Secrets of the Cosmic Microwave Background 

I admire the audacity of you guys even /attempting/ to explain such advanced topics and actually succeeding.

where discovery channel makes me bored out of my skull. this channel leaves me in the fetal position rocking back and forth. best content on youtube.

The amount of stuff scientists can figure out from something like CMB is unbelievable. And how it all comes together, independently verifying each other... Congratulations on very clearly presented video!

I will never fail to be amazed at the depth of measured and modelled evidence for the models of the universe, and frankly everything 'established' in cosmology. Anyone who doesn't appreciate the work put in by cosmologists and other professions involved in cosmology simply does not understand the multitude of information they account for. Thank you for everything, scientists and support workers.

That was one of the best explanations I've had the pleasure of listening to.

I’ve watched all of these videos and when you mentioned the geometry of the universe before you explained what that meant I knew it referred to whether triangles are 180deg or not!!! It seems the primary benefit of watching SpaceTime videos is being able to understand SpaceTime videos! 🤣🤣🤣

This was one of my favorite episodes ever. I'm amazed how we're able to find out so much from what seems like so little evidence.

One thing I love about these videos is that, even where the content gets more advanced than my current knowledge, they're explained in such a way that it's possible to understand the abstract concepts. Which also then makes it much easier to fill in the gaps of my knowledge. This is a brilliant series, and a great public service. Thank you.

I wish I'd've known that the Physics skill tree is required to unlock the Wizard class....

i have spent the last 2 days trying to understand this for my midterm tomorrow and this is the only helpful explanation i have found online. Thank you i feel so enlightened

Man: the universe is flat Alien: And I guess you think dark energy exists too. Alien: [aside to other Alien] These flat universers, are they for real or just trolling us?

PBS Space Time has to be the absolute best Science communicator I've seen. They don't really dumb things down in any significant measure and Matt is always careful to set the record straight to avoid falsely hyping things as the media so often does (ie. "That star over there might have an alien megastructure" one of my favorite examples of the media's clickbaiting pranks)

ah I was wondering about this!

"In that noise can be found, the secrets..." oh yeah here it comes "of the earliest epochs..." wait wtf "of space time." YOU TRICKED ME

Thanks man, you are one of my big motivations to get into astrophysics and particle physics. I'm currently at university and these videos still boggle my mind. Like "baryon-photon plasma" when I heard that I almost yelled "WHAT?!" I haven't even studied QM or relativity yet but I'm mind boggled at the idea that the speed of light is the same in all inertial reference frames. Physics RU-vidr like yourself absolutely make me crave my textbooks Just to be able to understand why things do thing.

We truly are blessed to have channels like this.

Wow your programs, are becoming better and better! Thank you so much! Fascinating :)

Sometimes I feel like I'm keeping up with you and I'm like "yes OMG, go on.."and then I get distracted for a spit second and I've lost it. I love this channel, and I love even half understanding what you say half the time. Don't ever leave :)

A tiny spot in the sky gave away the composition of the universe. What a time to be alive!

How this was even put into a coherent presentation is mind blowing which doesn't even scratch the surface on the science that went into figuring all this out. I am humbled.

I always feel sad when I hear "of space time" because that means the end of the video :'(

The best video on the CMB power spectrum in RU-vid period.

Finally. A Space time I can understand

I've heard this explained a few times before but it all went over my head. This is the first time it actually makes sense lol I seriously love this channel. You guys do excellent work.

"You Will Be A Wizard" - way to roast somebody...

You know, these guys do a good job at explaining things. I am a smart guy, but due to laziness when I was younger, I never really pushed myself. When I did go to college, it was for criminal justice. But you don't have to be super intelligent or educated in physics to understand what is going on. Clear and concise explanations and the great visuals (I am a visual guy) really make it easy to follow.

Oh.... Oh, 'oscillation stacking'... No wonder my calculations are so off the mark! * puts down the ocelots and frowns at the chalkboard *

Just wanted to say thanks for providing something I look forward to and also something that actually excites me all the while explaining some of the most advanced concepts in such a simple and elegant fashion. Million thanks to you Matt for making me feel alive and also question my place in this wonderful space-time

Wow, Matt, that was really great. And I thought the last CMB video was amazing. This was a really interesting extension love the confirmation of the relative amounts of dark matter, baryons, and dark energy.

