space Telescope (JWST) has confirmed that depending on what parts of space we look at, the universe appears to be expanding at very different rates.
We've suspected this for a long time. The phenomenon was dubbed 'Hubble Tension' back in 2019 - after findings from the Hubble Telescope - and it was checked by the JWST in 2023 for further confirmation.
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Now, researchers have triple-checked their work by using both telescopes together, to confirm that this is definitely a real thing.
According to lead study author Adam Riess, professor of physics and astronomy at Johns Hopkins University, this is a thrilling find: "With measurement errors negated, what remains is the real and exciting possibility we have misunderstood the universe".
Only an astrophysicist could say that without any thought to whether it's actually a bit of a scary concept, of course.
The two ways that we're able to check out the rate of expansion of the universe are equally impressive - one is the simplest, if you can call it that. It involves watching for tiny fluctuations in the cosmic microwave background (CMB), radiation that was emitted soon after the Big Bang.
We can get the speed of expansion from those fluctuations, or use another method entirely. This one takes advantage of pulsating stars, also known as Cepheid variables, in a pretty trippy way.
By measuring the flickering light of these stars and mapping them out, scientists can calculate what's known as a 'cosmic distance ladder', a way of measuring the relative distances between cosmic entities.
Using this to calculate how the Cepheid variables' light has been stretched out over time lets us again work out the expansion rate. Of course, if that makes those calculations sound simple, we can confirm that it's anything but straightforward.
It was these Cepheid calculations that first started to show discrepancies in our understanding of the universe's speed of expansion, and they have now been investigated pretty thoroughly.
Using both telescopes and both methods together appears to be a good way forward, though - Reiss explained: "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.
"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."
The findings were published in The Astrophysical Journal Letters.