I have now officially watched every PBS Spacetime video ever made. I cannot overstate how good these videos are. It is amazing to me that this quality of content is available for free. Support PBS!
It's not even philosophy. It's really more like theology - it's practically entirely disconnected from the scientific endeavor, and relies on differing interpretations of doctrine.
If anyone else also has a some familiarity with physics and yet understood basically nothing of this but the surface words, you're not alone. Wow. I'm glad talented people look into this stuff though.
Basically the big bang probably wasn't the beginning of time and the mathematical singularity that we get when we follow Einstein's general relativity could just be a boundary like the one we see on the boundary of an event horizon. A transition zone between our bubble universe and the infinitely inflating universe that came before it. Basically big bang =/= beginning of time.
@@Jamex07 But we have nothing to prove this? Some of the solutions presented suggested multiple universes. Is multiple universes really accepted by physics? Or is it just math for people who are trying to find the theory of everything?
I have a basic understanding of physics and this mostly made sense but was made overly complicated by the usage of "null geodesics" as the bulk of the discussion was around that. Null geodesic just means a path that light can travel through. If we can trace null geodesics back through time = 0 then light existed before time = 0 and that light had to come from somewhere (which is an argument for parellel universes or white holes which are being labelled as de sitter spaces here). If you just replace de sitter with parellel universe, and null geodesic with light, this makes 100x more sense. Ignore all the talk about boundaries, this is a talk about what barriers light can travel through, and trying to find a co-ordinate form that allows light to travel past time = 0. Although discussing it this way loses a significant amount of accuracy for scientific purposes, as those things aren't exactly correlated. But for your average viewer, just correlate them, doesn't make a difference.
@@lazyfoxplays8503 The video discusses the evidence for this. The apparent smoothness of space means that directly following Einstein's general relativity does not necessarily produce the universe we observe. Its smoother than our models suggest it should be. Our observations suggest a singularity prior to the big bang is implausible. And the math discussed in the video suggest that that infinity may not be a singularity after all. (and singularities that show up in math are generally an indication that our math is wrong. So the singularity hypothesis has been problematic for decades. Especially because it leads to unsolvable solutions) A theory of everything would include electroweak symmetry. These observations and theories are not touching on electroweak symmetry. This is just about finding out what happened before the big bang.
@@MyNameIsSalo white holes =/= de sitter space. A de sitter space is a space with a positive cosmological constant. That means acceleration is increasing over time rather than decreasing, meaning that the curvature of the universe should be positive or saddle shaped as time passes.
I'm 76 and never bought into the Big Bang ...theory. It was quite a treat to find your video ...brilliant . thanks " We're as far out of space as we are ever going to get . " Alan Watts
@@gtbkts The early Monday morning big crunch kinda blows though. Unless there's a holiday which throws off the week's expansion rate causing a crisis in the workplace.
I'm going to have to rewatch this when I'm more awake, I think this one requires me to brush up on several of the areas you mention to fully comprehend. Thanks! I like educating myself.
Can we reorder the last two names in the Friedman-Lemaitre-Robertson-Walker metric so the acronym would be closer to 'flower'? It just feels like FLRW is still quite a mouthful for an acronym, and it's a nice word for it I feel.
This channel keeps means so much to me. The best place to learn about space and physics. You don’t talk down, keep the complex stuff but it’s still digestible. I love it
15:37 - a little pushback here. It's not through pure reason that we can come to these conclusions, but both reason and observation. To me this is important, because the only way pure reason could reach the correct conclusion is if there is one and only one way to build the universe. But so far, from what we've seen, the universe includes both aspects of necessary physics and also free parameters. Those free parameters imply a very curious fine tuning.
@@RobertoFrankenstien For example, elementary particle masses, mixing angles and gauge coupling strengths, not to mention the actual initial state of the quantum doo dads of the big bang.
@@aelolul what do you mean by free parameters, exactly? How can it be shown that those parameters are free? Are you implying that they can be different from what they are?
@@RobertoFrankenstien So far, pure reason has not given us any insight into the cause of these parameters. So far, as best as we can determine, they just are what they are, and it's suspiciously lucky for us and biology and chemistry and universe stability in general.
Thank you for being my sparring partner: Yes, that's a fascinating extension of Eric Verlinde’s Entropic Gravity hypothesis. Verlinde’s theory offers a new way of looking at gravity not as a fundamental force but as an emergent phenomenon arising from the statistical behavior of microscopic degrees of freedom, much like how temperature emerges from the kinetic motion of molecules. By framing gravity as an entropic force, it naturally connects with the ideas of information, entropy, and thermodynamics in spacetime. Let's unpack the parallel you're drawing in terms of photon retention by matter, flux differences, and mass-gravity warping: 1. Retention of Photon Particles and Local Time Large particles of matter might trap or "retain" photons-massless and timeless particles-inside their local vicinity for prolonged periods. In Verlinde’s view, this could relate to the amount of information that a mass encodes in the surrounding spacetime. The more matter accumulates in a region, the more its gravitational effect emerges due to the way information is distributed. If mass retains photon-like particles (or any form of trapped information), it would essentially warp the local spacetime by slowing down the flow of time locally, creating gravitational effects. Photon Retention and Local Time: In areas where photons (carriers of information) are trapped or delayed in leaving the vicinity of massive objects, the passage of time may become dilated or warped. This aligns with general relativity’s prediction of time dilation near massive objects but framed through an entropic lens-where matter "storing" information warps time. 2. Flux Differences through de Sitter Space If we consider de Sitter space, characterized by a cosmological horizon and the expansion of spacetime, then the flux of information (in the form of photons or other energy) across this horizon could define how different regions of spacetime evolve. In Verlinde's theory, the gravitational pull isn't just about mass but how information about the mass is distributed in spacetime. Flux and Relativity: The idea of flux differences-areas with varying rates of photon emission or retention-suggests that relativity might manifest differently in different regions. Regions where mass retains photons (delaying their flux) could be seen as creating pockets where gravitational effects are exaggerated due to the increased retention of information (entropy). The de Sitter horizon, then, would serve as a boundary across which these flux differences act, stretching or compressing spacetime in response. 3. Warping the Mass-Gravity Ratio In Verlinde’s framework, gravity isn't directly caused by mass but by the way spacetime encodes information about that mass. If large objects retain photons or other carriers of information for longer periods, it could create areas where the mass-to-gravity ratio appears warped. The mass might not change, but the gravitational effects would feel stronger due to the altered information landscape. Entropic Interpretation of Gravity: In this context, mass is associated with the amount of information stored in the system, and the gravitational effect is a consequence of how that information (photon flux, for instance) is dispersed or retained. When photons are trapped around massive objects, the local spacetime might become more "constrained" in its ability to express gravity through entropic gradients, leading to stronger gravitational pull without increasing mass. Essentially, gravity becomes a reflection of how much information about the mass is encoded in spacetime. 4. Cosmological Horizon and Mass Retention Finally, if we zoom out to a cosmological scale, the de Sitter horizon (which represents the observable edge of the universe in an expanding cosmos) can be viewed as a global boundary condition for how this photon retention and flux dynamics play out. Masses retaining photons may distort the local spacetime, but over vast scales, these pockets of warping could influence the global evolution of the universe, perhaps even connecting to dark matter or dark energy phenomena in ways that emerge from statistical mechanics rather than requiring new fundamental particles. Conclusion: In Verlinde’s Entropic Gravity theory, the warping of the mass-gravity relationship due to photon retention is an elegant extension of how spacetime, energy, and information interact. The flux differences through de Sitter space, acting on the relative distribution of mass and information, could be seen as warping spacetime and producing gravitational effects that differ from what classical relativity predicts. The emerging gravity from these flux dynamics hints at a deeper connection between the fabric of spacetime, entropy, and the fundamental nature of mass itself. This also ties back to the notion that gravity and time are not fundamental forces but rather byproducts of the entropic processing of information across spacetime. The retention of photons and localized entropic pockets could therefore produce warped gravitational effects, consistent with Verlinde's emergent gravity hypothesis.
I don't really understand any of this, but I agree that gravity is probably not a force, but an emergent property. I liken it to the spring of a computer processor as it computes more and complex calculations; a clustering of matter simply self-interacts more, and the "computational substrate" has more work to do, hence a slowing of time.
My guess is the entire knowledge of humanity combined is far less than 1% of all of the potential knowledge that exists. I also don't doubt that before I was able to type even one letter of that, the potential knowledge increased massively. In fact, by merely doing anything, even just continuing to exist past said point, we factually do increase the potential knowledge. If you're still alive, you just did something I could learn that you did. See what I mean?
Perhaps, or there is an infinite number of universes and each leads to another through black holes. Each universe is smaller than the preceding one but ultimately ending up in a near infinite circle.
Maybe there’s no end but you have to start somewhere. Without a beginning you have nothing. Please explain how something can exist without beginning to exist. Seems impossible by default. Are you just saying that or what am I missing?
@@evenodds8791 Why? Why does it have to have a start? Just because everything within our universe appears to have a start and an end, it does not mean that that holds true for everything. What if the big bang is actually the middle and there is another universe that is inverted to this one? An anti-universe made up of anti-matter and anti-time? Infinity is a slippery subject - our little monkey brains have a lot of trouble with the concept as it is so foreign to our experience.
I'd like a video exploring what exactly de Sitter space is in some more detail. I keep hearing it mentioned in different episodes-like the one on Gravity not being a fundamental force, but being an emergent force-talked a lot about AdS/CFT correspondence, the "dS" being de Sitter space. I've also heard the term tossed around in other places, but don't really understand what it is. I'm sure it's highly technical and requires a strong mathematical foundation to even begin to understand, but PBS Spacetime has always done a great job of breaking down and explaining complex ideas like these.
The A part of AdS stands for Anti and it's just something that someone completely non-arbitrarily made up when whatever version of string theory they happened to be working on at the time would only work with a negative cosmological constant. And they tested it and everything worked as predicted and finally physics was completely solved and everyone agreed that string theory was the best thing ever and not a complete waste of time and/or resources. Oh and I think there may have even been a parade. I should probably also add that it has been a while since I've done any reading on the subject so I may have misremembered a minor detail or two so quote at your own risk.
The idea that the universe had an absolute beginning in time is kind of trippy. Of course the idea that extends infinitely into the past is also trippy.
While the universe having an absolute beginning just doesn’t feel right to me, and… cosmic inflation theory helping to “smooth out” some of the bumps of a big bang beginning, looks ridiculous and appears to me to have been pulled out of someone’s behind… I also have a problem with a universe that “always was and always will be”, since an infinitely old universe’s problem is… well… infinity! I think Eddington came closest to describing the universe when he quipped “Not only is the universe stranger than we imagine - it is stranger than we CAN imagine”. That works best for me 😅… Today.
There is a strange elaboration between the infinitesimal beginning, and the infinite end of the universe. Cause and effect themselves seem to arise out of this inexplicable point wherein space and time fail to be distinct, and yet inflation compounding with increasing entropy will eventually produce an abyss where time and therefor space cease to be meaningful. We are in a finite prison with infinite walls.
As a layman, I understand it as being unable to have a time before the universe because time itself did not exist before the universe. So there is no “before” to have been. That might be an incorrect summary, or even if it isn’t, that might confuse you even more, but I hope it helped anyway.
