Did cosmic inflation happen everywhere in the Universe?

[RobertSpencer]

General Relativity equations tells us that the earliest time of the universe which our physics can tell us had infinite space and infinite density (i.e. matter).

Then space started expanding, thus increasing the distance of any 2 points of that infinite dense matter, thus making it less dense and eventually creating galaxies and stars.

So, the big bang which is really a big expansion happened everywhere in the universe.

So, then, cosmic inflation suggested by Alan Guth tries to give an explanation as to what caused the big bang (expansion).

So, my question is, did inflation happen everywhere in the universe, or did it happen only in the region (infinitely small region) which led to our observable universe?

So, my understanding is that at the earliest time our equations tells us there was infinite space and infinite matter density. Then in some places in that infinite space inflation happened creating bubble universes like ours, but in other areas the universe just expanded. So, somewhere in the infinite universe even now inflation can happen creating more bubble universes. This is called eternal inflation.

Is this the current model of the big bang with inflation added?

Then what is there outside the bubble universes?? More galaxies, or more of that infinite dense matter which did not go through inflation to create a bubble universe?

 

[mfb]

General Relativity equations tells us that the earliest time of the universe which our physics can tell us had infinite space and infinite density (i.e. matter).

No, the earliest time where our laws of physics might work it had a finite density. Inflation happened later, going from a state of finite energy density to another state of finite energy density.

It is expected that inflation happened everywhere, but outside our observable universe we can't check it of course. It is less clear if it also stopped everywhere in the universe, or if we live in a region where it stopped while it is still ongoing elsewhere - this is the idea of eternal inflation.

 

[RobertSpencer]

No, the earliest time where our laws of physics might work it had a finite density. Inflation happened later, going from a state of finite energy density to another state of finite energy density.

It is expected that inflation happened everywhere, but outside our observable universe we can't check it of course. It is less clear if it also stopped everywhere in the universe, or if we live in a region where it stopped while it is still ongoing elsewhere - this is the idea of eternal inflation.

If inflation did not stop everywhere then wont' those inflating bubbles squish into other inflating bubbles and non-inflating bubbles (like our observable universae) thus destroying things or creating a catastrophic event?

Because inflation is where space expands at enormous rates, rates much higher than the normal big band expansion rate. So, if inflation does not stop, that inflating expansion will surely crash into other inflating expansions and the non-inflating (i.e. slow expanding) bubbles (which is one we live in)?

 

[mfb]

If inflation did not stop everywhere then wont' those inflating bubbles squish into other inflating bubbles and non-inflating bubbles

No. These processes are not the motion of things in space. They create new space between the things. This doesn't influence our universe at all.

 

[RobertSpencer]

No. These processes are not the motion of things in space. They create new space between the things. This doesn't influence our universe at all.

By our universe you mean our observable universe I presume?

I am trying to visualize this scenario for a 1 dimensional universe (i.e. a line) where there are infinite points in the line and each point is next to each other and each point is very small, smaller than an atom, the state of the points in the actual big bang.

BTW, have you calculated the actual size, i.e. volume, of this small dense blob of matter at the starting point of the big bang? Is there a value for it??

 

[RobertSpencer]

No. These processes are not the motion of things in space. They create new space between the things. This doesn't influence our universe at all.

This video from the Perimeter Institute of Physics shows the bubbles colliding at @02:38 minutes?

 

[mfb]

By our universe you mean our observable universe I presume?

I meant universe as "the part that looks like our observable universe" (in particular, the connected part that doesn't expand inflationary).

BTW, have you calculated the actual size, i.e. volume, of this small dense blob of matter at the starting point of the big bang? Is there a value for it??

We don't know how much the universe expanded during inflation.

 

[David Lewis]

...the earliest time of the universe which our physics can tell us had infinite space and infinite density (i.e. matter).

There was no space and no matter. There was only energy. It expanded and cooled off enough for subatomic particles to condense out.

 

[weirdoguy]

There was no space and no matter.

And where did you get that from?

 

[RobertSpencer]

There was no space and no matter. There was only energy. It expanded and cooled off enough for subatomic particles to condense out.

Problem is this. Matter and energy are the same thing. They are interchangeable (E=MC2).

But the problem is, that matter and energy has to reside inside space. Everything resides inside space.

Without space nothing can exist.

So, I don't think you are right when you say that there was no space and no matter.

 

[PeterDonis]

There was no space and no matter. There was only energy. It expanded and cooled off enough for subatomic particles to condense out.

