The Dark Ages of the Cosmos | Crash Course Pods: The Universe #3

[@Jonathan_Wall]

I love John casually rating the names of these universe epochs by how poetic they sound. Perfect combination of science and artistry

[@carmillachoate]

The perfect combination of science and artistry is kind of a wonderful explanation of the Green brothers

[@pacotaco1246]

i bet his next book will have an even spacier and more poetic name then The Fault in Our Stars

[@alanho6814]

A great throwback to World History too. He has been rating academic terms for a while now, and I love him for that!

[@geoffbrom7844]

@@carmillachoate ha, I need a book of John and Katie's revised astronomical glossary

[@SnappyWasHere]

I love how this is a conversation between a writer and a scientist. Helps me understand instead of getting lost in the lingo. Wonderful series

[@xela552]

This podcast is honestly something that should be shared in classrooms. Its the best explanation of how the universe formed I've ever heard

[@acetheenby1475]

He sounded so close to laughing during the transition to the ad. I love it.

[@DragoniteSpam]

"Favorite sponsored ad read" is a weirdly capitalistic thing to say but I think john's existential terror + life insurance might be mine.

[@janmelantu7490]

You’re correct, John. The guy who came up with “inflatons” is Dr. Alan Guth, who is alive, currently an MIT professor, and won the Boston Globe’s award for “Messiest Office in Boston” which is incredible

[@MarioJaker]

Everything in the whole world is stressful right now. These conversations have been so healing and informative. EDIT: big “we’re here because we’re here” energy from this 🙏

[@mrpearson1230]

Books help. Our world information centers (social media, news media, podcasts, etc) operate on controversy.

[@CliffSedge-nu5fv]

I haven't watched TV, listened to a radio, read a newspaper or magazine, or used any online social media in over 12 years. Everything seems fine to me.

[@lewi_figo]

Is it fair to assume that everytime there's a little bit of music it's so John can go and have a lie down?

[@wosdwde132]

It's the end of the early universe as we know it and John Feels Fine!

[@DominoPivot]

I don't know John enough, I don't even know if he plays video games, but I can't help but think he would love Outer Wilds. This image of two people in camping chairs watching the stars makes it hard not to think about that wonderful game.

[@raymanscape]

"The Surface of Last Scattering" would be a great darkambient CD album title (edit: but so does "The Dark Ages of the Cosmos" 😄 )

[@oophyte]

I knew dark matter didn't interact with light, and I knew touch was based on electromagnetism, but I never connected the dots that those two were due to the same reason! In this sense, they are so similar to neutrinos.

[@TatianaBoshenka]

This was a new realization to me too, that you can't touch dark matter or feel it or reach out and move it with your hands. It has mass, but not touch. Wild!

[@anton99413]

The freaking Policy Genius ad catches me by surprise every time :).

[@debrachambers1304]

Katie: This thing is big. John: AAAAAAAAAAHHHHHHHHHHH!!!

[@GregMcNeish]

So, when can we start pre-ordering "The Surface of Last Scattering" by John Green?

[@chaotic.nyc_vibes]

Astrophysics is literally life

[@pacotaco1246]

For real! We are literally Astrophysics happening right now!

[@juliegolick]

We need a whole podcast of John ranking the names of cosmic eras. If only he had a podcast where he ranked things on a 5-star scale!

[@AndrewTBP]

Like a SciShow Tier List of some kind? 👏

[@MakeMoneyWithAI_83]

It's awe-inspiring to think about the vastness and complexity of the universe, from the hot, dense early stages to the formation of stars and galaxies millions of years later. The interconnectedness and coherence of the cosmic timeline can evoke a sense of wonder and smallness in the face of such immense forces. The ability to understand and visualize these processes, from the first moments to the present day, is both thrilling and overwhelming, prompting questions about free will and determinism. The exploration of the universe's evolution can lead to a deep sense of awe and contemplation.

[@KidWithoutACamera]

This podcast is great! Please youtube... promote this to more people

[@162manoj]

This came right on time after boarding a bus. Thanks guys!

