…there are two different ways to measure this cosmic expansion rate, and they don’t agree. One method looks deep into the past by analyzing cosmic microwave background radiation, the faint afterglow of the Big Bang. The other studies Cepheid variable stars in nearby galaxies, whose brightness allows astronomers to map more recent expansion.
You’d expect both methods to give the same answer. Instead, they disagree—by a lot. And this mismatch is what scientists call the Hubble tension…Webb’s data agrees with Hubble’s and completely rules out measurement error as the cause of the discrepancy. It’s now harder than ever to explain away the tension as a statistical fluke. This inconsistency suggests something big might be missing from our understanding of the universe - something beyond current theories involving dark matter, dark energy, or even gravity itself. When the same universe appears to expand at different rates depending on how and where you look, it raises the possibility that our entire cosmological model may need rethinking.
JWST doing exactly what it was supposed to do ! That’s both exciting and terrifying !
What’s terrifying about learning more about his the universe works?
That’s just how all of science works.
It’s not kind JWST detected a black hole barreling towards us or anything.
The article over-dramatizes the story. This “deeply wrong” discrepancy is less than 10%. CMB measurements predict a Hubble constant of around 68km/s/Mpc. Distance ladder measurements get around 73km/s/Mpc.
Our current understanding of the universe the Lambda-CDM model is still wildly successful and it’s more likely that the true correct model of the universe will be a correction/extension to Lambda-CDM rather than a completely new theory (although if it is a completely new theory that would be pretty cool).
I think you’re understating things. The measurements don’t have to be 100 km/s/Mpc apart to cause problems for our understanding of the universe. Ruling out measurement error means we have to go back to the drawing board on cosmology. The problem isn’t sloppy telescopes or anything – it’s definitely a hole in our current model.
If they wanted to use the term “deeply wrong discrepancy”, maybe they should have gone with the difference between the universe’s expansion predicted by quantum vacuum energy and the actual, much slower observed rate of expansion.
By “much slower”, I mean that the theory and the observations differ by something like one hundred and twenty five (!!!) orders of magnitude.
I think the deeply wrong part of it is that the difference is now big enough for the error bars to stop overlapping
The instrumental error bars are no longer overlapping. But if we imagine all the modifications one could make to Lambda-CDM, then there is still a huge “theory” error bar that subsumes all these.
Basically I’m saying the model is wrong, yes, but it can very much be fixed.
But could you make these modifications without diverging from other observations? If it were as easy as you put it, why have scientists been talking about it for decades?
i agree with you that here, the difference between 68 and 73 seems very small.
For me, it’s even amazing that they get, for the CBM, any number even close to the same order of magnitude, given that it seems like a linear division of speed of light divided by light travel distance at the age of the universe, is the value for Hubble parameter (H)*_ at CBM.
That seems in contradiction to the fact that, when adding relativistic velocities (and incrementally up to the speed of light !), linear addition is out of question and general relativity has to be used.
This is just one of the apparent difficulties and obviously there are much more and harder challenges than this one.
_*(… and is the age of the universe defined or measured by other means than simply :
Δt = 1/H … ? That can’t be : since we have 2 parameters to evaluate, so, we need 2 independent experimental measurement variables. )
From previous articles, I do believe it is consistent enough across different approaches and precise enough that there really seems to be more than one answer. How can that be?
We really don’t have a solid reason for the increase in expansion rate of the universe. Dark energy seems most straightforward and consistent with everything else but it’s not proven until we can identify and measure that energy. This lends weight to the idea that it’s not that simple
Suppose we come to establish that the expansion rate accelerated from 68 to 73 km per second / Mpc (in the lapse of, say, 80% the ~14 B. years age of U.) if this is so, so be it. Why oppose it ?
Or, if for the same period, we have two different rates … this is not acceleration. This is two methods yielding different results for what is supposed to be one sigle thing. So, one of the 2 methods doesn’t measure exactly the same thing as the other … whatever.
Obviously, observation and measurement have to be the basis for any hypothesis and for any explanation proposals. So, we should not say : “since we have no explanation, there should not be acceleration of the expansion”. - - But rather we should say : “since there is acceleration of the expansion, we should build some theoretical models around this reality”.
