What does it mean for the universe to have a center? Could we ever travel to ours? What is a singularity? I discuss these questions and more in today’s Ask a Spaceman!

This episode is sponsored by BetterHelp. Give online therapy a try at betterhelp.com/spaceman and get on your way to being your best self. Visit BetterHelp to get 10% off your first month!

Support the show: http://www.patreon.com/pmsutter
All episodes: http://www.AskASpaceman.com
Follow on Twitter: http://www.twitter.com/PaulMattSutter
Read a book: http://www.pmsutter/book

Keep those questions about space, science, astronomy, astrophysics, physics, and cosmology coming to #AskASpaceman for COMPLETE KNOWLEDGE OF TIME AND SPACE!

Big thanks to my top Patreon supporters this month: Justin G, Chris L, Alberto M, Duncan M, Corey D, stargazer, Robert B, Tom G, Naila, Sam R, John S, Joshua, Scott M, Rob H, Scott M, Louis M, John W, Alexis, Gilbert M, Rob W, Denis A, Jules R, Mike G, Jim L, Scott J, David S, William W, Scott R, Bbjj108, Heather, Mike S, Michele R, Pete H, Steve S, wahtwahtbird, Lisa R, and Couzy!

Hosted by Paul M. Sutter.

 

EPISODE TRANSCRIPTION (AUTO GENERATED)

Its name is Yggdrasil. In Norse cosmology, it's a sacred tree. An immense ash that sits at the navel of the world. It is the axis of the universe. The gods assemble under the tree to make their deliberations.

Great creatures make the tree their home, including a dragon, an eagle, and 3 stags. Its roots stretch for miles beneath the earth, and its branches grow all the way to the heavens. And it is the source of Ragnarok, the end of days. Yggdrasil is just one of many great trees found throughout mythical cosmology. Indeed, it's just one variant of an almost universal theme, an axis mundi, an axis of the world.

In many cultures, it's a tree. In many others, it's a pillar, or a spire, or a mountain. In some cultures, it's a holy site within reach, something that exists on the far edge of the horizon or in the center of a city. In others, it's purely mythical, told of only in legends and stories. The axis mundi connects all the realms of existence from the subterranean to the earthly to the heavenly.

It is the central fulcrum of all existence. Every cosmology has an axis mundi. A center of the universe. But what about modern cosmology based on physics and observation? Where is the center of our universe?

The center of the big bang. Where did it all come from, and if conditions are right, where will it all return to? Well, let's follow the journey of modern cosmology from its birth in the Capernican revolution to see where the axis mundi, the all important center of the universe, has ended up. Throughout the middle ages, in Europe, astronomers gained an ever increasing understanding of the cosmos, and they developed a cosmology. This cosmological model, this structure of the universe traces its roots to, Claudius Ptolemy, who lived somewhere between a 100 and a 170 AD.

And, of course, it was tweaked and modified and expanded, but this is the roots if we're if we're looking at the Scientific Revolution, which started in earnest in the late 1500 in Europe. This is the model they were dealing with, and so it's called the Ptolemaic model. And in this model, the Earth is at the center of the universe. It is the axis moon d. It's not a location on the Earth that is the center of the universe, but the earth itself is the center of the universe.

And surrounding the earth were these series of crystalline spheres, because they had to be transparent because because you can't see them themselves. In each one of these spheres, they were all nested against each other, and then each one of these spheres carried with it a a object. There was one for the sun, one for the moon, one for each of the planets, and then at the outermost layer was the ultimate shell that carried the stars. And all these spheres circled around each other to give the appearance of the changing night day cycle, the changing of the stars, the movement of the planets, and so on. And the Earth being at the center wasn't just a matter of observational obviousness, like, duh, everything is moving.

We're not. Do you feel like we're moving? I don't feel like we're moving. Every everything else is moving, but not the Earth. Makes total sense.

And as the centuries went on, it also got folded in this this idea of the earth being at the center of the universe got folded into theology, into, into Christian mythology, mixing it in with the biblical narrative. Like, there was in in European Christian minds, there was something different about the Earth. We had people. We had plants. We had rivers.