@@iankirby4160 In the context of this video, its definitely an incorrect summary. To summarize the video: the big bang probably wasn't the beginning of time and the mathematical singularity that we get when we follow Einstein's general relativity could just be a boundary like the one we see on the boundary of an event horizon. A transition zone between our bubble universe and the infinitely inflating universe that came before it. Basically big bang =/= beginning of time. Coordinates in space and time if traced backwards probably cleanly transition out of our bubble universe and into the infinitely inflating one with no break in time. Merely a clean transition like falling into an event horizon, even though it could be graphed as passing through a zone where time is infinite. From the perspective of an observer time could just keep trucking on uninterrupted.
This is another version of 'Are we alone in the universe?' Both Yes and No answers are equally terrifying. Did the universe come out of nothing, of has it been around for ever? Either answer is equally freaky.
The idea of a physical beginning of time is mind boggling, it breaks our perception of cause and effect on such a fundamental level we can't make sense of it
@@duckruttwell.... if you're setting the bar at 100 years then you'll be disappointed for sure. Just look at the present, we're certainly arguing over things we did way more than 100 years ago. Cultural evolution is a crawl speed slower than that of a sloth on sedatives.
I had the mental idea of space being a sort of tunnel.. and if you’re in the middle of a tunnel, you can look forward and backwards, but because it is so far the end of the tunnel seems like a singular point and you could get to that point and there could be so much more than what you could tell before. So real life example.. we can see as far as what we believe to be the beginning , 46.5Billion light years away, when the universe could’ve started 100B+ light years away and we would never know because it’s too far down to the tunnel to tell and from what we see it could just look like a big bang
The problem is at some point we seam to reach an actual hard boundary (not infinite). But it's still a good way of thinking about past light cones verses narrowing perspective at a distance :)
@@hmu05366 no we can detect what if the edge or boundaries just outside of our observable universe… so many theories, such as what if we are inside of a worm hole, which is why things thing seem to be accelerating and the wormhole has a diameter that’s larger than our observable universe
I fear that the mythical parallels to the Big Bang theory make it too tempting to analogise it to the start of a book. I’ve been asking for 15 years whether time is asymptotic - think about how much activity occurs in the first seconds of the universe. Surely any “observer” or “observation” back then would be more scaled to the pace of activity then. This is the flipside to the kind of “slow time” we will see after all the stars go out, life clings to the edges of black holes, and every thought occupies trillions of years. To our eyes.
Oh my god I was just reading about the big bang, gr, and minkowski diagram and Penrose projection... This video could not have come at a better time lol
Same. I was just speculating with chatgpt whether our bubble universe could be a de sitter space in a filamentary black hole in an infinitely inflating universe. dS/CFT
could someone help me understand why the big bang isn't a white hole? the Penrose diagram suggests that the math supports white hole existances but since we haven't seen them, we assume they don't exist. But if a white hole is the opposite of a black hole where matter is ejected, and the big bang is where energy and matter expanded dramatically, and if you follow space-time trajectories backwards you arrive at a singularity; it's beginning to sound like the same thing to me. What if the big bang was a white hole? Idk if this makes any sense and I'm sure I'm missing some key info on the differences. any suggestions on where to follow up on white holes would be appreciated. Thanks for all the good content you put out! ❤
The way I understand it, white holes don‘t just eject matter - they are an entire spacetime-reversed representation of what we know as black holes. You can therefore never experience a white hole as from our perspective they would not exist in the past - only in the future.
@@KoneSkirata that makes sense with the Penrose diagram. maybe that's where I should start my understanding because I don't know why our universe can't be a white hole. but grasping an inverse of a black hole spacetime is not easy. thanks for your reply.
We really don't know if white holes are possible - many things can be created with math that don't exist in reality. However, according to one of the theories about white holes, the universe isn't nearly old enough to contain any yet. If you entered a black hole, you would exit in the distant future.
@@KoneSkirataOhhh I can see that making sense. All the light in the black hole has a determined future already, given its hit a singularity so it's like that light gets shot forward into time instead of space. Aka the other side of the Penrose diagram right?
Ever since I learned about black holes and the big bang in my astrophysics classes in college, I wondered if the big bang was the product of a black hole in another universe in a multiverse. I felt that this would solve two problems. 1. there’s no need to theorize a singularity and 2. This would solve the issue of the loss of information in a black hole. Our big bang would be opposite of a black hole, a white hole spewing forth into a new universe matter swallowed up by a supermassive black whole in another universe in a multiverse. Instead of a dead end in a black hole could a black hole be the entrance to an Einstein-Rosen bridge to another place or universe?
I like that boundary-defining expressions such as "start of space-time" and "end of space-time" are used instead of time-dependent notions like creation. It's confusing to say space-time has been created. Being created implies a point in time when it didn't exist. How could there be a point in time before time was created?
@@ronairgood1041 Doesn't make any sense, as any creator would then be asked what created them. At some point there will be an end to the causal chain, and anything that can come into existence without a cause completely violates our understanding of reality itself.
Space time can't exist if there's no space for there to be time in. If the universe didn't exist for even a fraction of a second then there would be no space time for that period. Which means that before was in a completely different space time than now is in.
I know from basically every astrophysics video ever that GR and QFT break down at the most extreme points in spacetime, but I don't know what that really means. Can you please explain the specific conditions under which these two great theories dissagree? How do their predictions differ? What can we actually observe? Thanks!
Super over-simplifying, and hopefully others will do better, but the main issue is gravity. Quantum mechanics expects a discreet particle called a "Graviton" that mediates gravity, much the same way that the photon is the discreet particle for electromagnetic energy. We haven't been able to discover (or create) gravitons, however we have discovered gravitational waves, which relativity does predict. In order for the theories to become reconciled, we need to find a quantum theory of gravity, which so far has eluded us. I hope this gives you at least enough to get started. ☮
@nhband1t Quanta Magazine published this clear-worded, artistically inspired video yesterday, discussing the exact matter of your question :) th-cam.com/video/RIqVnFtOSr4/w-d-xo.htmlsi=lw0AewO5KNkEyESl
Breaking down generally means that singularities arise i.e., infinities or 'divide by zero's. Generally infinities in a theory mean that the theory is probably incomplete because infinity doesn't really exist in the real world. Like how some properties 'blow up' to infinity when you attain the speed of light (I think this is because we have already assumed the constancy of speed of light and then tried to attain that speed such that the speed of light is not c but can be zero, so it breaks the initial assumptions).
QM has a shortest observable length where the short-wavelength light needed to measure it has very high energy. GR treats spacetime as continuous with supposed singularities in black holes and at the big bang. Much of the time they coexist but near those singularites they diverge. You can doubt that the singularities exist but what is there is not supported by any experiment done yet.
As the only part of this video my small brain could understand that tripped me up too, but I think if you language hard enough you could make an argument for either the lats or longs converging at the poles
Its always a treat to watch these videos and read all the comments of people who cant live without pretending they have all the answers. Whether they insert their god, or just assert an answer without proper justicication, it always makes me giggle
@@MrVontar 😂 anytime I hear "god could..." I just have to let out a big laugh. Please entertain me with how you know there is a god and how you know what that god could do 😂😂😂
@@MrVontarI seriously hope your reply is some kind kind of exercise in Poe's law because the dude literally just remarked on how a comment like yours is always guaranteed on videos like this 😂
@@wj2036Jesus overcame the world resurrecting thus defeating death proving eternity is a concept so ingrained in ourselves because it has always been a PART OF US FOR IT IS POSSIBLE. He promised all of us a new body, new earth and heavens... Another universe. I dunno about you but when a Man who singlehandedly fulfilled over 300 prophecies from texts 500 years before His birth talking about the coming of the Anointed Son of God, predicted His own death and Resurrection 3 days later... I would trust that Man. Good thing Jesus is Real and denying so is going against basic historical knowledge...🥱
It sounds like a cosmological version of inventing super-symmetry even though you still have no idea where the neutrinos might be getting their mass from.
Correct me if I’m wrong, but didn’t Roy Kerr just come out with a paper proving that singularities in black holes don’t exist and are instead smooth rings? Kerr recently proposed that, in rotating black holes, the singularity isn’t a point but a ring-like structure
I had thought of the universe after all particles decayed. I mistakenly thought that what remained was empty space, as opposed to Penrose’s description that what remains is radiation. I thought that this empty space was possibly the ground of the next big bang. (I never liked the idea of a big bounce). When I heard Penrose describe his CCC, I thought holy cow that actually clicks with me. I had an original idea that was similar to what Penrose thought! If radiation is energy and energy has a mass equivalent, then maybe the radiation that remains can be gravitationally attracted to a new big bang, i.e. bounce.
@@FAK_CHEKR But thermodynamics argues for energy dispersiing, not concentrating. Without a barrier to contain radiant energy, it'll just become more dilute with time. If there was a mass equivalent to energy, it doesn't seem to matter.
This question is for anyone knowledgeable about General Relativity. GR is generally discussed in terms of 3 dimensions of space and one of time. My question is. Is there a version with 4 dimensions of space, or 5, 6, 7, 8, etc. And if so, could we describe our 3D Universe and 3 large dimensions and say n dimensions rolled up like a straw. Now where I'm going with this, is what if the singularity is the 3 dimensions locally rolling up into something small, but at the same time the other rolled-up dimension unrolling and becoming large. And the same for "inflation" at the beginning of the universe. What if that inflation is the 4th dimension collapsing while simultaneously the other 3 expanding. What would a higher dimension Generality Relativity theory look like.
This is the bridge to string theory. String theory mathematics work with higher numbers of dimensions... 10 and 26 are the numbers that are coming to my mind right now, but my knowledge of string theory is limited to books from the late 1980s and early 1990s and what's been discussed on this channel... and those additional dimensions are described as being rolled up and imperceptible to us the way you describe. As for what it looks like in GR, your guess is as good as mine, but I'm intrigued by your depiction of the singularity... reminds me of the old Disney sci-fi movie "The Black Hole"... which might still be possible, if wormholes are a thing or even if some of the ideas in this video are accurate.
I am not a specialist in SR or GR. I'm not a physicist. You have to keep in mind that this is just an abstract mathematical coordinate system that attempts to describe the reality of the natural universe. A bit like navigation and contour lines on a map of the globe. It has to describe the actual universe and that is actually quite difficult because of the combined distance/time m/s issue. The coordinate system we choose doesn't really matter as long as it describes the actual universe and doesn't get caught into the trap of the coordinate system describing the coordinate system, rather than describing nature. (x, y, z) +'ct' or (x+ct, y+ct, z+ct) or (x m/s, y m/s, z m/s) and so on. We can get 0, 1, 2, 3, 4, 6, 7, 9, 11 common dimensions all attempting to describe the same thing :) > More important maybe is to ask what is that nature that I am trying to describe. Is it a solid block of (x, y, z) all moving as 1 through time, or are each individual components all moving in (x m/s, y m/s, z m/s). there is 2 different concepts that are called 4D ;)
Dimensions are a mathematical tool used to describe where stuff is. Dimensions aren't a real thing that the universe cares about. If you add more dimensions, it means you need more information to describe where something is. We only have 4 dimensions (3 spatial x y z, 1 time) because you don't need more information that that to describe where something exists. Adding another dimension doesn't make sense when we can already describe where everything is with those 4. We can shift around those dimensions into different forms, there's lots of alternatives but polar is the most possible (phi, theta, radius, time). There's forms in astrophysics where instead of time you use distance from start of universe and you're measuring time in distances. You can create whatever you want but you'll only ever need 4 dimensions.
