Does the expansion rate of the Universe CHANGE over time?! | DESI 1 year results

AD - Head to squarespace.com/drbecky to save 10% off your first purchase of a website or domain using code DRBECKY. | The first year of data from the Dark Energy Spectroscopic Instrument (DESI) survey has been released this month along with a few dozen scientific research papers delving into the data. The result that caught my eye was their investigation of the change in the expansion rate of the Universe with time using a "standard ruler" technique using Baryonic Acoustic Oscillations. The first year of data seems to be showing some disagreement with our best model of the Universe? But will those results hold with the next 4 years of observations...?
DESI 1st year public release: www.desi.lbl.gov/2024/04/04/d...
Papers that I showed plots from in this video:
DESI collaboration III (2024): arxiv.org/pdf/2404.03000
DESI collaboration IV (2024): arxiv.org/pdf/2404.03001
DESI collaboration VI (2024): arxiv.org/pdf/2404.03002
00:00 Introduction
02:20 Chapter outline
04:03 What are Baryonic Acoustic Oscillations (BAO)?
06:30 What is a "standard ruler"? And how they allow you to calculate the expansion rate of the Universe
08:04 What the DESI collaboration found
08:46 Do their results agree with our best model of the Universe?
11:26 Bloopers
Video filmed on a Sony ⍺7 IV
Video edited by Jonny Hyman
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👩🏽‍💻 I'm Dr. Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars.
drbecky.uk.com
rebeccasmethurst.co.uk

[@Rubrickety]

Trying to explain BAOs to a lay audience in a short video is quite a heroic feat! Well done.

[@mastpg]

Yeah, I'm sure most people watching this video were just fed it by the algorithm because of their interest in Mr Beast and Alex Meyers. /s

[@EyMannMachHin]

To be fair my first thought was "But there is no sound in space!". Until it dawned on me that we were talking about that far back in time before atoms formed. And then the matter density was high enough to promote sound waves.

[@satanicmicrochipv5656]

I had a dream where my dog was explaining quantum mechanics over coffee and a cigarette. When I woke up I told him that if he was going to smoke he'd have to do it in the garage.

[@mertkocogullar6485]

BAO is such a general name for it for what i know i'm hearing them

[@a.karley4672]

@@mastpg Who? And Who? Or are they the same person?

[@RenshawYT]

Becky Announcing Observations!

[@stuartl7761]

Peak content

[@EarlN2010]

I love your videos because you don't sugar coat the data or talk down to your audience . I might not understand the details but the overall point is very clear and very interesting thanks for being a genuine person . keep it up

[@musicfan89100]

She is an incredible science communicator

[@GameSmithPlays]

100%! I wish she did live lectures or Q&A's 💪

[@aliensarerealttsa6198]

​@@musicfan89100 she does misinformation. Dark matter doesn't exist. Space isn't a thing with any properties - it can't expand.

[@lethargogpeterson4083]

I like the advertisement annotation and the progress bar.

[@wgkgarrett]

Last time I was this early the expansion of the universe was progressing at a different rate

[@FLPhotoCatcher]

Literally true. 👍

[@a.karley4672]

The headline figure, or the mean plus/minus the error bars?

[@Bella_Kilcher]

Thank you for having the video sponsored by Squarespace rather than Better Help

[@BayAreaBerk]

I hear folks talking BetterHelp down but providing no reasons why. Why?

[@lanceokami3567]

@@BayAreaBerk I heard it had something to do about the therapists and a lot of them actually enable harmful behaviour rather than help overcome them. That’s what I heard mostly.

[@fanq_]

I also heard about some personal data leaks coming from BetterHelp

[@DannyJoh]

I've used Better Help for a few months. My therapist is awesome. Much better than any live therapist I've had.

[@christopherlperezcruz1507]

i dont get all the Betterhelp hate. Sure they aren't saints but they provide an important service. I've tried it. If someone has a health issue, where are you supposed to go? There is no mental health infrastructure. I researched and compared the best online chat offerings and Betterhelp was the best at that time, on price, on speed, on convenience, and has a wide array on specialties. I've heard they sell patient data. Every app (including their competitors), and digital network sells data. I sleep the same knowing my data is being sold. I don't buy anything I'm offered, I uninstalled the app when I didn;t need it.

