Hello PBS Space Time. I'm finishing up my REU with the Axion Dark Matter eXperiment (ADMX) with the University of Washington, and I just wanted to thank you for presenting axion physics in such a clear way. I was aware of the strong CP problem during the whole internship, but since I was focused on studying microwave cavities I never got the chance to learn more about it. This video helped me sound like a boss at the end of my presentation, and of course, the video was awesome regardless of the context it has to me. Just wanted to say thanks for helping me out.

I remember always thinking the Axion was one of the cooler names of all the theoretical particles. Kind of a let down that its named after detergent. Maybe we can get a Tide Pod particle next

It's refreshing to find a channel that's willing to talk about complex subjects without "pulling any punches". No simplified metaphors.

Matt. You are to physics what Bob Ross is to painting. You make me amazed and profoundly calm at the same time.

"If you're gonna nerd, why not nerd all the way?" Love it.

I’ve heard some of the words he said before.

Read the title as "Are Axioms Dark Matter?" Based on how much I understood about them in advanced calculus, they might as well be.

This video, my level of understanding kept oscillating between feeling like I am starting to get it, to feeling like you are speaking Klingon.

I read the title of this at first as "Is Dark Matter Anxious?" and I'm not sure what to do with that question

> "What do you do professionally?" "I study laundry detergent." > "So you work for a soap company or?..." "I'm astrophysicist."

I love episodes that explain how modern experiments are pushing the limits of the standard model

"If you're gonna nerd, why not nerd all the way?" is a challenge that I'm sure will never be regretted.

"This particle can explain dark matter" Yeah, I've heard this enough times to know where this is going...

Laundry detergent, dark matter, the biggest mystery in the universe... My missing sock is actually turned into dark matter by laundry detergent! I knew it!

“If you’re gonna nerd, why not nerd all the way?” This is the deepest insight any of the infinite version of me have ever gotten from PBS Spacetime video. Nicely done!

"Ten to the power of ten to the power of ten to the power..." I feel like I live in Whoville.

I get the feeling the editor messed up the framerate of the recordings for this episode...

Great upload 👍🏾 However, Axion laundry detergent should be the sponsor of this video

Wow! Big difference. You got a fiction editor to revise the flow of this episode! You opened in a way that set up the story arc that MUST end with "SpaceTime", and just as I realized that you began a narrative tale. Great presentation! I am 32 seconds in.

"CP Violation" Hehe... That's illegal.

can we somehow give this man an oscar or an grammy or an nobel prize or anything like that becouse he clearly deserves it

I love this show. I started watching in 2018, and I haven't stopped since. Thank for you incredibly high value content.

I used to watch these videos and then, frustrated for not being able to understand, go to the pub . Now I 've thought better and I go to the pub BEFORE watching the videos and suddenly they are crystal clear .

For a moment I thought it was "axon" and thought, 'then the antiparticle would be a dendrite?'

I'm just waiting for them to discover the particle that makes sure all this is so overly complex, that the math seems tediously intractable, and mind bogglingly confusing as a whole for us average people. I hope when they do, they call it the Vogon.

I like that the theory side of these very complex subjects is "easy" to understand and really illustrates reality in a beautiful way, I find the idea of particles being wavelengths in different fields to be really interesting but I could not imagine actually formulating maths to describe these ideas.

"That thing Newton wrote" is a weird way to pronounce "Opticks"

I got high and then started watching youtube videos. They recommended me the PBS Space Time guy explaining to me one of the leading theories about dark matter, one that I had tried to understand but never really did. You win, KZfaq algorithm.

8:57 you mention here that one of the possible reasons why we can't artificially detect axions is because we can't produce strong enough artificial magnetic fields. However, at 9:37, you mention that CAST uses its own strong magnetic field to convert potentially incoming axions back into photons. How are we sure that the magnetic field that CAST produces is strong enough to convert axions into photons?

while i saw and liked this video four months ago, i was directed here once again by the wonderful person anton petrov, who reported today on a new discovery seeming to give credence to the axion's existence. it use i think a 10,000 ton tank of liquid xenon, and they had far more detections than theorized. there are several other explanations, but the axion seems to be far and above the most likely answer. i would love a followup to this video that includes these new observations. but i'm thinking you'll probably give it a few months for confirmation of the data before making a video. still, can't wait to find out if we've finally found dark matter.

I feel like sometimes the " ...spacetime" suffix is forced. Today it was much more elegant. Bravo!

this channel makes me wanna cry but also gives me an immense joy at the same time

Back here from Anton Petrov. *hello wonderful person*

15:50 Cube root. Space is three-dimensional. 15:54 Taking the square (or cube) root of a double exponential doesn't change it much. E.g., the square root of 10^10^120 = 10^(5×10^119) ~ 10^10^119.7, not 10^10^60-ish.

Well done Matt, very concise... so many great concepts packed into this amazing lecture.

Thank you, thank you, thank you. I love Matt and the factoid that I can feel my mind expand with every episode of Space Time I watch.

I'm watching this with my cat Lenny right now... and Lenny is like: "Duuuuuude! This is deep!"