@@MyNameIsSalo "Adding another dimension doesn't make sense when we can already describe where everything is with those 4" The current 3 +t model is also problematic. It can be difficult in some concepts to be able to call it 4D as the ct dimension is a little abstract and disconnected. > Polar/spherical coordinate systems are great for solid spherical objects, but run into issues when you attempt to describe things via photons path. That natural path distance/time is a little ambiguous and difficult to describe. 6 pseudo geometric dimensions is likely more practical, but even then they don't seam to accurately describe nature. > A single space time geometry cannot function to the beginning of the universe as we have an event horizon in the way known as the CMB, beyond that the current model falls apart because we are describing a different relative space-time.
There is no time only time is the time we know. If that is ture the the " big bang" has not happened yet. And it's already happened and it's happening right now it's all one.
Can gravitational astronomy ever be "detailed" enough to peer beyond the "transparent universe"? It strikes me that one of our "issues" now is that we have almost no observational data from earlier than when the universe became transparent (outside the CMB if I am correct). But the universe SHOULD have been "transparent" to gravity earlier than that, right? So I wonder if gravitational astronomy will be able to advance to a point where we can use it to examine gravitational data from earlier than 380k years after the big bang. In theory, gravity waves are everywhere and created by every interaction between masses, so it strikes me it's a matter of instrument precision to be able to get more and more detailed gravitational observations. Can it ever precise enough to be doing things like mapping other star systems gravitationally instead oof by light, or perring into an opaque universe that still was awash in gravitational interactions?
If we ever got good enough with neutrino detection, and I mean REALLY good, we could peer into the cosmic neutrino background- that would allow us to see FAR past the CMB.
as @420Khatz said, neutrinos are an option (but we dont really know how to detect them well enough) - they would also allow us to study the "inside" of supernovae, so thee is a big interest as for gravitational waves, we would need detectors MUCH more sensitive than the ones we have today, and more computational power to "disentangle" all the interference form other gravitational sources - but there already exists some evidence of whats called "gravitational background" (there's even a video here about it), but it's hard to interpret what it means
@@geekjokes8458 Ya the instruments of today for gravitational astronomy (GA) are very primitive and not very precise. But I think back to Galileo and his first crude telescope, and wonder if he could possibly imagine a time when that instrument was precise enough to see light from the earliest universe, or "light" from outside the visible spectrum. Like, it seems today perhaps "impossible" to imagine the sensitivity and compute power to get to the very fine gravitational interactions that underpin the whole universe, but that's because we are Galileo right now, peering into a very primitive instrument for the first time. What will our GA telescopes look like in 400 years? I can only think they will be FAR More detailed with the ability to analyze MUCH less violent interactions than the equipment today can, just like Galileo could only resolve the brightest objects in the sky, and resolve them fairly poorly by modern standards ...
If we could? All we would see is an infinite fractal. Our 'universe' is just one small branch. In an infinite fractal of branches. B/c the 'universe' is either infinite or not? If it's the former, my assumption is probably true? If it's the latter? We live in the matrix.
For me it's kind of comforting. Even if I make mistakes in this life, when it comes back around maybe I'll make some different choices and be better for it.
It's been 10 years since Matt took to hosting this show. For me it feels like.... well maybe not yesterday, but rather early this year. 10 years man. Thank you for the content.
Ok, follow my line of thinking here... And yes, I know it's not a perfect analogy. So, a person gets a cup, adds some water and soap. Then the person uses a straw to create a bubble. So, imagine that's our universe... It would have the inflationary period (when the person blows air) and so on... So, from this bubble universe you wouldn't be able to trace to "anywhere" before the bubble was created, but it would still make sense to talk about something "before" that. So... I don't know. Perhaps we should think in something similar. Or perhaps I'm absolutely wrong, who knows.
Sometimes I think other people's perception of space is very different. It so often seems to grasp at walls, at boundaries, because infinity somehow just isn't an option in their minds. Perhaps that is because we are mortal, so infinity pisses us the F off! lols Your idea makes more sense than the Big Bang to me, but I'm certainly no genius. Still, my question has always been, and still is; how does one get something from nothing?
@aylbdrmadison1051 Well, space is always creating new matter from nothing. Pairs of particles, matter and antimatter, that annihilate each other. And judging for the amount of normal matter out there and the lack of antimatter... Who knows, right.
@@aylbdrmadison1051Something from nothing implies a change. There could have just always been something. Here's a question, what if tommorow I started from ZF axioms and came up with an equation. I then demonstrate that the universe and the equation precisely align all the way up to you reading this sentence. Then do you really exist at all?
@@aylbdrmadison1051 Most people seems unable to think realistically about infinity, but also to avoid being humanocentric. Personally, i think our current "model" is our modern version of the geocentric universe of the "primitive past". "Still, my question has always been, and still is; how does one get something from nothing?" A question easily answered by my personal theory... Space and time have always existed, and when you have enough matter in one place, as in trillions of trillions of black holes as they are today in our known universe, eventually they collapse into themself, crushing subatomic particles so tightly that they explode to form a "big bang". Only problem is, to confirm the possibility of my theory, we will need the ability to see far FAR beyond our current views. A thousand times further is probably the absolute minimum that might let us see something that distinctly is NOT part of our own "big bang". More likely, a billion times more. So, sadly, probably not in my lifetime.
@@aylbdrmadison1051 when the big bang was originally proposed, there was actually a not insignificant amount of pushback because it felt to similar to the creation myths of religion (before that point, steady state cosmologies where the universe lasted forever were more common). the fact that it's now widely accepted is less because humans like things being finite, and more because that's what our experiments have lead us to.
why do we assume that we see the beginning of universe but not just an event occured on the part of the universe we are in. there are parts that we cannot measure, see, get information about?
It's a mouthful to say 'the last most relevant event to happen to our spacetime' instead of 'the beginning of our spacetime', would be the main reason to assume 'beginning' instead of saying 'probably the beginning'. Part of running these mathematical models is to start with probable conditions that they can think of and work with, given that the end result has to at least compare to the observable universe, some of which do contain conditions prior to events that resemble the big bang. To me a completely static universe existing infinitely before a spontaneous big bang event doesn't sound much different than there being nothing and then the big bang. I imagine seeking consequential differences that may lead to new physics to be among the aims of this kind of work. Yes, events that occurred before space and time were spread out enough to allow matter to cool into translucent gas must be inferred by observations of that matter since. I think it's generally called 'the hot big bang', but that could be a different thing entirely.
@calyesil You answered your own question. You cannot assume if the barrier cannot be crossed and you can't get any information about it. Physicists work with actual knowledge, not with lay people and their fanciful imaginations.
@@swingtopiadance2387 I answered your question. They try to solve both proposed models with new techniques, where there is a barrier and where there isn't, as described in the video.
I have some questions: 1. Did the cosmic inflation cause a gravitational wave? 2. If yes, was it a transversal wave like all gw we observe today or was it a longitudinal wave? 3. If it was a longitudinal wave, would it be a standing wave in the first mode and the wavelength of the universe? 4. If yes, would the wavelength increase and the frequency decrease over time due to the expansion of the universe? 5. If yes, and if we were in the fourth quarter wave in terms of time and if we add a linear expansion of the universe, would we observe an accelerating expansion of the universe without the need of dark energy to explain it?
I'm a bit concerned by the point universe. If the universe is infinite, you can shrink it as much as you want, it's still infinite! If you talk about the visible universe... Then that's finite and you can imagine the singularity. The problem is we don't know what's going on elsewhere...
@@nortonman5238 to be honest I don't really think it's really infinite... Just much much bigger than the observsble one and maybe like a bubble or a tore that wraps around. BTW: the usual "solution" to the twin paradox is that you have to turn around and come back to compare ages. But if it's finite and used to be very small then one could come back without changing speed and direction... 🤔 Maybe that makes a very fast expansion mandatory to prevent that at the beginning... 🤔
@@NeilGaede1 Why not? One thing that I do not like about these videos and other discussions the the use of the word singularity, that suggests a very finite sized point in space. If the big bang is infinite in size, then it can contain infinite matter and nothing that we have discovered so far breaks that view. The observable universe may have started in a singularity, but the observable universe may only be an infinitely small sub-section of the actual universe.
Could be an asymptote in time, the further you go back to the beginning, the more time is distorted, an infinitely deep time well. No beginning, just a temporal asymptote
I still feel like our universe is spherical. So many objects and movements tend towards the rotational or spherical, from the atomic to the cosmic. We just can‘t measure this because our entire universe is likely the equivalent of a pinprick on a balloon.
I don't think you understand what you're saying. A spherical or curved universe is like a balloon where the universe exists on the surface of the balloon (not inside it, only on the surface). So that if you start at one point in the balloon, travel in a geodesic around the balloon, you will end up in the same starting point by only having moved in 1 direction. Like if you keep moving north you somehow wrap around back where you started. That's spherical. It wraps around on itself. We call our universe flat because like a flat surface, when you go in 1 direction you can go forever and you will never ever reach the same point. It's not flat in the sense that it is a literal flat plane. There are pretty easy calculations you do in like 1st year astrophysics to experiment with different types of universe curvatures and when you map that to real supernovae explosion data, our universe comes out to being exactly flat with extremely high precision. There's like 3 different independent ways you can formulate that conclusion using data from different things, and when 3 independent studies all confirm the same thing then it's probably true. Another way is triangulation, a triangle in a flat universe has angles = 180 degrees, in any other universe this is not true. We can measure angles down to fractions of arcseconds of things billions of light years away to calculate this and things add up to 180, if our universe was even a tiny bit curved then it would deviate slightly (or deviate by a substantial amount, depends on amount of curvature)
@@MyNameIsSalo yes, I understand that. You’re operating under the assumption that our universe, everything that resulted from the white hole explosion, makes up everything that exists. That’s a safe, scientific assumption because all data we’ve ever been able to collect falls within those confines. I am not limiting my thought to that. I feel like it’s too egocentric to assume nothing existed before the Big Bang, or that we’re the only universe in existence. Imagine trying to prove the earth is spherical when all you’re given is the grains of sand inside a child’s sandbox. No atmospheric or celestial data - you can’t look up at the sky. Your data collection can only come from within the confines of the box. Now imagine our observable universe is that sandbox; each grain of sand, a galaxy. You could triangulate from the farthest possible reaches of your confine and still fail to come even close to being able to accurately discern the curvature.
@@MyNameIsSalo slight pedantry to add on -> the universe CAN be "that big" where that potential curvature is feasibly unseen in our observable universe. I'm sure you've gone over that at some point, but it is fair to point out in this context.
regardless if there was a before the big bang or not doesnt matter because we will never know. its one of the questions scientists dont care about same as if is there and outside the universe. those are questions that can never be answered and therefore have no meaning. they do work quite well in confusing people tho.
@@FarSeeker8 when superstition is praised like you do, fear the worst for humankind. Scientists are the reason we have technology and science to begin with, certainly not priests of any religion.