We had Jesus. Jupiter didn't get Jesus. We did. That's kind of important. The planets were just dots of light that moved.

The stars were dots of light that mostly didn't move. Occasionally, they would move, and that'd be very weird. But, generally, like, they just all followed their own tracks. The sun and the moon were, you know, the sun and the moon, but the the model just worked. It didn't, like like all non physical cosmologies, this model of the universe worked on multiple levels.

It didn't just explain physical observations, but it also explained certain spiritual needs. And it worked. Ptolemy's model worked. I mean, almost beginning as early as 13th century, Arabic astronomers had started to find some inaccuracies. And so, by the time Nicholas Copernicus rolls around in the late 1500s, everybody who was anybody knew that something was up with Ptolemy's model and that it needed to be replaced with a better model, but nobody knew what that better model was.

If that sounds familiar, that's basically the progress of human understanding. So Copernicus really did propose something revolutionary. He changed the axis mundi. He changed the world tree, the center of the universe, to not be the Earth, but to be the sun. He placed the sun at the center of the universe.

I'm saving a discussion of Copernicus and the Copernican revolution for another day, so please feel free to ask because it's very nuanced, and it is not very much not the narrative that's told of yeah. Well, I'll save it for another day. We'll just we'll just leave it at that. Feel free to ask. It's a very interesting, fascinating subject, with so many facets in it.

I'd love to dive into it. But, anyway, this idea of placing the axis mundi, the center of the universe, at the sun, he published it on his deathbed and it was met with mixed reception. Like, a controversial movie that everybody agrees is a work of art, but it doesn't necessarily have a great plot. And and, by and large, it took over a generation for people to even start debating this idea fiercely. And there were pros and cons to this idea.

On the pro side, there were observations made by Tycho Brahe, perhaps the greatest astronomer to ever live, especially if you ask Tycho Brahe, where he was able to measure the distance to a comet that passed by, and he discovered that the comet was well outside the orbit of the moon. And so this is weird because, like, what crystal sphere does the comet belong to and why doesn't it fit into all the other crystal spheres? This is kinda messed up. We have his student, Kepler, which I did do some episodes on, who is an amazing person, who figured out that the planets move any ellipses, and it's kind of hard to have nested ellipsoids rotating within each other in a nested way, that kind of grinds to a halt very quickly, and so that that doesn't quite work. We have Galileo, and Galileo obviously deserves an entire episode to himself, who discovered all sorts of imperfections in the universe, like the phases of Venus, the moons of Jupiter, the Milky Way has tons of stars, the moon is full of piles of rubble.

All of this pointed in the direction that, hey, maybe the Earth isn't at the center and maybe Copernicus was on the right track with putting the axis mundi on the sun. But there there were some solid arguments against this idea. Tycho Brahe, again, the same comet person, said, like, hey, if the earth is orbiting around the sun, we should be able to measure a parallax distance to a star. I can't. And so either the sun is not at the center of the universe and the earth is not moving, or, the stars are ridiculously far away.

And nobody liked how far away the stars had to be in order to make that work, and so everyone's like, yeah. Okay. Fair point. Fair point, Brahe. Score 1 for you.

And then also there is the obvious thing, like, wait. You're saying the entire planet Earth, this gigantic ball of rock that we live on, is moving? I don't feel any wind. I don't feel any lurching. I'm not getting motion sickness.

What is going on? How how do you get a giant ball of rock to move? It would take over a century for these debates to finally be settled and it wouldn't really be resolved until Newton developed his theory of universal gravity. And once he did, once there was this combination of both powerful observations and a powerful theoretical framework, once you had both, then the intellectual community agreed that, okay, the axis Mundi is placed firmly on the Sun. The Sun is at the center of the universe.

In 17/85, 2 centuries after Copernicus moved the axis Mundi to the Sun, another great astronomer, William Herschel, attempted the unfathomable, a map of the entire universe. Now keep in mind, he's doing this before we even know the distance to the nearest stars. We have no confirmed distance that wouldn't come until 1833. So we have no idea how far away the stars are, except that they're super far away. We had figured that out.

