Relative size "universe in universe"

[sunshaker]

This is not a theory just a question, I was wondering about relative sizes.

 

People often talk about what was before the Big Bang, Or what our universe is expanding into.

 

 

if our universe was a virtual particle expanding into another universe just like a virtual particle that pops into existence into our universe,

I was wondering how "entities" in this newly expanding universe would see the universe they were expanding into, while not realizing their universe was expanding into another universe.

 

If from their view point a atom of "our hydrogen" was a star, how would they actually view "our" planet/stars/galaxies?

 

what if this newly expanding universe was expanding into somewhere like our Oort cloud, where a single atom was like a star to them (a swirling of dust a galaxy), would they see larger rocks/rubble/planetoids like we see "Dark matter"'?

 

 

[Strange]

 

People often talk about what was before the Big Bang

 

Asking what was "before" the big bang is like asking what is further north than the North Pole. It doesn't really mean anything.

 

 

Or what our universe is expanding into.

 

It isn't expanding into anything. The universe is all there is.

[sunshaker]

 

Asking what was "before" the big bang is like asking what is further north than the North Pole. It doesn't really mean anything.

 

 

It isn't expanding into anything. The universe is all there is.

Irrelevant.(also not every ones opinion) many worlds/multiverses.

 

I was not asking any of those questions. I was just wondering what certain objects would look like to us if we where many orders of magnitudes smaller.

 

Let me put it another way, If "Earth" was shrunk until a lone hydrogen atom was the size of our sun, how would that proton/atom look to us from Earth? what sort of heat would it radiate?

 

How then would rubble/asteroids (Oort cloud) look to us from Earth?

 

Please put aside the problems how light would effect us seeing these objects.

Edited September 3, 2015 by sunshaker

[Strange]

Please put aside the problems how light would effect us seeing these objects.

 

OK. Putting aside science means you can choose whatever answer you want. But, based on the images we currently have of atoms and molecules, a hydrogen atom would look like a fuzzy sphere of cloud. And it wouldn't radiate anything. Unless it had absorbed a photon, in which case, it would enit it again some time later.

[Thorham]

Asking what was "before" the big bang is like asking what is further north than the North Pole. It doesn't really mean anything.

 

It's a perfectly valid question. What you're talking about is just an assumption.

 

 

It isn't expanding into anything. The universe is all there is.

Yes, but is what we see the whole universe or just a small part of it? And if it is a small part, how small?

[Strange]

It's a perfectly valid question. What you're talking about is just an assumption.

 

Not really, I am talking about how the universe is described in GR (i.e. the big bang model).

 

Yes, but is what we see the whole universe or just a small part of it? And if it is a small part, how small?

 

There are various estimates of how much bigger than the observable universe is the whole universe is. Based on the flatness determined from the CMB, it is thought to be at least 150 times larger than we can see. On the other hand, it might be infinite.

[Thorham]

Not really, I am talking about how the universe is described in GR (i.e. the big bang model).

That doesn't prove that before the big bang makes no sense. How do you prove that anyway?

[Strange]

That doesn't prove that before the big bang makes no sense. How do you prove that anyway?

 

In the mathematics of GR there is a singularity at time t=0. That is roughly equivalent to a pole: in the same way that the lines of longitude converge at the north pole and go no further, space=time converges at the singularity and goes no further.

 

Of course, most people don't think that the singularity represents physical reality. We probably need a theory of quantum gravity to better understand the universe at that stage. It may turn out that there was no "big bang" in the sense of an initial starting point. The universe may be infinitely old. Or it may have collapsed and re-expanded. Or it could have been in some unknown state prior to expanding.

[Thorham]

 

Of course, most people don't think that the singularity represents physical reality. We probably need a theory of quantum gravity to better understand the universe at that stage. It may turn out that there was no "big bang" in the sense of an initial starting point. The universe may be infinitely old. Or it may have collapsed and re-expanded. Or it could have been in some unknown state prior to expanding.

 

And that's exactly why the 'before' question is valid and saying that 'before' doesn't make sense an assumption. If you know this yourself, why argue against it?

Edited September 3, 2015 by Thorham

[Strange]

 

And that's exactly why the 'before' question is valid and saying that 'before' doesn't make sense an assumption. If you know this yourself, why argue against it?

 

But the question still doesn't make sense; if there was no starting point, then what does "before" mean? Before what? Is the question just "what happened earlier than the earliest time we know about"? In which case, the answer is a rather obvious "we don't know (yet)".

[Thorham]

if there was no starting point, then what does "before" mean?

 

'Before' makes sense because the big bang is simply an event. It's either the first event to have occurred, or it isn't. If it's the first event then there's no before. If it wasn't the first thing to ever happen, then there was a before.

 

*Edited*

Edited September 3, 2015 by Thorham

[StringJunky]

 

And that's exactly why the 'before' question is valid and saying that 'before' doesn't make sense an assumption. If you know this yourself, why argue against it?

Just an example why "before" can make no sense: if time started with the BB, but the BB was just one stage in the evolution of the universe, what does "before" mean if time had not emerged before the BB? What are we using to gauge 'before' with since time did not exist? In this situation the universe operated under a different set of physics... possibly.