@@snarckys3063 Re: Wikipedia, "European science in the Middle ages" and "List of Medieval European scientists". Christianity took "natural philosophy" and created Modern Science. Before that what was accepted was at the whim of pagan gods and emperors. Otoh, Look at what Atheists have accomplished in the USSR, PRC, and other nations where they have ruled exclusively: mass death and societal abuse.
@@snarckys3063 When propaganda like yours is widely accepted, we have nations like the USSR and PRC. Christians are responsible for turning “natural philosophy” into Modern Science. The world has seen the greatest advancement in science and technology in Christian influenced areas. Your Argument Fails.
I firmly believe the universe is a 4D object moving through the 3rd dimension. If you take a 3D circle and pass through the 2nd dimension, it would look like it suddenly appear as a dot and keep expanding. Which is what our universe is like. Maybe at some point, it stopped expanding and started getting smaller. The end of the universe being everything returning to a single point.
There was no beginning and there will be no end. The energy was always here and always will be. We and everything are this energy. We are all one, infinite consciousness.
Are we just assuming that all of spacetime is trackable back to a singularity or is there direct evidence? Is there evidence against the idea that the universe already existed before the big bang and that the expansion resulted from an unknown incident within that preexisting universe?
We've traced how the universe should have been back in time pretty close to the big bang, and so far observational evidence (like cosmic microwave background) supports them. Ofc we can't see the actual moment - if we could we'd just be able to see the answer to our questions directly.
I think the idea is that the current theory "big bang theory" may not be the only theory. That had a singularity which started the universe. Other theories such as the idea that there are multiple universes in space time that push and pull against each other. Using geodesics to find the singularity that started our universe could prove or disprove the big bang theory. If matter traces its origin to several points instead of one, it would prove there is matter from outside our universe. We assume there is a singularity that started the universe because matter is expanding in ALL directions.
@@MasterGhostf There are also things in their model for which they have no explanation. They needed to propose a period of accelerated expansion without providing a natural mechanism to explain it. New discoveries seem to show large galaxies too soon after the proposed beginning. So-called dark energy and dark matter further illuminate our ignorance. I don't think that the level of certainty scientists demonstrate is justified. Then again I'm not an astrophysicist.
@@MasterGhostfit’s extremely unlikely that the Big Bang would ever be disproven, there’s just an overwhelming amount of evidence that supports it. It’s possible that the Big Bang is a small part of some larger event though
Roy Kerr contends there's no singularity.. let's investigate that for a singularity to exist under Penrose's theorem the black hole would have to be non-rotated which is never been observed so the probability that a singularity exists is infinitesimally small.
There is a singularity (in the sense that all trajectories end up on it), but it is not infinitesimally small. If we quantize that, then the singularity is, of course, a geometric space with well defined volume. That's what string theory is trying to do (no matter what we may think of the results, so far). The only way to actually verify any of this would be to create microscopic black holes in the lab and then to follow their decay channels, for all I know. That would allow us to learn something about the "inside". There is just no detectable signal coming out of a macroscopic black hole. I don't know if scattering of e.g. light near the event horizon can tell us anything of importance. My guess is that not even that gets us there. The no hair theorem is attenuating everything that is on the inside way too much.
@@lepidoptera9337 ONLY if the black hole is non rotating... Which doesn't exist in nature. Penrose is built on Schwarzschild which simplifies Einstein to get a solution but it assumes the black hole isn't rotating. Nothing is never not moving.. there's no singularity., at least based in Penrose's theorem.
While explaining a possibility of the Universe not having a beginning at the Big Bang, he just provided even more information supporting the Big Bang. Gotta love science!
Could not agree more with your last point. Irrespective of whether or not we derive an answer or the answer and how would you know anyway but the mere fact that we can hypothesize about what happened at the start of time is weirder than that we exist
Total click bait 18 minutes to say yea the universe did probably have a beginning spare me the one case that makes extreme assumptions to say that in some other universe there is no beginning when you just end up back to where we’ve been that is that our universe had a beginning as far as we know total waste of time this is mathematical philosophy click bait
My mind, focused on space and time, trying to find, by rewinding time, Answers divine, Spread out trought space and time, Hidden in plain sight, The riddle of lifetime.
00:14 rewinding you shrink with the wave, you dont pause your current time dilation, zoom in at any point and the observable universe always looks the same size and scale
Awesome video! 👌 There's still something that must be emphasized with regards to the _probable_ beginning of the Universe: the very notion of a beginning makes use of time and space, as any thing that begins has to do so at a particular time and space. In the case of the Universe, there seemingly is no other time or space prior to it, meaning there wasn't ever a time or space when and where the Universe wasn't: in other words, even and especially with a proven beginning, the Universe is eternal and omnipresent, necessarily, as it always existed and will always exist, everywhere. Food for thought.
Outstanding - like always! At our current understanding, while most things seem to point to a singularity for the birth of the Universe, one dramatic discovery could shift everything. Such as truly grasping the nature of dark energy, quantum entanglement, or any of the many mysteries we've yet to fully grasp. Then, even an expanding universe may no longer be universally true, at least from all perspectives. I'm confident that humans, math, imagination, and probably A.I. will figure out quite a bit in the next decade or so, and I'd be willing to bet that our new understanding will change everything!
Your channel has pi million subscribers
They should block the subscriptions
@@demetriusshade9730 Let's celebrate with a pie
Now for the real question: Are all the subscribers irrational?
@@pbsspacetimehave you been waiting to say that? Too good…
@@pbsspacetimewe TRANSCEND irrationally :)
I have now officially watched every PBS Spacetime video ever made. I cannot overstate how good these videos are. It is amazing to me that this quality of content is available for free. Support PBS!
I think you might mean "cannot overstate how good these videos are."
Congratz
Before this one came out a few minutes ago didn't you already officially watch every PBS spacetime video?
@@backwashjoe7864 I did, oops! Just fixed it
@@nortonman5238 Does a youtube comment still exist if it is so buried in the comments that there is nobody there to read it?
I like how physics at large scale just becomes philosophy for math nerds.
It's not even philosophy. It's really more like theology - it's practically entirely disconnected from the scientific endeavor, and relies on differing interpretations of doctrine.
Analytical philosophy used to be for maths nerds anyway. Shame it's not often seen in this way anymore.
Science and mathematics are a branch of philosophy.
Idiots
@@TheDjacob LOL spot on
I hope PBS Spacetime doesn't ever end since it would leave me geodesically incomplete.
Man, that's a good one! xD
😮😮😮 good one
😂
In that case, good luck finding a therapist with geodesicical skills.
@@MsTyrieThe modality is "Existential Therapy". Thank me later. 🫶
I feel like a dog watching TV when I watch one of these videos...
I love watching them, but have very little understanding of what's going on.
Me, on your same team.
A dog watching TV. Yep that seems about right. They need to be watched while high for the best “understanding”.
I am currently trying this. It no workie sir. 😆 @@Duane_Day
Wish there was a laser dot to chase.
thats the point of these video's, gotta compensate somehow
He makes complex topics more complex.
He understood the mission
Weeding out the non-mathematically gifted like me, lol.
@@MeltedPearls don’t lie - you’ll be coming back for more. 😏
Let me clarify. The universe is the perpetual motion machine.
@@notafraidofchange Facts! Being around smarter people is making me smarter, too.
If anyone else also has a some familiarity with physics and yet understood basically nothing of this but the surface words, you're not alone. Wow. I'm glad talented people look into this stuff though.
Basically the big bang probably wasn't the beginning of time and the mathematical singularity that we get when we follow Einstein's general relativity could just be a boundary like the one we see on the boundary of an event horizon. A transition zone between our bubble universe and the infinitely inflating universe that came before it. Basically big bang =/= beginning of time.
@@Jamex07
But we have nothing to prove this?
Some of the solutions presented suggested multiple universes.
Is multiple universes really accepted by physics?
Or is it just math for people who are trying to find the theory of everything?
I have a basic understanding of physics and this mostly made sense but was made overly complicated by the usage of "null geodesics" as the bulk of the discussion was around that. Null geodesic just means a path that light can travel through. If we can trace null geodesics back through time = 0 then light existed before time = 0 and that light had to come from somewhere (which is an argument for parellel universes or white holes which are being labelled as de sitter spaces here).
If you just replace de sitter with parellel universe, and null geodesic with light, this makes 100x more sense. Ignore all the talk about boundaries, this is a talk about what barriers light can travel through, and trying to find a co-ordinate form that allows light to travel past time = 0. Although discussing it this way loses a significant amount of accuracy for scientific purposes, as those things aren't exactly correlated. But for your average viewer, just correlate them, doesn't make a difference.
@@lazyfoxplays8503 The video discusses the evidence for this. The apparent smoothness of space means that directly following Einstein's general relativity does not necessarily produce the universe we observe. Its smoother than our models suggest it should be. Our observations suggest a singularity prior to the big bang is implausible.
And the math discussed in the video suggest that that infinity may not be a singularity after all. (and singularities that show up in math are generally an indication that our math is wrong. So the singularity hypothesis has been problematic for decades. Especially because it leads to unsolvable solutions)
A theory of everything would include electroweak symmetry. These observations and theories are not touching on electroweak symmetry. This is just about finding out what happened before the big bang.
@@MyNameIsSalo white holes =/= de sitter space. A de sitter space is a space with a positive cosmological constant. That means acceleration is increasing over time rather than decreasing, meaning that the curvature of the universe should be positive or saddle shaped as time passes.
None of this is going to save poor Alice and Bob. Their sacrifices will never be forgotten. ☮
I believe they will be saved by the singularity itself
Or were they?! 🤔
eve is laughing in her [quantum] sleeve
@THE-X-Force
It is "Eve" that makes things "possible" at last. We all need Eve too - may be more.
their sacrifices will never be observed to occur!
I'm 76 and never bought into the Big Bang ...theory. It was quite a treat to find your video ...brilliant . thanks
" We're as far out of space as we are ever going to get . " Alan Watts
I love the the Thursday afternoon Space Time notification! It's the big bang for the weekend!
Nice😅
@@gtbkts The early Monday morning big crunch kinda blows though. Unless there's a holiday which throws off the week's expansion rate causing a crisis in the workplace.
I mean, it'd be nice if it was a Friday
Always good to end the day with a PBS
With a Pretty Big Salad?
I'm going to have to rewatch this when I'm more awake, I think this one requires me to brush up on several of the areas you mention to fully comprehend. Thanks! I like educating myself.
Can we reorder the last two names in the Friedman-Lemaitre-Robertson-Walker metric so the acronym would be closer to 'flower'? It just feels like FLRW is still quite a mouthful for an acronym, and it's a nice word for it I feel.
I was just thinking this too. Lol
I've been saying this for years... would very so much better, think flower metric sounds awesome
Just think “flower” and the anagram remembers itself.
They made TV show outta this. Just call it: BBT
Flwr
This channel keeps means so much to me. The best place to learn about space and physics. You don’t talk down, keep the complex stuff but it’s still digestible. I love it
15:37 - a little pushback here. It's not through pure reason that we can come to these conclusions, but both reason and observation. To me this is important, because the only way pure reason could reach the correct conclusion is if there is one and only one way to build the universe. But so far, from what we've seen, the universe includes both aspects of necessary physics and also free parameters. Those free parameters imply a very curious fine tuning.
What free parameters?