So to build this map, he had to make a couple assumptions. One, he assumed that all stars have the same intrinsic brightness, that they all have the same fundamental level of brightness. And so that the dimmer they were, that meant that farther away they were. And that if he counted all the stars he could see in a given patch of sky, then this was proportional to the total number of stars in that direction, even the ones he couldn't see. Looking back from the 21st century, these are two really, really bad and incorrect assumptions.

But considering that he had no idea what he was doing and he was making it up on the spot, you know, we have to give him some credit. If only he had a Patreon, that's patreon.com/pmsutter. If he had a patreon.com/wherschel with some decent fan support behind him, I think he could've taken some better guesses and gotten more progress, but he didn't. But, thankfully, I do. And that is how you can keep this show going.

I truly appreciate every single contribution. It is making this show possible. That's patreon.com/pmsutter. If you want if you're asking, how can I keep getting Ask A Spaceman? This show is so wonderful.

1, thank you for saying that. And 2, if you're saying, how can I keep this going? Patreon.com/pmsutter is your answer. I really, really do appreciate it. So with these assumptions, getting back to our story, Herschel made a map.

And it's an amorphous blob. It kinda looks like a giant amoeba with the sun kind of near the center, but offset just a tiny bit. And this amoeba was definitely wider than it was thick. Cool. That was that was our first attempt at a physical map of our universe based on observations.

Fast forwarding a bit to 1920, the Smithsonian Museum hosted The Great Debate. The original topic was supposed to be Einstein's theory of relativity, but the organizers quickly discovered that not enough people understood the theory of relativity in order to debate it even coherently. So instead, they went with an easier problem of the size of our universe and our position within it. Essentially, they were asking in this great debate, according to the best that modern astronomy could offer, where was the axis Mundi? In one corner was Harlow Shapley of the Harvard College Observatory arguing that the Milky Way was the entirety of the universe and that these weird spiral nebulae like Andromeda were simply small bits of the Milky Way, which was synonymous with the universe.

And that the sun sits away from the center of the universe, and that the universe was was large, like over a 100000 light years. You know, that's that's large for the time. He had evidence for it. He said that for Andromeda, this spiral nebula to be both big and faint, it had to be if you want it to be big and you want it to be kinda dim, it has to be enormously far away, which I mean, we're talking way more than a 100000 light years away, which is just ridiculous. He also observed a nova in Andromeda that briefly outshone the entire thing.

And if Andromeda was a separate galaxy away from the Milky Way, then the Nova was hilariously comically way too powerful. This is I mean, what kind of energies are we talking about here? In the other corner was Hebert Curtis of the Alleghany Observatory arguing that the Milky Way was but one of many island universes with the Andromeda Galaxy another island universe separated by a vast gulf of nothing. Bauotti argued that the sun was at the center of the Milky Way and that the Milky Way was on the small side about 30,000 light years in diameter. And the winner was Edwin Hubble who didn't even participate in the debate and showed that everyone was a little bit right and a little bit wrong.

The sun was not the center of the Milky Way galaxy. The Milky Way galaxy is huge. It's about a 100000 light years across. Island universes, aka galaxies, are a thing, and that the universe is indeed ridiculously, comically gigantic. Oh, and that Nova scene in Andromeda, yeah, it turns out that those are, amazingly powerful after all.

And, yeah, supernova can briefly outshine an entire galaxy. Okay. New information, new map, new data. You know, it's not so much. I I I'm a fan of the Ptolemaic model.

We can do the get more into this when I talk about Copernicus. It was a valid model for the data that we had available. I mean, come on. That's science. I hope a 100 years from now, a 1000 years from now, we have a different cosmological model.

That means progress is happening. Don't knock it. And the Ptolemaic model put the axis mundi at the earth, which was already an inch towards physical cosmology because it wasn't some mythical place where we put it. It wasn't like a mountain spewing fire over there. Like, oh, that must be the center of the universe because, duh, it's it's a mountain spewing fire.

I mean, come on. Instead, it was based on observations. Everything else is moving earth, so we must be the center of the universe. And then more data came in, more theories came in. We moved the axis mundi to the sun.

