Near the border of our volume, there is interaction with stuff outside of the volume — Cornwell1

Does it not come down to whether or not, what you say here is true or false?
How would we obtain evidence of such interaction?
Are the hubble volumes described in Tegmark's level 1 multiverse, 3D volumes is a 4D space?
I followed your link and read what I had the time to read but I think I would have to dive in a lot deeper to make any significant contribution to this thread.

Does it not come down to whether or not, what you say here is true or false?
How would we obtain evidence of such interaction?
Are the hubble volumes described in Tegmark's level 1 multiverse, 3D volumes is a 4D space? — universeness

I think I see why you write about the 4d space. I don't think you need a 4th spatial dimension to leave the observable universe.
Let's go one dimension smaller. I remember you brought up the balloon model for our universe. A 2d closed space embedded in 3d space. On this balloon you can draw small circles. These represent our observable universe (Hubble spheres are not exactly the same as the visible universe but let's assume them equal). There are a loooot of these volumes and the balloon is actually to small to draw a visible circle (so it's in good scale to the size of the balloon). That's why space seems flat.
So. There are a loooot of these Hubble volumes in the totality of space, behind the horizon. If you consider space infinite, Tegmark hypothesizes that in an infinite number of different Hubble volumes you will encounter a universeness and Cornwell1 doing exactly the same as we do now. Now, apart from the fact that I don't think the universe is infinite, but a closed 3d balloon, how can this be? It seems to me that near the edges of identical volumes there is information exchange with spheres outside, making the spheres different from each other, contradicting the assumption.
What thinks thou?

I think I see why you write about the 4d space. I don't think you need a 4th spatial dimension to leave the observable universe. — Cornwell1

But why not? I took the term hubble volume to mean our observable/detectable Universe.
If there is another hubble volume and its contained 'beside' ours. I can't do any better than beside/above/below, then both volumes would have to be in 4D container of space, surely?

I understand your sensible move to a 2D circle within a 3D balloon, but does this not add credence for a 3D hubble volume to require a 4D spacial container?

It seems to me that near the edges of identical volumes there is information exchange with spheres outside — Cornwell1

But what exists between two hubble volumes? what separates them?
When I imagine the universe as a balloon, I consider the INSIDE of the balloon as containing the universe in its entirety. Not that the surface of the balloon is the universe.
As a 3D creature, you cannot exist outside of the balloon, there is no outside.
Unless space is 4D?

I can't get past this point, never mind getting to the idea that there are other Balloons with copies of me on them and whether or not individual/independent changes on one sphere as related to another, negates the existence of all of them, except 1.
I thought the multiverse posit was partly to explain the fine-tuning problem and help answer the logic posit that every possible mathematical outcome of a process has to happen in reality somewhere.

I don't think my maths and physics are strong enough to 'conceptualise' what you and Mr Tegmark are conceptualising. My head hurts but I love it! (no masochism involved! Just the pleasure of challenging thought!

Once one moves beyond 3D, higher dimensional "space" for me becomes an algebraic geometric concept rather than a reality. Very useful for predictions but that doesn't imply it truly exists.

The universe as a dynamical system certainly contains those critical points showing SDIC that create butterfly effects. At such points, in the continuum of time, the universe splits, with one trajectory prevailing. What of the alternate trajectories? Do they exist in alternate worlds, or simply as ghost-like speculations? Memories of non-events?

Tegmark is an interesting guy, but his ideas read like science fantasy.

Once one moves beyond 3D, higher dimensional "space" for me becomes an algebraic geometric concept rather than a reality. Very useful for predictions but that doesn't imply it truly exists. — jgill

I don't have too much difficulty, conceptualising other dimensions of the very small.
I can appreciate the curved pipe example, viewed from above. You see a rectangle, as the third dimension is 'wrapped around.' So from this, I can conceive a 4th dimension of the very small, wrapped around every spatial point in 3D 'cubic' space. I can accept the possibility of the 10 spatial dimensions in string theory, using this concept.
I have much more difficulty conceptualising extended spatial dimensions beyond our 3.
The best I can do is 'spheres spread out equally in a box' to try to conceive 'Hubble Volumes.'