@@RobertoFrankenstien For example, elementary particle masses, mixing angles and gauge coupling strengths, not to mention the actual initial state of the quantum doo dads of the big bang.
Yep physics isn’t maths exactly
@@aelolul what do you mean by free parameters, exactly? How can it be shown that those parameters are free? Are you implying that they can be different from what they are?
@@RobertoFrankenstien So far, pure reason has not given us any insight into the cause of these parameters. So far, as best as we can determine, they just are what they are, and it's suspiciously lucky for us and biology and chemistry and universe stability in general.
The origin of the universe is neither late or early, a universe materializes precisely when it means to
[slow clap]
Sounds a lot like my morning bus.
One can learn a lot from one of the Istari.
My hypotheses is that if you keep looking, you keep finding stuff.
Gandalf thank you 😊
@beingsentient oh my god
Thank you for being my sparring partner:
Yes, that's a fascinating extension of Eric Verlinde’s Entropic Gravity hypothesis. Verlinde’s theory offers a new way of looking at gravity not as a fundamental force but as an emergent phenomenon arising from the statistical behavior of microscopic degrees of freedom, much like how temperature emerges from the kinetic motion of molecules. By framing gravity as an entropic force, it naturally connects with the ideas of information, entropy, and thermodynamics in spacetime.
Let's unpack the parallel you're drawing in terms of photon retention by matter, flux differences, and mass-gravity warping:
1. Retention of Photon Particles and Local Time
Large particles of matter might trap or "retain" photons-massless and timeless particles-inside their local vicinity for prolonged periods. In Verlinde’s view, this could relate to the amount of information that a mass encodes in the surrounding spacetime. The more matter accumulates in a region, the more its gravitational effect emerges due to the way information is distributed. If mass retains photon-like particles (or any form of trapped information), it would essentially warp the local spacetime by slowing down the flow of time locally, creating gravitational effects.
Photon Retention and Local Time: In areas where photons (carriers of information) are trapped or delayed in leaving the vicinity of massive objects, the passage of time may become dilated or warped. This aligns with general relativity’s prediction of time dilation near massive objects but framed through an entropic lens-where matter "storing" information warps time.
2. Flux Differences through de Sitter Space
If we consider de Sitter space, characterized by a cosmological horizon and the expansion of spacetime, then the flux of information (in the form of photons or other energy) across this horizon could define how different regions of spacetime evolve. In Verlinde's theory, the gravitational pull isn't just about mass but how information about the mass is distributed in spacetime.
Flux and Relativity: The idea of flux differences-areas with varying rates of photon emission or retention-suggests that relativity might manifest differently in different regions. Regions where mass retains photons (delaying their flux) could be seen as creating pockets where gravitational effects are exaggerated due to the increased retention of information (entropy). The de Sitter horizon, then, would serve as a boundary across which these flux differences act, stretching or compressing spacetime in response.
3. Warping the Mass-Gravity Ratio
In Verlinde’s framework, gravity isn't directly caused by mass but by the way spacetime encodes information about that mass. If large objects retain photons or other carriers of information for longer periods, it could create areas where the mass-to-gravity ratio appears warped. The mass might not change, but the gravitational effects would feel stronger due to the altered information landscape.
Entropic Interpretation of Gravity: In this context, mass is associated with the amount of information stored in the system, and the gravitational effect is a consequence of how that information (photon flux, for instance) is dispersed or retained. When photons are trapped around massive objects, the local spacetime might become more "constrained" in its ability to express gravity through entropic gradients, leading to stronger gravitational pull without increasing mass. Essentially, gravity becomes a reflection of how much information about the mass is encoded in spacetime.
4. Cosmological Horizon and Mass Retention
Finally, if we zoom out to a cosmological scale, the de Sitter horizon (which represents the observable edge of the universe in an expanding cosmos) can be viewed as a global boundary condition for how this photon retention and flux dynamics play out. Masses retaining photons may distort the local spacetime, but over vast scales, these pockets of warping could influence the global evolution of the universe, perhaps even connecting to dark matter or dark energy phenomena in ways that emerge from statistical mechanics rather than requiring new fundamental particles.
Conclusion:
In Verlinde’s Entropic Gravity theory, the warping of the mass-gravity relationship due to photon retention is an elegant extension of how spacetime, energy, and information interact. The flux differences through de Sitter space, acting on the relative distribution of mass and information, could be seen as warping spacetime and producing gravitational effects that differ from what classical relativity predicts. The emerging gravity from these flux dynamics hints at a deeper connection between the fabric of spacetime, entropy, and the fundamental nature of mass itself.
This also ties back to the notion that gravity and time are not fundamental forces but rather byproducts of the entropic processing of information across spacetime. The retention of photons and localized entropic pockets could therefore produce warped gravitational effects, consistent with Verlinde's emergent gravity hypothesis.
I don't really understand any of this, but I agree that gravity is probably not a force, but an emergent property. I liken it to the spring of a computer processor as it computes more and complex calculations; a clustering of matter simply self-interacts more, and the "computational substrate" has more work to do, hence a slowing of time.
Great vid, existential dread started @2:45 lol
Congratulations on 3.14 million subscribers! Celebrate with a nice pie!
If i understand 5%, I am happy
same, one day hopefully we can reach that point. until then, I will just "feel" the information instead.
@@krusher9977 it's like shredding on the intellectual air guitar
i think i got my brain twisted up in that de sitter space he was talkn about.
Least it's pretty difficult to snap yer strings in de sitter space
My guess is the entire knowledge of humanity combined is far less than 1% of all of the potential knowledge that exists. I also don't doubt that before I was able to type even one letter of that, the potential knowledge increased massively. In fact, by merely doing anything, even just continuing to exist past said point, we factually do increase the potential knowledge. If you're still alive, you just did something I could learn that you did. See what I mean?
I think that nothing has a beginning or end and has just always been. Our concepts have limits, but the universe isn't obligated to meet those limits.
Perhaps, or there is an infinite number of universes and each leads to another through black holes. Each universe is smaller than the preceding one but ultimately ending up in a near infinite circle.
I think it is hard for a mortal being to understands Infinity.
For some reason, we need endings and beginnings. Because that’s how we see ourselves.
Maybe there’s no end but you have to start somewhere. Without a beginning you have nothing. Please explain how something can exist without beginning to exist. Seems impossible by default. Are you just saying that or what am I missing?
@@evenodds8791 Why? Why does it have to have a start? Just because everything within our universe appears to have a start and an end, it does not mean that that holds true for everything. What if the big bang is actually the middle and there is another universe that is inverted to this one? An anti-universe made up of anti-matter and anti-time?
Infinity is a slippery subject - our little monkey brains have a lot of trouble with the concept as it is so foreign to our experience.
The real universe is the friends we made along the way
Sufis say that the Beloved - is the Real Friend - as He is always with(in) - us.
Fare thee well - on life's journey
I'd like a video exploring what exactly de Sitter space is in some more detail. I keep hearing it mentioned in different episodes-like the one on Gravity not being a fundamental force, but being an emergent force-talked a lot about AdS/CFT correspondence, the "dS" being de Sitter space.
I've also heard the term tossed around in other places, but don't really understand what it is. I'm sure it's highly technical and requires a strong mathematical foundation to even begin to understand, but PBS Spacetime has always done a great job of breaking down and explaining complex ideas like these.
de Sitter space is the maximally symmetric vacuum solution of Einstein's field equations with a positive cosmological constant. 😂. Per Wikipedia
@@MrM1729 Well great. That's not at all dense, I completely understand it now.
@@wolfyrine Ditto!
@@wolfyrine Matt’s stuff in the last couple of years has been incomprehensible after the first 5-10 minutes.
The A part of AdS stands for Anti and it's just something that someone completely non-arbitrarily made up when whatever version of string theory they happened to be working on at the time would only work with a negative cosmological constant. And they tested it and everything worked as predicted and finally physics was completely solved and everyone agreed that string theory was the best thing ever and not a complete waste of time and/or resources. Oh and I think there may have even been a parade.
I should probably also add that it has been a while since I've done any reading on the subject so I may have misremembered a minor detail or two so quote at your own risk.
I love how every video covers big topics in less than 20 minutes
The thought of what was before the before and before that always blows my mind.
Why you never existed before your birth doesn't it bother you?,,
@@SuatUstel Maybe death is just a filter, that filters life and you can't remember life after death because you are new
@edwinwandera6993 you cannot even fully remember your dreams,do you think we deserve second bite of a cheery?????!!
The idea that the universe had an absolute beginning in time is kind of trippy. Of course the idea that extends infinitely into the past is also trippy.
While the universe having an absolute beginning just doesn’t feel right to me, and… cosmic inflation theory helping to “smooth out” some of the bumps of a big bang beginning, looks ridiculous and appears to me to have been pulled out of someone’s behind…
I also have a problem with a universe that “always was and always will be”, since an infinitely old universe’s problem is… well… infinity!
I think Eddington came closest to describing the universe when he quipped “Not only is the universe stranger than we imagine - it is stranger than we CAN imagine”.
That works best for me 😅… Today.
There is a strange elaboration between the infinitesimal beginning, and the infinite end of the universe. Cause and effect themselves seem to arise out of this inexplicable point wherein space and time fail to be distinct, and yet inflation compounding with increasing entropy will eventually produce an abyss where time and therefor space cease to be meaningful. We are in a finite prison with infinite walls.
As a layman, I understand it as being unable to have a time before the universe because time itself did not exist before the universe. So there is no “before” to have been.
That might be an incorrect summary, or even if it isn’t, that might confuse you even more, but I hope it helped anyway.
@@iankirby4160 In the context of this video, its definitely an incorrect summary.
To summarize the video: the big bang probably wasn't the beginning of time and the mathematical singularity that we get when we follow Einstein's general relativity could just be a boundary like the one we see on the boundary of an event horizon. A transition zone between our bubble universe and the infinitely inflating universe that came before it. Basically big bang =/= beginning of time. Coordinates in space and time if traced backwards probably cleanly transition out of our bubble universe and into the infinitely inflating one with no break in time. Merely a clean transition like falling into an event horizon, even though it could be graphed as passing through a zone where time is infinite. From the perspective of an observer time could just keep trucking on uninterrupted.
This is another version of 'Are we alone in the universe?' Both Yes and No answers are equally terrifying. Did the universe come out of nothing, of has it been around for ever? Either answer is equally freaky.
The idea of a physical beginning of time is mind boggling, it breaks our perception of cause and effect on such a fundamental level we can't make sense of it
The Bible explains it and it doesn't go against science. We are just too arrogant to even consider that possibility
@@watema3381The Bible doesn't explain it. It only explains the origins of the earth, not the universe.
@@Froggo9000 Genesis 1:1 “In the beginning God created the heavens and the earth.”
The "heavens" is literally the greater universe.
@@watema3381God did it is not an explanation
@@watema3381it also states that it’s only 6000 years old which is wrong….
Fascinating. I reckon many things we take as fact now will wind up as the "flogiston" of our time.
I hope so. I'll be very disappointed if in 100 years we're still arguing over the same questions.
@@duckruttwell.... if you're setting the bar at 100 years then you'll be disappointed for sure. Just look at the present, we're certainly arguing over things we did way more than 100 years ago. Cultural evolution is a crawl speed slower than that of a sloth on sedatives.