[@mrpearson1230]

Reading Neil Degrasse Tyson's books helps a lot with these concepts for those looking for a better understanding, like "Origins: Revised & Updated, Fourteen Billion Years of Cosmic Evolution", "Astrophysics for People in a Hurry", and "Welcome to the Universe" not to mention Katie's book of course.

[@adarkerstormishere]

And if you want to learn from the man who taught Neil (the man whom Neil idolized), please read Carl Sagan's Cosmos. Just as poignant and informative and beautiful today as it was 50 years ago.

[@kennedypatterson8652]

There’s also the KZbin channel @HistoryoftheUniverse that does a piece by piece breakdown of all of this including the scientists that discovered each step of the universes formation that’s very good

[@louisalowry6229]

So enjoying these podcasts, Katie really is able to explain things in a way that makes sense. I’ve just borrowed her book from the library.

[@Campfire_Bandit]

This is the kind of content that motivates me to buy my Crash Course Coin every year!

[@DigitalEelRich]

The definition of awe. Wonder, and yet a kind of fear and terror. The word you're looking for is "sublime".

[@acetrainer5564]

Something that I really love about this series is how GENUINE both of their love for the subject is. I am so tired of how deeply steeped in irony everything is these days, all media has to quip and look at the camera and wink or crack some joke about how rediculous the subject matter is and that the characters KNOW how rediculous it is. I'm tired of it. I want more works of love made by people who love them. I want genuine real joy, not joy that someone flinches at expressing and twists into ironic enjoyment. Hearing John come back to how beatuiful "the surface of last scattering" is and revel in it's beauty every time is soooooo refreshing. Thank you both.

[@GENERIC_CHANNEL_HANDLE]

John really proves that the line "they should have sent a poet" from _Contact_ is absolutely true. I love space stuff on its face, but his enthusiasm and perspective is just astonishingly lovely. I feel more connected to reality as I understand it from the way he's framed so much of these episodes. ❤

[@etienneporras7252]

14:03 And here you can hear John almost choke on his Awesome Coffee

[@jonathanbyrdmusic]

I love how much joy John takes in his sneaky intro to the sponsor.

[@hweigel528]

I need to know if Dr. Katie Mack has seen the classic video "History of the entire world, i guess". Does it give an accurate depiction of the early universe? Loving every episode. Thanks again

[@Finvaara]

I love this entire podcast, and I love every part of Dr. Mack's explanation's, but I also love dumb stuff like the Advertisement read.

[@williammiller3317]

Please hurry up and get on with it because this is all I want to listen to

[@tarabates7088]

John and Katie never disappoint. This is simply awesome. Thanks!

[@pedrostormrage]

19:23 "And that's why there's life insurance" I can hear the "tee-hee" in that segue 😛

[@EnjoySunlessDays]

I just want to say. This series is absolutely blowing my mind. I feel like I'm having fundamental revelations about my existence and like you said, it's terrifying but exciting!

[@DaniClover14]

The way John tries so hard not to laugh with every ad segue is SENDING me lmaoo

[@DataSoong101]

I love this so much. Need to rewatch the whole series when I can pay closer attention.

[@burrito-town]

This series is wonderful. I love the talking stars visualization.

[@jameslaporta8689]

This show gives me so much joy.

[@tophee7462]

I just wanna say that I absolutely adore this series. It brings me so much joy to hear someone else learn about the things I've been fascinated in my entire life. Thank you John!

[@gibberishname]

another AMAZING pivot from existential dread to life insurance advertisement. Bravo John.

[@petdoiseauR.H.]

Merci!

[@shawnholbrook7278]

I love this, all of it. Thanks Y'all!.

[@katelillo1932]

I love this series. It feels like a little indulgent treat I’m having as I do my daily tasks ❤

[@clearlyrebecca]

"I'm gonna not panic," he said, panicking.

[@kimcosmos]

the cooling that allows compression by gravity is why fridges and aircons have to radiate heat whilst they cool and compress their gas

[@deathdoor]

Have a question. "We" can see the cosmic background, and we can see the universe "expanding". Now image if the expansion stopped, and lets assume that the universe immediately started shrinking, and it shrinks in a speed lower than the speed of light. Would "we" be able to notice the change when looking far? Not only detect that the expansion had stopped, but also would the data reveal that it was reverting back?