Morning universeness (without a universe? Appropriate for this thread!). There is a whole lot of 3d space beyond the horizon. If the universe didn't expand there would become more and more visible. The universe goes on beyond the horizon, like the Earth. We see only a small part. I did a back of the envelope (litterally!) calculation. There fit about 10exp11 observable universe diameters in the whole... It inflated all in existence around the singularity, which is part of a 4d substrate into which it expands, together with another 3d universe on the other side of the singularity wormhole. The problem is how to keep matter in our three dimensions without it moving in the fourth.

So there are a lot of Hubble volumes (they are defined as the volumes within the surface that recedes with lightspeed). If you near such a surface (or anywhere else from its center) you see different things, so there can't be two equals. This holds for all spheres that you suppose equal, so there are no equal volumes of any size.

In the Library of Babel, there is a book that contains a precise description of your, your past and your future. It provides details of what will happen to you tomorrow. And the library is not even infinitely big.

Perhaps if you understand how the library works, you will also see how under certain conditions there can be exact copies of yourself.

There is a copy of me in the Babel Tower?

Morning universeness — Cornwell1

Morning Cornwell1!

(without a universe? Appropriate for this thread!). — Cornwell1

What? this text flew right past me! What does it mean?

There is a whole lot of 3d space beyond the horizon. — Cornwell1

Yep, I get this, wherever we are positioned inside a flat 3D space or a curved 3D space or a saddle shape etc. I get that you can only observe to a horizon in any direction. I get the 'light cone' concept.
So yeah, there may be much more beyond all currently observable/detectable distance.

If the universe didn't expand there would become more and more visible. — Cornwell1

I get this too, because the light from other objects would reach us over time, if there was no expansion and the universe was flat.

There fit about 10exp11 observable universe diameters in the whole... It inflated all in existence around the singularity — Cornwell1

What do you mean by 'observable universe diameters?' Are you taking the universe as a sphere, cutting it into circular slices and then conceptualising viewing the circumference of each circle as a single universal horizon?

It inflated all in existence around the singularity — Cornwell1

So are you saying the singularity still exists somewhere by 'around the singularity?'

which is part of a 4d substrate — Cornwell1

A substrate is defined as 'an underlying substance or layer,' but such must have extent or dimension, as you call it 4D so you are suggesting a 4D space. I don't see how the term 'substrate' helps much.

another 3d universe on the other side of the singularity wormhole — Cornwell1

What do you suggest for the shape of this wormhole concept you suggest?
I know that cosmology has very little idea as to what a singularity is but if we just go with a really small point at the centre of a black hole, then I can conceive that. But does the black hole not surround the singularity as a spherical extension? Can you fly all the way around a black hole in a spaceship of the imagination?
If you can, then in my head, the only way anything could exchange anything (including information) with this other 3D universe you posit would be directly through this singularity, acting as some kind of gateway.

Does Mtheory not suggest floating brane structures within multidimensional space and at every point of collision between two branes, a singularity forms and a new Universe begins.
Are you a fan of Mtheory?

So there are a lot of Hubble volumes (they are defined as the volumes within the surface that recedes with lightspeed). — Cornwell1

Which surface in the Universe is receeding?

If you near such a surface (or anywhere else from its center) you see different things, so there can't be two equals. This holds for all spheres that you suppose equal, so there are no equal volumes of any size. — Cornwell1

Can you exemplify this? What kind of difference might you see and why?


Sorry Cromwell1, I realise that all I have offered you is questions but perhaps this will allow you to air more details about your own hypotheses and I can be a 'useful sounding board.'
Others may be able to contribute more.

What? this text flew right past me! What does it mean? — universeness

I wondered about "universeness". Doesn't this mean "without a universe"?

Which surface in the Universe is receeding? — universeness

The imaginary surface where the redshift of receding galaxies seems infinite. All galaxies seem to accumulate on this surface. It's like the event horizon around a black hole. Seen from our perspective all matter seems to end up on that horizon. Likewise for the cosmic horizon.
I wrote "seems" to end up. If you fall through the event horizon of a BH you will just end up at Its center. For me watching you fall from far away, you will freeze at the horizon (what joy for me to see you freeze... finally a silent forum... :wink: ). For you falli7ng in it takes, say, a second to the center, while for me it seems you take infinite time. The evaporation takes the blink of an eye (Hawking radiation originates in the entangled vacuum; the vacuum around the hole is excited by the heavy gravity present) from your inside perspective, but for me you radiate freely away over a large timespan, dependent on the BH mass.

