How many of us continued the quote in our head? "I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."
This was the BEST explanation of the subject I've ever seen! I understand the principles but had difficulty conceptualizing the 'edges' of the universe. It will take a few rewatches and lots of pausing, but I'm certain I will finally wrap my head around this. Thank you!
@@paulhopkins8148 yeah I too had to re-watch the episode to properly conceptualize the space-time diagrams and to better understand how those later started to curve.
“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space...” Thanks so much for the *Hitchhikers' Guide to the Galaxy* reference -- there is a tiny corner of my heart that is forever Douglas Adams.
I love that you're wearing a shirt that says, "Heat Death is Coming" while talking about the expansion of the observable universe. We appreciate the little things as well
PBS Space Time is the best! I always struggled to grasp the idea behind diagrams for each of this horizons and hoped that someone will make a video explaining it and there is no surprise that Matt did it. I will still need to watch this episode again to be able to understand it fully but it is great to have this video.
GR seems to be one of the most reliable theories besides QM and it's CC, one of the few constants we can count on. I wonder if dark energy can be explained by expansion alone or if properties of empty space taken for granted might play a role, for example, space that has never seen certain waves in the layers of std model particles like neutrinos. Don't forget comoving space!
Not only I am impressed by how much new information on a topic I thought I grasped I learned from this episode, the way it was presented was absolutely beautiful. I greatly appreciate the effort spent on making this episode. Give the person responsible for the graphs a raise!
This is one of the best episodes, describing the basic concepts and definitions leading to a better understanding of time and expansion and the CMB that I've seen in a while. Good Job.
This is hands-down the best reference I’ve seen to study conformal diagrams in FRW spacetimes. I’ve struggled with them a lot in the past from books and papers; the effort put into this animations has made them my go-to reference right now. Keep up this amazing work!
This has to be the best-animated video on TH-cam for an educational topic. Coupled with the writing and Matt's ability to present the material, and you've got some of the most beautiful work ever done on this platform, something I do not say lightly. Mad props to you guys, and thank you for absolutely everything you do.
How many time can we rediscover the spacetime diagram ? It'll always blow my mind ! Quick edit : this is how to science vulgarization works. I'm not a fan of math, never been easy. Yet, from particules interaction, to the physics of black holes, expansion, dark matter/energy, geodesics ... We've learned a lot of complicated ways to represent GR to quantum mechanics, it's awesome ! Thanks Matt and your team
New tools always gives us a fresh look. Look at how neural networks sped up interpretation of the data we had for decades. That blackhole picture we took came from collaboration between labs around the planet allowing us to use the size of the Earth as an instrument. Quantum physics that led to really high definition T.V.s also lead to us understanding how to communicate better in space, calculate travelling salesman problem much faster, get to look for Higgs and find it and so on. As long as our understanding improves so will our interpretation of current data I suppose. But it is likely that we will find ourselves having to have to recreate rare events closer to home as we slow down in that progress. Edited to add: I say this because some basic things like the periodic table or the Standard Model really seems to be it for the foreseeable future. There are possible game changers out there but more on the disproving side. A weird one is the Kastler Brossel labs result vs. the Berkeley result for measuring the g-2 factor for ruling out non-observed phenomenon thus far. It's odd when only like 3 people can carry out an experiment and they disagree but certainly interesting to see. Afterall there are candidates for dark matter like the weakly interacting massive particles but none globally accepted. It's definitely worth keeping an eye on, though I'm really expecting more from anti-matter experiments.
As you told me to imagine being a photon spat out by a star near the beginning of time, racing towards the Milky Way against expanding spacetime, I could feel myself red shifting across the decelerating horizon. Thank you for that superb imagery!
I'm sorry I didn't mean to interrupt your super physicist video. It hurt my brain. I was just looking for a clowder video. 😂 Btw, Awesome video. I'm sure I will understand the universe before all the galaxies go cold.
I loved this episode!!! So beautiful and eloquently explained to someone familiar with some of the concepts here (space-time diagram for example) but then going further and expanding on those concepts to explore some of the largest meta-questions in cosmology; How much of the Universe will we ever see? When will the Universe past the Local Group start to recede away? and many other questions on the same topic. So excited to watch the next episode of Space Time!
This video was made for me! I have been drawing these things I called light leaves with the same teardrop shape and then someone pointed me to the Davis and Lineweaver paper and it explained everything but I understand it a lot better after watching this video!
Thank you for FINALLY providing an explanation of where the CMB comes from and how it relates to the size and geometry of the universe. I have seen the CMB invoked so many times without a real explanation other than "it comes from the big bang"
This is one of my favorite episodes.I have never fully understood how we can map the CMB but there are objects whose light has not yet had time to reach us. 🤩 This makes so much sense now. Thanks!
I loved that shell analogy and spacetime diagram; it was very intuitive. I am happy I got to live at a time where there are still stars and galaxies in the sky.
it’s tragic yet strangely beautiful at the same time, that we can never discover everything. There will always be places to see and new things to discover. We will never get to see them all, but we will also never run out of new discoveries. We will always be explorers to the very end.
Idk if it’s my headache, but this is the first video in a while that I struggle to understand the material. That is GREAT NEWS, I love learning new stuff! Great video!!
"Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." Great video :)
I like to think I know something about the universe. I like it more when Space Time proves me wrong, and I have to watch again to try figure it all out. Definatly something new and mind bending.
That graph at 8:18 is trippy. As I oscillate my eyes through a range of different focuses, the vertical lines change from greenish to blueish to reddish when viewed on my TV.
I still find it rad that we only need around 50 digits of pi to calculate the circumference of the currently observable universe to within the accuracy of a single proton.
Not true. There's a lot of uncertainty in the measurements of the age of the universe and its radius. The hubble constant if famously difficult to pin down. EDIT: Misinterpreted the comment. Kumquat is right about his statement.
@@DKFX1 Requiring more certainty in measurements that aren't pi doesn't mean you need more than fifty digits of pi. Do youtube commenters have to hold their breath when they type because they can't do two things at once I wonder?
@@plat2716 Nice one. I recognize the difference upon considering your classy comment, but digits of pi mean very little theoretically in terms of accuracy measurements if your constants are not equally precise or more so.
@@DKFX1 No problem. Maybe after one more classy comment you'll finally understand what people mean when they say you only need 50 digits of pi for this. They're saying IF you had perfect measurements you would only need 50 digits of pi to get that level of accuracy. I shouldn't have to explain this to someone who can write complete sentences but hey I guess my expectations are too high for people who seem otherwise intelligent and articulate.
@@plat2716 The comment can easily be misinterpreted. A more correct way to phrase it according to your interpretation would be "you would need only 50 digits of pi" as opposed to "you only need 50 digits of pi". But one thing that cannot be misinterpreted is your terrible personality and attitude.
I've criticized this (relatively minor) point on a previous video, but it popped up in this one, too: The spacetime diagram at 5:49 contains an infeasible path that is incorrectly labeled as feasible. Around the fourth white dot from the left of the diagram, one of the paths slopes upward at less than 45 degrees, implying FTL travel.
"You could imagine the night sky as a set of shells" So the geocentrics and their heavenly spheres weren't entirely wrong, funky! I love when coincidences/connections like this happen
Geocentrism and heliocentrism describe the relative movement of bodies in the solar system. That is not relevant to the ideation of the night sky as a set of shells, which is relative only to the observer’s position and does not imply any movement.
While watching this video, I realized that space and time really are the same thing. When we look into the sky, we are looking into the past just as much, if not more than, we are looking at a far-off object. It just never truly occured to me that at night we are looking into the distant past I knew the light we were seeing was old but it still felt like I was looking at an object that was far away. But that's actually a weird way to think about light that is depicting phenomena that may not even exist anymore, especially as the space continuously changes. I was just so used to "oh, the far off stars! Maybe someday we will explore them, like distant mountains!" But no, they are so unfathomably far away that we cannot experience them as we are now. And it seemed like the past was just a concept, an artifact of memory, and the only thing that really existed was the present. But my whole life I could physically look into the past from the light of other stars as soon as my planet shielded the light of the star nearby. Every dozen hours we have the chance to look into far distant times. Wild.
I can't say I understood everything said in this video but it was fascinating all the same!! I hope that one day,when my mind has expanded along with my consciousness, I'll be able to intuitively comprehend every aspect of the world around me.
Thanks! I was just trying to calculate this exact thing a few weeks ago... and came to the conclusion that I didn't know enough about it to produce an answer. I'm honestly shocked that the cosmological event horizon is so much smaller than I expected... only ~1.5 times the current observable radius, and only 10 billion years away!
It's about time "Observable Universe" term is being used more often. Now just waiting (may take a couple of hundred years!) to finally prove the actual birth of Universe and start of Big Bang as we claim to know is actually wrong!
06:36 - I think you're right when saying DE "took over" at a certain point, billions of years ago. I think it likely started right at the beginning, but its effects only started to 'dominate' later on. If it didn't exist at the beginning, the Universe would've collapsed back in on itself and we wouldn't be here. You can see how the rate of change of the curve starts from right at the beginning - Dark Energy (expansion) must've therefore been having an effect, albeit a weaker effect earlier on. My hypothesis is that spacetime (whatever it's made out of) is a substance, and that substance is entering our universe at all locations simultaneously. The more spacetime we have in our universe, the more "space" and "time" there is for new spacetime to enter from outside, so it gradually accelerates in expansion. Probably wrong, though! Just some thoughts about the multidimensional realm in which we exist. I'd love to see someone with expertise to try to figure out my hypothesis on a mathematical level, though. Perhaps someone already has. I mean, every other idea I've had, I've found out some great mind had the idea decades/centuries ago! Ideas are timeless.
I’m reminded of a well written video about the simultaneous agoraphobia of just how kind bogglingly big the universe is and the claustrophobia of not being able to explore all of it and being trapped by the speed of light. It also talked about the paper clip maximizer game.
Yeah it is very hard for our brain to process the size of the universe accurately but there's an easy trick you can try if you want. Close your eyes and picture in your mind the entire size of your mom, and then double it... That's pretty impressive isn't it?
My thoughts exactly. Tbh, they didn't explain very much how exactly we are able to see it. But the video gave enough visualization tools to work it out ourselves intuitively. Especially the non-conformal chart showing how in the early universe, the things beyond the hubble horizon, has space expanding much faster than the speed of light despite the small size of the universe, then slowing down, and speeding up. It really made it click why we can see the cmb 14 billion light years in every direction. And yet, at the time the cmb occupied a small space(relative to the current hubble horizon).