[@misterphmpg8106]

Hi Becky, that was by far absolutely the best explanation of BAO that I’ve ever heard on KZbin. Thank you so much. Finally, I understood.

[@stancartmankenny]

its neat to get a description of something we haven't already heard a million times, like "black holes are places where nothing can escape - not even light!"

[@TuxedoMaskMusic]

Bloopers Becky has so much charm and we adore her!

[@njg5942]

You are totally awesome at this.

[@LuisAldamiz]

Brings to mind the Monty Python's song: "🎼🎵"The Universe itself keeps on expanding and expanding..."🎶🎵

[@timhaldane7588]

🎶 In all of the directions it can whiz 🎶

[@gavinbroughton]

Choon. 70/80s child.. 😊

[@a.karley4672]

70s song - reflecting, obviously, 1970s cosmology. What the Pythons would have made, lyrics-wise, of the *accelerating* expansion of the universe ...

[@LuisAldamiz]

@@a.karley4672 - Not sure, the surviving Pythons are very upset at the cancelling/censorship world we live in now. They were a product of the "cultural revolution" of the 60s-80s, today they'd be buried under accusations, disdain and silencing. Sad but probably true.

[@CaseyW491]

Love your stuff, Dr Becky! Edit: I can always rely on these videos to clearly breakdown headlines etc into reasonable bits.

[@user-ww5mk1nd4m]

The video turned out to be informative, thank you Becky!

[@jojojojo2529]

Thank You, Dr. Becky

[@timsexton]

Publish, publish, publish! Sounds groovy. *_TRUST !!_*

[@MarkOfShameGaming]

Best video yet!!!! Hubble tension has nothing on this. My mind was blown! Thank you for such an amazing educational video!

[@richiebricker]

Thanks Dr. Becky for being so damn cool and showing us all these things

[@TheHappyhorus]

Great video, really clear explanation. Thanks Dr. B.

[@balaji-kartha]

Amazing the amount new knowledge that is coming at us

[@randymorrow9252]

Thanks, Dr. Becky.🤜💥🤛

[@PDPLAYZ2299]

You explained that so well!

[@bobjackson6669]

Loved the video and sent it to my grandsons to watch.

[@padraiggluck2980]

Really excellent lecture, Dr. B. 👍

[@rtg_onefourtwoeightfiveseven]

Was waiting for this video ever since the paper dropped.

[@marcusdirk]

Fascinating, thank you!

[@timthomson5674]

The explanation of what BAOs are blowed my mind. Science is beautiful. Thanks!

[@seraphuziel]

Fun filled informative segment!! ❤

[@antoninstefka]

superb...the universe is truly a living process

[@chongli297]

Love this one! Very technical! Definitely one to follow up on as the experiment continues! Also love the B.A.O. story! Soooooo relatable as a fellow nerd frequently talking to non-nerds!

[@file83]

This is so fascinating! I wish I had focused harder as a kid and stuck with my early interests as in Astronomy/Physics. These videos are helpful for us laypeople.

[@mikkohernborg5291]

Is the assumption that BAO's are the same size based on timing conditions during the rapid expansion and cooling of the universe? For them to be standard rulers, the pulsation timing would have to have been very uniform - any difference in pulse occurrence would cause an appearance closer to a water surface flash-frozen during rain, with ripples of varying sizes instead of uniform distribution.

[@davidking-kw3fh]

Love your videos.. 👏 thanks 🙏 I’ve long wondered this me self…

[@Budjarn]

Squarespace is a great sponsor, thank you :)

[@stephenwatts7734]

You BAO video is the best science video I have seen. Brilliant

[@syoung6126]

You rock Dr B

[@shaunfarrell3834]

Thank you, despite having had an interest in all things space since childhood I had never heard of BAO. Now I have the beginnings of an understanding!

[@mwangangimaina1445]

I love that you throw astrophysics acronyms at the general public. Honestly, it super on brand!

[@ExxInferis]

You explained that carefully and succinctly. Thank you. I mean, I still didn't get it, but I love your infectious enthusiasm despite myself sadly being the reason shampoo bottles have instructions on them.

[@OldBenOne]

That bumped up my knowledge.

[@tykjpelk]

Thank you for having the video sponsored by Squarespace rather than Better Help!

