[petelamana (OP)]

If...
 - the universe is isotropic
 - and has an observable radius of roughly 14 billion parsecs
 
Then...
 - doesn't the word "radius" infer a geocentric universe?
            - if so,  would that mean that the "center" of the Big Bang was right here?  (well, probably Lawrence, KS.    )
 - additionally, the word "isotropic" would mean that regardless of where an observer is located in the universe there will always be an ever-growing radius from that location, currently 14.3 billion parsecs, then wouldn't the universe be expanding into itself?

[chiralSPO]

Yes, in an isotropic and unbounded space, there is no special point that can be considered the center, any choice is equally valid. Because all points are equivalent in this scario, it is up to our discretion to choose the coordinate system that makes the most sense for whatever question we would like to answer. Thus the radius of the 'observable universe' is set with respect to the 'observer'.

And yes, the universe appears to be expanding outwards from every point. If the universe is actually infinite, we can regard the expansion as a process in the context of Hilbert's Grand Hotel. ( https://en.wikipedia.org/wiki/Hilbert%27s_paradox_of_the_Grand_Hotel ) Imagine a hotel with infinitely many rooms, and infinitely many guests. If every morning every guest moves to a room with a number twice that of the room they staid in the night before (n →2n), then every day the density of occupied rooms will decrease by a factor of 2, but the number of guests and number of rooms remain infinite. You can also think of this as the distance between occupied rooms increasing at an increasing rate--essentially, this is an ever-expanding hotel with the same amount of people in it from each day to the next.

[evan_au]

Did the Big Bang happen where Earth now is?

I would reverse it.

My rationale:
- The Big Bang filled the entire universe (at the time).
- The size of the universe expanded at the speed of light (and sometimes faster).
- The Big Bang continued to fill the universe, gradually red-shifted to the 2.7K temperature of the CMBR.
- The Earth is inside the universe.

My conclusion: The Earth is now where the Big Bang happened.

[Bill S]

I believe the original point of Hilbert's Hotel was to demonstrate that an infinite number of rooms, filled with an infinite number of people, could still accommodate more.  This was achieved by moving all the occupants, successively, into the room with the next higher number.  This appears to work only because one can never reach the “infinite” room.  I think David Hilbert had a sense of humour, and wanted to see how many intelligent people would be drawn into discussion of this insoluble problem.

Using the “Hotel” to demonstrate that distances between points in an infinite space can increase, without increasing the “infinite space” itself, is similarly “unreal”.   

[jeffreyH]

Hilbert developed the idea of infinite dimensional vector spaces so the hotel was not simply an academic exercise.
https://en.m.wikipedia.org/wiki/Hilbert_space

[opportunity]

"If" the big bang happened where we are now, and we believe in that, where we are, we're asking ourselves to explain an event others have faith in, like explode first and explain later. Any ideas?

I know it sounds absurd, yet every theory proposed needs to acknowledge how well or badly it can be believed in, for those who are to accept any new learning.

[opportunity]

I think the big bang theory in the context of faith is dangerous. It's a daa; to have faith in it beckons a type of allegiance I'm thinking. Of course we're scientists, yet, for a more fundamental approach it "is" dangerous.

"Here's the bang, now explain this". That's not good.

[chiralSPO]

I do agree that it makes sense for scientists to present the level of certainty that a theory currently has, as well as ways in which the theory is falsifiable.

But I don't see why you are saying that the big bang is a belief. It's not like there is no evidence of the big bang...

We can see the current expansion of the universe, and because of the speed of light, we can also see the history of the expansion by looking farther and farther away (longer and longer ago). It is very clear that the universe was much more crowded a long time ago than it is now. Just extrapolating back to a simple point would certainly a stretch, if this were the only data we have.

There is also the cosmic microwave background, which allows us to "see" the very earliest moments of the universe once it became transparent to light. We know that for the first few million years, everything was really hot.

This lead us to do experiments here on Earth (astronomy and cosmology rely entirely on observation and theoretical work, but can be supported by experiments here). Using particle accelerators and other nifty experimental setups, scientists have been able to study how matter behaves in conditions with as much energy density as the early universe appears to have had. Low and behold, the data we have gotten from high energy physics has given rise to new theories of fundamental physics that allowed us to predict the ratios of H, D, He, Li and other elements formed during the big bang, and it agrees almost perfectly with what we actually find in our observations of the early universe. This is important, because it shows two independent lines of study finding the same answer.

Now there are a few shortcomings in the theory as it stands:

1) Rapid expansion--based on our measurements and the theory used to interpret them, it looks like the universe must have expanded far, far faster than the speed of light for a very brief period right after the big bang. Is it a problem with our theory of the big bang? Maybe our observations are wrong, or the interpretation of those data? Maybe our understanding of the speed of light as the ultimate speed limit is wrong. Or our understanding of time... Something needs tweaking there, but this alone doesn't invalidate the whole theory.