@@oracleofdelphi4533 I haven't watched the video yet, but I don't know how one could use gravitational lensing to see more distant objects. It should allow people to see distant objects more clearly, but not from farther away than the speed of light would allow. Am I missing something?
@@oracleofdelphi4533 That would actually reduce max range ( light covering a longer distance for not being in a straight line). It does let us see distance objects better in some cases. But C is a hard limit so max distance is limited by time.
@@oracleofdelphi4533 It makes objects appear distorted or at a different angle from where they actually are. But it can't make us see beyond the visible universe.
Y'all are getting into the weeds in terms of optics. Gravitational lensing collects light that would otherwise be too dispersed to see. This really has little to do with observable distance. Rather this is a helpful telescopic lense, thus the lensing part
10:50 An analogy I thought of is that of an ant standing on infinitely stretchy rubber band. The ant starts at one end which is racing away at 100 miles an hour. As the ant walks to other side, though, the ratio of rubber band in front compared to behind is always decreasing (even though the length of the rubber band keeps increasing, and increasing much faster than the ant can walk). But because this ratio will eventually go to zero, that means the ant must eventually reach the other side.
I have a couple questions. This popped into my head during watching. Imagine humanity developed instant time-travel, instant as in the communication between quantum entangled particles, to any point in the universe at any time without the passage of time occuring over any distance or time traveled. If the distance between us and those distant galaxies increased 1100x over time due to the expansion of the universe and we would travel there instantly to the point where the light that reaches us now was created would the subatomic particles in our bodies and "time machine" be 1100x bigger than the ones those distant galaxies are made of? In other words would a relatively giant spaceship arrive at a relatively dwarf universe? That imaginary sci fi scenario gave me several more questions, let me summarize them. - Do any particles; molecules, atoms, neutrons, quarks, etc expand in actual physical size with the expansion of the universe or is it only the space in between all of matter that expands? - If particles do expand, do any of the quantum fields stretch out with the expansions of the universe or only the particles excited by them? - If particles don't expand or maybe some do and others don't and the quantum fields do expand does that mean their effect on particles that don't expand changes over time effectively gradually warping the laws of physics? - If it's none of any of those situations then what does and what doesn't expand with the expansion of the universe? In other words would there be any drastic differences between objects from our expanded version of the universe and that distant 1100x smaller version of the universe?
Redshifting is based on the wave-like tendencies of light, and so while the total energy of light will be the same, the energy will be spread across a larger time, appearing as a lower frequency/higher wavelength or redder.
The interaction of light with fermions is quantized... photons are a useful mathematical abstraction for calculating the interaction, but photons are not actually a "thing" that exists. It's just a way to talk about a very small part of the continuous electromagnetic field.
AFAWK, quarks can't be separated to large distances from each other because the color force increases with distance, so at some distance the binding energy between two distant quarks exceeds the rest energy of two more quarks, so quarks will be created in the vacuum.
@@ludermathwig7022 Well of course there are. Quarks are tiny particles, just like electrons and just like the neutrons and protons they are a part of. Therefore, as all quantum objects can exist in a superposition, the answer is of course. Moreover, a superposition is not an undefined state, it’s a combination of every state possible, we just have no idea which and in what proportions.
I actually thoroughly enjoyed the explanation of it all and I understood nearly all of it and it amazes me how us Bipedal apes that somehow are aware of our own existence is able to witness and understand things like this in some form. No matter if it's how things work or don't. It's still amazing that life exists as it does. ❤️🐦🥚🐣🐥🐤🐦❤️
I love these videos and learning about the universe, but there are times that I'd rather add videos to the watch later list in order to prevent being sad for the rest of the day hahahaha. Sometimes my mind is not up to the task.
Matt, your episodes are always… brilliant! And I always come away from them, or out of them, feeling smarter, a good-feeling illusion! But this time, this once, I must say I lost my footing! My head went spinning and I went reeling. Boy, I’ll need to read up on the (new to me) concepts you introduce here, and then re-watch and re-re-watch this video until the moving coordinates and shifting and stretching spacetime eventually sink into my kilogram and a half of wet slushy mush that neuroscientists call the brain. You’re right: I had never seen those diagrams before. They’re fascinating. Thanks again for all the effort you put in making these videos a piece of art. Have you thought of getting GPT4 etc. to help you with them? 😉
“Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s long way down the road to the chemist’s, but that’s just peanuts to space.” - Douglas Adams, Hitchhiker's Guide to the Galaxy
what's so funny is that what sounds like one of those hackneyed hyperboles is in fact a dramatic understatement it is a little bit like that comedy staple where poor white trash imagines fabulous wealth as owning 10 trailers
The nobel prize was awarded for demonstrating (among other things) that information can be sent between entangled particles without the need for a classical third party. In earlier episodes, you've said this violated physics -- how does it violate physics, and if this phenomena truly exists but doesn't violate physics what would that look like? Thanks. Long time watcher.
Best intuitive explanation and depiction of space-time universe. The traditional depiction from big bang to inflation to present as an ever expanding cone is confusing because everything we observe in the universe is in the past. Thank you for putting it in words and pictures.