I had the mental idea of space being a sort of tunnel.. and if you’re in the middle of a tunnel, you can look forward and backwards, but because it is so far the end of the tunnel seems like a singular point and you could get to that point and there could be so much more than what you could tell before.
So real life example.. we can see as far as what we believe to be the beginning , 46.5Billion light years away, when the universe could’ve started 100B+ light years away and we would never know because it’s too far down to the tunnel to tell and from what we see it could just look like a big bang
The problem is at some point we seam to reach an actual hard boundary (not infinite). But it's still a good way of thinking about past light cones verses narrowing perspective at a distance :)
@@axle.studentthere is no hard boundary and no edge or centre
@@hmu05366 no we can detect what if the edge or boundaries just outside of our observable universe… so many theories, such as what if we are inside of a worm hole, which is why things thing seem to be accelerating and the wormhole has a diameter that’s larger than our observable universe
Matt is a good listen, I do enjoy most of the PBS videos. Peace ✌️ 😎.
Watching him on mute. Still understand a lot. His hand Italian is superb :)
I got the same listening to a German explain a feature of their railway system (hillside pulley around Dusseldorf).
HHHhAhaha
I fear that the mythical parallels to the Big Bang theory make it too tempting to analogise it to the start of a book. I’ve been asking for 15 years whether time is asymptotic - think about how much activity occurs in the first seconds of the universe. Surely any “observer” or “observation” back then would be more scaled to the pace of activity then.
This is the flipside to the kind of “slow time” we will see after all the stars go out, life clings to the edges of black holes, and every thought occupies trillions of years. To our eyes.
Thank you for speaking with pauses. It gave me time to think of saying thank you.
Oh my god I was just reading about the big bang, gr, and minkowski diagram and Penrose projection... This video could not have come at a better time lol
Just finished a brief history of time in which Stephen Hawking talk about this no boundaries scenario
Same. I was just speculating with chatgpt whether our bubble universe could be a de sitter space in a filamentary black hole in an infinitely inflating universe. dS/CFT
I agree with you since you said “ oh my God”. That explains how the universe began 👏👏
@@ronairgood1041 hahaha real stuff
@@Jamex07 Did you know about ads/CFT correspondence in hyperbolic space? It's one heck of a thing to learn
could someone help me understand why the big bang isn't a white hole? the Penrose diagram suggests that the math supports white hole existances but since we haven't seen them, we assume they don't exist.
But if a white hole is the opposite of a black hole where matter is ejected, and the big bang is where energy and matter expanded dramatically, and if you follow space-time trajectories backwards you arrive at a singularity; it's beginning to sound like the same thing to me.
What if the big bang was a white hole?
Idk if this makes any sense and I'm sure I'm missing some key info on the differences. any suggestions on where to follow up on white holes would be appreciated.
Thanks for all the good content you put out! ❤
The way I understand it, white holes don‘t just eject matter - they are an entire spacetime-reversed representation of what we know as black holes. You can therefore never experience a white hole as from our perspective they would not exist in the past - only in the future.
@@KoneSkirata that makes sense with the Penrose diagram. maybe that's where I should start my understanding because I don't know why our universe can't be a white hole. but grasping an inverse of a black hole spacetime is not easy.
thanks for your reply.
@@mxbranesic3933 that would be interesting, but what about the universe "outside" of our own? Its really just passing the buck.
We really don't know if white holes are possible - many things can be created with math that don't exist in reality. However, according to one of the theories about white holes, the universe isn't nearly old enough to contain any yet. If you entered a black hole, you would exit in the distant future.
@@KoneSkirataOhhh I can see that making sense. All the light in the black hole has a determined future already, given its hit a singularity so it's like that light gets shot forward into time instead of space. Aka the other side of the Penrose diagram right?
Ever since I learned about black holes and the big bang in my astrophysics classes in college, I wondered if the big bang was the product of a black hole in another universe in a multiverse. I felt that this would solve two problems. 1. there’s no need to theorize a singularity and 2. This would solve the issue of the loss of information in a black hole. Our big bang would be opposite of a black hole, a white hole spewing forth into a new universe matter swallowed up by a supermassive black whole in another universe in a multiverse. Instead of a dead end in a black hole could a black hole be the entrance to an Einstein-Rosen bridge to another place or universe?
Wow.
I like that boundary-defining expressions such as "start of space-time" and "end of space-time" are used instead of time-dependent notions like creation. It's confusing to say space-time has been created. Being created implies a point in time when it didn't exist. How could there be a point in time before time was created?
How can you move north if you're at the north pole? Sometimes a coordinate system reaches an end point.
There’s a lot more out there than the north pole n our planet isn’t there. Perhaps it’s the exact same.
If it was created there must be a creator!
@@ronairgood1041 Doesn't make any sense, as any creator would then be asked what created them. At some point there will be an end to the causal chain, and anything that can come into existence without a cause completely violates our understanding of reality itself.
Space time can't exist if there's no space for there to be time in. If the universe didn't exist for even a fraction of a second then there would be no space time for that period. Which means that before was in a completely different space time than now is in.
I know from basically every astrophysics video ever that GR and QFT break down at the most extreme points in spacetime, but I don't know what that really means. Can you please explain the specific conditions under which these two great theories dissagree? How do their predictions differ? What can we actually observe? Thanks!
Super over-simplifying, and hopefully others will do better, but the main issue is gravity. Quantum mechanics expects a discreet particle called a "Graviton" that mediates gravity, much the same way that the photon is the discreet particle for electromagnetic energy. We haven't been able to discover (or create) gravitons, however we have discovered gravitational waves, which relativity does predict. In order for the theories to become reconciled, we need to find a quantum theory of gravity, which so far has eluded us. I hope this gives you at least enough to get started. ☮
@nhband1t Quanta Magazine published this clear-worded, artistically inspired video yesterday, discussing the exact matter of your question :)
th-cam.com/video/RIqVnFtOSr4/w-d-xo.htmlsi=lw0AewO5KNkEyESl
@@THE-X-Force discrete
Breaking down generally means that singularities arise i.e., infinities or 'divide by zero's. Generally infinities in a theory mean that the theory is probably incomplete because infinity doesn't really exist in the real world. Like how some properties 'blow up' to infinity when you attain the speed of light (I think this is because we have already assumed the constancy of speed of light and then tried to attain that speed such that the speed of light is not c but can be zero, so it breaks the initial assumptions).
QM has a shortest observable length where the short-wavelength light needed to measure it has very high energy. GR treats spacetime as continuous with supposed singularities in black holes and at the big bang. Much of the time they coexist but near those singularites they diverge. You can doubt that the singularities exist but what is there is not supported by any experiment done yet.
The quality of this free content is fantastic. What an exiting time to be alive!
And after we’re done here, we can watch a guy fall off a roof or something.
Space is lumpy gravy.
04:52 "...at the poles, where lines of *latitude* converge." Um... Um...
Longitudes converge
Latitude becomes a single point in …. Here we go again…
As the only part of this video my small brain could understand that tripped me up too, but I think if you language hard enough you could make an argument for either the lats or longs converging at the poles
@@Billionth_KevinLines of lat are parallel everywhere. They get shorter towards the poles. Lines of longitude converge at the poles. Matt made a slip.
Its always a treat to watch these videos and read all the comments of people who cant live without pretending they have all the answers. Whether they insert their god, or just assert an answer without proper justicication, it always makes me giggle
God could literally make the universe in an infinite amount of ways. No big bang doesn't actually mean anything much if it was true.
@@MrVontar 😂 anytime I hear "god could..." I just have to let out a big laugh. Please entertain me with how you know there is a god and how you know what that god could do 😂😂😂
@@MrVontarI seriously hope your reply is some kind kind of exercise in Poe's law because the dude literally just remarked on how a comment like yours is always guaranteed on videos like this 😂
@@wj2036Jesus overcame the world resurrecting thus defeating death proving eternity is a concept so ingrained in ourselves because it has always been a PART OF US FOR IT IS POSSIBLE.
He promised all of us a new body, new earth and heavens... Another universe.
I dunno about you but when a Man who singlehandedly fulfilled over 300 prophecies from texts 500 years before His birth talking about the coming of the Anointed Son of God, predicted His own death and Resurrection 3 days later... I would trust that Man.
Good thing Jesus is Real and denying so is going against basic historical knowledge...🥱
@@SisypheanRoller ya, obviously not everyone is going to agree with the premise of the video.
It sounds like a cosmological version of inventing super-symmetry even though you still have no idea where the neutrinos might be getting their mass from.
Correct me if I’m wrong, but didn’t Roy Kerr just come out with a paper proving that singularities in black holes don’t exist and are instead smooth rings? Kerr recently proposed that, in rotating black holes, the singularity isn’t a point but a ring-like structure
I'm pretty sure we've known about Kerr black holes since the 60s. In the sense we had the solution to the Einstein field equations that represent them
I read thru the comments here and my head is about to explode. Profoundly awesome.
So just like the Penrose diagrams, will this be another win for Penrose with his cyclic cosmology model?
you are in the know
I had thought of the universe after all particles decayed. I mistakenly thought that what remained was empty space, as opposed to Penrose’s description that what remains is radiation.
I thought that this empty space was possibly the ground of the next big bang. (I never liked the idea of a big bounce).
When I heard Penrose describe his CCC, I thought holy cow that actually clicks with me. I had an original idea that was similar to what Penrose thought!
If radiation is energy and energy has a mass equivalent, then maybe the radiation that remains can be gravitationally attracted to a new big bang, i.e. bounce.
My man, no it absolutely will not. It will be the most epic win of all time for Turok and Boyle's CPT-symmetric LCDM model
@@FAK_CHEKR But thermodynamics argues for energy dispersiing, not concentrating. Without a barrier to contain radiant energy, it'll just become more dilute with time. If there was a mass equivalent to energy, it doesn't seem to matter.
@@MsTyrie that was a last minute thought I added. I know it’s not Penrose’s thinking re CCC
This question is for anyone knowledgeable about General Relativity.
GR is generally discussed in terms of 3 dimensions of space and one of time. My question is. Is there a version with 4 dimensions of space, or 5, 6, 7, 8, etc. And if so, could we describe our 3D Universe and 3 large dimensions and say n dimensions rolled up like a straw.
Now where I'm going with this, is what if the singularity is the 3 dimensions locally rolling up into something small, but at the same time the other rolled-up dimension unrolling and becoming large.
And the same for "inflation" at the beginning of the universe. What if that inflation is the 4th dimension collapsing while simultaneously the other 3 expanding.
What would a higher dimension Generality Relativity theory look like.
This is the bridge to string theory. String theory mathematics work with higher numbers of dimensions... 10 and 26 are the numbers that are coming to my mind right now, but my knowledge of string theory is limited to books from the late 1980s and early 1990s and what's been discussed on this channel... and those additional dimensions are described as being rolled up and imperceptible to us the way you describe. As for what it looks like in GR, your guess is as good as mine, but I'm intrigued by your depiction of the singularity... reminds me of the old Disney sci-fi movie "The Black Hole"... which might still be possible, if wormholes are a thing or even if some of the ideas in this video are accurate.
I am not a specialist in SR or GR. I'm not a physicist.