[@tbird81]

Squarespace has unsavoury business practices. I can't believe you consider yourself woke, yet still support them.

[@Stadtpark90]

I find it funny that all the sponsors do stuff we only need because of the drawbacks of social media: Ground News we need to break through our filter bubble, Better help we need to get out of our Social Media caused Depression, and DeleteMe to get rid off part of the giant Data Gathering / „Stolen Data“; it’s like selling blue pills on pron sites… - this is like a protection racket. We only used to need „Anti-Virus“… - now we expect our OS to come with an inbuilt solution, but now we have three other problems we didn’t have before… Edit: forgot the VPN‘s we need to get beyond the geographical market restrictions the media companies placed on us… (To be honest VPNs are probably legal loopholes, so the security services get the data of the local population without breaking the law (that in some countries forbids spying on your own people), because the data is now seemingly via a different country.)

[@Bohr2um]

Yep. It still surprises me how many youtubers just take the money, and dont really care about their audience. One time, i even got trash talked by a sizable youtuber, by pointing out his Better Help sponsorship.

[@sandra.helianthus]

Genuine question: Why is Better Help a bad place to advertise for?

[@tykjpelk]

@@sandra.helianthus They sell their customers/patients' health information to Facebook and other ad companies, and they use unqualified therapists.

[@gavinbroughton]

Mind blown at that part where you said space was square!

[@corlisscrabtree3647]

Thank you 🙏

[@frankgulla2335]

Thank you, Dr. Becky, for keeping us informed at a street-level understanding.

[@ShaharDolev]

תודה!

[@richardkohlhof]

Thank you, for sharing your brilliant self!I love the new information I find watching every single one of your shows! If I could ask you a question- it may sound stupid, however I wonder if anyone takes into account baryenters of all of the matter in the universe for the apparent odd movement of the matter in the universe and gravitational lensing, when there's apparently nothing massive causing it to occur-does that make sense? eek! Rich

[@davidwood351]

Interesting stuff. My mind hurts to think about this fantastic universe, and what exists out there.

[@robertparadis6840]

Hi Becky ! The expansion rate observable is 20% minus a diminishing rate of production of dark matter since the Big Bang. The result is an apparent acceleration of the space expansion although it was and is still 20%. The production of dark matter contradicts the belief that matter is energy. Instead, matter is a producer of energy in the form of new particle of matter (dark, photon and electron) that constantly produces gravity effect, energy of a fall in space. Due to the expansion, less and less new matter is produced with time by dispersion.

[@hplovecraftmacncheese]

Brilliant!

[@Platanov]

I used to have a car with a license plate that started 'MWG' and I don't think everyone else was as excited about that as I was.

[@martynspooner5822]

Just love your stuff, most of it goes above me but that makes it even more fun ie trying to get a taste at least.

[@philochristos]

I started reading your book yesterday.

[@joen0411]

Every astrophysics paper should have a doodle version. Could dark energy changing over time also explain the problem with Hubble tension (cosmology crisis)?

[@ClaireLamman]

Thanks :) (I made the doodle version) Evolving dark energy is not enough to explain the Hubble tension.

[@tonywells6990]

@@ClaireLamman It could be enough, if there is actually a Hubble tension.

[@joen0411]

@@ClaireLammanI hope you start a trend with the doodles. Thanks for answering my question

[@ahcapella]

@@ClaireLamman I’d *_LOVE_* to see a doodle version HR diagram showing the evolutionary treks of a

[@a.karley4672]

@@ClaireLamman "Evolving dark energy is not enough to explain the Hubble tension." Because the tension exists between differing measurement techniques at differing epochs? [Thinks bubbles form, doodle, scrunch doodles up and project bin-wards.) No, that can't be it. Well, there's a comment for @DrBecky to unpack in more detail if she can.

[@MCsCreations]

Fascinating! Thanks, dr. Becky! 😊 Stay safe there with your family! 🖖😊

[@richardkohlhof]

Great show I used to contemplate the idea that the Universe had a couple of bounces against itself so it's like two layers that's why that's a question of why they're so little antimatter because there have been a couple of fast bounces off two layers of the universe with a 1st pop, I can only make an analogous to a solar storm leaving the sun's surface and blowing all of the material out of the way of a second blast leaving shortly thereafter making it travel faster than the first blast and possibly bouncing off of each other slowing one back down and then speeding the other back up but they're just so many different ideas that is almost impossible to contemplate finding the truth lol, thank you for the great show and your brain!