[Strange]

 

'Before' makes sense because we don't know whether or not the big bang was the first event to have ever occurred. How would you even test that?

 

In classical GR there is a singularity at t=0, therefore the is no "before".

 

If there is no singularity then there is no "time zero", no "first event" and therefore there is nothing to be "before".

 

Either way, I can't see that the question makes sense.

As to how you would test it: hopefully a theory of quantum gravity would make some predictions about what to look for on the CMB (or elsewhere) to confirm its predictions. For example, Penrose has claimed that there are patterns in the CMB that confirm his ideas.

[Thorham]

In classical GR there is a singularity at t=0, therefore the is no "before".

 

Now you're just repeating what you said earlier, while you also said this:

 

Of course, most people don't think that the singularity represents physical reality. We probably need a theory of quantum gravity to better understand the universe at that stage. It may turn out that there was no "big bang" in the sense of an initial starting point. The universe may be infinitely old. Or it may have collapsed and re-expanded. Or it could have been in some unknown state prior to expanding.

 

Saying that there's no 'before' because singularity at t=0 is a little too easy. Prove the singularity, and prove that time started at the big bang. In addition you have to prove that there are no multiple 'bubble universes' each with their own time. Good luck with that.

 

Asking the before question makes just as much sense as asking whether or not there was a before to begin with.

[sunshaker]

 

But the question still doesn't make sense; if there was no starting point, then what does "before" mean? Before what? Is the question just "what happened earlier than the earliest time we know about"? In which case, the answer is a rather obvious "we don't know (yet)".

with my question I never asked about a "before".

I was asking about relative sizes.

 

I admit I see our universe has a fractal of a larger universe, it is why I mentioned "virtual particles".

 

 

A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle. A particle is a nice, regular ripple in a field, one that can travel smoothly and effortlessly through space, like a clear tone of a bell moving through the air. A “virtual particle”, generally, is a disturbance in a field that will never be found on its own, but instead is something that is caused by the presence of other particles, often of other fields.

So I was imagining a virtual particle(universe's) expanding into an older universe,(dark energy?).

And how the entities in newly expanding universe would comprehend the old universe that it is expanding within, when they are many orders of magnitude smaller.

 

rough sketch showing a "virtual universe" expanding within a older universe, slowly overlapping.

There is a lot of talk about dimensions where physics is slightly different, so I was trying to imagine a fractal universe where a proton was the size of a star and how they would then view other objects has their universe overlaps ours and whether these objects would be similar to how we view dark matter.

 

But I wanted to know if a proton radiates heat from its internal kinetic energy. (which would then seem like a star to these fractal entities. And if a proton was like a star to them how would they then view these larger objects like boulder/asteroids/planets/stars from their smaller view point.?

 

Perhaps "dark matter" is part/objects of a older universe we are expanding into which we do not yet comprehend(belonging to two universes).

 

[StringJunky]

 

Now you're just repeating what you said earlier, while you also said this:

 

 

Saying that there's no 'before' because singularity at t=0 is a little too easy. Prove the singularity, and prove that time started at the big bang. In addition you have to prove that there are no multiple 'bubble universes' each with their own time. Good luck with that.

 

Asking the before question makes just as much sense as asking whether or not there was a before to begin with.

You are blinded by commonsense.

[Strange]

prove that time started at the big bang.

 

It didn't "start".

 

Prove the singularity

 

It is pretty well understood that there is a singularity at t=0 in the FLRW metric. If you are claiming otherwise, it is up to you to support that claim.

 

More discussion here, if you are interested: http://physics.stackexchange.com/questions/151027/interpretation-of-a-singular-metric

"the FLRW spacetime is a combination of the manifold [math]\mathbb{R}^{3,1}[/math] and the FLRW metric [math]g[/math]. The metric [math]g[/math] has a singularity at [math]t=0[/math] because at that point the proper distance between every pair of spacetime points is zero."

[Thorham]

Let me try that again in a different way.

 

Of course, most people don't think that the singularity represents physical reality.

Then why are you bringing it up?

 

It may turn out that there was no "big bang" in the sense of an initial starting point.

In which case the before question isn't relevant.

 

The universe may be infinitely old.

In this case any number of events could've lead to the big bang and the before question makes sense.

 

Or it may have collapsed and re-expanded.

In that case the before question makes sense as well, and is easy to answer: The collapse happened before the big bang.

 

Or it could have been in some unknown state prior to expanding.

In this case it also makes sense to ask what came before.

 

Then there's the possibility of bubble universes, in which case the before question yet again makes sense.

 

The before question doesn't make sense if the relevant part of GR is true, but is it? I'm not claiming that it isn't, I'm claiming we don't know, and that therefore the before question makes perfect sense.

 

More discussion here, if you are interested: http://physics.stackexchange.com/questions/151027/interpretation-of-a-singular-metric

Thanks.

Edited September 4, 2015 by Thorham

[Strange]

Let me try that again in a different way.