[@Jeewanu216]

After some time, maybe a few years, yes. Where expansion has redshifting as an effect, compression would result in blueshifting.

[@magneticflux-]

It would take time for the newly-blue-shifted light to be strong enough to be noticed. The Hubble parameter (the relation between how far away something is to us and how fast it's moving away from us, which is what would be "reversed" in your hypothetical) is ~73 km/s/megaparsec. If we waited 4.2 years after the reversal and then carefully observed Proxima Centauri, we would see its radial velocity lower by 180 millimeters per second (90 mm/s from removal of the expansion and another 90 from adding contraction, so we double the Hubble parameter). This is not feasible to measure because its radial velocity as reported in "Proxima's orbit around Alpha Centauri" using data from HARPS, -22.204±0.032 km/s, is so much higher it completely dominates the feeble effects of Hubble's law. Assuming we want to see a -0.032 km/s velocity change (to move it outside the radial velocity error bars for Proxima Centauri) it would need to be 750ly away. In other words, with the telescope used for that particular measurement of Proxima Centauri's radial velocity (the HARPS spectrograph at the ESO 3.6m telescope in Chile) it would be 750 years before light that is blue-shifted enough to detect would arrive. However, according to "State of the Field: Extreme Precision Radial Velocities", state-of-the-art telescopes that are continuously focused on a single target can achieve precision down to 1m/s, which would only need to be 24ly away for detection. My best guess if the Hubble parameter suddenly reversed is that it would take 50-100 years for us to get lucky with precise enough radial velocity measurements of a star from just before and just after the shift became visible in its light.

[@TheKaIibak]

Loved the show ❤

[@adpirtle]

I am only here for the killer segues into the sponsor.

[@EmilyB42]

This is such a lovely series! If I could make a suggestion, I think a gallery of images relating to the discussions (cosmic background, early galexies etc) could really enhance the audio experience. Maybe a link to a webpage include with the video and podcast.

[@AdamPFarnsworth]

"The History Of The Entire World, I Guess" really helped me visualize the concepts described here! 😆

[@azkon7975]

One does not learn and study about the Universe and not find it hauntingly beautiful.

[@merlinthewizard]

Love this series, thank you!

[@braylorcasual9016]

thanks John

[@tcuisix]

I think of the big bang as something continuously unfolding even today rather than something that happened once a long time ago

[@wearwolf2500]

"The only thing that could have happened... happened". I forget the name of it but this feels related to the idea that we can only exist in the universe that we exist in. If things had happened a different way we wouldn't be here to know about it.

[@AndrewTBP]

It’s called the Anthropic Principle

[@reginat5749]

So, can dark matter interact with other dark matter? Could there be dark matter 'planets' ? Obviously I do not understand much here.

[@Jeewanu216]

Yup! And it DOES, which is the only reason we even know it's there. It makes galaxies spin faster than they otherwise should. I don't know about planets, but dark stars are a hypothetical object.

[@oliverniemann2541]

It doesn’t interact with the electromagnetic force, so it wouldn’t form a planet. Like the force that makes atoms stay separate, so it forms a clump from gravity pulling it together but not a solid planet type thing. I’m not that well educated on this tho so there’s a possibility that it would form a type of gas giant, but it doesn’t seem like it.

[@storyls]

1. Yes it can. 2. No, dark matter does not interact with the electric force at all by its definition. Planets are balanced by gravity pulling matter in and matter’s electric force pushing out. Without that push out, each particle of dark matter would dance around each other.

[@reginat5749]

​@@Jeewanu216 is that not because it is influenced by gravity and not other dark matter? Sorry for being so ... dense (I apologise, sometimes I cannot resist)

[@reginat5749]

​@@oliverniemann2541thank you for answering, this slightly makes my head hurt, though 😊

[@basslinedan2]

Oh wow. I did not know about the light of older galaxies leaving them when they were closer to us, hence them appearing larger. Very cool.

[@neurosharky]

The way the life insurance ad is coming in makes me giggle!

[@Davlavi]

Informative as always.