Of all the videos that he does this is by far my most favorite one it's something I you can relate to as a kid when you look at the static on the TV and wonder where does that come from.

im a biologist, this is like the "omics" approach being applied in physics (to great results!)

Fantastic program. I've seen the power spectrum graph before but did not understand what it meant. Amazing how much information scientists are able to tease out of the CMB. That this analysis agrees with other estimates is awesome. It indicates our understanding of physics is on the right track. Considering we have barely left our little planet and our brains evolved to keep from getting eaten by tigers being able to figure this stuff out is a testament to our capabilities.

This explains wandavision

I love PBS spacetime, without it I would be purposeless, existing in a reality without the slightest idea of the rules that govern it

Wouldn't the "moment" of recombination depend upon the local density? I would expect high-density regions to reach recombination a little later than low-density regions. It also seems like the speed of sound would be density-dependent.

i'm with you on that feeling, i LOVE that feeling, when you peel back the layers of the world and discover more new and amazing things. when i learned to program, when i learned how to use sockets, when i learned how to use ajax, when i learned C and C++, when i learned how to make leather, when i learned how to smith metal, when i learned about the fourier transform, when i learned about the lorentz transformation, when i learned about Noether's theorem (thanks btw), and many many other discoveries that have changed my view of the world, not radically in most cases, but like...shifted, like when you finally see the image in a magic eye....or when the you are looking at a picture of a duck and then you look at a certain spot and it becomes a rabbit. and the best is that feeling like "I AM INVINCIBLE!" to quote boris from goldeneye, like armed with this new ability you can do anything. when i learned about sockets the entire internet opened up, complex things became so simple, insurmountable problems became trivial, when i learned about ajax i finally had a way to bridge the client side and the server side, my code became simpler, my server side code became less and my client side code became more, but overall my code became simpler and complexity fell, i no longer needed to maintain some state from one load to another every time someone interacted with an element, i didn't need to load the whole page again. when i learned C i became able to control my computer at a deeper level, not just use other people's programs. it's just an amazing feeling.

The combination of oscillations of many sizes... sounds like Fourier Analysis

Finally somebody explained how the CMB shows the universe is flat. Yes, I knew about the triangles the missing piece was knowing the measured size of the hotspots verses the expected size of the hotspots. Now it makes sense. Thanks!

I always wanted a video on this, great content!

Physics has always been a fascination. If only I could have seen a way, in that time before time, to be able to earn enough with it to be able to stay alive. Admiration to those of you that find that way.

Im in love with these radiation videos lel

the music you guys have had in the videos for the past couple weeks has been great. really nice touch, and subtle enough to not distract.

Thank you for explaining physics in clear English. What do you think of Quantized Inertia vs Dark matter?

It was about 8:00 that I finally understood how the math worked for the "we tested the flatness of the universe with trig" claim from all those episodes ago. I had never caught how the opposite length could be known. Cool to see.

But can I use the CMB to microwave my leftover pizza?

I've watched 10^3s presentations - this is the first time I've wished that I could give more than one "like". In fact, this deserves 5. Beautiful! Thanks for the goosebumps.

Those early Rings. Sauron was there.

i’m totally down with the collared shirt. you’re making physics look fresh

My brain feels better when I'm here.

Amazing episode! I've tried to read about the CMB power spectrum a number of times and have always had my eyes glaze over. Thanks for making it approachable, you guys rock!

If the universe is currently geometrically flat but still expanding due to dark energy, does that mean in deep time (post the baryonic / dark matter era after all particles have broken down) there will eventually be enough curvature introduced purely from dark energy to cause it to folk in on itself?

Being a big fan from this channel for years, i just discovered this amazing video today (12/2020) almost two years after it was pubished. So much good and well thought out content content, BEST RU-vid CHANNEL EVER !!

17:04 he still have whole 17 years to rethink his career choice.

Matt you are great. I enjoy this non-dumbed down scientific divulgation immensely: the audacity of what scientists do is inspiring, and the conclusions are breathtaking. When I was little and watched Cosmos on TV I was equally fascinated by Carl Sagan's voice and presence and the message he conveyed. It's beautiful that Cosmos, as his wife says in the anniversary edition, needs little revision. Since then, I have read lots of divulgation but only the Feynman lectures have fascinated me so much, with his approach of explaining QM how we know it but without the mathematical machinery. I'm glad to be able to say that you continue on that tradition of accurate divulgation, obviating the maths. Your work is wonderful.