[@StevenStyczinski-sy8cj]

Love your videos. The more BAO data we get the better we will realize that it is diverging from the model and that “the world is in fact not flat”. And again we will learn more.

[@ahcapella]

I think you’re missing the fact that it’s the _sea monsters_ that surround the Antarctica “ring” that prevent us from learning the TRUTH about the flat Earth! (jk. And these people always love to capitalize “truth,” lol!)

[@PlanetEchelone]

I am not sure how to fully articulate how cool the theory of BAO is from this so I am just going to go "Oooooo". Great video.

[@FirstLast-ml7yf]

I discovered dark energy today when I dropped a bolt fixing my bike and it bounced further than existing physics would suggest..

[@tyrport]

The lighting in your new office / studio is vastly superior to your old one. Have you thought of using the blue background as a green screen ( don’t need to change color ) to show graphics you can point at while you explain them.

[@a.karley4672]

That would imply a monitor showing the composited video, which is in @DrBecky 's line-of-sight, plus her *learning* to invert her proprioception (sense of "knowing where your hand/ foot/ pseudopod is) to correspond to the composited view, not normal sensations. There is a reason weather presenters do screen tests, then undergo a lot of training before you see them. This is a large part of it. The sticky symbols were relatively simple. to handle. (I got presented with this one day in Siberia - on top of having to deliver my presentation through an interpreter. It is difficult.)

[@james-zl4il]

Love the bloopers, especially when she sings. Woman got a voice.

[@Petertronic]

Playing to the camera

[@ReginaldCarey]

Ok, Dr Becky please do a video explaining baryonic acoustic oscillations. It’s a wave of what because it’s locally connected how across how many light years. These are awesome effects and interactions playing out across millions of light years.

[@spladam3845]

It feels like we are at the edge of important fundamental answers.

[@disasterarea9341]

that's so cool, i thought for a while that the expansion rate of the universe could be variable but i didnt think there was any way we could determine that. but it looks like this method makes it feasible?! may be able to resolve the hubble tension with more data and analysis

[@toadoftoadhall2837]

Great explanation. Nice new studio, but there is a resonant frequency there spoiling the audio. Not sure how you would get rid of it.

[@and_I_am_Life_the_fixer_of_all]

i love how you present the CMB as spherical

[@a.karley4672]

Around our observation base, it is. And it'll be a *very* long time before we have to deal with observing it from two points with a significant mutual red shift. I'm not even sure if the theoretical non-sphericity would be detectable in an Einsteinian (i.e. light-speed limit) universe.

[@robbierobinson8819]

These videos where you cover new results and clarify them are extremely welcome. Expansion of the universe and the increase in rate of expansion are things which keep bewildering me. The first thing is; into what is the universe expanding - simply coming into "appearing" further and further away into a void? More confusing for me, though are aspects of space-time. Is space-time absent beyond the edge of the universe? What is the warping effect of the expansion of the universe on space-time? As the "edge" of the gravity well of the universe expands into surrounding space-time what would the "ripple look like"? I need more than a normal life time to be able to be alive as all these answers are found.

[@killfalcon]

It's stretching. The universe always contains the same amount of stuff (atoms, quarks, photons, etc etc etc), it's just wider. The analogy that I understood first was a balloon inflating. The universe is the *surface* of the balloon [or a higher dimensional version of a balloon's surface]. As the balloon inflates the surface gets bigger. It doesn't expand into anywhere, it doesn't replace anything, it just stretches out and gets bigger and bigger. That said, there's still debate as to if the balloon is 'inside' anything - it's pretty much unprovable, but potentially our universe could be just one bubble expanding in a higher-dimensional space that contains countless other bubble universes!

[@tonywells6990]

The simple answer is that space is expanding, it is increasing in size, it does not push anything out of the way.

[@user-ds7uk1ft2x]

Actually, the simple answer is that the universe is not expanding at all.

[@BiswajitBhattacharjee-up8vv]

Higgs too have acoustic signature. Not head stone , but head hair band.