[@YvonTripper]

I have theorized that the National Hockey League is currently expanding at a faster rate than the universe and so will eventually consume all matter and occupy every empty space in existence except Quebec City

[@DeannaGilbert616]

Ouch. 😮

[@neogoo123]

I absolutely love how John is in a constant flux of going from "Oh god oh no" to "Oh that's good" to "OH GOD OH NO" ending with a little "That makes me... I'm a little more comfortable now"

[@bn1142]

The music here is just beautiful - is there any way to listen to a compilation of the compositions made for this series?! I would listen to that on a loop while marking! Just so lovely 51:16

[@antispeedrun]

John Green working through his anxiety by doing ad reads for Policy Genius makes me want to reconsider my long-held position that the existence of paid ads on the interent is, while definitely a huge boon to a great many content creators, potentially a net loss for society as a whole. I never knew an ad read could feel so therapeutic. Would that all of them could be so.

[@d0onut]

The analogy of the cosmic microwave background to the suns photo sphere blew my mind

[@chezvanessa]

Loved the ep! Also, Hozier fans, check in!

[@Strange_Nothings]

Eating left over corn salsa while listening to this and having my mind expanded by cosmic inflation. The universe is good. multiverse me: agreed multiverse me: here here multiverse me: pass the chips Me: woah Everyone in the dovetail effect experiencing reality at the same time as me: WWWWWWHHHHHHAAAATTTT?

[@EnergyAnn]

This is absolutely fantastic. I've listened to each episode 2x. And Surface of Last Scattering needs to be a Pearl Jam album title. (I mean they did make Dark Matter)

[@geoffbrom7844]

I want John and Katie's Revised Astronomical Glossary! and may I propose Daybreak or Crepuscularity to replace Re-ionisation?

[@thethirdjegs]

that was a lot of new things and terms learned and i had never heard before

[@NathanaelNewton]

'It's like Rich, Get richer and poor get poorer' John: ahh that makes sense 😂

[@JackFoy]

When Dr. Mack talks about fully modern galaxies within the first two to four hundred million years, what does that mean? Do they have supermassive black holes at their core? Do they contain roughly the modern proportions of heavy elements? Thanks!

[@Jeewanu216]

They would likely have black holes at the centers, yes, however the composition would be more hydrogen and helium.

[@gailaltschwager7377]

Thank you!

[@patrik5123]

The universe made protons, electrons and so on, which eventually turned into us. That's cool and all, but the real mind-blowing bit is this: Those protons, electrons etc eventually made at least one type of organism that were able to contemplate the creation of those protons. In a sense, the Universe made a thing able to contemplate itself.

[@AMSkaterDad]

"Matter is the visible reminder of invisible Dark Matter."

[@AarreLisakki]

a trivial slip of the tounge I wanted to note -- around 41:50 , "just a tiny amount of helium" was prob supposed to be "just a tiny amount of lithium". That same phrase was used in the series before, so it was likely intended here as well, and afaik it wasn't a particularly tiny amount of helium anyhow, about a quarter of total by mass (so since its heavier, 8% of the nuclei).

[@capnkwick4286]

I've always understood that the CMB marks the point where the plasma has cooled sufficiently for electrons to be captured by atomic nuclei. It was at that point when light from the plasma was "visible" in the universe. Due to redshift that light has now been stretched out to become detectable as microwaves.

[@francoislacombe9071]

Was there enough lithium made in the Big Bang to make some dust, and that would have helped cool those first gas clouds forming the first generation or stars?

[@deathdoor]

Oh, just in time for lunch. It's really a unique experience, trying to digest food while feeling existentially hopeless.

[@TheVirtualFashionista]

Well. Never thought I'd be crying over astrophysics at 3 am on a random Thursday night, and yet... here we are. Crying over astrophysics at 3am, like a crazy person. Hello existential dread, my old friend.

[@sarahleonard7309]

What is really sinking into my brain on this episode is that the existence of the universe as we know it was founded by what could be considered the flaws in the system at the very beginning. It was the asymmetry, the non-uniformity that made matter itself possible in those first precious seconds, and then allowed that matter to arrange itself into atoms and go on to form stars. It feels so... random. But as she talks about it, she makes it clear that once everything got started it follows a logical progression that borders on inevitability. It's this odd combination of disturbing and deeply comforting for me. Also, did it strike anyone else that her description of the center of a star was really similar to Dante's description of the heavenly spheres at the end of The Divine Comedy?