Can you exemplify this? What kind of difference might you see and why? — universeness

Imagine this. You find yourself 80 billion ly away from here. You can see things from there that I can't see, like you can see a part of the world where you live that I can't see. When 80 billion ly apart we can still see each other but we both can see things the other can't. Which means there can't be two identical Hubble spheres. Because if so, everything around it should also be the same, contrary to assumption. Now I can post!

Hubble — Cornwell1

Hubble bubble, toil and trouble! :grin:

I wondered about "universeness". Doesn't this mean "without a universe"? — Cornwell1

Nah! that would be UniverseLESS, universeness means something OF the universe.... :halo:

The imaginary surface where the redshift of receding galaxies seems infinite. All galaxies seem to accumulate on this surface — Cornwell1

But is this not expansion of an entire 3D volume in all directions, rather than any kind of surface expansion? Some galaxies are blue-shifted, such as andromeda as it is moving toward us. We would also be red-shifted, if observed from most other galaxies, so we are part of the expansion. All galaxies are moving away (receding) from each other, including the milky way. Every part of the volume of space
expands at the same increasing rate. At that scale, the cosmological principle suggests a homogeneous and isotropic space so why use 'an imaginary surface model?'

I get the time issues and the 'freeze at the event horizon' of a black hole from the point of an observer stuff.
I get the spaghettification idea of what would happen to you if you fall into a black hole
I get the hawking radiation and black hole evaporation.
But why would all matter end up at the event horizon of black holes?
In the 'big rip' and 'heat death,' the expansion continues until we can't see any other galaxies and then everything just ultimately disassembles and fade's away. Why would everything end up at black hole's?

Imagine this. You find yourself 80 billion ly away from here. You can see things from there that I can't see, like you can see a part of the world where you live that I can't see. When 80 billion ly apart we can still see each other but we both can see things the other can't. Which means there can't be two identical Hubble spheres. Because if so, everything around it should also be the same, contrary to assumption. — Cornwell1

But if we live on opposite sides of a really big spherical universe then we don't need two 'hubble volumes', we could just be on opposite hemispheres of the same big Universe.

Double Hubble --->
No more rubble
but nubble gubble
and pubble
in the inflated dubble

That's what the universe is. God blowing a bubble in his chewing gum.

Dunning-Kruger meets Method-Feynman.

Alright, my post about the library was "lazy", because I didn't give much thought to the OP. I referenced a similar problem without further explanation. To summarise the Library of Babel,

Now that I took extra time to think about the point made in the OP about the interaction between Hubble volumes, I think I came to a conclusion. It was a fun exercise thinking about this, and I'm sure you will be able to figure this out, and you'll enjoy the experience. I have two metaphors for this.

Let's say the Universe is an infinite sheet of cookie dough. It was super dense 14 billion years ago, but since then it has risen just enough for us to start making cookies. It so happened that exactly 14 billion years ago we drew a small circle on that dough, and this circle has been expanding with the dough this entire time. Besides that, there is a second circle that initially was equal to the first circle, but its expansion was at the speed of light. We know that dough expands slower than the speed of light, so the second circle ended up being larger than the first one. Within the inner circle is out cookie (Hubble volume). Within the outer circle is all the dough that has ever interacted with the cookie (Particle horizon). Outside of the outer circle is the rest of the dough. We cut our cookie out of the dough, dispose of its surrounding dough, and then we repeat this process again in a new location on our infinite sheet. We end up with an infinite number of cookies that have never interacted with each other in 14 billion years. Moreover, no two cookies have ever interacted with the same piece of dough. The cookies are so far apart that they could have came from different Universes. If we assume that within a finite area of the dough there can only exist a finite number of arrangements of particles that make up the dough, then some cookies will have multiple copies inside an infinite jar. It can also happen that the cookie that we live in is unique, or that an infinite number of possible cookies can exist within a finite area of the dough, which would mean that no two cookies are unique.