[@onebylandtwoifbysearunifby5475]

👍 This is one of the best BAO explaimer vids of its kind. Well done. (Also the BAO joke is like 90% of astrophysicist jokes- meaning completely hilarious.)

[@preutzen]

Great video! Why do the BAO bump lines sometimes not go through the bars from each measurement? Doesn't that mean that the BAO line can't be where it is drawn as it because it is outside the measurments error?

[@cricadi291]

Hello ma'am I'm from India and highly interested in cosmology and astrophysics. I'm pursuing that. Love your work Bought your book "brief history of black hole".

[@smokeyninja9920]

I love your accent, got a giggle off your pronunciation of customize and customers.

[@LivrodosMisterios]

My nickname is Desi, it was specially fun watching this video

[@RegisDee]

Excellent content as usual, thank you. Dr. Becky would you consider getting some pro audio input on your new studio? There is room reverb and your narration sounds a bit like it's coming from inside a cave. I would also suggest getting input on lighting and... makeup to reduce skin shine. This may not be super important compared to the amazing content you provide, but you do such a pro job and you have so many subscribers that you deserve the best setup! Sorry if you did talk to pros already, maybe a second opinion would help 🙂

[@slolerner7349]

9:40 I love it when "Science Explainers" let their XKCD roots show

[@user-sl1sf6ps1h]

Always enjoy and learn from your content . I have a movie suggestion for you The Dish not si fi rather the part the Parks radio telescope played in the 1st moon landing with a healthy dose of Australia humour l think you would like it and would love to hear your thoughts on the choice of the cricket pitch

[@raywhitehead730]

Throw a big wrench into that scientific theory. Stand back and watch the fun.

[@user-du4mk2th6k]

Wow! It could be a little breakthru into understanding the dark energy and dark matter ? As in this discovery could be a step forward in this direction....(?)

[@IanZainea1990]

Man. This is built on so much "if this is right then..." ... Like so circumstancial

[@shaunfarrell3834]

Yep, that’s science for you, evidence, theory, test, revise.

[@lindsayforbes7370]

Best explanation of BAO I've seen 😊. Think i may understand it 🤔 now. Is Dark Energy getting stronger or weaker?

[@tsaiflol]

What's the explanation behind the first and bigger bump on the plot at 7:35 where you first introduce the BAO peak, which is smaller and at larger scale? Thanks Becky, keep up the good work!

[@raywhitehead730]

Well things change. I remember taking the first computer programming course offered at my major state University. Little did we suspect where that would lead. That was not that long ago, on the scale of human endeavors. So new instruments bring new measurements.

[@vaunjeis6751]

A thought: if spacetime turns out to be an emergent phenomenon, like say a result of entanglement playing out on information on the Beckenstein bound of the Universe, then it wouldn't be surprising that "dark energy" is actually emergent too and depends on information density of a particular region. So it wouldn't only change with time, but with location. And the regions of some tracers, like large elliptical galaxies, might experience different rates of expansion than others.

[@juzoli]

Wouldn’t there be more expansion inside the galaxies than between the galaxies?

[@vaunjeis6751]

@@juzoli the same explanation as for conventional "dark energy" applies - since galaxies are small compared to the scales at which the expansion of space is apparent, they hold themselves together gravitationally and the 'extra' spacetime ends up in between them.

[@Keith_Butcher]

Great video. Is it cheesy to say Dr Becky is a star. Such a pity that broadcast tv can’t make programmes of this quality and reach a wider audience. I despair at the dumbed down level with all the ‘awesome ‘ music and presenters gazing into the distance. This video again shows it’s perfectly possible to present complex subjects to an audience with a curious mind.

[@mikehipperson]

They used to but suddenly dumbed down because stuff like this is not popular with the mass audience. We used to have the Royal Society's Christmas Lectures but they were replaced with umpteen repeats of Mrs Brown's Boys! Feck!

[@Keith_Butcher]

@@mikehipperson the RI lectures are still on. But they used to do 5 and now it’s 2 or 3. And they are more about the props and explosions. No where near as in depth as they used to be

[@ndowroccus4168]

The most mine boggling thing to me, is time seems to move at a certain pace (unit) when I’m just sitting at my desk, noticing how it feels, time, when I am motionless and in the moment. I don’t know where I’m going with this, just that time & time space is going to be one of the deepest dives science will delve into.