Then more data come in, more theories come in. Now where's the axis mundi? It's not the sun. We're not at the center of the Milky Way, but is the Milky Way the center of the universe? Where is this axis Mundi?

The last time the axis Mundi moved from the Earth to the sun, it moved through a combination of observations in theory. Starting with Copernicus and ending with Newton. And this new shifting, this new placement of the axis Mundi would require not just observations, not just Hubble's observations like, hey, galaxies exist. That's kinda cool. The universe is gigantic.

It would also require a massive theoretical update in our understanding of gravity, which came of course through Einstein's theory of relativity. Gravity is essential for understanding the large scale universe Because if you think about the forces of nature, you've got what? Strong nuclear force, which is atomic scales. Okay. That's not going to affect the large scale evolution of the universe.

You've got the weak nuclear force, which is kind of the laughing stock of all the forces. Let's be honest. That's not going to affect the large scale evolution of the universe. You've got electromagnetism, infinite range. That's cool.

But on average, the universe is neutral. There are as many positive charges are there are there are negative charges. So, yeah, electromagnetism just isn't gonna do much. The only force left that can impact large scale things is gravity. And so as soon as you develop a theory of gravity, you're going to start asking about the large scale evolution of the universe.

Newton did it when he figured out gravity his way. Einstein did it when he figured out gravity his way. Early on, Einstein developed a rudimentary cosmological model. He found that the universe was naturally in a state of motion, which went against the prevailing wisdom at the time. Everyone thought that the universe at large scale was, Yeah.

Like planets move and stars move, but the universe itself is static. Einstein found that this was a highly unnatural and unstable situation, but Einstein didn't like this result. It's one of the few times in his life that he preferred observations over the statements of his own theory. So it was for other scientists to pick up the slack. There's the Belgian Georges Lemaitre, the Russian Alexander Freedman, the American Howard Robertson, and the British Arthur Walker, which sounds like the start of a joke.

But really, these were 4 scientists all working quasi independently to form the cosmological a team to give us our modern picture of cosmology. And that's why the modern picture of cosmology is called the FRLW. It's the initials of the last names of the 4 people, model of cosmology, growing out of general relativity to provide a picture of the universe, and the final lesson of the FRLW model is that we live in an expanding universe originating from a big bang about 13,800,000,000 years ago. I'm skipping over about a century's worth of cosmology to get make that statement, but it's good enough. And folks, we need to take a brief break because I need to mention that this show is sponsored by BetterHelp, and I want to talk about comparison.

They say that comparison is the thief of joy, and that is so true. I have spent so many years in my life in a hyper competitive environment, academic research is beyond competitive. You're constantly comparing yourself. Oh, they're doing better research. They're they're publishing more papers.

They gave a better talk, or they have a better tie than me. It's like and and you just sink yourself lower and lower and lower because you constantly compare another person's best to your internal worst, and that is so damaging. It is one of the hardest things to overcome. So the way I went around that and I worked with my own therapist to develop these kinds of skills and tools was not to was to keep comparing, but not compare myself to others, but to compare myself to my past self. What was old Paul doing 10 years ago, 5 years ago, last week?

Am I a better person? Am I more kind and giving? Am I more, generous? Like like, am I more successful in my career? Am I having more fun in my career, in my job, in my daily life than I was last week, a year ago, 10 years ago, 20 years ago?

And if the answer is yes, then I'm winning. I'm winning the game of life, and the only competition is me. It's like when you play a racing game and you're fighting the ghost car of your previous best lap, that's that's the comparison that I like to make. And therapy helped guide me to that conclusion. If you're thinking of starting therapy, give BetterHelp a try.

It's all online, designed to be convenient, flexible, suited to your schedule. Fill out a brief questionnaire, and you're good to go. Stop comparing and start focusing with BetterHelp. Visit betterhelp.com/spaceman today to get 10% off your 1st month. That's better help, he l p, dot com slash spaceman.

Okay. We live in an expanding universe. That's cool. That's nice. We like that.

