Has JWST SOLVED the crisis in cosmology?!

the crisis in cosmology is one of the biggest problems facing astrophysics today but now there's a research group that claims to have solved it using data from jwst now if you've been following me for a while you'll have heard me talk about the crisis in cosmology before and so you'll know how incredibly huge of a deal this is so to quickly recap we have two main methods for calculating the current rate of expansion of the universe one from our model of the entire universe and one from observations of nearby galaxies and as telescopes and Analysis methods have improved over time those two methods have started to give us very different numbers for the rate of expansion what known as the Hubble constant to the point where they very strongly disagree with each other this is known as the Hubble tension or the crisis in cosmology if you want to be a bit more dramatic but last weekend a conference of the American physical Society in Sacramento California a giant in this field Wendy fredman presented her research group's latest work using data from jwst and now they're claiming a value of the Hubble constant that within error agrees with our best model of the universe they're claiming now that there is no Hubble tension that the crisis in cosmology has been solved of course I had to make a video on this but everything I'm about to say comes with a very big disclaimer no research papers have been released yet this work is not peer reviewed all we have to go on is the 35 minute talk that Wendy Freeman gave at this conference and the slides that go with it that is not what I usually like to do on this channel just last week I mentioned how I like to wait for papers to be re-reviewed before I make videos on them so I'm aware this is very hypocritical of me to be covering this but just didn't feel like I could ignore this this feels like the proper Cutting Edge of research and discussion especially since the results we've got from another research group using Jade T data to investigate this have been suggesting jst couldn't help us solve the Hubble tension at all it made things worse and I've covered that in a video just a few months ago on this channel so there is so much to impact here but it comes with the caveat that everything I'm about to say could all change in the peer review process in the next couple of months so in this video we're going to chat first what the Hubble tension actually is in a lot more detail and I'll pop chapter markers down here for all of you who've heard me say this before and you might want to skip that recap second the possible explanations for the tension and what could solve it three what Freeman and collaborators are claiming to have found using their data from jwst four how this compares to previous work on the Hubble tension with j and five what now is the crisis really over because it seems like what we've got is two research teams claiming two different things both using data from jst now when you have two sides like that in science the data and the observational evidence will eventually come down on one side or the other but in politics or Society it tends to be a bit more complex than that which is why I like to use ground news the sponsor of today's video to help me Wade through the different opinions discussed in the media to see through the bias and the misleading narratives ground news is an app and website that compiles sources from all the world's media in one place is the brainchild of harleen core an ex NASA engineer who even worked on jwst so of course they have great space news coverage but where I think ground new particularly shines is with their blind spot feed which gives you a look into news stories that you might have missed depending on where you typically read your news take this story for example about how Austria is likely to be largely ice free with in 45 years as glassiers recede quickly but you can see that people who only read exclusively right leaning media sources might have missed this story but thanks to ground news's blind spot feed it won't be lost in the mix we can also see that 77% of the sources are rated highly factual so we know that there aren't as many sensationalized headlines I particularly love ground news's comparison features for example right leaning media sources put quotations around largely or ice free whereas left leaning sources frame it around this is what experts have said so this is why I'm proud to be partnering with ground news again they're an independent platform that works on a subscriber based model so they can be free of any advertising bias so if you head to ground. news/ Dr Becky you'll not only receive a 40% discount on their Vantage plan when you subscribe but you'll also be helping to keep the media transparent so thanks again to ground news for sponsoring this video and now let's get back to chatting about this huge news about the Hubble tension and chat in a bit more detail about what the problem actually is so I've talked a lot on this channel about the Hubble tension or this crisis in cosmology before I'll link a playlist of videos down below if you want a real deep dive on this but essentially this all boils down to our measurement of the current rate of expansion of the universe what's known as the Hubble constant or h n the N subscript here refers to a red shift of zero I.E the universe around us today the rate of expansion now now the rate of expansion does change with time and we can also measure that how H changes as a function of red shift Zed and that's something that the recently launched ukl Space Telescope will focus on and it's what the recent Desi collaboration have done more on that in next week's Night Sky News video but that's a separate thing to this current rate of expansion h n which is the measurement that's caused all of the issues now one way to measure this current rate of expansion is to measure both the distance to nearby galaxies