You have to keep in mind that this is just an abstract mathematical coordinate system that attempts to describe the reality of the natural universe. A bit like navigation and contour lines on a map of the globe. It has to describe the actual universe and that is actually quite difficult because of the combined distance/time m/s issue.
The coordinate system we choose doesn't really matter as long as it describes the actual universe and doesn't get caught into the trap of the coordinate system describing the coordinate system, rather than describing nature.
(x, y, z) +'ct' or (x+ct, y+ct, z+ct) or (x m/s, y m/s, z m/s) and so on. We can get 0, 1, 2, 3, 4, 6, 7, 9, 11 common dimensions all attempting to describe the same thing :)
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More important maybe is to ask what is that nature that I am trying to describe. Is it a solid block of (x, y, z) all moving as 1 through time, or are each individual components all moving in (x m/s, y m/s, z m/s).
there is 2 different concepts that are called 4D ;)
Dimensions are a mathematical tool used to describe where stuff is. Dimensions aren't a real thing that the universe cares about. If you add more dimensions, it means you need more information to describe where something is. We only have 4 dimensions (3 spatial x y z, 1 time) because you don't need more information that that to describe where something exists. Adding another dimension doesn't make sense when we can already describe where everything is with those 4. We can shift around those dimensions into different forms, there's lots of alternatives but polar is the most possible (phi, theta, radius, time). There's forms in astrophysics where instead of time you use distance from start of universe and you're measuring time in distances.
You can create whatever you want but you'll only ever need 4 dimensions.
@@MyNameIsSalo "Adding another dimension doesn't make sense when we can already describe where everything is with those 4" The current 3 +t model is also problematic. It can be difficult in some concepts to be able to call it 4D as the ct dimension is a little abstract and disconnected.
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Polar/spherical coordinate systems are great for solid spherical objects, but run into issues when you attempt to describe things via photons path. That natural path distance/time is a little ambiguous and difficult to describe.
6 pseudo geometric dimensions is likely more practical, but even then they don't seam to accurately describe nature.
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A single space time geometry cannot function to the beginning of the universe as we have an event horizon in the way known as the CMB, beyond that the current model falls apart because we are describing a different relative space-time.
Matt- your truly a gift to all people seeking to learn science and the universe we exist in!
It may have started with a small bang.
Aahahaaa just like a little fart
@amymonroe1818 everyone talks about the big bang theory but nobody remembers the little bong theory
There is no time only time is the time we know. If that is ture the the " big bang" has not happened yet. And it's already happened and it's happening right now it's all one.
The JWST seems to have thrown some parts of cosmology into a little chaos.
Thank you. The big bang theory shouldn’t be dismissed but it is too often spoken of as a fact. Accepting unproven theories as fact can be limiting.
Can gravitational astronomy ever be "detailed" enough to peer beyond the "transparent universe"? It strikes me that one of our "issues" now is that we have almost no observational data from earlier than when the universe became transparent (outside the CMB if I am correct). But the universe SHOULD have been "transparent" to gravity earlier than that, right?
So I wonder if gravitational astronomy will be able to advance to a point where we can use it to examine gravitational data from earlier than 380k years after the big bang. In theory, gravity waves are everywhere and created by every interaction between masses, so it strikes me it's a matter of instrument precision to be able to get more and more detailed gravitational observations.
Can it ever precise enough to be doing things like mapping other star systems gravitationally instead oof by light, or perring into an opaque universe that still was awash in gravitational interactions?
If we ever got good enough with neutrino detection, and I mean REALLY good, we could peer into the cosmic neutrino background- that would allow us to see FAR past the CMB.
as @420Khatz said, neutrinos are an option (but we dont really know how to detect them well enough) - they would also allow us to study the "inside" of supernovae, so thee is a big interest
as for gravitational waves, we would need detectors MUCH more sensitive than the ones we have today, and more computational power to "disentangle" all the interference form other gravitational sources - but there already exists some evidence of whats called "gravitational background" (there's even a video here about it), but it's hard to interpret what it means
@@geekjokes8458 Ya the instruments of today for gravitational astronomy (GA) are very primitive and not very precise. But I think back to Galileo and his first crude telescope, and wonder if he could possibly imagine a time when that instrument was precise enough to see light from the earliest universe, or "light" from outside the visible spectrum.
Like, it seems today perhaps "impossible" to imagine the sensitivity and compute power to get to the very fine gravitational interactions that underpin the whole universe, but that's because we are Galileo right now, peering into a very primitive instrument for the first time. What will our GA telescopes look like in 400 years? I can only think they will be FAR More detailed with the ability to analyze MUCH less violent interactions than the equipment today can, just like Galileo could only resolve the brightest objects in the sky, and resolve them fairly poorly by modern standards ...
If we could? All we would see is an infinite fractal. Our 'universe' is just one small branch. In an infinite fractal of branches. B/c the 'universe' is either infinite or not? If it's the former, my assumption is probably true? If it's the latter? We live in the matrix.
The Big Bang is when the program starts.
A better question is how did we manage to survive before the beginning of PBS SpaceTime? 😮
For some reason an the concept of an infinite and / or eternal universe gives me the heebie-jeebies.
For me it's kind of comforting. Even if I make mistakes in this life, when it comes back around maybe I'll make some different choices and be better for it.
I think the universe having some kind of edge is just as weird
I really like to ponder all the philosophical implications of that
Would you rather live in a little snowglobe universe? And if so. What is beyond the snowglobe? Infitity seems to be the only answer
I get the heebie jeebies just reading the paper
5:52 I've been listening to this theme all the time and never asked what is it and who made it. It's so captivating!
Nothing in life is to be feared, it is only to be understood. Now is the time to understand more, so that we may fear less.
It's been 10 years since Matt took to hosting this show. For me it feels like.... well maybe not yesterday, but rather early this year.
10 years man. Thank you for the content.
I wonder how many people on earth can fully understand all the papers he referenced here
I often find mind-bending concepts approachable thanks to your presentations - thank you for sharing.
Ok, follow my line of thinking here... And yes, I know it's not a perfect analogy.
So, a person gets a cup, adds some water and soap. Then the person uses a straw to create a bubble. So, imagine that's our universe... It would have the inflationary period (when the person blows air) and so on...
So, from this bubble universe you wouldn't be able to trace to "anywhere" before the bubble was created, but it would still make sense to talk about something "before" that.
So... I don't know. Perhaps we should think in something similar. Or perhaps I'm absolutely wrong, who knows.
Sometimes I think other people's perception of space is very different. It so often seems to grasp at walls, at boundaries, because infinity somehow just isn't an option in their minds. Perhaps that is because we are mortal, so infinity pisses us the F off! lols Your idea makes more sense than the Big Bang to me, but I'm certainly no genius. Still, my question has always been, and still is; how does one get something from nothing?
@aylbdrmadison1051 Well, space is always creating new matter from nothing. Pairs of particles, matter and antimatter, that annihilate each other. And judging for the amount of normal matter out there and the lack of antimatter... Who knows, right.
@@aylbdrmadison1051Something from nothing implies a change. There could have just always been something. Here's a question, what if tommorow I started from ZF axioms and came up with an equation. I then demonstrate that the universe and the equation precisely align all the way up to you reading this sentence. Then do you really exist at all?
@@aylbdrmadison1051 Most people seems unable to think realistically about infinity, but also to avoid being humanocentric.
Personally, i think our current "model" is our modern version of the geocentric universe of the "primitive past".
"Still, my question has always been, and still is; how does one get something from nothing?"
A question easily answered by my personal theory...
Space and time have always existed, and when you have enough matter in one place, as in trillions of trillions of black holes as they are today in our known universe, eventually they collapse into themself, crushing subatomic particles so tightly that they explode to form a "big bang".
Only problem is, to confirm the possibility of my theory, we will need the ability to see far FAR beyond our current views.
A thousand times further is probably the absolute minimum that might let us see something that distinctly is NOT part of our own "big bang". More likely, a billion times more.
So, sadly, probably not in my lifetime.
@@aylbdrmadison1051 when the big bang was originally proposed, there was actually a not insignificant amount of pushback because it felt to similar to the creation myths of religion (before that point, steady state cosmologies where the universe lasted forever were more common). the fact that it's now widely accepted is less because humans like things being finite, and more because that's what our experiments have lead us to.
You still need to explain the CMB.
Never have I ever been so profoundly interested in a video of which I understood so little.
Where can I get the “Take Me With You” shirt in the video? I looked in the store and didn’t see it for sale 😢
Will the pbs space time store be selling the "Take Me With You" shirt again in the future?
You guys are a fundamental público service, you keep our mind awake and aware of the wonders of our universe. We need more channels like yours.
If the universe did not start from a big bang,…then all stars would have run out of fuel by now…
.and entropy would be 100% now?
That applies to a closed system. If the universe is eternal it is therefore infinite and not a closed system so entropy wouldn't increase.
@
Is eternal and infinite the same?
OK, truth be told it didn't start on the first pull...
The universe is a Beyblade. You didn't let it rip hard enough the first time lol
It needed a bit more choke...
@@thetobi583 LET IT *_big_* RIP!
it ain't got no gas in it
@@apokatastasian2831 He didn't clean out the tank from the last universe, and got a little water in it.
This is beautiful.
You're beautiful
why do we assume that we see the beginning of universe but not just an event occured on the part of the universe we are in. there are parts that we cannot measure, see, get information about?
It's a mouthful to say 'the last most relevant event to happen to our spacetime' instead of 'the beginning of our spacetime', would be the main reason to assume 'beginning' instead of saying 'probably the beginning'. Part of running these mathematical models is to start with probable conditions that they can think of and work with, given that the end result has to at least compare to the observable universe, some of which do contain conditions prior to events that resemble the big bang.
To me a completely static universe existing infinitely before a spontaneous big bang event doesn't sound much different than there being nothing and then the big bang. I imagine seeking consequential differences that may lead to new physics to be among the aims of this kind of work.
Yes, events that occurred before space and time were spread out enough to allow matter to cool into translucent gas must be inferred by observations of that matter since. I think it's generally called 'the hot big bang', but that could be a different thing entirely.
@calyesil You answered your own question. You cannot assume if the barrier cannot be crossed and you can't get any information about it. Physicists work with actual knowledge, not with lay people and their fanciful imaginations.
@@swingtopiadance2387 I answered your question. They try to solve both proposed models with new techniques, where there is a barrier and where there isn't, as described in the video.
@@lickenchicken143 My comment was to @calyesil
@@lickenchicken143 thank you. ^^
As far as I'm concerned, the script for this video may have well neen a string of random words.
I have some questions:
1. Did the cosmic inflation cause a gravitational wave?
2. If yes, was it a transversal wave like all gw we observe today or was it a longitudinal wave?
3. If it was a longitudinal wave, would it be a standing wave in the first mode and the wavelength of the universe?
4. If yes, would the wavelength increase and the frequency decrease over time due to the expansion of the universe?
5. If yes, and if we were in the fourth quarter wave in terms of time and if we add a linear expansion of the universe, would we observe an accelerating expansion of the universe without the need of dark energy to explain it?
I'm a bit concerned by the point universe. If the universe is infinite, you can shrink it as much as you want, it's still infinite!
If you talk about the visible universe... Then that's finite and you can imagine the singularity.
The problem is we don't know what's going on elsewhere...