Great video! Is it me or they are using a new microphone? It sounds really good.

Outstanding!!! We are living in the Golden Age of Astronomy/Cosmology!!! What an awesome time to be alive!

How's the cosmic neutrino background coming? That's very exciting

you explaining space and vaatividya explaining dark souls must have the same amount of big brain thanks for existing

Question - I'm more of a layman than most in this comment section, having never studied any science but actively following this channel, so this might be a dumb question, but: could we literally spot on an image of a lot of galaxies these circular ring patterns, and if so, where can I watch that picture?

This is such an insane channel. Thanks for blowing my mind each time.

[Contains Question] You say it jokingly, but it has been my belief, since I was a small child, that Science *IS* Magic. It's the only form of Magic which actually worked! We tried so many forms, and we *did* find the 'One True Magic'. We then went on to miscatagorize all the ones which *didn't* work as 'Magic,' though Science more fits the definition. Mighty Google defines Magic as, *"The power of apparently influencing the course of events by using mysterious or supernatural forces."* 'Supernatural' is a non-sequitur, as 'Nature' is really a synonym for "The whole Universe, excluding stuff we make, but not really." So we'll replace 'Supernatural' with 'Natural'. Mystery is merely a matter of perspective, as something can be Mysterious to the uninformed, but old-hat to the expert. We'll replace 'Mysterious' with 'Understandable.' Our definition is now, *"The power of apparently influencing the course of events by using understandable natural forces."* So, Yes, you *ARE* a Wizard, though I've often thought of Physicists as 'Sorcerers.' You work more directly with the Primal Forces. Engineers are Wizards, and we make Golems and Enchanted Tools, Weapons and Armor! ;P [*Question Begins here*] Now, with all that said, I have a question to be of the Grand Sorcerer Supreme: It has to do with Black Holes, I'm afraid... It seems to me, in all the explanations I've ever heard, that crossing the Event Horizon of a black hole is actually on the Table as a reasonable question, but it only makes sense, to me, if you don't factor in Time Dilation, especially as we now understand that black holes evaporate. Imagine that we had a probe with a magical warp shield. It is immune from outside gravity wells, though it can still experience time dilation due to being in one. Again, it's magic. Doesn't matter how it works, all we want to do is track a single 'camera' inside the black hole's region of affected space-time. Now we line the probe up with the middle of the singularity and give it a nudge. As it falls in to the gravity well, it'll experience time-dilation, relative to the outside universe. It'll see stuff 'out-there' speeding up and we'll see _it_ slowing down. But the part that never seems to be discussed is, "What does the probe see the Black Hole doing, time-dilation-wise?" Well, we know that the Event Horizon is shrinking, via Hawking's radiation, if ever so slowly from our point of view. However, the probe is now much closer to the Black Hole, so it's deeper in the gravity well, so it's clock is running at a speed more comparable to the one in the Singularity, so the Black Hole appears to speed up, to the probe. We see the Event Horizon shrinking more quickly, pulling away from our probe. Let's speed up our probe. As we do, we see the Event Horizon slip away even faster, because we're falling deeper and deeper into the gravity well and our internal clock is slowing down so much that even the glacial timelines of a Black Hole seem fast. We'd never be able to cross the Event Horizon, because accelerating (or even drifting) toward it would cause it to zoom away, until it was a tiny as the matter inside could be compressed to be (whatever the minimum 'packing distance' of 'stuff' is in our Universe) then it would explode as a GRB. But our probe would be billions and billions of years in the future. If our probe could hover just beyond the Event Horizon at the instant of a Black Hole's creation, and 'follow' the Horizon in, the probe wouldn't even notice a 'Black Hole' at all, or only for an instant; the length of time it takes the Horizon to sweep the space from the edge of the Schwarzschild radius to the edge of the 'Sphere of Minimal Packing,' at [C-(distance from Horizon)] or nearly the speed of light. Ergo: Black Holes both Exist and Don't exist, depending on how close you are to them?!?

Good follow up to last video. This is what the public needs, good explanation of how data from the last video can now prove the universe is geometrically flat. I always wondered how Astronomers were so sure of these results, but after this video it's apparent. Thank you.