My second metaphor is the following. Let's say that you're standing in a line of people that are one light year apart from each other (socially distancing). When you're looking at the person next to you, you see them 1 year younger than they actually are. This is because the light from them had to travel one year to reach you. In this example, all people in the line have the same age, because they were all borne at the time of Big Bang. Then, you look at the person next to your neighbour. This person is now 2 years younger than you. You keep looking farther and farther, and you keep noticing people getting younger, until you reach a 1 year old baby, and there is no one beyond the baby. It's not that this is the end of the line, but this is the horizon of your vision. You know that there are more people out there, but you just haven't got a chance receive any light from them. Now, here is something interesting. The one-year-old baby that you're seeing is actually a full grown woman. You just don't know it yet. At the same moment that you're looking at the baby version of her, she is looking far ahead and seeing many more people in the line. The baby version of her hasn't registered any people at all, so you have no way to learn about other people in the line beyond her. You never know. There may be someone in the line far away that is an exact copy of you. It can even be that the baby that you're looking at is a copy of yourself.

Gubi gubi!

Nah! that would be UniverseLESS, universeness means something OF the universe.... — universeness

Ah! Of course! Like universality...?

But if we live on opposite sides of a really big spherical universe then we don't need two 'hubble volumes', we could just be on opposite hemispheres of the same big Universe. — universeness

I think I see how you envision it. If we are on opposite sides of the universe we are not on opposite sides of a 3d sphere.
The balloon (2D). Draw, on a huge balloon of say Earth size, a circle on it. Diametrically opposed points on this circle are you and I on opposite sides of the visible universe (which you can see from the center).
In reality the balloon is much bigger. If you draw a circle of one meter radius on the balloon, then the circumference of the balloon is about 10exp11 meter... About a hundred million kilometers. There's more behind the horizon!

But why would all matter end up at the event horizon of black holes?
In the 'big rip' and 'heat death,' the expansion continues until we can't see any other galaxies and then everything just ultimately disassembles and fade's away. Why would everything end up at black hole's? — universeness

The matter seems to end up on the horizon because there time seems to stop. If you fall in as a particle you get radiated away in a wink. All matter ends in black holes which seem to last long. Evaporation to photons takes a wink though for the matter inside them. Information of this matter resides in the virtual particles, the closed one particle propagators in Feynman diagrams. A negative energy solution is sent inside, so the mass of the hole reduces bit by bit. Positive energy solutions, particle-antiparticle pairs, annihilate to send information outside (some photons can go back in the hole too, but slowly the information about the inside particles gets out). So if you throw in a bike you can still see the bike in the Hawking photons. Somewhat fucked up, but still...

Two good thought scenario's:

Let's say the Universe is an infinite sheet of cookie dough. — pfirefry

This suggests that only one Universe exists and what you are about to describe are possible limitations for any lifeform living within it, yes?

It was super dense 14 billion years ago, but since then it has risen just enough for us to start making cookies. — pfirefry

So we could call this state the singularity, yes?

14 billion years ago we drew a small circle on that dough, and this circle has been expanding with the dough this entire time — pfirefry

So our current observable/detectable 'section' of this one Universe you posit.

Besides that, there is a second circle that initially was equal to the first circle, but its expansion was at the speed of light — pfirefry

So we now have a section of the Universe that expands faster than our section.

We know that dough expands slower than the speed of light, so the second circle ended up being larger than the first one. — pfirefry

So the Universe has a section that expands faster than the rest of the surface.
In my head, this would be the same idea as one of my organs moving faster than the rest of my body was running. Ouch! OR your cookie image indicates that during the initial expansion, something happened to break up the expanding dough into 'cookie' sections. What happened? where did the cookie cutter come from? etc. I can conceive the fundamentals of what's going on in your scenario but I cant see why this is a multiverse. It suggests we started off with a universe of dough that became a multiverse of cookie's, instead of a multiverse of dough's.

so the second circle ended up being larger than the first one. — pfirefry

So what did this cookie expand into? would it not crunch against its surrounding slower moving dough?
Does each cookie create a new layer to the Universe depending on its expansion rate?

Infinite exact copies of myself needn't be adjacent to each other. :grin:

I think I see how you envision it. If we are on opposite sides of the universe we are not on opposite sides of a 3d sphere.
The balloon (2D). Draw, on a huge balloon of say Earth size, a circle on it. Diametrically opposed points on this circle are you and I on opposite sides of the visible universe (which you can see from the center).
In reality the balloon is much bigger. If you draw a circle of one meter radius on the balloon, then the circumference of the balloon is about 10exp11 meter... About a hundred million kilometers. There's more behind the horizon — Cornwell1

Ok, yes, I understand what you have typed but what is the inside of the volume of the balloon you are describing in relation to the Universal structure you suggest?