and the speed that they appear to be moving away from us because of the expansion of space we then plot one against the other and the slope of the line that you get is the current expansion rate hn when we do that we get a value of around about 74 km/s per Mega par other way we can get the current rate of expansion of the universe is to model the entire universe starting with the earliest light from when the universe was just 380,000 years old what's known as The Cosmic microwave background and then come up with a model that can evolve that into the universe that we see around us today we then find the best fit model to you know the observed Universe in terms of like all the laws of physics that we know what the universe is made of and and how much of everything that is and then from that model we can then determine lots of other different parameters and properties of the universe one of those is how the expansion of the universe changes with time but in particular we can also get the current rate of expansion H nor which when we do that we get a value of around about 67 km/s par so this Hubble tension or crisis is because these two different methods are giving us two very different answers there's a gap between them that's bigger than the uncertainty on our measurements a gap which is only been widening over time as our uncertainties decrease as our analysis techniques got better and our observations of the universe supposedly improved due to bigger and better telescopes so how are we going to solve this because for them not to agree either there's something wrong with our observations of nearby galaxies perhaps how we're calculating their distances something like that or there's something wrong with our best model of the universe either we'd be missing some law either we're missing some law of physics that we don't know about yet or there's some component of the universe that we don't know about yet that we haven't included in our model like this is the option I think people get most excited about because it mean we'd learn something new there'd be brand new physics to explore and to try and understand here's a non-exhaustive list from a review paper last year of all the different hypotheses that have been raised to try and explain this with new physics and it's why I got so excited when I first saw that this talk was happening at this APS conference last weekend because the title was new jwst results is the current tension in hnot signaling new physics I thought that that's what this research team had found that they were going to present evidence with jdst that showed that we needed some new physics which is why I got so excited and put out a short an Instagram a Tik Tok and from the poll I put out it looks like all of you thought the same thing but I guess we should have known better V's law of headlines right so it's looking like it was something to do with option one now option one really is where the majority of my colleagues Focus has been you really do have to be meticulous with your science exhausting all the possibilities that you could have got something wrong in terms of your observations before you start considering new physics and the sort of thing that everyone was suspicious of that they thought was going to be the issue was our measurements of the distances to nearby galaxies which get with something known as The Cosmic distance ladder before you can calculate the distances the nearby galaxies you have to take a few steps of the ladder first and the first step on the ladder is calculating the distances to nearby stars in our own Milky Way galaxy one way of doing this is to use parallax this is essentially using the fact that our perspective here on Earth changes as we orbit the Sun so we view stars from slightly different angles at different times of the year which means that nearby Stars seem to change their position slightly compared to more distant stars from how much those nearby Stars wobble around we can work out how far away they are using simple trigonometry once you've got that you can then take the next step up the ladder where you work out the distance to our nearest neighboring galaxies and to do that we use something called standard candles types of stars that have like an absolute maximum brightness and we know what that is because we've observed them in our own Galaxy and we know how far away they are there so that from how bright or faint they appear in more distant galaxies we can then say okay well from how bright they are there compared to how bright we know they should be we can work out how far away they are and therefore how far away that Galaxy is there's a few different types of stars you can use to do this the most famous being seid variables these are stars that pulse in proportion to that maximum brightness that they can reach we know this from observing them in our own Milky Way galaxy so if you can measure the time between pulses and seids in neighboring galaxies you know what their maximum brightness should be so from how bright they appear you can then work out the distance to those nearby galaxies there's other types of stars we do this as well known as the tip of the red giant Branch stars trgb or the J region asymptotic giant Branch Stars j a GB which again have a known brightness in the Milky Way and a known distance which again we can then compare them to in nearby galaxies that means that those distance measurements all rely on our previous Rong of the ladder the distances of stars in the Milky Way itself now that's great for our neighboring galaxies where you have a hope of resolving these individual types of stars but for even more distant galaxies you have to go another rung up the ladder cuz those individual normal stars are just too faint for us to pick out at those distances but we can do it if a star gets incredibly bright in a supernova specifically what's known as a type 1 a supernova when a dead star known as a white dwarf