 

 

Then why are you bringing it up?

 

I guess I don't really understand what people are asking when they say "before the big bang". It sounds as if they are referring to the big bang as an event (which it isn't). The only thing I can think of which, theoretically, counts as such an event is the idea of the singularity at time zero. Even though this is probably not physically realistic it is still the only scientific theory we have. (There are all sorts of hypotheses and speculations about how to remove the singularity but none are confirmed or generally accepted yet.)

 

If by "before the big bang" people just mean "before the earliest known hot dense state" then I agree the question make sense (it is just badly phrased).

[Thorham]

The only thing I can think of which, theoretically, counts as such an event is the idea of the singularity at time zero. Even though this is probably not physically realistic it is still the only scientific theory we have.

 

Didn't the math somehow break down before t=0?

 

(There are all sorts of hypotheses and speculations about how to remove the singularity but none are confirmed or generally accepted yet.)

Doesn't that tell you there's a problem with the current theory?

 

If by "before the big bang" people just mean "before the earliest known hot dense state" then I agree the question make sense (it is just badly phrased).

 

It depends on what a big bang actually is. If it's something that just was then 'before' indeed doesn't make any sense. If it was caused by something, then it does make sense. In the case of your collapse example, you had a big crunch that lead to the big bang (yes, speculation)

[Strange]

Didn't the math somehow break down before t=0?

 

The singularity at t=0 is sometimes described as "the math breaking down". But it is, perhaps, more accurate to say that the theory no longer works (provides meaningful results) at that point. All theories have a limited domain where they are valid. You tend to get invalid results when you go outside those limits.

 

Doesn't that tell you there's a problem with the current theory?

 

I don't think anyone doubts that. But it is the only one we have!

 

 

It depends on what a big bang actually is. If it's something that just was then 'before' indeed doesn't make any sense. If it was caused by something, then it does make sense. In the case of your collapse example, you had a big crunch that lead to the big bang (yes, speculation)

 

The big bang is a model (cosmology based on the FLRW metric, commonly described as the Lambda-CDM model). It isn't a "thing" or a point in time.

 

So if there was a "big crunch" then that would be part of the same model. If the universe is infinitely old (which some attempts to merge quantum theory with GR suggest) then that would be part of the model.

[Thorham]

The singularity at t=0 is sometimes described as "the math breaking down". But it is, perhaps, more accurate to say that the theory no longer works (provides meaningful results) at that point. All theories have a limited domain where they are valid. You tend to get invalid results when you go outside those limits.

Okay.

 

I don't think anyone doubts that. But it is the only one we have!

Yeah, but if it doesn't work at some point then what good is it at that same point?

 

The big bang is a model

 

A model of what? I'm talking about the 'what'. It's just like gravity. It's a theory, but it's also the name of what causes something to appear to fall when we drop it.

 

So if there was a "big crunch" then that would be part of the same model. If the universe is infinitely old (which some attempts to merge quantum theory with GR suggest) then that would be part of the model.

This is just a language usage issue. There was still something that physically collapsed, and after that physically expanded. That's what 'before' refers to. It refers to what physically happened, not to the model. What happened before in a model that deals with a beginning obviously makes no sense.

 

[Strange]

Yeah, but if it doesn't work at some point then what good is it at that same point?

 

No use at all. That's the point. The big bang model says nothing about what happens then.

 

A model of what?

 

Of the universe and, more specifically, how it evolves over time. This is part of my problem with the phrase "before the big bang"; does it mean "before the universe"? If so, why would anyone think there was anything before the universe? By which I mean, why would anyone think there was a time when the universe didn't exist (in some form)?

 

This is just a language usage issue.

 

Maybe. But I am always worried when people seem to be referring to "the big bang" as an event (rather than a process or a model).

 

 

What happened before in a model that deals with a beginning obviously makes no sense.

 

Right. But there is no reason (as far as I know) to think there is a "beginning" (other than t=0 in the current big bang model, which we agree probably doesn't represent reality).

[Thorham]

Maybe. But I am always worried when people seem to be referring to "the big bang" as an event (rather than a process or a model).

But that's what people are referring to. They're referring to things that happened physically, they're not referring to the model. The 'before the big bang' question really means: 'What happened before the expansion, if anything happened at all?'. The current theory doesn't work at this point so it's a perfectly valid question (which is perhaps worded in the wrong way).

[Strange]

But that's what people are referring to. They're referring to things that happened physically, they're not referring to the model.

 

Maybe we are talking slightly at cross purposes here. I am not trying to make a distinction between the model and reality (although that is an important to distinction to keep in mind).

 

Rather, I am trying to make a distinction between the (arguably incorrect) use of the term "big bang" to refer to a one-off event which is popularly described as an explosion or creation of the universe, versus the use of "big bang" to refer to the way the universe evolves over time.

 

 

The 'before the big bang' question really means: 'What happened before the expansion, if anything happened at all?'.

 

I agree that is a perfectly valid question and an active area of research. So, ultimately, you are right: it is just a matter of words. I just happen to think the common use of the words "big bang" is, or can be, very misleading.