10:04 “Space itself can move at any speed relative to other space and it carries objects with it.” This somewhat clears up my confused layman brain on how the distant past could be captured given the speed of light and how we came from the same point. Thanks for the clarification.
This really helped explain the comoving diagram, thanks! One flaw in the photon traveling video; I couldn’t figure out what I was confused by until I held a pencil in front of my screen and moved my phone so the photon stayed in place while the rest of the diagram moved. The Milky Way moves away from the photon at first, but starts moving back towards the photon after the pause at the 2X sphere. I know you care about accurate representation! For next week’s video, I would like to see this video redone without the pause and nail the expansion accurately. Also please be consistent with the photon being represented at the center of the wave packet. Then show a split screen, top, middle and bottom, where in each, the Milky Way is held in place, the photon is held in place, and the original galaxy is held in place, respectively. Thanks!
This one wound up being a lot more complicated than I was expecting 😅. I'm very much looking forward to the next episode! Thank you for another informative episode and the super helpful charts! God be with you out there everybody. ✝️ :)
It's interesting that the changes in the rate of expansion have so much influence on what we can see. If expansion was constant you could "see" the entire universe if you could see past the CMB, but acceleration at any point in the past or future can put parts beyond our view.
![Beyond the Observable Universe [4K]](/img/n.gif)
Douglas Adams quotes will win my heart every time ❤️
This quote is subject to a copyright dispute filed from a time machine whose own existence is being debated in the next courtroom.
NORMAL SERVICE WILL BE RESUMED AS SOON AS POSSIBLE……
I had the 42nd like 😅
Take A Moment
Hi there Monkey Man.
42.
Get over it
Stay Safe and
Stay Free 😅🎉❤
How many of us continued the quote in our head?
"I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."
Kudos for the team involved in doing this animations. They REALLY help understanding these advanced topics
Speak for yourself. I don't understand anything after "Space" and "Time"
Is it the and part
@@vkvk3525😂😅
What a magnificent episode. And that's saying a lot, all of your videos are incredibly good.
Up for this
no such thing as magnifix or lot or etc or not, bix s 1uferiox bloat, doesnt matter, cepuxuax, outx, can outx any nmw s perfx
I subscribe to this completely. I wanted to praise it in a comment too, but there is actually nothing to add.
@@zes7215 adverb verb noun adjective, noun verb noun adjective adverb noun adjective!
This was the BEST explanation of the subject I've ever seen! I understand the principles but had difficulty conceptualizing the 'edges' of the universe. It will take a few rewatches and lots of pausing, but I'm certain I will finally wrap my head around this. Thank you!
Definitely gonna be watched a few more times by me.
Kurzgesagt did a video on the topic a year ago. Check it out: th-cam.com/video/uzkD5SeuwzM/w-d-xo.html
I agree.
@@paulhopkins8148 yeah I too had to re-watch the episode to properly conceptualize the space-time diagrams and to better understand how those later started to curve.
and then forgetting it 🙁
Props to the camera man for going that far just to get the footage.
Incredible, dedication..
Hope he got enough per diem.
Outdated joke
@@SamiSyed-br4uk Can a joke truly be outdated? 🤔
@@mrfake5251 its irritating after so much of use
“Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space...”
Thanks so much for the *Hitchhikers' Guide to the Galaxy* reference -- there is a tiny corner of my heart that is forever Douglas Adams.
I love that you're wearing a shirt that says, "Heat Death is Coming" while talking about the expansion of the observable universe.
We appreciate the little things as well
Nice detail.
So cool...
Typo at 2:18 wrt plasma years.
PBS Space Time is the best! I always struggled to grasp the idea behind diagrams for each of this horizons and hoped that someone will make a video explaining it and there is no surprise that Matt did it. I will still need to watch this episode again to be able to understand it fully but it is great to have this video.
I absolutely love these videos deep diving on conformal mappings! It's such a powerful tool in GR.
You ain't mapping
It ain't happening
GR seems to be one of the most reliable theories besides QM and it's CC, one of the few constants we can count on. I wonder if dark energy can be explained by expansion alone or if properties of empty space taken for granted might play a role, for example, space that has never seen certain waves in the layers of std model particles like neutrinos. Don't forget comoving space!
Not only I am impressed by how much new information on a topic I thought I grasped I learned from this episode, the way it was presented was absolutely beautiful. I greatly appreciate the effort spent on making this episode. Give the person responsible for the graphs a raise!
Always a great day when a new Space Time episode is released!
This is one of the best episodes, describing the basic concepts and definitions leading to a better understanding of time and expansion and the CMB that I've seen in a while. Good Job.
This is hands-down the best reference I’ve seen to study conformal diagrams in FRW spacetimes. I’ve struggled with them a lot in the past from books and papers; the effort put into this animations has made them my go-to reference right now. Keep up this amazing work!
This has to be the best-animated video on TH-cam for an educational topic. Coupled with the writing and Matt's ability to present the material, and you've got some of the most beautiful work ever done on this platform, something I do not say lightly.
Mad props to you guys, and thank you for absolutely everything you do.
How many time can we rediscover the spacetime diagram ? It'll always blow my mind !
