The Scariest Place in the Universe Nuclear Engineer Reacts to Kurzgesagt

So, assuming faster than light, tech. Alright, uh... It's time for some more Kurzgesagt. Specifically, Supervoid. The scariest place in the universe? Maybe the loneliest. For those of you who don't know me, I'm Tyler Fulce, I'm a nuclear engineer with a little over 10 years of experience in the commercial nuclear power industry. I'm engineering operations to emergency response. I don't claim to know everything there is nuclear, but I can certainly share some knowledge. Let's see what's so scary about it. The cosmos is voids. Gigantic, unfathomably large spaces of empty nothingness. Yeah, density figures out to about a hydrogen atom every few cubic meters, compared to a densely packed nuclear reactor at thousands of kilograms per cubic meter, or air at about one kilogram per cubic meter. So, the universe in general is pretty empty, but the voids are that extreme end of emptiness. Though, it isn't exactly nothing. It's still something. You still have dark matter, trace gas, radiation, and quantum fields. After all, even the best vacuum chambers that you design on Earth still have millions of particles per cubic centimeter. But these voids are going to be the largest low-density regions that have been observed. Bubbles of eternal night stretching hundreds of millions of light-years, almost entirely devoid of galaxies, stars, or light. So, let's think about this for a sec. Hundreds of millions of light-years. The Milky Way galaxy is only about 100,000 light-years across. So, this super-void is thousands of times larger. And galaxies itself are already fairly sparsely populated. You could theoretically fly through the entire galaxy without hitting it. But you still have some dark matter kind of acting as the scaffolding of the fabric of the universe. And galaxies form where that structure becomes dense. Theoretically, anyway. There's a whole lot about this sort of stuff that we just don't know. These voids are where the structure never accumulated enough mass to collapse in the galaxy. The loneliest places in existence. Voids are not just the absence of stuff, but weird worlds of darkness that are growing. Thank you for saying that. Similar to plasma physics or fluid instability. When density variations exist, they have a tendency to grow over time. So, you end up with something that looks kind of foamy or bubbly. Or this cosmic sponge, dark sponge here that you see right here in the illustration. Drifting, colliding, and merging with each other. Inside them, space itself is stretched violently. So, it's about matter flowing outward to denser regions. And cosmic expansion is going to be a little faster in low-density regions. Kind of like air bubbles rising in water. The density gradient is driving motion. Now, there's nothing really stopping you from any of them over time. Point a spacecraft at them, you'll get there eventually. But there's nothing really remarkable worth visiting there. Maybe that's what they're getting at. It's more of the why, not the you can't. But provided you could leave your galaxy and expend that much energy to do so, that energy cost is larger than anything the void would do to stop you from going there. Voids are weird and scary. But they sculpt the entire universe and may ultimately decide its fate. That's a good description. Kind of like astrophysicists referring to it as the cosmic web, where you've got filaments, sheets, clusters, bubbles. Those voids take up a lot of that volume and push it into clusters. Today, we know of over 8,000 voids and supervoids, and we keep discovering more. No matter how large a cluster or supercluster of galaxies gets, there always seems to be an even larger void nearby. Kind of like a fractal system where patterns repeat at multiple scales. I mean, no, this isn't going to be a perfect fractal, but certainly a resemblance. Jump off the cosmic cliff and drop into the heart of cosmic nothingness, the loneliest place in the universe. Okay. You're zooming away from Earth at thousands of times the speed of light, leaving our... Okay. So assuming faster than light tech. All right. I'm sure it's just to visualize it. Otherwise, it would take too long to explain there. But, yeah, unfortunately, we haven't found out a way to go faster than the speed of light. Darn special relativity gets you every time, doesn't it? Our solar system and our solar neighborhood behind. Now, we see the entire Milky Way with its 200 billion stars and dozens of dwarf galaxies zipping around it. And each star is a massive nuclear fusion reactor with enormous energy output, planetary systems, raw materials, which just shows you the sheer resource potential of galaxies. Of course, in this video, if we have technology capable of going faster than light this quickly, leaving our galaxy behind, going that much faster than the speed of light, yeah, we're probably beyond these material resources at this point. Probably a Kardashev type three civilization is the assumption in this video. Two and a half million light years away on a collision course is giant Andromeda and its own swarm of satellite galaxies. That one's bigger. We're now moving a million times faster than the speed of light, seeing the local group of over 50. If we went that fast in a matter of seconds, we're going way over a million times faster than light. A million times faster than light would still take you over a month to go from one side of the Milky Way to the other