[@darkflip]

So fancy!

[@c.h.4126]

Congratulations to BAO!

[@juskahusk2247]

Baryonic Acoustic Oscillations? They used to be called Cadbury Galaxy Ripples.

[@EnglishMike]

Mmm... Galaxy Ripples...

[@gbcb8853]

Wispa it softly

[@mikehipperson]

But the anomaly there is that it's two different companies. Maybe another chocolate company can muddy the water like the JWST?

[@juskahusk2247]

@@mikehipperson It's a crisis in confectionery.

[@varkenvarken]

video is great as usual, but the sound not so much 😢

[@ifkekanrunning4768]

Thanks! The doodle was really informative, but I wonder how the note ”1 third of the size after 1 fifth of the age” matches an *increase* of the expansion of the size of the universe?

[@xniperzincaid]

Last week I had a chnace to listen to David Schlegel's talk. He talked about the first year of DESI's results and it was noïce. He also talked about upgrading DESI.

[@a.karley4672]

Ignore the first 5 minutes of preamble - too much background noise. This will probably answer my "nuclear time, or plasma time" question up-thread. [It didn't.] YT doesn't allow comment on one video, while watching (listening to) another? "Dark Energy was discovered a quarter of a century ago" !! but yeah, it's true! "We sawed off the top of the telescope" ... 1.1m diameter lens !! A 1970s telescope constructed so it could be fitted with a 6m mirror!. That is AMBITION! Very interesting (and taste-bud whetting) presentation. Now, will YT please accept my comment?

[@xniperzincaid]

@@a.karley4672 bruv, you ight?

[@PhilHibbs]

I was explaining this to a friend last weekend. You can’t measure the rate that the universe is expanding at. Because wherever you look, you are seeing the older universe. So we can only measure how fast it was expanding in the past, and that’s different depending on how far away we look.

[@tonywells6990]

Actually we can measure the rate that the universe is expanding at now, it is called the Hubble constant, H0, where the 0 means 'now'. We can measure the redshift of a galaxy and plot that against distance (using standard candles such as Cepheid variables) and we get the 'Hubble redshift distance relation', which is a straight line graph, and the gradient of the line gives us the Hubble constant. We can also calculate how fast the universe was expanding at different times by using calculations that model the expansion, for example about 200 million years after the big bang the universe was expanding about 60 times faster than today.

[@Demobius]

Would you discuss the effect of gravitational red shift on the CMB?

[@haraldmilz8533]

What model function did they fit their data against? Some plots look slightly outlier-y.

[@Shaden0040]

Hey Dr Becky thanks for doing what you do. I have a question and I don't understand why the hubble tension is a problem. my thinking is this no explosion travels equally in all directions at the same time there are mortises and convolutions and areas where the fabric of the material that is being expanded contracts cools so that the hotter material can expand past it and that will then cool and then recycle back into the center and will heat up again in the continue expansion why does the universe do that why isn't it the fact that what we're seeing is a different expansion rates are could be due to vortices in the space time fabric? is that possible? And why if it is possible has anybody thought that that was the answer Or a possible answer?. I had another thought I was watching a program about pizza electrical generation where things like silicon rods get compressed and they generate electricity small amounts What if we made just to test it we made a silica rod a kilometer long and used gravity waves or to see if we could use gravity waves to compress and contract it to create electricity? Is anybody looking into this? if so is it possible by using this this could be another way for detecting gravity instead of using Lego and other programs like that and the space ones they're going to put up soon to detect these gravity waves and generate electricity at the same time? if possible could we then generate enough sufficient electricity they just bearing these rods in the ground hundreds of them all over the world to generate electricity freely I mean we're still paying for the cost of the silica in creating these silica rods but if it can create electricity wouldn't it be a nice new free source of electricity for us That we haven't thought of before to use gravity waves and silica. do you think that's feasible At all even just to use to detect the gravity waves Would be a breakthrough I think is anyone had to put everything with light and and mirrors and the refractors and splitters you just have a rod of quartz crystal silicon crystal and you just detect whether or not it's creating electricity From being contracted compressed and uncompressed.