Quick edit : this is how to science vulgarization works. I'm not a fan of math, never been easy. Yet, from particules interaction, to the physics of black holes, expansion, dark matter/energy, geodesics ... We've learned a lot of complicated ways to represent GR to quantum mechanics, it's awesome ! Thanks Matt and your team
The left path at 5:48 looks suspiciously fast though.
Spacetime is strangely arousing...
Too bad Hermann Minkowski was long dead before the rest of the world knew how to use it.
New tools always gives us a fresh look. Look at how neural networks sped up interpretation of the data we had for decades. That blackhole picture we took came from collaboration between labs around the planet allowing us to use the size of the Earth as an instrument. Quantum physics that led to really high definition T.V.s also lead to us understanding how to communicate better in space, calculate travelling salesman problem much faster, get to look for Higgs and find it and so on. As long as our understanding improves so will our interpretation of current data I suppose. But it is likely that we will find ourselves having to have to recreate rare events closer to home as we slow down in that progress.
Edited to add:
I say this because some basic things like the periodic table or the Standard Model really seems to be it for the foreseeable future. There are possible game changers out there but more on the disproving side. A weird one is the Kastler Brossel labs result vs. the Berkeley result for measuring the g-2 factor for ruling out non-observed phenomenon thus far. It's odd when only like 3 people can carry out an experiment and they disagree but certainly interesting to see. Afterall there are candidates for dark matter like the weakly interacting massive particles but none globally accepted.
It's definitely worth keeping an eye on, though I'm really expecting more from anti-matter experiments.
@@Mishanya442 -- Yes. They've made the same mistake in at least one previous video. I thought the visuals were great overall, though.
I'll be re-watching this one a few times to understand all of the nuances. Great episode!
As you told me to imagine being a photon spat out by a star near the beginning of time, racing towards the Milky Way against expanding spacetime, I could feel myself red shifting across the decelerating horizon. Thank you for that superb imagery!
That was genius
So are you a particle or a wave.
i'll have what he's having
@@Duiker36 probably
@@Duiker36 😂
Great episode! Very well explained, and a spacetime diagram that Georgia O'Keeffe would be proud of. Thank you, Matt.
Being early to a PBS Space Time TH-cam video is great, Quality content is always worth a watch.
I'm sorry I didn't mean to interrupt your super physicist video. It hurt my brain. I was just looking for a clowder video. 😂
Btw, Awesome video. I'm sure I will understand the universe before all the galaxies go cold.
I loved this episode!!! So beautiful and eloquently explained to someone familiar with some of the concepts here (space-time diagram for example) but then going further and expanding on those concepts to explore some of the largest meta-questions in cosmology; How much of the Universe will we ever see? When will the Universe past the Local Group start to recede away? and many other questions on the same topic. So excited to watch the next episode of Space Time!
A very good reference right at the start.
So long, and thanks for all the vids. This is only a reference in return.
This video was made for me! I have been drawing these things I called light leaves with the same teardrop shape and then someone pointed me to the Davis and Lineweaver paper and it explained everything but I understand it a lot better after watching this video!
Simply the best cosmology source on you tube.
Thank you for FINALLY providing an explanation of where the CMB comes from and how it relates to the size and geometry of the universe. I have seen the CMB invoked so many times without a real explanation other than "it comes from the big bang"
This is one of my favorite episodes.I have never fully understood how we can map the CMB but there are objects whose light has not yet had time to reach us. 🤩 This makes so much sense now. Thanks!
Yes 🙌🏻 for the Hitchhikers Guide to the Galaxy reference!
I loved that shell analogy and spacetime diagram; it was very intuitive. I am happy I got to live at a time where there are still stars and galaxies in the sky.
you do such a good job please never quit making these
it’s tragic yet strangely beautiful at the same time, that we can never discover everything. There will always be places to see and new things to discover. We will never get to see them all, but we will also never run out of new discoveries. We will always be explorers to the very end.
The whole concept of dark energy "kicking in" always makes my nose twitch. Was it waiting for an invitation?
Idk if it’s my headache, but this is the first video in a while that I struggle to understand the material. That is GREAT NEWS, I love learning new stuff! Great video!!
I was literally the opposite, mostly dont get it, but these diagrams, makes it sense.
"Seeing is believing", knowing is power, and Virtual Work, being here-now-forever instantaneously.
"Space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." Great video :)
Shame on the scientists who failed to call it the Hubble Bubble
😏I mean.. there's no one stopping us😂😂
Love it that you also use These cool tranforming graphics on this topic, not seen like this before 😎
I've always been confused about how space time diagrams and light cones worked until now. Phenomenal animation and explanation. 🤓
"the sky will finally be dark."
chills imagining that. just chills.
Really unique way of representation through layers. 👍
I like to think I know something about the universe. I like it more when Space Time proves me wrong, and I have to watch again to try figure it all out. Definatly something new and mind bending.
At 2:20 there is a typo: I says the CMB was emitted after 380,00 years, instead of 380,000. 🙂
I came to the comments to see if the observant viewers saw the typo, too. I was not disappointed.
This video was right on the edge of my event horizon of understanding, and expanded it, thank you.