In classical Latin, C is pronounced as a K. Remember, English is three languages hiding under a trenchcoat pretending to be an adult.

Physicist: I sense a disturbance in the forces! Axion: Come to the dark side! of physics!

Wonderfully informative and fantastically interesting. Thank you kindly @PBS Space Time for making this.

"Why not nerd all the way" i legitimately laughed. Thank youm

I sometimes think that when a photon is produced, it’s non-electromagnetic counterpart the ‘Axion’ also gets produced with it. Massless, undetected but gravitationally inclined due to its mere existence.

Wow! Even though, the Consiousness influencing QM video is more to my liking, I am glad I did not miss this one. I went in it without a clue what an Axion is, but your explanation with the graphics was top notch. If only i was a kid way back in school, your content is really inspirational.

I literally had an ad of a washing-up detergent play at the beginning of the video!

Are Axioms Dark Matter ? Maybe ! I like Matt O'Dowd's presentations.

Phew, just in time - thought this was due yesterday? I was going into withdrawal there!

Love just getting home from work and binging this channel

Hey! This is the stuff I am researching right now for a Undergrad presentation. I love this stuff so much.

I love this show! Thank you!

_"To Always go full N.E.R.D. or to Never go full N.E.R.D.?"_ _- and other seemingly absolute-therefore-false propositions_ (according to minds of a finite existential experience that is)

I am so happy I found this channel! Fairly sure I've watched every video twice and some of them 10x!!! I'm constantly pausing and going on a google wormhole lathered in critical thinking lol it truly gives me so much joy that words fall short!!!! Love that I can still watch PBS just like when I was a kid!!!

3:36 okay wow, the strong CP problem really sounds like the intersection in which we need to keep a very close eye on. Our error, our missing connection, lies somewhere in the maths which cause this mismatch. I absolutely love it! I almost want to go to college to learn everything about these problems, just so I can help figure it out. It's so exciting and enticing, to see things like this unsolved to this day

Hey there! Amazing show, keep it up, guys. I'd want to clarify one thing, though. In Polish, the letter 'W' is read/pronounced just like the letter 'V' in English (there's no 'V' in the Polish language'). So Frank Wilczek's last name should be pronounced just like you'd pronounce the English name 'Vilcheck'. Have a great day, science buffs! ;P

You might want to re-evaluate your relationship with Nord VPN given their recent difficulties and their shady response to those difficulties.

Saying "Principia Mathematica" wrong but nonetheless getting the information across > Saying "That thing Newton wrote". The channel is great because it teaches. Do not stop teaching to please egos.

Great episode! Thanks guys.

I thank God for people that love physics. I most certainly wouldn't be able to dedicate a lifetime to it. Keep on making discoveries.

I've been thinking about... kind of a similar idea behind the theta field: a bunch of constants dont actually seem to be well, constant - what if they are fields themselves? All of them?

Good episode Quality answers at the end Love it

Genius. I pareticularly liked the answers to questions, but the whole thing was just gorgeous.

Thanks for the amazing content! On the Penrose diagram, is the «infinite space» from the right corner different from the one in the left corner since they don't represent directions but rather space in itself? Like the infinite past and infinite future look intuitively different but not the «spaces» corners, are they in fact the same corner? Also, could we be in a black hole right now and what we perceive as time would in fact be that space flowing in the direction of singularity?

Could you do a video on quantum spin and relativity, and how spin gives bosons and fermions different properties?

Excellent video. Interesting and informative. Max Tegmark has authored some relevant papers. And thanks for the reminder to head out to buy some Axion!

Matt's turning into a legend. Great job again.

"That thing Newton wrote" ... I LOVE IT!!!

"If you're gonna nerd, nerd all the way." Translation: "GET ON MAH LEVEL!"

Excellent explanations

PBSSpaceTime always produces an in-depth understanding of the fundamental methods in which our universe functions. But sometimes you hit the nail on the head in such an unerringly correct fashion that the episode sinply outshines other attempts by our peers in the fields of physics. This episode is such a one.Thank you. Bravo. Well done by the crew. Kudos to you Just remember, observation causes effect. Getting around that is next to impossible. But embracing it might just lead away from it. See you on the flip side. All the best.

InB4 *The Axion Axiom™*

"The universe may be truly spatially infinite" Even though I already had that idea in my head, hearing the words out loud from someone else really melted my mind. There's so many things we will never even begin to understand before the heat death of our own part of the whole universe. I mean, we used to think the milky way was the whole universe. And we were calling Andromeda an "island universe" What's to make anyone think the universe we observe isn't just one of... Billions? Trillions? Infinite? Universes. Guess we will never know 🤷‍♂️ I havent slept in 27 hours, go easy on me if you reply 😅

;Love this channel so much, i am always nerding out on this! :)

Congrats! This exceptional lecture indicates that you (unlike many others) really understand what you're talking about.

Can you imagine how amazing it would be if this turns out to be true? If we perfect the technology, we could create axion telecommunications. You could send out a radio signal that gets turned into axions and then have a receiver that turns it back into photons and because axions can pass through everything you would get a zero interference signal.