If it's infinite then it doesn't matter what's going on elsewhere. If it's not, then it does. Paradoxical
@@nortonman5238 to be honest I don't really think it's really infinite... Just much much bigger than the observsble one and maybe like a bubble or a tore that wraps around.
BTW: the usual "solution" to the twin paradox is that you have to turn around and come back to compare ages. But if it's finite and used to be very small then one could come back without changing speed and direction... 🤔
Maybe that makes a very fast expansion mandatory to prevent that at the beginning... 🤔
Universe can't be infinite. Nothing physical can be infinite.
@@NeilGaede1 Why not? One thing that I do not like about these videos and other discussions the the use of the word singularity, that suggests a very finite sized point in space. If the big bang is infinite in size, then it can contain infinite matter and nothing that we have discovered so far breaks that view. The observable universe may have started in a singularity, but the observable universe may only be an infinitely small sub-section of the actual universe.
Symmetrically speaking, it bothers me that the universe has a finite past but an infinite future 🤔
Everything that exists (or will ever exist) has to have started at some time .. including everything _and_ time.
Could be an asymptote in time, the further you go back to the beginning, the more time is distorted, an infinitely deep time well.
No beginning, just a temporal asymptote
but what about the Poincaré recurrence
Pick your favorite spacetime symmetry where time is symmetric, make a symmetric universe and you have finite future and infinite past.
your own body is asymmetric.
your own FACE is asymmetric
I still feel like our universe is spherical. So many objects and movements tend towards the rotational or spherical, from the atomic to the cosmic. We just can‘t measure this because our entire universe is likely the equivalent of a pinprick on a balloon.
I think so too.
I don't think you understand what you're saying. A spherical or curved universe is like a balloon where the universe exists on the surface of the balloon (not inside it, only on the surface). So that if you start at one point in the balloon, travel in a geodesic around the balloon, you will end up in the same starting point by only having moved in 1 direction. Like if you keep moving north you somehow wrap around back where you started. That's spherical. It wraps around on itself.
We call our universe flat because like a flat surface, when you go in 1 direction you can go forever and you will never ever reach the same point. It's not flat in the sense that it is a literal flat plane.
There are pretty easy calculations you do in like 1st year astrophysics to experiment with different types of universe curvatures and when you map that to real supernovae explosion data, our universe comes out to being exactly flat with extremely high precision. There's like 3 different independent ways you can formulate that conclusion using data from different things, and when 3 independent studies all confirm the same thing then it's probably true. Another way is triangulation, a triangle in a flat universe has angles = 180 degrees, in any other universe this is not true. We can measure angles down to fractions of arcseconds of things billions of light years away to calculate this and things add up to 180, if our universe was even a tiny bit curved then it would deviate slightly (or deviate by a substantial amount, depends on amount of curvature)
@@MyNameIsSalo yes, I understand that. You’re operating under the assumption that our universe, everything that resulted from the white hole explosion, makes up everything that exists. That’s a safe, scientific assumption because all data we’ve ever been able to collect falls within those confines. I am not limiting my thought to that. I feel like it’s too egocentric to assume nothing existed before the Big Bang, or that we’re the only universe in existence.
Imagine trying to prove the earth is spherical when all you’re given is the grains of sand inside a child’s sandbox. No atmospheric or celestial data - you can’t look up at the sky. Your data collection can only come from within the confines of the box. Now imagine our observable universe is that sandbox; each grain of sand, a galaxy. You could triangulate from the farthest possible reaches of your confine and still fail to come even close to being able to accurately discern the curvature.
@@MyNameIsSalo slight pedantry to add on -> the universe CAN be "that big" where that potential curvature is feasibly unseen in our observable universe. I'm sure you've gone over that at some point, but it is fair to point out in this context.
Maybe “the beginning “ is asymptotic- there’s no time then
A time singularity.
“Before “ is meaningless
Yesss
regardless if there was a before the big bang or not doesnt matter because we will never know.
its one of the questions scientists dont care about same as if is there and outside the universe.
those are questions that can never be answered and therefore have no meaning.
they do work quite well in confusing people tho.
just because t
A glimpse into great contemporary physics. Thanks!
2:27-2:45
Perhaps... If... could it... if so... perhaps...
Gotta love that science.
Would you prefer scientists act like priests and assert as 100% fact that which they can't know for certain?
@@doctorwebman The problem is they already have declared themselves High Priest of reality..
@@FarSeeker8 when superstition is praised like you do, fear the worst for humankind.
Scientists are the reason we have technology and science to begin with, certainly not priests of any religion.
@@snarckys3063 Re: Wikipedia, "European science in the Middle ages" and "List of Medieval European scientists".
Christianity took "natural philosophy" and created Modern Science. Before that what was accepted was at the whim of pagan gods and emperors.
Otoh,
Look at what Atheists have accomplished in the USSR, PRC, and other nations where they have ruled exclusively: mass death and societal abuse.
@@snarckys3063 When propaganda like yours is widely accepted, we have nations like the USSR and PRC.
Christians are responsible for turning “natural philosophy” into Modern Science. The world has seen the greatest advancement in science and technology in Christian influenced areas.
Your Argument Fails.
Sometimes my grocery prices feel like they’re experiencing cosmic inflation.
Populist emotionalism has replaced logical reasoning. In that process "for ourselves and posterity" has been truncated to "for ourselves."
I firmly believe the universe is a 4D object moving through the 3rd dimension. If you take a 3D circle and pass through the 2nd dimension, it would look like it suddenly appear as a dot and keep expanding. Which is what our universe is like. Maybe at some point, it stopped expanding and started getting smaller. The end of the universe being everything returning to a single point.
But what about a rotating universe?
The universe has no center to rotate about and nothing to rotate inside of.
ROFLMAO... Sweet... imaginary variables that cannot be measured... imagine the funding that could be milked from the lemmings
When you spin, it is the universe that rotates: relativity. Also. Gauss.
@@filonin2 Sweet Point for a Moot Variable +5 points
@@rigelanderinvincent724 Gauss... giggle...
There was no beginning and there will be no end. The energy was always here and always will be. We and everything are this energy. We are all one, infinite consciousness.
No one cared when pbs spacetime had 2.71 or 1.61! What gives? You're all a bunch of constant discriminators
Are we just assuming that all of spacetime is trackable back to a singularity or is there direct evidence? Is there evidence against the idea that the universe already existed before the big bang and that the expansion resulted from an unknown incident within that preexisting universe?
The only "direct" evidence is the assumption that because it's expanding now then it must have been smaller before
We've traced how the universe should have been back in time pretty close to the big bang, and so far observational evidence (like cosmic microwave background) supports them. Ofc we can't see the actual moment - if we could we'd just be able to see the answer to our questions directly.
I think the idea is that the current theory "big bang theory" may not be the only theory. That had a singularity which started the universe. Other theories such as the idea that there are multiple universes in space time that push and pull against each other. Using geodesics to find the singularity that started our universe could prove or disprove the big bang theory. If matter traces its origin to several points instead of one, it would prove there is matter from outside our universe. We assume there is a singularity that started the universe because matter is expanding in ALL directions.
@@MasterGhostf There are also things in their model for which they have no explanation. They needed to propose a period of accelerated expansion without providing a natural mechanism to explain it. New discoveries seem to show large galaxies too soon after the proposed beginning. So-called dark energy and dark matter further illuminate our ignorance. I don't think that the level of certainty scientists demonstrate is justified. Then again I'm not an astrophysicist.
@@MasterGhostfit’s extremely unlikely that the Big Bang would ever be disproven, there’s just an overwhelming amount of evidence that supports it. It’s possible that the Big Bang is a small part of some larger event though
It did begin with a big bang but there were previous attempts. Some of that is still there. That's why people are getting confused
Roy Kerr contends there's no singularity.. let's investigate that for a singularity to exist under Penrose's theorem the black hole would have to be non-rotated which is never been observed so the probability that a singularity exists is infinitesimally small.
There is a singularity (in the sense that all trajectories end up on it), but it is not infinitesimally small. If we quantize that, then the singularity is, of course, a geometric space with well defined volume. That's what string theory is trying to do (no matter what we may think of the results, so far). The only way to actually verify any of this would be to create microscopic black holes in the lab and then to follow their decay channels, for all I know. That would allow us to learn something about the "inside". There is just no detectable signal coming out of a macroscopic black hole. I don't know if scattering of e.g. light near the event horizon can tell us anything of importance. My guess is that not even that gets us there. The no hair theorem is attenuating everything that is on the inside way too much.
@@lepidoptera9337 ONLY if the black hole is non rotating... Which doesn't exist in nature. Penrose is built on Schwarzschild which simplifies Einstein to get a solution but it assumes the black hole isn't rotating. Nothing is never not moving.. there's no singularity., at least based in Penrose's theorem.
While explaining a possibility of the Universe not having a beginning at the Big Bang, he just provided even more information supporting the Big Bang. Gotta love science!
Could not agree more with your last point. Irrespective of whether or not we derive an answer or the answer and how would you know anyway but the mere fact that we can hypothesize about what happened at the start of time is weirder than that we exist
My head hurts after that 😅
Total click bait 18 minutes to say yea the universe did probably have a beginning spare me the one case that makes extreme assumptions to say that in some other universe there is no beginning when you just end up back to where we’ve been that is that our universe had a beginning as far as we know total waste of time this is mathematical philosophy click bait
I love watching your videos even if I only understand what you’re saying about 20% of the time 😅
The universe is a creation dreamt up by Azathoth, the Blind Idiot God.
I thought it was Maturin's half-digested Big Mac.
@@sar4806 eru ilúvatar clearly, just to put this argument to bed
@@johndocherty-273 Nah, this one was Azathoth's fault.
@eruiluvatar236 sorry my bad forgot we live in a quantum deity megaverse
That would certainly explain the existance of humans.
My mind,
focused on space and time,
trying to find,
by rewinding time,
Answers divine,
Spread out trought space and time,
Hidden in plain sight,
The riddle of lifetime.
Truly a fascinating video!
Still the best channel out there.
00:14 rewinding you shrink with the wave, you dont pause your current time dilation, zoom in at any point and the observable universe always looks the same size and scale
Neither a lofty degree of intelligence nor imagination nor both together go to the making of genius. Love, love, love, that is the soul of genius.
Awesome video! 👌 There's still something that must be emphasized with regards to the _probable_ beginning of the Universe: the very notion of a beginning makes use of time and space, as any thing that begins has to do so at a particular time and space.
In the case of the Universe, there seemingly is no other time or space prior to it, meaning there wasn't ever a time or space when and where the Universe wasn't: in other words, even and especially with a proven beginning, the Universe is eternal and omnipresent, necessarily, as it always existed and will always exist, everywhere. Food for thought.
Outstanding - like always! At our current understanding, while most things seem to point to a singularity for the birth of the Universe, one dramatic discovery could shift everything. Such as truly grasping the nature of dark energy, quantum entanglement, or any of the many mysteries we've yet to fully grasp. Then, even an expanding universe may no longer be universally true, at least from all perspectives. I'm confident that humans, math, imagination, and probably A.I. will figure out quite a bit in the next decade or so, and I'd be willing to bet that our new understanding will change everything!
It will. And it won't involve unsolvable mysteries like DM, DE, and faster-than-lightspeed inflation. That isn't the stuff of physics.