The matter seems to end up on the horizon because there time seems to stop — Cornwell1

I am still very far away from getting this one.
Is this theory based on the idea that the black hole at the centre of a galaxy will eventually expand/grow so that it will consume all of the matter in that galaxy?

However, it doesn't mean that all books will have more than one copy. Some books may be absent, and some books can appear only once. — pfirefry

Reminds me of the 18 000 000 trees where I live. If every tree has 100 000 leaves, how many trees at least must have an equal number of leaves?

I'll contemplate later. State is calling me... i don't have a job now and they want me to order the flora in town... Djeeeezus!

Ok, yes, I understand what you have typed but what is the inside of the volume of the balloon you are describing in relation to the Universal structure you suggest — universeness

And there it's exactly where it gets interesting! I'll explain later. Right now I gotta an appointment at 3. I'm invited by state. To discuss my working possibilities...

The matter seems to end up on the horizon because there time seems to stop
— Cornwell1

I am still very far away from getting this one.
Is this theory based on the idea that the black hole at the centre of a galaxy will eventually expand/grow so that it will consume all of the matter in that galaxy? — universeness

It's the theory of black holes. If you look at a collapsing sphere of dust from a distance, the sphere seems to slow down in collapsing. When the sphere has a radius equal to the Schwarzschild radius it seems to have frozen and starts to emit Hawking radiation over a long time. On the inside the process takes a small time, about the time it takes light to travel over the Schwarzschild radius (so for the Sun about 1/100 000 seconds as the SR is about 3km.

Tegmark on his website does not directly address the question of the opening post. But he does address this curious query:

Will I run over a squirrel?

To spare unnecessary anxiety - or perhaps to spoil the surprise - Tegmark's answer is clear and unambiguous:

From Mike Sanders, mikedotsandersatpearsoneddotcom, Apr 6 2004 at 14:37
Q: Within the context of the multiverse, doesn't every conceivable physical possibility occur? If I'm driving my car and stop abruptly to keep from hitting a squirrel, don't I purposely run over that same squirrel in an alternate universe. And if so, isn't the number of universes that follow each outcome approximately the same?
A: No - and that's the crux. The laws of physics and your behavior evolved through natural selection create much regularity across the multiverse, so you'll try to spare that squirrel in the vast majority of all parallel universes where "you" are pretty similar to the copy reading this email (just as regards the above-mentioned gas station robbery). The fractions only split close to 50-50 for decisions that you perceive as a very close call.

It's the theory of black holes. If you look at a collapsing sphere of dust from a distance, the sphere seems to slow down in collapsing. When the sphere has a radius equal to the Schwarzschild radius it seems to have frozen and starts to emit Hawking radiation over a long time. On the inside the process takes a small time, about the time it takes light to travel over the Schwarzschild radius (so for the Sun about 1/100 000 seconds as the SR is about 3km — Cornwell1

I understand the material on the death of large stars and all of the 'types of supernovae, hypernovae) involved. involved.
I understand collapse to the size of a white dwarf, a neutron star (or pulsar) and the final possibility based on the mass of the original star, a black hole. I understand the basics of the forces involved and the subsequent events. Still doesn't suggest that all matter in the Universe is destined to fall into black holes.

All matter resides in galaxies. The space between galaxies doesn't expand. All that visible matter is matter with internal friction. I'm convinced that dark matter consists of primordial black holes. It seems a lot, if not most, of big galaxies harbor a giant black hole. All visible matter is doomed to fall in these, as the evaporate veeeery slowly. If the acceleration of expansion really gets a grip, then what happens to the black holes?

This suggests that only one Universe exists and what you are about to describe are possible limitations for any lifeform living within it, yes? — universeness

Yeah, I'm talking about the single infinite 3D universe introduced in the OP: "In an infinite universe <...>". I think you contributed with the idea of a 4D space with many 3D universes, but for the purpose of the OP I'm assuming a single infinite 3D universe. I'm also assuming that the universe has a finite age and it's expanding similar to our universe. The finite age allows us to consider the regions of the infinite universe so far removed from each other that there is there no way for them to interact with one another. If they sent beams of light towards each other at the moment of the Big Bang, the light wouldn't have reached the destination by today. I'm just trying to play by the Tegmark's rules. Personally, I don't find the idea of infinity very realistic. I'm also subscribed to the idea of isolated pockets of the universe, most of which I know from this video. This sets the ground for a multiverse within a 3D universe.

