The universe is undergo an accelerated expansion . The so - called Hubble constant indicates the rate of that expansion , and there are a few ways for astronomers to measure it . But there is a major trouble . The master method acting profoundly disagree with each other . This is the saga of theHubble tension , take exception everything we get it on ( and some of the thing we do not jazz ) about the macrocosm .

The two main approach to working out the enlargement rate are as follows . you’re able to measure the cosmic microwave background ( CMB ) , the first light that was released in the cosmos , around 400,000 year after the Big Bang . Alternatively , you may value the length of a lot of galaxy and how fast they appear to move aside from us due to the quad in between expand .

The first method give a economic value of 67.4 kilometers per 2nd per megaparsec . This unit of measurement might seem a moment weird at first . It means that if two galaxies are 1 megaparsec ( 3.26 million light - class ) apart , the universe expanding makes them reckon like they are move away from each other at a stop number of 67.4 km ( 41.9 statute mile ) per second . Using the beetleweed aloofness method instead , the value is 72.8 kilometers per second per megaparsec . The doubt on each time value are pocket-sized and they do n’t overlap .

The [ JWST ] measuring give the same results as the Hubble telescope for the same objects , so it tone up the shell for the tension .

TheHubble Space Telescopewas the generator of the Hubble tenseness saga ; its reflection have been a crucial part of the challenge . Astronomers have been using its heir , the James Webb Space Telescope ( JWST ) , to substantiate or deny this data point .

The team , lead by Nobel laureate Adam Riess , has used the largest sampling of JWST data point to well estimate the Hubble constant and once again , see that the tautness remains . The JWST data , although with panoptic precariousness , find the expansion charge per unit to be 72.6 kilometer per 2d per megaparsec .

" The [ JWST ] measure give the same results as the Hubble telescope for the same objects , so it strengthens the caseful for the tension because it rules out that the tenseness was because of a defect in the Hubble telescope measurements,“Professor Riess , from John Hopkins University , tell IFLScience .

Earlier this year , work carried out by Professor Wendy Freedman , of the University of Chicago , and her team used a data sample from JWST to estimate the expanding upon rate and found a note value between Hubble data and the CMB . This was not seen as the end of the discussion , but it make some Leslie Townes Hope that mayhap the solutions were in truth in between .

Inour interviewwith Freedman , she stated how more observations from JWST were require for more data ; this newfangled oeuvre incorporate the Freedman datum and other observations . It is dead possible for small sample of like or overlapping objects to find different central value and large uncertainties . This is know as sampling variance .

" Here is a utilitarian doctrine of analogy : you are attempt to measure the stop number of traffic on a highway . You use a radar hit man to measure several cars and get an average . Someone else uses a unlike radio detection and ranging hit man . When they measure the same cars they get the same norm . That is what has happened with [ JWST ] and Hubble and confirms Hubble , " Professor Riess told IFLScience .

" However , if they measure the velocity of a unlike set of car and both samples were small , you might see differences . The result is to value a bigger sampling ( to reduce sample variance ) or compare the same cars ( apples - to - apples ) to cross - hold back the microwave radar guns . "

The JWST datum by itself has orotund uncertainties , and while the agreement with the Hubble data strengthens the case , more data will need to be collected from even more distant galaxies to strengthen the claim . Few other methods have been able to sustain one camp or the other . It might be possible that either or both approaches are not estimating their uncertainty correctly and the answer is in the middle . Or , it could be that our theory of the universe needs to be change . Is the fault in our stars , or ourselves ?

“ The divergence between the observed expansion pace of the world and the prediction of the received model suggests that our understanding of the universe may be incomplete . With two NASA flagship scope now confirming each other ’s findings , we must take this [ Hubble tension ] problem very seriously — it ’s a challenge but also an unbelievable chance to learn more about our universe , ’’ explain Professor Riess in astatement .

The study is published inThe Astrophysical Journal .