reaches the maximum Mass it can support and then goes Supernova always with the same brightness because that maximum mass is always the same so again these are a standard candle but because they're so bright we can see them in galaxies much further away and we can then use them to calculate the distances to those galaxies it's using these Supernova and these more distant galaxies that we Ed to measure that rate of expansion of the universe and it's this measurement that's so at odds with the one that we get using our best model of the universe but you've got to remember that the distances to those galaxies rely on those previous rungs of the cosmic distance ladder and all of the observations and calibrations that have been done to get to that stage this is why this is thought to be the most likely explanation for the Hubble tension the thought has always been that somewhere in this house of cards of the cosmic distance ladder if just one thing is wrong it could all come crashing down and the Hope has always been that the Jame web Space Telescope jwst would be the savior of This research field and that the data from it would help us figure out what's going on one idea was that the middle rung of the cosmic distance ladder using the stars in those neighboring galaxies was affected by something called crowding so the hobble Space Telescope couldn't actually separate the individual stars out very well it didn't have a high enough resolution so the individual Stars light couldn't be isolated from the Stars around it so your measurement is then biased but with jdst being a much larger telescope it could resolve smaller things and therefore resolve the individual Stars so much better giving you a better calibration then for the next rung up the cosmic distance ladder to those galaxies with Supernova which is the data we use to calculate the current rate of expansion of the universe now one research group led by Adam Reese has already looked at this with jdst data and made a video about it earlier this year and they claim that this crowding problem is not responsible for the Hubble tension the brightness you get for the seid variables are very similar between J and the hobo Space Telescope so it doesn't change your results again this is why I got so excited when I saw this title from the other research group led by Wendy Freedman that are also working on this with Jade wst te I thought they might have found something similar and be claiming that no it's not the cosmic distance ladder that's responsible but that's not what fredman presented in her talk so that brings me to what have they found and what are they claiming instead so what they've done is focus on that middle rung of the cosmic distance ladder with J they observe these neighboring or nearby galaxies where you have a hope of resolving out these individual either seid variable stars trgb stars or JB stars that they can then use to calculate the distance to those galaxies now crucially the galaxies they've chosen also have Supernova in them as well so you can use them to calibrate the distances to all of those more distant galaxies that have Supernova observed in them and they've done this for the three different types of stars separately so they can compare the three different methods of getting at the distances now they've done all this with what's known as a blind analysis so this is where you don't actually see any of the real numbers or any of the real values until the very end so you know you put together your analysis code that's going to take the images and work out the brightnesses of the stars and therefore work out the distances and use those distances to calibrate the more distant galaxies and then finally spit out a value for the Hubble constant the current rate of expansion of the universe but you don't actually see the numbers as you do that as you develop the analysis code and you double and triple check that everything is working as it should be at every single step along that chain don't see any of the real numbers because you either add like random noise to your data or you use fake data it's only when you're certain that everything is working as it should be that you finally put your real data in there and that's a process known as unblinding when you finally get to see the real value and the real answer and what it means is that that analysis stage is then free of bias of what you expect the answer to be team apparently got to do the unblinding in mid-march I reached out to them and they sent me these pictures of when they did the unblinding and I just think it's incredible to see that sort of joy that science creates not only did the they do this blind analysis you know with the new jwst data but they also completely reanalyzed all of the old archival Hubble Space Telescope data as well for all the Seas and reanalyzed all the Supernova data too after doing all of this the first thing they found is that for those three different types of stars they used they all agree on the distances to those neighboring galaxies which is great news it means their data is consistent and from there they could then recalibrate the distances to those you know more distant galaxies with the Supernova and then recalculate the current expansion rate of the universe and they get a value of 69.1 km/s per megap Parc a value that within the uncertainties of about 1.3 km/ second per MEAP Parc now agrees with the value from our best model of the universe using the plank satellite data of the cosmic microwave background it's not perfect but there is some overlap and statistics thankfully tells us not to worry the fact that they're ever so slightly different could just be explained by random noise it's nowhere near the level of difference that we had before where statistics told us we really do have to worry here and interestingly I mentioned the Desi collaboration before that have just looked into that change in the rate of expansion over time also