It was super dense 14 billion years ago, but since then it has risen just enough for us to start making cookies.
— pfirefry

So we could call this state the singularity, yes? — universeness

Exactly. I'm assuming that singularity was uniform. When the universe started expanding, the areas of space appeared everywhere at the same time, so that space was already infinitely large the moment it appeared.

14 billion years ago we drew a small circle on that dough, and this circle has been expanding with the dough this entire time
— pfirefry

So our current observable/detectable 'section' of this one Universe you posit. — universeness

Not exactly. I'm trying to outline the observer here. We can observe the universe from a single point in space, but it's hard to fit a person or a copy of a person into one point. It's also hard to reason whether two points can be exact copies of each other, since a point doesn't have volume. Instead, I'm allocating a chunk of space in which an observer will exist. This area of space can be the size of our observer, or our planet, or our galaxy. Arbitrarily, I chose the size of a Hubble volume to connect with the OP. I will introduce the second circle to outline the observable/detectable 'section' of the universe, where the first circle acts as the observer.

So we now have a section of the Universe that expands faster than our section. — universeness

Yeah, that's when my metaphor starts breaking down. I stared with one circle in mind, but I then realised that I needed two. The first circle represents spacial boundaries, but things can move within space at the speed of light. So the second circle is the horizon of information that travels through space. Coming back to our dough metaphor, let's say that yeast bacteria is living inside the dough. It can travel through the dough over time, regardless of its expansion. The second circle represents how far the bacteria could have gotten in 14 billion of years while traveling through the expanding dough

In my head, this would be the same idea as one of my organs moving faster than the rest of my body was running. Ouch! — universeness

The first circle is the boundary of your heart. But the second circle represents a wave produced by a heart beat, travelling outside of your body and expanding over time. If someone in another galaxy sent an impulse to impact your heart, the moment your heat beat reaches them is the moment their impulse reaches you. The wave produced by your first heartbeat outlines the area of the universe that can impact your heart, assuming that nothing existed before the heartbeat happened.

Sorry, I'm not sure my explanation holds together well at this point. I have a very specific idea of what happened at the time of the Big Bang, but I'm not sure that I can articulate it, or that anyone can grasp it just from my description.

So what did this cookie expand into? would it not crunch against its surrounding slower moving dough?
Does each cookie create a new layer to the Universe depending on its expansion rate? — universeness

It just expands because new space appears for it to expand into. New bubbles of space are forming in the dough, while no new dough is being created. We don't know where the space is coming from, but we know that it just appears and it causes the expansion of dough. It's not important where the space is coming from for the purpose of the OP.

I think the idea of layers is the result of attempting to look at the Universe from the 4D point of view. I don't want to disregard this view. I think it's interesting, and I'd like to give it a go. But as far as my analogy goes, I'm not concerned about what the "outside" of the universe looks like, or how the universe is arranged in a higher-dimensional space. I think that's consistent with Tegmark.

But consider now two volumes incredibly far apart. No information could have traveled between them. Assume the volumes have identical configurations of particles. Now imagine yourself not far from the border. What do you see? You should see different things from both. The surroundings of both are different. But if you see different things on the outside from the inside, then both volumes can't be identical, as you assumed.

I'm assuming that both the volumes and their observable surroundings are identical. That seems far-fetched, but not impossible in an infinite universe. I'm also assuming that the volume and its observable surroundings have a finite age. This way, the surroundings that I'm observing have not been 'observably' impacted by their surroundings. They may have been impacted in the present, but I'm only seeing their past when they haven't been impacted yet. Given sufficient time, the surroundings will change and our exact copies will diverge.

I'm assuming that both the volumes and their observable surroundings are identical — pfirefry

But how can there be two different volumes then? With two copies of you?

One at position (x0, y0), and the second at a different position (x1, y1). Everything in the observable radius R around these points is identical. Things outside the radius R can diverge.