because the Milky Way is 100,000 light years across. ...woven together by gravity, rivers of gas, and invisible scaffolds of dark matter. What's interesting is this one is bound, this local group, meaning that cosmic expansion will not tear it apart. It's bound gravitationally. I guess we can think of it as being on the same scaffolding, the same universal structure that isn't going to expand away from each other. This is our pocket of the universe, 10 million light years across. No human will ever leave it. Okay, so they're getting at the accelerating expansion rate of the universe that distant galaxies will eventually become unreachable, even if you travel near light speed forever. But if you're traveling faster than light, this much faster than light, then yeah, sure, you can absolutely reach it. But again, we're talking hyper-advanced type 3 civilization technology here, which is far beyond our horizon. So yes, it would be as impossible as traveling faster than light. For you, apparently. As we zoom away even faster... Does that mean I'm not human? ...the Virgo Supercluster, a colossal wall of more than 2,000 galaxies spread over roughly 100 million light years. Careful now, you're right on the edge of the cosmic cliff where the true deep darkness begins. Cosmic cliff. The local void, a gigantic empty bubble 200 million light years across. So that's the adjacent structure to our galaxy group. It's one reason why our galaxy is apparently moving away from that section of the universe. That is to say, we're being gravitationally pulled to denser structures and away from emptier ones. If it was a bright thing and not absolute darkness, it would fill 40% of the night sky we see from Earth. All around us are dozens of such superclusters and gigantic voids filled with suffocating emptiness. I appreciate the delivery, but no more suffocating than space in general. Traveling towards the greatest and emptiest nothing in existence, right into the center of the Boötes Supervoid, a cosmic desert around 300 million light years wide. So gigantic it should contain thousands of galaxies. But instead, what do you see? You're surrounded by perfect darkness, the most absolute blackness the human mind can conceive. I mean, you'd still probably see some distant galaxies faintly. Ironically, if you're in that much of a dead zone, the universe is transparent enough that light from billions of light years away can still reach you. So it's weird you could technically see farther because there's nothing blocking you. Kind of analogous to if there's a lot of light pollution in your area, you can't see stars. But if you go out into the country where there isn't any, then you can see more stars. Just on a much, much grander scale. There is no up or down. No motion. Nothing to order. I mean, other than those microscopic things you can't see and the really big things that are really far away from you, but I get the picture he's trying to paint here. There's not a single sign that the outside universe even exists. It's an inescapable prison. And this isn't some exotic corner of the cosmos. This is how the vast majority of the universe feels to human eyes. I mean, this is all based on assumptions here. Just silent blackness without any movement. Everywhere, forever. Although there is something mysterious hiding in the dark, faint tendrils of dark matter penetrating into the void like cosmic lichen. It's believed to make up about 85% of the universe's matter content. I mean, without it, galaxies probably wouldn't have formed at all. The gravitational skeleton of the universe, if you will. A miniature echo of the much larger forest of dark matter filaments that forms the scaffold of galaxies and galaxy clusters outside the void. And at their tips, we find faint bluish specks in the ocean of darkness. Void galaxies. Lonely fireflies unable to light up the night. These are fascinating. And blue is actually a good choice. It's not just an artistic thing. Because they're smaller, they're gas rich, and they have younger stars. Hence the blue. But they rarely collide with other galaxies like what Andromeda Galaxy is supposed to do to the Milky Way. Hopefully it'll turn out better than that. But anyway. Rarest galaxies we know. Very isolated. Very lonely. A universe of bubbles. Before we could look deep into space, astronomers thought we lived in a uniform cosmos with galaxies spread out evenly. But instead, we found that galaxies, cosmic gas, and dark matter were arranged into a vast cosmic web. A recurring pattern of sheets and filaments organized around enormous empty gaps, meeting at dense knots with galaxy clusters and superclusters. But this structure is not static. It just seems to be because the distances between galaxies are so incredibly vast. In reality, galaxies shoot through space at speeds of millions of kilometers per hour. They're on collision courses, orbiting each other, moving towards the center of larger galaxy clusters, millions of light years away. But they always seem to stick to the rims of voids like reflections of light on soap bubbles. Which is kind of weird. If they're this dynamic, shouldn't a galaxy shoot into a void occasionally? Well, voids are actually extremely hard to enter for galaxies from the outside, at least naturally, because gravity becomes weird at their edges and even weirder deeper inside them. That could be one evidence, like how people talk about allegedly seeing structures orbit distant stars. This could be the next