Anyway, you probably already know all of this.
The majority of physics is done with very high precision. This is especially true for fundamental values that apply to everything. For example know the mass of an electron with an error of 0.3 parts per billion. I think this discrepancy is evidence of a significant hole in cosmology theory.
Yes i agree that, doing physics in a very well controlled laboratory, physicist can measure things accurately.
Unfortunately we don’t have a laboratory big enough to reproduce a big bang and study it in a controlled fashion. So, in cosmology, measurement are difficult and not so precise 😋.
Lambda-CDM is fully aware of general relativity. Some people may try to explain it with nonrelativistic pictures to help you build intuition, but the actual theory and calculation is fully relativistic so you don’t have to worry about that.
since we have 2 parameters to evaluate
I don’t follow. What two parameters?
Yes i agree with you that, of course, physicists working on this have to be well aware of general relativity. Still, there is this linear relationship that bothers me for the Hubble parameter.
What two parameters ?
i should have put more effort in understanding before writing my comment … and this confusion about “two parameters” is nothing of importance for what i try to say in that comment. Sorry if you don’t see anything interesting in what i said.
I fully expect scientists of the 25th century to roll our current level of knowledge of the universe in one with flat earth and geocentrism.
But how could light pass through nothing? Surely there must exist a lumeniferous aether!
Exactly. People have been convinced of numerous “scientific” ideas over the centuries that later turned out to be totally bogus. “Dirt creates vermin”.
And maybe, in a few decades or centuries, they laugh at the notion of Dark Matter. Or what the stupid cavepeople of the 21st century still believed was gravity or speed of light.
I mean, the recent discoveries actually do not dispute most of the previous theories. Most of the time the old theories are fringe cases where some parameters are simplified so you get the new theory that is actually a general case of the classical one. It’s not like our old formulas stop working when we discover new cases…
If you’re interested in this stuff, Thomas Kuhn’s The Structure of Scientific Revolutions describes a lot of how science actually happens, where most normal science builds up accumulated information under an accepted paradigm, but occasionally those old models slowly become untenable with repeated observations that are anomalous or not explained by that existing accepted scientific paradigm. Then a scientific revolution occurs, the old paradigm is cast aside or limited in its scope, while the new paradigm takes over as the generally accepted set of theories. The book is one of the most cited works of the post-war era.
Geocentrism Heliocentrism didn’t have a clear advantage over Heliocentrism geocentrism, until Kepler made the observation that the planetary orbits were elliptical. (One big objection to geocentrism was that the stars should have some kind of observable parallax if the earth were moving around the sun, but that ended up being explained by learning just how freaking far away the stars are.) Heliocentrism with elliptical orbits, though, laid the groundwork for Newton’s theory of gravitation.
Later on, Mercury’s anomalous orbit just couldn’t be made to fit Newton’s theory, but astronomers held onto Newton’s theories for decades before Einstein’s general relativity was enough to explain it. Einstein’s own cosmological theories needed to be fit in with the discovery of the cosmic background radiation and our expanding universe, and eventually we got to our current paradigm of the lambda-CDM model, which postulates the existence of dark matter to account for galactic structures, dark energy to account for the acceleration of the expansion of the universe. All along the way, there were discarded theories that just don’t hold up.
The history of how we got here can help inform how we should speculate about where we might go next. New normal science might try to figure out what dark matter actually is (different theories can be tested by looking for different observations), without actually challenging the overarching lambda-CDM model. Or research into the Hubble Tension might allow enough observation to propose a new model entirely, for a revolution into a new paradigm.
And of course, Kuhn wrote his hugely influential book in 1962, so many decades of thought have refined and challenged some of those ideas. It’s interesting stuff.
To be fair, there’s always been something deeply wrong with how most people understand the universe.
To be fair, there’s always been something deeply wrong with how most people understand
the universe.
FTFY
To be fair, there’s always been something deeply wrong with
howmost peopleunderstand the universe.
FTFTFY :P
This website is slop even if it overlaps with reality at times.