Really hard for me to follow and grasp.. but I trust you know what you're talking about Matt! :D I'm glad it makes sense to you lol
That graph at 8:18 is trippy. As I oscillate my eyes through a range of different focuses, the vertical lines change from greenish to blueish to reddish when viewed on my TV.
Loved the hitchhiker reference. Well explained as always.
Wow, those bloopers were so funny and personalizing. WE need to do that!! Great work. Keep it going!
I still find it rad that we only need around 50 digits of pi to calculate the circumference of the currently observable universe to within the accuracy of a single proton.
Not true. There's a lot of uncertainty in the measurements of the age of the universe and its radius. The hubble constant if famously difficult to pin down.
EDIT: Misinterpreted the comment. Kumquat is right about his statement.
@@DKFX1 Requiring more certainty in measurements that aren't pi doesn't mean you need more than fifty digits of pi. Do youtube commenters have to hold their breath when they type because they can't do two things at once I wonder?
@@plat2716 Nice one.
I recognize the difference upon considering your classy comment, but digits of pi mean very little theoretically in terms of accuracy measurements if your constants are not equally precise or more so.
@@DKFX1 No problem. Maybe after one more classy comment you'll finally understand what people mean when they say you only need 50 digits of pi for this.
They're saying IF you had perfect measurements you would only need 50 digits of pi to get that level of accuracy. I shouldn't have to explain this to someone who can write complete sentences but hey I guess my expectations are too high for people who seem otherwise intelligent and articulate.
@@plat2716 The comment can easily be misinterpreted. A more correct way to phrase it according to your interpretation would be "you would need only 50 digits of pi" as opposed to "you only need 50 digits of pi". But one thing that cannot be misinterpreted is your terrible personality and attitude.
I've criticized this (relatively minor) point on a previous video, but it popped up in this one, too:
The spacetime diagram at 5:49 contains an infeasible path that is incorrectly labeled as feasible. Around the fourth white dot from the left of the diagram, one of the paths slopes upward at less than 45 degrees, implying FTL travel.
"You could imagine the night sky as a set of shells" So the geocentrics and their heavenly spheres weren't entirely wrong, funky! I love when coincidences/connections like this happen
Geocentrism and heliocentrism describe the relative movement of bodies in the solar system. That is not relevant to the ideation of the night sky as a set of shells, which is relative only to the observer’s position and does not imply any movement.
Any point in an infinite plane or sphere is legitimately "the middle" from its perspective. Hence, the Universe actually does revolve around us.
@The Program you can never quite tell though
The animation makes it so much easier to grasp the concepts and ideas! Thank you!!!
While watching this video, I realized that space and time really are the same thing. When we look into the sky, we are looking into the past just as much, if not more than, we are looking at a far-off object.
It just never truly occured to me that at night we are looking into the distant past
I knew the light we were seeing was old but it still felt like I was looking at an object that was far away. But that's actually a weird way to think about light that is depicting phenomena that may not even exist anymore, especially as the space continuously changes.
I was just so used to "oh, the far off stars! Maybe someday we will explore them, like distant mountains!" But no, they are so unfathomably far away that we cannot experience them as we are now. And it seemed like the past was just a concept, an artifact of memory, and the only thing that really existed was the present.
But my whole life I could physically look into the past from the light of other stars as soon as my planet shielded the light of the star nearby. Every dozen hours we have the chance to look into far distant times.
Wild.
I can't say I understood everything said in this video but it was fascinating all the same!! I hope that one day,when my mind has expanded along with my consciousness, I'll be able to intuitively comprehend every aspect of the world around me.
THIS clearly reflects that the mind does not produce consciousness on its own. It is an evolution with the environment.
What a fantastic mind bending episode! Thank you!
Thanks! I was just trying to calculate this exact thing a few weeks ago... and came to the conclusion that I didn't know enough about it to produce an answer. I'm honestly shocked that the cosmological event horizon is so much smaller than I expected... only ~1.5 times the current observable radius, and only 10 billion years away!
"Where we're going we won't need speed limits" ☺️
Beautiful video Matt; in my opinion one of the best of your great channel. I had to watch it twice.
4:15pm release for me! Do this more, please
Gmt - 8 ?
Same lmao
It's about time "Observable Universe" term is being used more often. Now just waiting (may take a couple of hundred years!) to finally prove the actual birth of Universe and start of Big Bang as we claim to know is actually wrong!
06:36 - I think you're right when saying DE "took over" at a certain point, billions of years ago. I think it likely started right at the beginning, but its effects only started to 'dominate' later on. If it didn't exist at the beginning, the Universe would've collapsed back in on itself and we wouldn't be here. You can see how the rate of change of the curve starts from right at the beginning - Dark Energy (expansion) must've therefore been having an effect, albeit a weaker effect earlier on.
My hypothesis is that spacetime (whatever it's made out of) is a substance, and that substance is entering our universe at all locations simultaneously. The more spacetime we have in our universe, the more "space" and "time" there is for new spacetime to enter from outside, so it gradually accelerates in expansion. Probably wrong, though! Just some thoughts about the multidimensional realm in which we exist. I'd love to see someone with expertise to try to figure out my hypothesis on a mathematical level, though. Perhaps someone already has. I mean, every other idea I've had, I've found out some great mind had the idea decades/centuries ago! Ideas are timeless.