Quick question here. If the universe is expanding, what is it what is it expanding from? And if the universe is expanding, what is it expanding into? Oh, we came from a big bang. Where is it?

Where did Where was it? Was it over there? Was it over here? Was it right here? Am I standing on it?

Where is the new axis moon? If it's not the earth or the sun, it's not the center of the Milky Way, where is the center of the universe in the big bang model? And this is the part where I'm going to be honest with you, my brain melts. If your brain doesn't melt, then you're made of stronger stuff than I am. Because I can understand things mathematically, and we'll talk about this, but conceptually, I I can't wrap my head around it.

The universe has no center. It has no edge. It's not expanding into anything, and it's not expanding from anywhere. I it doesn't make sense to me. I can say it, and I know it's observationally correct.

I can look at the mathematics. I can look at the predictions. I can look at the observations. I can look at the data. There's a saying in physics that you don't understand things.

You just get used to them. I think this is one of those cases. But let's explore this a little bit to to help us maybe not reform our brains. There there's our my brain is gonna be gooey every time I think about this, but maybe we can put some of the pieces back together. Let's start with the lack of an edge because that helps us figure out the lack of a center of a universe.

The universe can't have a wall or an edge because what is a wall? A wall is a thing that separates one region from another. You have a wall of your house or your apartment that is separating the inside of your apartment from the outside of your apartment. That is the definition of a wall. That's the definition of an edge.

It's a thing that separates one region from another. But the universe, by definition, is all the regions. It's all the stuff. It's all the things. So if you put a border on the universe, you're just separating one thing from another, but but the definition of the universe is all the things.

So the universe can't have a wall. It can't have a border. It can't have an edge. One option is for the universe to be infinite. We simply live in an infinitely large universe.

In which case, an infinitely large universe cannot have a center. If it's infinitely big, you can just go and go and go and go and go forever. There's no center because it's infinitely big. If I take a piece of paper and I stretch it to infinity, literal infinity, that piece of paper no longer has a center. It loses that sense of center because it has no edge.

That's how you define a center. It's like, where is the point that is, equidistant from all the edges? That's your center. If you have no edges, you have no center. Here's where things get really fun.

The universe can be finite and still but not have a center or an edge. Yeah. I know. It sounds weird, but let's run with it. The best analogy I can give you, and I don't have a lot of options here, is to talk about the edge of the Earth.

Right? Walk around the earth. Show me the edge. You you start walking, you get in a boat, you get in a car, you get a train, get in an airplane. You'll see some fantastic places you might visit, The North Pole, you might visit, I don't know, Madagascar, the middle of the Pacific.

You'll never find the edge. You'll if you go far enough in one line, you'll end up where you started. That's how you know the earth is finite. It does have a size. It does have a surface area, a circumference.

You can circumnavigate it, but you can't find the edge. No matter where you are, there's always an Earth. That's a finite Earth with no edge. Okay. If there's no edge to the surface of the Earth, that means there's no center.

I mean, if I ask you to point to the center of the Earth, you're you're gonna point to the hot and molten bit. Right? In the core. But that's the three-dimensional Earth. That's the ball of the Earth.

What if I asked you to point to the center of the surface of the Earth? Pretend you can't dig through a rock. Pretend you're stuck on the surface. Two dimensions. Latitude and longitude.

Give me the center of the surface of the Earth. We've decided that the surface of the Earth has no edge. You can walk or boat or hang glide, you know, whatever. Anywhere you want on the globe, you will never find the edge. It has no edge.

It's still finite because you can measure the total surface area of the Earth. It is finite, but it has no edge. Where is the center? Where on the globe is it? Go ahead.

Point it. Get a globe. Point to me the center of the surface of the Earth. Is it at 0 degrees latitude, 0 degrees longitude? I mean, that's totally arbitrary.

We could've drawn those lines anywhere. Is it one of the poles? It can be anywhere. It's arbitrary. It could be New Zealand.

It could be Cleveland, Ohio. Let's not make Cleveland, Ohio the center of the Earth, But just it's arbitrary. It doesn't matter. There is no edge. There is no center, and it's still finite.