Next vexing question: Where did every 10th frame quantum-tunnel to? Srsly, I think the framerate on this video is a bit janky.

Spectacular explanation wow

Really interesting episode

Me: aha, hmm, aha, yep. Nope, don't get it. Basically watching it to hear him say spacetime at the end.

The strong CP problem has a completely different meaning on the internet.

Matt, you put out the best KZfaq videos on cosmology and related topics. I wish you would put out (or I would see) more. On the other hand I've the impression you put out one a week, or one every few weeks, yet I don't seem to come across that many or somehow overlook them. How can I be sure of seeing them all? (Thanks, BTW.)

Thoroughly impressed with this video, one of the best.

Wow, so many new particles to discover. We need bigger particle colliders 😂

Wow, what a trip. Have to review this again. Love the fact that a constant can be transmogrified into a field, and then call into existence a particle because thats how fields and particles work.

I'd be curious to know more about how axions could fit within the framework of what we expect of that as the source of dark matter. Could that help to drive additional experiments to confirm or deny their existence? Great episodes always PBS Space Time team :)

When I watch PBS SpaceTime on Valentines Day and am sleep deprived, I Write stuff like this: -Quantum Love 0- -Time... to travel „You are not here!“ says the voice from the Navigation tool, while marking my position with an X. „Typical...“ I sigh so loud my ears might start bleeding. So neither there I am... Just lost in a time between the spaces. Remembered only by future dreamers long forgotten. They look like you and I, in the Review mirror of my Not-Delorian. Dancing in the Starlight, that in the end might just have been an incoming truck. I curse causality for making time as it always has been. No chance for us pushing further to go back and help you against whatever came your way. Fixing your past before you would have known that it would break. So you would not be scarred by the sharp edges. Even if this means making me obsolete in your life. A footnote in the diary you then never could have written. At least like this, I could sleep in knowledge of you never having loved me to begin with, a price that's worth to carry with me. Alas... not even my mind belongs to me. So how could I change the past by going forward on this path of shattered chances? How much I ever wished your tears would flow backwards, to turn your frown upside down. It was never meant to be. My rage without a target to hit. Nothing to kill but time itself. This goal is just unreachable, like a Star that explodes backwards in Time. So vast and simply... impossible. I cannot accept these facts and keep fighting against a past where I am, Not as now I will never be... ...and you not even known to me. Still: I'd burn a Galaxy to keep your pain away. to never let it happen again for a first time. But as all of us: You cannot stop to run. Because time always just falls in step with you. Might as well make the best of it while the metronome keeps ticking. My heart beats 32768 times a second. So by all that it has done, my heart should be; with all the rights of Mass/Matter conversion, just be stone. Your presence softens it a bit. By bit, by bit, by bit. Trying to change the past is a goal just made for fools and errors. To shape the future by the Actions in the now is a task for heroes. With a sense of wonder, how you ever got so strong. Not wanting for the past to change at all. Just packing your Backpack on your back to never look back. I focus my Rearwardview on my Backtracking Machine.Put it from driving backwards once more and never, into reverse to return from the past into the now. To see my yet. And all that is; still, not done in it. 88 miles per Hour into my here, seems so slow compared to you. Walking with confidence inside yourself, while I stumble between the strings of a past reality. No one knows what path you will choose, once a fork has been presented. Your lifepath is like, the most beautiful double slit experiment! But am I, with you entangled? Your Love, in some of the times. just a particle. Cannot touch it, to my dismay. Sometimes your love was, and may be, a wave sweeping me away. I do not mind. As long as you find laughter on your way.

I kind of want there to be evidence of axions just because the joke behind the name is so funny! XD "that thing Newton wrote"

I need to dig a few tons of salt out of my personal salt-dome deposit to take with these new ideas...

I understand less than I'd like of this channel's content, but jeez you do incredible work. I love your work.

Matt, at 15:51 I believe you meant that the distance would be the cubic root of 10^10^123 (or 90), which would be 10^(3,33*10^122 (or 89))-ish times the radius of the observable universe, which I believe means Rick has invented just an ultra-overpowered teletransport gun.

science: we found a new particle/force/field/effect/metal genre science: is it dark matter??

I'm so early that the video is at 15 FPS. Wait a minute...

Could make for a cloaking device, turn the light you emit or reflect into invisible axions.

Good vid PBS

I believe that in Latin the letter "c" is always pronounced as the letter "k". So the second way you pronounced it would be the most correct.

"If you are going to Nerd, Nerd all the way." :) Challenge accepted!

Principia was probably called “princhipia” by Newton when it was written. In Classical Latin, "c" was always pronounced as "k". Since Medieval Christian times, the pronunciation of "c" before "e" or "i" became “ch”. Only in the 19th Century did Latín scholars outside the church go back to classical pronunciation.

Would the duplicate universe have a duplicate Matt presenting another, equally awesome, Spacetime show?

15:50 don't you mean the cubic root because volume is proportional to radius cubed and so radius is proportional to volume to the third root?

Short answer: maybe Longer answer: how much infinite time do u have...

wow, this is such good content!

Love it what the dude at the top said!