[@Beryllahawk]

I dunno, this idea of "the only thing that could have happened...happened" - I'm finding great comfort in that. Because if the whole dang universe has just HAPPENED. That means I'm here through mathematical inevitability. And maybe I was always gonna be here, in this time, in this place, in this life. And maybe I was always gonna have a rough childhood and a confusing time as an adult (so far). But also. Maybe. Just maybe! Maybe that also means that, inevitably...I'm gonna be okay. I'm gonna be able to do all these things I so desperately want to do before I die. And maybe, somewhere way in the future where I can't yet see, maybe that person, a year from here and now, ten years from here and now... maybe she's happy. And maybe here-and-now me got her there.

[@infinite1der]

So, how many generations are "we" from the "first stars"?

[@AndrewTBP]

At least 3 IIRC See _Stellar population_ in Wikipedia.

[@pvtpain66k]

"it would not annihilate us all. No, no. Anyway, yeah."

[@StrayVagabond]

Recombination bad. Should be prime combination

[@BogeyCDogRosey]

Do the slightly cooler areas in the CMB indicate that the “lower” energy in those places allowed mass to gather creating the gravitational effects causing the structures wherein we now see galaxy superclusters?

[@devilseye361]

Nice

[@ManfredGeorgPhd]

How much self friction or friction with regular matter does dark matter experience? (And do we know the mechanism?) How intense is the surface of last scattering at these various epochs? Should I be thinking about early stars forming under a perfect green glow? How bright would it be? I assume that the matter/antimatter imbalance cannot be due to there just happening to be more matter in the section of space that got inflated to be us (because otherwise I would have heard of that argument). But why do we know that's the case? I know the actual generation of the matter/antimatter was afterwards, but couldn't the imbalance just be a heightened value in a field? Or maybe I'm misunderstanding, since I don't really know what field that would be.

[@EnergyAnn]

Are light and heat synonymous in astrophysics?

[@AndrewTBP]

No. Light is electromagnetic radiation (photons) of all frequencies from gamma rays down to radio waves. Heat (temperature) is the motion of atoms & particles.

[@sukhdevmishra8631]

Great 👍

[@LA-MJ]

Those insurance ads...

[@KaylaCakes87]

I find this fascinating. But I don't understand how we could know what happened within a trillionth of a second at the beginning of the universe. Maybe my mind is just too blown?

[@aceofdatabase]

Idk I rather like the word inflaton.

[@divineculturetalk99.9]

Unfortunately we are universal beings ❤❤❤

[@jamesmorseman3180]

Inflation is a sick name gotta completely disagree

[@pacotaco1246]

Inflaton sounds like a particle made of growing

[@ibrahiymmuhammad4773]

Progress doesn’t need a process

[@from_fresno2443]

🎉🎉🎉

[@juanitarodriguez8238]

I still believe that dark matter is just the space in the upper dimensions that we can't interact with directly due to our position in time So basically we do interact with it, we just don't have the "sense", like we have sight/hearing/taste etc, to notice it. Some higher beings somewhere probably can and probably already have contact with us, we just can't see them. I like to imagine the space between the planets as a huge open field full of mesmerizing landscapes, untouched by man, that are connecting the planets together in 7th dimensional beauty. Perhaps what lies beyond a black hole... Is actually a larger part of a reality we couldn't fathom.

[@user-ug2dd6jk1t]

You say epochs, I say epochs.

[@MsManomen]

I came up with a theory, what if the 4 combined forces are a Gravity and what we call gravity is what's leftover after the forces separate. What if dark matter is its medium. (like photons are to light)

[@yourbuddyunit]

Is EVERYTHING technically inside the sun? If there's no surface of the sun???

[@AndrewTBP]

I've heard it described that the Sun's atmosphere extends over the whole Solar System, and that it ends at the heliopause.

[@yourbuddyunit]

Can we just call it J-dub-street? Jay double-u ess tee, is a mouthful and JWST (j-dub-st) sounds like a cool DJ spinnin cosmic records for humans to vibe to.