It's just like the universe. Either the universe is infinite, in which case it loses an edge and also it loses a center, or it's finite, in which means it still has no edge because by definition, the universe is all the things so it can't have an edge, and you can still have a finite universe with no center. Okay. Let's take this knowledge, This lack of a center, lack of an edge and use it to help understand the expansion of the universe, the big bang. Where did the big bang come from?

What are we expanding into? Well, imagine the Earth was getting bigger. You know, you you stuck an inflator hose in Mount Vesuvius or something and and you and you started inflating the Earth. It started getting bigger. But we're stuck here on the surface.

What would that look like? Well, from our perspective, you know, the continents would be getting bigger. You know, it's it's an analogy. Okay. Like, just run with me.

The oceans were would be getting bigger. Everything would be getting stretched out. You know, your town was was was yay big before, and then the universe or sorry, the world inflates. Now your your town is a little bit bigger. You know, it's it's a longer drive.

It's a longer walk to get to the other side of town, to get to the grocery store. Everything gets bigger. Okay. Where is the center of that expansion? Remember, you're stuck on the two dimensions.

And I know it's so tempting. It's so tempting in these analogies, which I know it's not the greatest analogy. It's so tempting to say, well, the center of the earth is the molten bit in the core, and it's expanding from there. But that's why I'm insisting on focusing on 2 dimensions. I know this is brain melting.

It is melting my own brain. We're we're on this journey together. We are going to melt each other's brains, and it's going to be glorious. To visualize an expanding earth, you have to jump into a third dimension. You have to launch yourself off the surface, and then you see the inflating ball of the earth.

You're like, okay. Now everything makes sense. It's starting in the hot molten bit in the core, and it's expanding outwards radially into space. And that's why this analogy isn't so great because I'm focusing on the surface of the Earth. Point to me where the center of the expansion on the surface is.

The expansion isn't coming from anywhere, and it's not going anywhere. It's just 2 you draw 2 markers on the Earth, and then you wait a while, and those markers are farther apart. And you can do that with any markers anywhere on the surface. You had to play a mental game. You had to play a trick.

You had to jump into a third dimension in order to realize this, in order to visualize it. But you can't do that with the universe because the universe is already all the dimensions. Three spatial dimensions with no center, no edge expanding. You don't get to jump into a 4th spatial dimension to explain this because there isn't a large 4th spatial dimension. We would've noticed by now.

Yeah. There might be some microscopic ones that's that's different episodes. There isn't a big one that we are embedded in. Where did the big bang happen? It happened everywhere.

The big bang happened in the room you're in right now. The big bang happened in the Andromeda Galaxy, where the Andromeda Galaxy sits right now. The big bang occurred everywhere throughout the entire universe simultaneously. The big bang was an expansion of space, not an explosion in space. You can't point in any direction and say, well, the universe came from there because the universe came from everywhere.

It is the everywhere. It is everything. It's like standing on the surface of the Earth, restricted to the surface of the Earth and saying, where is the expansion coming from? It's coming from everywhere. Back in the day, things were closer together.

It was easier to go to your grandma's house. Now it's harder. In an expanding universe, everybody is expanding away from everybody else. The Big Bang isn't a point in space, it's a location in time. It's a past to all of us.

It's an event that lies in our past. Not a location that we can point to. Modern cosmology destroys the axis mundi. It burns the world tree to the ground. And I do believe that future historians, 100, 1000 of years from now, writing about this epoch right now, the one we're living in right now, we'll call it a revolution.

It is a revolution in thought because we're not just moving the axis mundi. We're not just changing the the location of the center of the universe. We are rendering the concept itself obsolete. This is a brand new idea. This is something we haven't thought of before.

That's not just like a debate. Oh, is the center of the universe here or here or here? No. There's no such thing. In an expanding universe, there's no such thing as a center or an edge.

But that's not the end of the story. And there's a funny little twist to this that I want to share before we go. And that twist owes it's thanks to the constancy of the speed of light. You see the universe is only so old. And light only moves so quickly.