The idea is called Emergent gravity. Spacetime is a condensed matter/many-body system. There are a lot of papers on the subject.
I could tell you more if you were interested.
I’m reminded of a well written video about the simultaneous agoraphobia of just how kind bogglingly big the universe is and the claustrophobia of not being able to explore all of it and being trapped by the speed of light.
It also talked about the paper clip maximizer game.
link?
but if you find _that_ claustrophobic, the fact that you will be dead in what cosmologically amounts to no time at all, must be paralysing!
The visible universe is but one subatomic particle in a giant spacewhale.
Yeah it is very hard for our brain to process the size of the universe accurately but there's an easy trick you can try if you want.
Close your eyes and picture in your mind the entire size of your mom, and then double it...
That's pretty impressive isn't it?
@@Reth_Hard A spacewhale is bigger than any human can comprehend.
i am a proud cosmos nerd who usually knows it all, but this... this has battered me back down to a silent and humbled heap of jaw-dropped-ness
I've always struggled to visualize how the light from the CMB reaches us, this is an amazing video. Thank you for making these
My thoughts exactly. Tbh, they didn't explain very much how exactly we are able to see it. But the video gave enough visualization tools to work it out ourselves intuitively. Especially the non-conformal chart showing how in the early universe, the things beyond the hubble horizon, has space expanding much faster than the speed of light despite the small size of the universe, then slowing down, and speeding up. It really made it click why we can see the cmb 14 billion light years in every direction. And yet, at the time the cmb occupied a small space(relative to the current hubble horizon).
I don't think I've ever actually heard a clear description of the particle horizon until now. Awesome!
Before watching video: Well I know the observable universe is our hard limit.
There are exceptions. We've used gravitational lensing to see beyond the sphere that is the observable.
@@oracleofdelphi4533 I haven't watched the video yet, but I don't know how one could use gravitational lensing to see more distant objects. It should allow people to see distant objects more clearly, but not from farther away than the speed of light would allow. Am I missing something?
@@oracleofdelphi4533 That would actually reduce max range ( light covering a longer distance for not being in a straight line). It does let us see distance objects better in some cases. But C is a hard limit so max distance is limited by time.
@@oracleofdelphi4533 It makes objects appear distorted or at a different angle from where they actually are. But it can't make us see beyond the visible universe.
Y'all are getting into the weeds in terms of optics. Gravitational lensing collects light that would otherwise be too dispersed to see. This really has little to do with observable distance. Rather this is a helpful telescopic lense, thus the lensing part
Topics like this are so interesting.
10:50 An analogy I thought of is that of an ant standing on infinitely stretchy rubber band. The ant starts at one end which is racing away at 100 miles an hour. As the ant walks to other side, though, the ratio of rubber band in front compared to behind is always decreasing (even though the length of the rubber band keeps increasing, and increasing much faster than the ant can walk). But because this ratio will eventually go to zero, that means the ant must eventually reach the other side.
I have a couple questions. This popped into my head during watching.
Imagine humanity developed instant time-travel, instant as in the communication between quantum entangled particles, to any point in the universe at any time without the passage of time occuring over any distance or time traveled. If the distance between us and those distant galaxies increased 1100x over time due to the expansion of the universe and we would travel there instantly to the point where the light that reaches us now was created would the subatomic particles in our bodies and "time machine" be 1100x bigger than the ones those distant galaxies are made of? In other words would a relatively giant spaceship arrive at a relatively dwarf universe?
That imaginary sci fi scenario gave me several more questions, let me summarize them.
- Do any particles; molecules, atoms, neutrons, quarks, etc expand in actual physical size with the expansion of the universe or is it only the space in between all of matter that expands?
- If particles do expand, do any of the quantum fields stretch out with the expansions of the universe or only the particles excited by them?
- If particles don't expand or maybe some do and others don't and the quantum fields do expand does that mean their effect on particles that don't expand changes over time effectively gradually warping the laws of physics?
- If it's none of any of those situations then what does and what doesn't expand with the expansion of the universe? In other words would there be any drastic differences between objects from our expanded version of the universe and that distant 1100x smaller version of the universe?
If light is quantized, why doesn't it begin to stutter as it reaches the edge of where we can see it?
Light is quantized at a given wavelength, so if you stretch out the waves the quanta becomes smaller
What edge? There is no edge from the light's perspective.
Redshifting is based on the wave-like tendencies of light, and so while the total energy of light will be the same, the energy will be spread across a larger time, appearing as a lower frequency/higher wavelength or redder.
Light took speech lessons as not to stutter
The interaction of light with fermions is quantized... photons are a useful mathematical abstraction for calculating the interaction, but photons are not actually a "thing" that exists. It's just a way to talk about a very small part of the continuous electromagnetic field.
There is something strangely beautiful about this, something poetic.
You might think it's a long way down the road to the chemist, but that's just peanuts to space.
I have been trying to visualize what this video did for months now. Even thought about going into coding for this purpose. GJ, PBS.
I'm kind of curious to know if it would be possible for the CMB to fit in with with one of the latest theories that our universe is in a black hole...
By definition, the universe is, as long as it meets or exceeds critical density. It'd be a time-like black hole.
This seems to be the clearest explanation I've ever seen. Would have liked a summary at the end of the sizes of all horizons defined, though.