[@peteredwards2318]

Something I always wondered, is with current maps of the observable universe, are the locations of objects like galaxies and such, represented as they are seen, or are they temporally corrected, using observation and modelling, to put the object where we THINK they ought to be NOW relative to our position? I feel like there would be something to be gained from knowing where stuff actually is, rather than where it used to be.

[@festusmaximus4111]

We tend to only think of it how it appears now, as we observe it. It is meaningless to try and project from where they were because light (and gravity) travels at the speed of light. They (to us) behave as if they really are there right now. This is all because of relativity. There is no useful definition of where things are 'now' except that all the events on our past light cone are happening 'now'. This is why we see the stars as they were so long ago (for them). (for intuition on this, recall that a photon travelling at the speed of light does not experience any time) As a side note, even if we wanted to try to do it, it is not meaningfully possible because of galaxy collisions and the N body problem being chaotic (so integrating forward in time by billions of years would be inherantly inaccurate - therefore unhelpful)

[@jimk8520]

They are represented as they are seen though you’re also correct in a way to wonder about that. Everything in the universe is in motion relative to everything else and due to the sheer distance to the observable universe we can see and the time it takes for the light from them to travel to us, very little of what we can see is where we observe it to be. For instance, a universe located 10 billion light years from us naturally would have had 10 billion years to move to somewhere else since the light we are seeing was created.

[@jimk8520]

Another example, if the sun stopped shining at the very moment you read this comment, the speed of light (speed of causality) dictates that it would be 8 minutes before we would know it. In that 8 minutes, we would still perceive the sun to be shining.

[@tonywells6990]

Usually astrophysicists just use the redshift of the galaxy, but using models we can calculate how old they are, how far away they were when they emitted that light (and it is possible to do that since the motion of galaxies is only a small fraction of the motion due to expansion, recession velocity), and how far away they should be now after expanding in space for all of that time. We can also estimate their distance from using standard candles, such as Cepheid variables.

[@ahcapella]

@@tonywells6990 Do you feel it’s possible that the parallax data (from Hipparcos, HST Wide Field Camera) could be “off” enough - due to the puny 1AU baseline (and resultant skinny triangles) - to cause _all_ of the standard candle measurements to be off, and that THAT’S a big factor in the current “crisis in cosmology?” As I understand it, if that first rung on the cosmic distance ladder is off, the whole _thing_ is off!

[@mikeybhoutex]

Dr. Becky, I know you just moved in to that new place and studio, but I feel after these last few videos I need to say it: The studio has a pretty bad bass-y echo going on. I think you need to figure out on some noise cancelling stuff in that room. Perhaps it's the windows and some curtains are in order, or a piece of art on the ceiling... *shrugs* I'm not an audio expert. I just know my ears are being rattled with extra bass. :) Thanks for all you do and keeping us informed about the universe out there! Edit: Now getting to the 'pressure waves' bit, and that's kinda ironically funny right there.

[@CloudhoundCoUk]

Brilliant presentation. Challenging to understand nevertheless I like having to stretch my cognitive abilities.

[@davidstromback7739]

Hey! Huge fan of your work, but I gotta chime in with the people saying that sound quality has degraded recently. Maybe consider bringing the mic closer? It's picking up a lot of room reverb.

[@shubinternet]

The previous filming location had a lot of work done to it to soften up the surfaces and reduce the unwanted reverb. I suspect that Dr. Becky may want to do more of that type of work in this new location as well. But you are right that bringing the microphone closer could also help.

[@SidneyCritic]

The lack of treble/sharpness and slight booming is too distracting for me so I'll sit this one out.

[@davidstromback7739]

@LesterJamesMusic I think the disproportionate amount of reverb is mostly to blame, the room likely absorbs the high end, leaving us with a muffled echoey mess. It’s a shame, this content deserves the crispest sound in the multiverse. It could also be an impedance issue, but it doubt that the mic itself is solely responsible.

[@McPilch]

I assume you're aware of this channel, but in case not, I can't recommend "History of the Universe" highly enough!!! The most recent episode (documentary) was kinda related to this. Also, I can't wait to see the LEGO Milky Way Galaxy on your wall in the background!!! 🤩

[@laurachapple6795]

Should have told everybody at the wedding that you were talking about bao, delicious Chinese dumplings!

[@rogerphelps9939]

he Hubble constant today is half the value it had when the scale factor of the universe was half its current value.