We can only see so much. Light takes time to reach us. It takes light 8 minutes to reach us from the sun. Takes hours for the light from distant planets to reach us. Years to the nearest star.

Millennia to the rest of the Milky Way. 1000000 of years to the nearest galaxy and so on. What we see from our perspective is a progressively younger universe as we go out. We see the Earth, like, right now as it is right now. We see the sun as it was 8 minutes ago.

We see the planets as they were a few hours ago. We see the stars as they were 1000 of years ago. We see galaxies as they were 1000000 of years ago. We see the cosmic microwave background as it was 13.8000000000 years ago. The farther out we go, we see a progressively younger and younger universe.

It's like shining a flashlight in a dark room. There is an edge to our observable universe. Not the whole thing. Just the part that we can see. We only see it what our light illuminates.

There's a hazy edge and then darkness beyond. We can't see beyond that limit, which is currently about 45,000,000,000 light years away. So even if the universe is infinite or it's finite in some strange way where it loops back on itself, it's on a scale much larger than we can ever possibly observe. And that expansion in an expanding universe, everybody is expanding away from everybody else. From our perspective, it looks like all galaxies are flying away from us.

But if you were to move over to the Andromeda galaxy, it would look like all galaxies are moving away from you. If pick a random galaxy. Look in a telescope. Look at that galaxy and imagine transporting yourself there instantaneously to that galaxy. It's like moving the center of your flashlight, the center of your spotlight on a stage.

Like, the spotlight illuminates one section of the stage and we're sitting at the center of that spotlight. But then if you go to the edge of that spotlight, the spotlight moves with you. And you're always in the center. If you're watching the actors on the stage, the spotlight follows them wherever they go. Wherever they go, they are at the center of the spotlight.

They are at the center of their universe. Pick any galaxy that you can see. Imagine transporting yourself there. The spotlight, the ed the their observable universe is centered on them. And, yes, that means they get to see galaxies that we can't and vice versa.

They get a different spotlight. And from their perspective, the universe is expanding away from them. And then they can pick another galaxy on the edge of their spotlight. Some galaxy that we can't access because it's in darkness to us, but they can because it's at the edge of their spotlight. They can transport over to there.

And then that galaxy appears to be the center of the universe with the universe expanding away from it. That's the the cute little trick. If the universe has no true edge, it has no center, the big bang comes from nowhere and is not going anywhere, that means the center is us. It's you and me. It's the Earth.

It's the solar system. It's the Milky Way. The lack of a defined center of the cosmos means that anyone can claim to be the center. In an expanding universe, anyone can rightfully claim to be the center of the expansion and nobody is wrong. So in our searching through millennia, for the Axis Mundi, the true center of the universe.

Yeah, it renders the idea obsolete. There is no center. There is no edge to the modern universe. But but from our perspective, that matters. Our perspective matters.

This is the only universe we can access. The edge of our observations. The limit given to us by the speed of light. In the age of the universe, there's only so much we can see. That perspective matters.

And that means the Axis Mundi, the world tree, the pillar of creation, Yggdrasil, it was right here all along. Thank you to Mihail E on email, Ethan L on email, Anya d on email, and CL Wiskinik on email for the questions that led to today's episode. And thank you to all my Patreon contributors. That's patreon.com/pmsutter. I would like to thank my top ones this month.

We've got Justin g, Chris l, Humberto m, Duncan m, Corey d, Stargazer, Robert b, Tom g, Nyla, Sam r, John s, Joshua, Scott m, Rob h, Scott m, Louis m, John w, Alexis, Gilbert m, Rob w, Dennis a, Jules r, Mike g, Jim L, Scott j, David s, William w, Scott r, BB JJ 108, Heather Mike s, Michelle r, Pete h, Steve s, Watt, WattBird, Alisa r, and Koozie. Those are the top contributors, but all deserve thanks. Please keep those questions coming. Askaspaceman@gmail.com, or just go to the website, askaspaceman.com. Leave a review on Itunes or Spotify.

Those really help the show visibility. And thank you so much for letting me take you on all these fantastic journeys. And I will see you next time for more complete knowledge of time and space.

2 Comments