Please give a reference for this. I don't know what, if any, features of the actual model used by cosmologists you are trying to describe.

 

[David Lewis]

Without space nothing can exist.

There was first a singularity. If space existed first then the Big Bang would have a location.

 

[PeterDonis]

There was first a singularity.

Not in the actual model cosmologists use. See post #2.

 

[David Lewis]

There apparently was a singularity if the laws of nature as we currently understand apply to the high density and temperature present before the Big Bang. That is a big "if".

 

[PeterDonis]

There apparently was a singularity if the laws of nature as we currently understand apply to the high density and temperature present before the Big Bang.

Please give a reference for this statement.

 

[David Lewis]

"At about .01 s, the earliest time about which we can speak with any confidence, the temperature of the universe was about 10¹¹ degrees C. This is much hotter than the center of even the hottest star. None of the components of ordinary matter, molecules, or atoms, or the nuclei of atoms, could have held together." The First Three Minutes - Steven Weinberg

 

[PeterDonis]

"At about .01 s, the earliest time about which we can speak with any confidence, the temperature of the universe was about 10¹¹ degrees C. This is much hotter than the center of even the hottest star. None of the components of ordinary matter, molecules, or atoms, or the nuclei of atoms, could have held together." The First Three Minutes - Steven Weinberg

First of all, while this is a very good pop science book, it's still a pop science book.

Second, which of your statements do you think this is a reference for? It certainly isn't a reference for your claim about a singularity.

 

[David Lewis]

...the earliest time of the universe which our physics can tell us had infinite space and infinite density (i.e. matter).

My statement was that ordinary matter did not exist in the early stages because it was too hot.

 

[David Lewis]

"At this time, the Big Bang... the density would have been infinite. It would have been what is called, a singularity." - Hawking, Stephen

 

[mfb]

Matter and energy are the same thing. They are interchangeable (E=MC2).

They are not.
That equation tells you that mass has energy, but it doesn't say mass and energy are the same thing.

My statement was that ordinary matter did not exist in the early stages because it was too hot.

The particles that make up our matter did exist. They did not form atoms or molecules, but this is a completely different topic.

"At this time, the Big Bang... the density would have been infinite. It would have been what is called, a singularity." - Hawking, Stephen

Note the conjunctive.

 

[PeterDonis]

My statement was that ordinary matter did not exist in the early stages because it was too hot.

You didn't say "ordinary matter". You just said "matter":

There was no space and no matter. There was only energy. It expanded and cooled off enough for subatomic particles to condense out.

This is not supported by what you quoted (which is a pop science source anyway, as I said). In our best current model of the early universe, quarks and leptons, which are what the term "matter" usually means in the actual physics literature, existed. They did not "condense out" of anything. (And don't even get me started on "no space".) So your statement is (a) not supported by the reference you gave, and (b) wrong.

Please do not post about this again until you have learned the correct model.

 

[RobertSpencer]

A lot of scientists say that there is lot of evidence for Inflation and evidence is mounting and it's just a matter of time that Alan Guth gets the Nobel prize. So I think we can say with quite a lot of confidence like over 99% that Inflation happened and is also currently happening now else where.

So, according to the Inflation the entire universe, not just our observable universe, will look like this:

The purple balls are where the Inflation field collapsed to form new 'bubble' universes. These universes are shaped like actual balls and have a center (as you can see from the picture very clearly) and also a boundary. We live in one such bubble universe. Brian Greene calls this the "inflationary multiverse".

What the black region, the region beyond the bubble universes is now getting quite clear. That is is the "Inflation" field which is in the process of undergoing inflation even right now. So, our universe, our bubble universe is expanding into the inflation field.

The only thing I don't get is how some of those bubble universes cannot bump into one another?

 

[JLowe]

A lot of scientists say that there is lot of evidence for Inflation and evidence is mounting and it's just a matter of time that Alan Guth gets the Nobel prize. So I think we can say with quite a lot of confidence like over 99% that Inflation happened and is also currently happening now else where.

So, according to the Inflation the entire universe, not just our observable universe, will look like this:
View attachment 223418

The purple balls are where the Inflation field collapsed to form new 'bubble' universes. These universes are shaped like actual balls and have a center (as you can see from the picture very clearly) and also a boundary. We live in one such bubble universe. Brian Greene calls this the "inflationary multiverse".

What the black region, the region beyond the bubble universes is now getting quite clear. That is is the "Inflation" field which is in the process of undergoing inflation even right now. So, our universe, our bubble universe is expanding into the inflation field.