Did anyone catch a view of the planets last night?
It was too cloudy in my area😞
You made me smile with your starting quote and then I sighed a bit with sadness. I miss Douglas Adams.
42 = F.I.S.H. ( F = 6 ; I = 9 ; S = 19 ; H = 8 ). 6 + 9 + 19 + 8 = 42.
Belief in the evolution of man from fish. 😉
could single quarks exist in an undefined state?
How could anything exist in an undefined state? By definition, you’ve not defined if it exists.
AFAWK, quarks can't be separated to large distances from each other because the color force increases with distance, so at some distance the binding energy between two distant quarks exceeds the rest energy of two more quarks, so quarks will be created in the vacuum.
@zzasdfwas by undefined, I mean a sort of super position. How should we know there arent quarks like that?
@Aaron Perelmuter same answer to you 👆
@@ludermathwig7022 Well of course there are. Quarks are tiny particles, just like electrons and just like the neutrons and protons they are a part of. Therefore, as all quantum objects can exist in a superposition, the answer is of course. Moreover, a superposition is not an undefined state, it’s a combination of every state possible, we just have no idea which and in what proportions.
This is in the top 3 of the best PBS Space Time Episodes!
🎉 yay science
I actually thoroughly enjoyed the explanation of it all and I understood nearly all of it and it amazes me how us Bipedal apes that somehow are aware of our own existence is able to witness and understand things like this in some form. No matter if it's how things work or don't. It's still amazing that life exists as it does.
❤️🐦🥚🐣🐥🐤🐦❤️
Oh - its gonna be depressing one ;D
Hahah thought the same and the commercial isn't over
I love these videos and learning about the universe, but there are times that I'd rather add videos to the watch later list in order to prevent being sad for the rest of the day hahahaha. Sometimes my mind is not up to the task.
Thanx to Dr. Dowd for these videos... I know they are difficult to put together but they are excellent!
Matt always finds a creative & unique phrase to end each video with “Space Time” ☺️👍
This is one of the best Space Time episodes of all time!
Just some words... Mind, Blown, As, Always, Rinse, And, Repeat... It is how I know I am alive!
All i can say is 'ouch!" That hurt. Cudos that I understood about %70 of that. Well done.
Matt, your episodes are always… brilliant! And I always come away from them, or out of them, feeling smarter, a good-feeling illusion! But this time, this once, I must say I lost my footing! My head went spinning and I went reeling. Boy, I’ll need to read up on the (new to me) concepts you introduce here, and then re-watch and re-re-watch this video until the moving coordinates and shifting and stretching spacetime eventually sink into my kilogram and a half of wet slushy mush that neuroscientists call the brain. You’re right: I had never seen those diagrams before. They’re fascinating. Thanks again for all the effort you put in making these videos a piece of art. Have you thought of getting GPT4 etc. to help you with them? 😉
“Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s long way down the road to the chemist’s, but that’s just peanuts to space.” - Douglas Adams, Hitchhiker's Guide to the Galaxy
what's so funny is that what sounds like one of those hackneyed hyperboles is in fact a dramatic understatement
it is a little bit like that comedy staple where poor white trash imagines fabulous wealth as owning 10 trailers
This stuff is great. Can't express how much I love this.
The nobel prize was awarded for demonstrating (among other things) that information can be sent between entangled particles without the need for a classical third party. In earlier episodes, you've said this violated physics -- how does it violate physics, and if this phenomena truly exists but doesn't violate physics what would that look like? Thanks. Long time watcher.
Best intuitive explanation and depiction of space-time universe. The traditional depiction from big bang to inflation to present as an ever expanding cone is confusing because everything we observe in the universe is in the past. Thank you for putting it in words and pictures.
Quoting Douglas Adams might be my favorite start of an episode so far.
10:04 “Space itself can move at any speed relative to other space and it carries objects with it.”
This somewhat clears up my confused layman brain on how the distant past could be captured given the speed of light and how we came from the same point. Thanks for the clarification.
This really helped explain the comoving diagram, thanks! One flaw in the photon traveling video; I couldn’t figure out what I was confused by until I held a pencil in front of my screen and moved my phone so the photon stayed in place while the rest of the diagram moved. The Milky Way moves away from the photon at first, but starts moving back towards the photon after the pause at the 2X sphere. I know you care about accurate representation! For next week’s video, I would like to see this video redone without the pause and nail the expansion accurately. Also please be consistent with the photon being represented at the center of the wave packet. Then show a split screen, top, middle and bottom, where in each, the Milky Way is held in place, the photon is held in place, and the original galaxy is held in place, respectively. Thanks!
Great video, thanks!
This one wound up being a lot more complicated than I was expecting 😅. I'm very much looking forward to the next episode! Thank you for another informative episode and the super helpful charts!
God be with you out there everybody. ✝️ :)
It's interesting that the changes in the rate of expansion have so much influence on what we can see. If expansion was constant you could "see" the entire universe if you could see past the CMB, but acceleration at any point in the past or future can put parts beyond our view.
10 billion years left to see the universe. Just a couple of billion years after the sun goes out. We truly do live in a golden age of the universe.
but we would _have to_
Slit scan photography (various sorts) is a space time diagram!
*The best explanation of a spacetime diagram I have ever seen*