So Chuck Norris used a microwave once,so what?)

The fact that we can make such observations and calculation about the entire (observable) Universe, while still sitting on our tiny speckle of dust, is absolutely mind blowing.

Lays in bed a hears static: I guess I'm studying history tonight

That project must win a contest for the most important information taken by one series of observations. And the most amazing.

nice

Finally! A proper shirt! I can't tell you how happy this makes me.

I love you, Matt, but you don't have to try do hard on your Rs when you talk. Your accent is wonderful on its own.

This was your best video yet. Truly great inference from minimal information. Very well presented. Thanks

I'm asking this question again. How do astronomers distinguish the very small temperature differences in the CMB from the microwave noise of all the stuff the CMB has to shine through to reach their instruments?

Mind: Blown. Thanks again PBS Space Time!

Magic is real, but we call it science.

Indeed this is "a insane wealth of information" revealing the secrete of the Universe. Thank you this wonderful, trustful PBS channel 🙏🙏🙏

I’m a new subscriber

Sometimes I feel like an ant waving it's antenna while watching these videos as most goes over my head. I still love them so much tho

Q.does elecrtomagnatic field affect space time?

Great tutorial on the CMB! Our lab at UCSD is on the forefront of experimental cosmology on the CMB and collaborating on building the Simons Observatory. Polarization matters!

Here before the background radiation was.

Best episode of Space Time right here.

After you are done with the CMB, do an episode on quantum loop gravity

Holy carp! I've always heard so much about the CMB, but never really understood the implications of it. Even though I'm a fairly skeptical person, I've always had a trust in science, so I figured that when scientists were so hyped about the CMB, it had some merit. This video really shows it. My trust was completely justified. Damn, scientists are smart, and damn is science the most powerful tool ever. Thanks for making me finally understand a little bit about this!

Since the universe is expanding, will it eventually gain negative curvature?

Its around about 35 mins videos but took 3 hours to complete and literally explained everything I have heard about universe

A whole video about me! 🙃

Proud supporter of pbs spacetime. Ive watched every vid

Why is the CMB shown as an oval ?

You guys have amazing content. I'm back in college and as I make my way through my math classes I gain just a little more insight to your videos. Keep up the good work!

But can it heat my hot pockets properly?

My mind is blown. Thank you. I don’t have enough time for these topics, so your videos are a real treat!

1 down vote... It's been up for 4mins. Does this person like to be uninformed?

Big thumbs up for the fun-yet-inspiring pep talk at the end. Nice one Dr. O'Dowd.

I suspect 'dark matter' is a theological idea - we can 'explain' what we see but are only at a ptolemaic understanding, equivalent to epicycles and deferents.

All those secrets were taken from .01% variations in the brightness of a dim microwave glow. That's kinda like taking a sculpture, pulverizing it into a fine powder, and having an expert determine what the sculpture was from the powder.

One of the best videos on this channel

One video I'd like to see is Matt explain how we've come to the conclusion that the CMB originated 380,000 years after the big bang. I understand that that period of time is when the universe cooled down enough for visible light to escape the "quark soup" that existed in the early universe. But how do we know the rather specific value of 380,000 years? This is always glossed over when science educators are relaying this subject to an audience who doesn't necessarily have a degree in physics. I asked this question a few months back and got a very good response from a fellow commentor who had a background in astrophysics, but I think a video with graphics would help me wrap my mind around it a little easier.

This episode reminded me of the time he mentioned that the universe is expanding faster than the speed of light. At some point those galaxies won't be observable because they are moving to fast. Our ability to peer into the darkness keeps expanding. Will we ever be able to "see" beyond the threshold of light speed?

The important thing is to use an analog tv tuner, not that you hook up any tv to the analog antenna. It is the detection circuitry in the old ntsc tv that you can see the cmb with.

Suggestion for a word to describe the oscillating expansions and contractions of these sound waves: They are like the *bubbling* in boiling water. Heat and vaporization expand into a bubble, and then cooling and the ever-present water pressure collapse the bubbles again. Just like the photon pressure vs. gravity *bubbling.* Then the metaphor extends to observing the sizes of these 'bubbles' in the placement of galaxies and the CMB.

This is a really clear description of the BAOs.