The only thing I don't get is how some of those bubble universes cannot bump into one another?

I'm no expert, but I wouldn't take those bubble pictures too literally.

 

[PeterDonis]

These universes are shaped like actual balls and have a center (as you can see from the picture very clearly)

The picture is misleading you (which illustrates why you should not try to learn science from pop science sources). The individual universes are spatially flat and spatially infinite (at least in the current best-fit model).

our bubble universe is expanding into the inflation field

No, it isn't. It's not expanding "into" anything. It's disconnected from the inflaton field and from all the other bubble universes. See below.

The only thing I don't get is how some of those bubble universes cannot bump into one another?

Because they are not "bubbles" the way the picture is making you think (see above on how the picture is misleading you). Once each bubble universe forms, it is disconnected from all the others and from the prior inflaton field that it condensed from. You can't draw a picture that represents that faithfully, but it's perfectly consistent as a model.

 

[RobertSpencer]

The picture is misleading you (which illustrates why you should not try to learn science from pop science sources). The individual universes are spatially flat and spatially infinite (at least in the current best-fit model).
No, it isn't. It's not expanding "into" anything. It's disconnected from the inflaton field and from all the other bubble universes. See below.
Because they are not "bubbles" the way the picture is making you think (see above on how the picture is misleading you). Once each bubble universe forms, it is disconnected from all the others and from the prior inflaton field that it condensed from. You can't draw a picture that represents that faithfully, but it's perfectly consistent as a model.

You mean the current best-fit model with or without inflation?

If the individual bubble universes are also spatially infinite, then there is no room for other bubble universes to exist. So what do you mean by this?

 

[puppypower]

I am going to play devil's advocate. Has anyone or any team ever expanded space-time in the lab, without using matter to lead the expansion process? We can expand space-time by simply lowering the mass density of an object, such as with an explosion. This can be proven in the lab and satisfies the philosophy of science. I was wondering has anyone been able to expand naked space-time, without using matter to lead, to show this is even possible? What we see appears to be happening, but have we been able to duplicate this is the lab to make sure it is not a mirage?

We infer that space-time is leading the expansion, and we infer that dark energy is responsible for expanding space-time. However, has either of these inferences been directly proven in the lab with repeatable experiments? We can prove matter leading space-time via General Relativity experiments where mass density is leading. Can we ignore the philology of science in cosmology?

I am not trying to be contrary, but I was wondering whether we are arguing how many angels can stand on the tip of a needle. This is where you lead with an inference that lacks lab proof and then extrapolate as though the main premise had been proven in lab.

 

[mfb]

You mean the current best-fit model with or without inflation?

We are discussing a particular model of inflation. A model of inflation without inflation doesn't make sense.

If the individual bubble universes are also spatially infinite, then there is no room for other bubble universes to exist.

You are still stuck at this misleading image.
There is no conflict with multiple infinite "bubbles" because these bubbles are not "something in space".

@puppypower: "Expanding spacetime" in the way you use this expression doesn't make sense.

We infer that space-time is leading the expansion

What do you mean by "leading the expansion"?

and we infer that dark energy is responsible for expanding space-time

No we do not. It only influences the rate. And it only does so in gravitationally unbound things, something we cannot reproduce in the lab. We can observe its effect in the universe. This is common - we also don't have a whole planet in our lab, or a whole star. That doesn't mean we should question the existence of planets or stars. It just makes some aspects of them harder to study.

 

[PeroK]

You mean the current best-fit model with or without inflation?

If the individual bubble universes are also spatially infinite, then there is no room for other bubble universes to exist. So what do you mean by this?

Mathematically, and physically, something being of infinite spatial extent does not mean that there cannot be other spatially infinite objects.

The simplest mathematical example would be vector spaces, although that is not the model here.

 

[RobertSpencer]

Mathematically, and physically, something being of infinite spatial extent does not mean that there cannot be other spatially infinite objects.

The simplest mathematical example would be vector spaces, although that is not the model here.

How can there be other spatially infinite objects.

If there is ONE specially infinite object, then surely that is what occupies EVERYTHING, because it is infinite.

How can there be OTHER spatially infinite objects?

PS: Mathematically maybe, but physically how can 2 infinite spatially objects exists??

 

[PeroK]

How can there be other spatially infinite objects.

If there is ONE specially infinite object, then surely that is what occupies EVERYTHING, because it is infinite.