level of that and say, hey, this is an evidence of a type 3 civilization that's just going to take galaxies and flick them into voids. This would be a pretty powerful type 3 civilization, by the way, in order to do something like that. To know better, you might think voids spit out anything trying to get inside, pushing galaxies to the edge. The way gravity works is that everything with mass... That's actually a decent explanation of that. Is gravity from the surrounding dense matter just going to pull things out? Kind of like how mass flows away from lower pressure regions and fluid mechanics. That's something that you optimize all the time in a reactor cooling system. It's all about fluid flow, mass flow rates, thermal profiles, heat flux, radiation flux profiles. It's really all about fluid flow. Doing this on a massive intergalactic scale is interesting. ...attracts every other thing with mass. And since there's almost no mass inside, the cosmic web of galaxy superclusters on their edges are pulling things out of voids. The emptier a void is, the harder gravity is pulling on what remains. Dense regions pull matter outward more strongly than the relatively weak matter inside the void. So matter migrates towards filaments and clusters. It's really like a tug-of-war where one side isn't even trying. Over time, voids are really only getting even emptier and the walls and knots around them denser and brighter. Would it be hard to fly into a cosmic void with a spaceship? Well, not technically. The hardest part is escaping the gravity of your home galaxy. Yes. It also doesn't make much sense because what exactly do you want to visit inside a void? It makes sense to fly into a void if you want to hide. Yeah, you could hide, or maybe it's a shortcut to get to galaxies on the other edge of the filament. Of course, you're already using some sort of faster-than-light hyperspace technology to do this anyway. So, and hyperspace might not be structured the same way as real space. Okay, we're getting into sci-fi territory, I know. But, yeah, I'm trying to think of reasons myself. Really, really hard. But what cosmic horror would be scary enough for a civilization to try to escape into a cosmic void? Galaxies in the crowded cluster regions like our Milky Way are very active. Since its neighbor's gravity tugs and pulls at it, they collide and merge. Void galaxies are so isolated that they're aging in slow motion. They tend to be smaller, bluer, and full of gas, birthing new stars slower and calmer. So void galaxies could be the last places that will stay habitable in our dying universe. That's plausible. I mean, these small galaxies with reserves could have stars that last on the order, well, not individual stars, but they could be forming stars on the order of many trillions of years instead of mere billions. The last star in the universe will likely be born here. So maybe in 100 trillion years or so, a desperate alien race will embark on an impossible journey to stretch their existence just a bit longer inside a void galaxy. There's one more thing that makes voids unique places. Dark energy. The mysterious force that most scientists think is accelerating the expansion of the universe and will ultimately cause its demise. Okay, this is what was observed through supernova observations. I think as early as the 90s. Yeah, dark energy makes up a lot of the energy density of the universe, and we don't exactly know how it works. I know, frustrating. We can't see dark energy do anything inside our galaxy or inside clusters because there's too much stuff putting things together via gravity, but we can see its effects inside voids. Yeah, there's very little matter, so all you really have to go by is the whole cosmic expansion. Here, dark energy blows up the bubbles of nothing. This is where the acceleration of cosmic expansion becomes visible. As voids are getting larger and larger, they're breaking the structure of the universe. The beautiful galaxy filaments are... I have to say, I really like the sound design in this video. I mean, I guess visually they're showing so much empty stuff that's kind of where they got to put all their energy, and I really appreciate it. ...being ripped apart. As the emptiness encroaches, walls of thousands of galaxies are thinned out and pulled towards the edges, attracted by much denser regions at the margins, giving space to the emptiness of two void bubbles becoming one. In the far, far future, supervoids will take over the observable universe, crushing clusters and expanding further and further until the entire observable universe I mean, the main structures will eventually become isolated on long enough timescales. So he's getting at distant galaxies disappearing beyond the Hubble horizon, and galaxies merging into local clusters. Yeah, that was real uplifting. So to me, what's fascinating is this just reveals that the universe's average energy density is insanely low. I mean, galaxies have stars and black holes and all other kinds of big, fascinating celestial phenomena, but they occupy almost none of the volume of the universe. Kind of like in nuclear power plants, where we deal with really dense fuels, very high energy densities, but very compact reactors. I mean, after all, the galaxies do consist of a lot of nuclear reactors, but there's a lot of really big fusion reactors called stars. So that's really interesting. Thanks so much for the recommendation, and thanks so much for watching. I'll see you next time.