managed to calculate a current rate of expansion using a completely different method entirely something known as bionic acoustic oscillations and again they found a very similar result at 6 8.52 km/s per megap Parc again more on that in this month's Night Sky News episode coming out next week so it seems like we might finally be seeing some agreement between all these different methods of calculating the current rate of expansion of the universe at least that's what Freeman and collaborators seem to be claiming at the moment with all of their careful blind analysis that they've done but again the big caveat that this could all change during the peer review process yes but if we take it as this is going to stay like this how does this then tie in with what we just saw earlier this year from another research group led by recent collaborators who claim there's no difference between the jwst and Hubble results in terms of this crowding problem of the stars and it can't explain away the Hubble tension honestly I don't know at this stage like this isn't just like Cutting Edge science this is like standing on the knife edge and just staring into the void of confusion you know this isn't something that's going to be explained in a minute of a YouTube video after I've puzzled over it for a few days especially since I'm a black hole expert and not a cosmologist right this is going to take dedicated work by each of the collaborations and I'm sure a lot of this is what's going to end up in the discussion sections of the research papers by Freeman and collaborators that will eventually come out after peer review perhaps it'll turn out that the crowding problem wasn't the issue and that there is no conflict between what the two research groups have found maybe it's something else in all those endless steps of the blind analysis that freemen and collaborators have done that you know has just come out in the wash and that's what's reduced the Hubble tension perhaps there is actually a conflict here between what these two research groups have found and maybe it's something to do with how they've analyzed the data and I do not want to wade into the middle of that but just to highlight how difficult it's going to be for the re Arch team to like pinpoint which step in the analysis like has actually resolved this Hubble tension or whether there is a conflict or not a difference of just 0.1 in the magnitude of these stars are the brightness of the standard candles you're measuring leads to a 5% difference in the current expansion rate that you calculate or in other words it can take you from a value of hn of 73 IE there is a tension to 69 km/s per MEAP Parc I.E there isn't attention and so finally that leads me to what is next is the crisis actually solved and to be honest I think the only simple answer I can give here is we don't know yet there's a lot more work to do which is why I enjoyed one of the questions after Freedman and finished giving her talk like in the Q&A section was some a theorist in the audience who was like should I stop working on the Hubble tension then is it solved should I find something else to go and do like I think everybody wants to know the answer to this question but I think you know there's so much more work involved not just for you know the two different research teams using jst to do this but if it turns out there's something in the reanalysis of archival data that's led to this dissolving of the tension then that might cause even more research groups to reanalyze a load of their old data and recalibrate it using jwst data and that might have then a KnockOn effect in other places so if this result that's been claimed by Freeman collaborators holds through peer revieww then this is not like a you know like a done and dusted this is kind of like a heads up everyone needs to redo all of their homework so I'm very intrigued to see what happens next what sort of discussions start popping up everywhere especially as Freeman and collaborators continue to present this work on sort of like the the lecture and Conference circuit this spring and summer Freeman is talking again on this topic at the Royal Society in London in a few days time at a meeting on go beyond the standard cosmology which has been organized by some Giants in the fields which if I wasn't already at a conference myself I would definitely be going to because I would love to be in that room to hear those discussions I'm sure it's going to be a very productive meeting for them uh when this work finally gets you know published in a peer-reviewed journal I will link it in the video description down below so that you can have a read of it yourself I'll also make another video on this channel after reading all of the discussion section that you know Freeman and collaborators put together and and what they reckon might be responsible for this solving of the Hubble tension and of course I'm excited for the Deluge of like reaction research papers that are inevitably coming after a result like this is announced so if you don't want to miss out on any of that make sure you subscribe because I'll be covering it all right here on my YouTube channel so to quickly recp recp every time but last weekend is it American physics Society or American physical Society American physical Society it is the American physical society which just makes me think of ol Livia Newton John like let's get about yet so we haven't been able to include in our models this is the one so to solve this then I oh gosh sry my B just gave in the most Almighty Grumble we've got so much left to film you can't Grumble yet it is like an hour from lunch time herbal tension always it's sof

Channel: Dr. Becky

Views: 454,409

Keywords: dr becky, dr beckie, dr beccy, dra becky, astronomy, astronomie, cosmology, cosmologie, NASA, JWST, james webb space telescope, hubble, expansion rate, universe

Id: yKmPJmaeP8A

Length: 23min 44sec (1424 seconds)

Published: Thu Apr 11 2024