How can there be OTHER spatially infinite objects?

You already have that with, say, lines in the plane. Each line is infinite in extent, and there are infinitely many parallel lines, all disjoint from each other.

You can do the same with parallel planes in 3D.

To have infinitely many disjoint 3D spaces, you simply need a 4th spatial dimension.

Again, this is the simplest mathematical example.

And, if you were to postulate a 4th physical spatial dimension, then it's all good. You could use your 4D mathematical model and you'd have a multiverse theory with many spatially infinite universes.

 

[puppypower]

I am not sure how to quote yet.

@puppypower: "Expanding spacetime" in the way you use this expression doesn't make sense.
↑
We infer that space-time is leading the expansion
What do you mean by "leading the expansion"?
↑
and we infer that dark energy is responsible for expanding space-time
No we do not. It only influences the rate. And it only does so in gravitationally unbound things, something we cannot reproduce in the lab. We can observe its effect in the universe. This is common - we also don't have a whole planet in our lab, or a whole star. That doesn't mean we should question the existence of planets or stars. It just makes some aspects of them harder to study.

Here is what I am mean. Say we placed a clock in a large empty vacuum chamber. We will infer changes in space-time by the clock changing time. We need to tweak space-time in the chamber, near the clock, however, we can't use matter to do this, such as by moving to the walls to alter the mass density around the clock. Instead, we need to use dark energy or something similar, but in this experiment, we nee dot make sure matter cannot lead. The vacuum is there to prevent the unknown darkish energy from expanding any gas, which will then lead to subtle space-time expansion changes, via matter. We do this experiment to show this is possible and not just theoretical.

Let me show you an alternate experimental way to create an inflation simulation. Say you were traveling on a spaceship close to the speed of light. You look out the window and notice that universal space-time appears contracted, due to your relative motion; relative reference affect. If we were to put on the brakes, and look out the window, the universe would appear to expand. This expansion is not due to dark energy or due to moving of matter. It is simply a window reference artifact, due to braking from relativistic speeds. Inflation may well be a record of a window view, of an earlier time, when energy reference; C, condenses into the inertial reference; matter references. This we can do in the lab. If we were energy at C, and suddenly condensed to matter/mass, there would be instant braking from C to below C.

Say we could theoretically travel at the speed of light; as energy. The universe will appear as a mass point instant. Say we slow to C-, by condensing our energy back into matter, which has to go less than C. As the condensation happens, we look out the window, the point universe appears to expand to finite size, instantly,. We get a window view of inflation, due to rapid energy to matter condensation and universal reference changes. We can still see things from the distant past, so inflation may be a reference thing, that still lingers throughout the universe.

 

[PeterDonis]

If the individual bubble universes are also spatially infinite, then there is no room for other bubble universes to exist.

Sure there is. The inflating region and the bubble universes do not occupy the same spacetime. You are trying to apply intuitions that simply don't apply here.

To have infinitely many disjoint 3D spaces, you simply need a 4th spatial dimension.

That's one way to do it, but not the only way. There is no requirement that the different bubble universes lie "in the same space" even in a higher dimension.

 

[PeterDonis]

Let me show you an alternate experimental way to create an inflation simulation.

Your suggestion won't work because the "expansion" observed will not be isotropic--it will be different in different directions. Inflation is the same in all directions.

Say we could theoretically travel at the speed of light; as energy. The universe will appear as a mass point instant.

No, it won't. We can't travel at the speed of light ("as energy" makes no sense). And the universe does not "appear as a mass point instant" to a light beam anyway; the concept of "how the universe appears" doesn't apply to light.

 

[PeterDonis]

I am not sure how to quote yet.

Highlight what you want to quote; a "Reply" button will pop up next to the highlight. Click it and the quoted text will appear in the edit window where you type in your posts. (Javascript will need to be enabled in your browser for this to work.)

 

[puppypower]

Your suggestion won't work because the "expansion" observed will not be isotropic--it will be different in different directions. Inflation is the same in all directions.

No, it won't. We can't travel at the speed of light ("as energy" makes no sense). And the universe does not "appear as a mass point instant" to a light beam anyway; the concept of "how the universe appears" doesn't apply to light.

I used the window as an analogy to help with visualization. A condensation of an energy point, into matter, can change the reference parameters in an isotopic way. We go from everything having the speed of light, to everything having less than speed of light. The condensation speed can create reference changes in the universe that appear to occur faster than C. If this affect lingered, we may be seeing traces of this along with the brake heat.