2) Where is the antimatter? We are able to account for all of the matter formed in the big bang (very accurately), but the same model predicts equal formation of antimatter, which we have yet to find any evidence for. (Some have hypothesized that the universe has parts that are made of matter, and parts made of antimatter, but we should be able to see the boundary between those regions as random bits of dust and antidust meet)

3) How do dark matter and dark energy fit in? We have excellent understanding of matter and energy, but together these represent a small fraction of the universe. Dark matter and dark energy appear to make up the remainder, but we have basically no idea what it is, or how it should fit in to our current frameworks.

[Bill S]

My conclusion: The Earth is now where the Big Bang happened.

And so is everything/everywhere else in the Universe.

[opportunity]

I do agree that it makes sense for scientists to present the level of certainty that a theory currently has, as well as ways in which the theory is falsifiable.

But I don't see why you are saying that the big bang is a belief. It's not like there is no evidence of the big bang...

We can see the current expansion of the universe, and because of the speed of light, we can also see the history of the expansion by looking farther and farther away (longer and longer ago). It is very clear that the universe was much more crowded a long time ago than it is now. Just extrapolating back to a simple point would certainly a stretch, if this were the only data we have.

There is also the cosmic microwave background, which allows us to "see" the very earliest moments of the universe once it became transparent to light. We know that for the first few million years, everything was really hot.

This lead us to do experiments here on Earth (astronomy and cosmology rely entirely on observation and theoretical work, but can be supported by experiments here). Using particle accelerators and other nifty experimental setups, scientists have been able to study how matter behaves in conditions with as much energy density as the early universe appears to have had. Low and behold, the data we have gotten from high energy physics has given rise to new theories of fundamental physics that allowed us to predict the ratios of H, D, He, Li and other elements formed during the big bang, and it agrees almost perfectly with what we actually find in our observations of the early universe. This is important, because it shows two independent lines of study finding the same answer.

Now there are a few shortcomings in the theory as it stands:

1) Rapid expansion--based on our measurements and the theory used to interpret them, it looks like the universe must have expanded far, far faster than the speed of light for a very brief period right after the big bang. Is it a problem with our theory of the big bang? Maybe our observations are wrong, or the interpretation of those data? Maybe our understanding of the speed of light as the ultimate speed limit is wrong. Or our understanding of time... Something needs tweaking there, but this alone doesn't invalidate the whole theory.

2) Where is the antimatter? We are able to account for all of the matter formed in the big bang (very accurately), but the same model predicts equal formation of antimatter, which we have yet to find any evidence for. (Some have hypothesized that the universe has parts that are made of matter, and parts made of antimatter, but we should be able to see the boundary between those regions as random bits of dust and antidust meet)

3) How do dark matter and dark energy fit in? We have excellent understanding of matter and energy, but together these represent a small fraction of the universe. Dark matter and dark energy appear to make up the remainder, but we have basically no idea what it is, or how it should fit in to our current frameworks.

Good answer.

I'm wondering though, we understand quantum-entanglement as faster than light travel, yet why has no one proposed quantum-entanglement as an initial feature of the big bang, as a part of the initial-conditions that give our reality the features it has? For the current big-bang model it would seem logical to marry these two issues.

This also echoes what bill said:  And so is everything/everywhere else in the Universe. That sounds like a quantum entanglement feature to me. In fact, the way the big bang became about seems to hold quantum entanglement (faster than light dynamic) in place as a feature of our reality.

[evan_au]

Dark matter (and dark energy) appear to make up the remainder, but we have basically no idea what it is, or how it should fit in to our current frameworks.

A number of cosmic simulations have tried to incorporate Dark Matter into their models, using the presumed characteristics of "WIMPy" Dark Matter: non-interacting subatomic particles.

They have demonstrated that their models look realistic with the Dark Matter present.

...or maybe they saw estimates of the amount of Dark Matter, and tweaked their models to suit?
See: https://en.wikipedia.org/wiki/Bolshoi_Cosmological_Simulation

[Bored chemist]

Did the Big Bang happen where Earth now is?

I would reverse it.

My rationale:
- The Big Bang filled the entire universe (at the time).
- The size of the universe expanded at the speed of light (and sometimes faster).
- The Big Bang continued to fill the universe, gradually red-shifted to the 2.7K temperature of the CMBR.
- The Earth is inside the universe.

My conclusion: The Earth is now where the Big Bang happened.

Interestingly, my extraterrestrial friend Zog who lives 10 billion light years away told me the same thing about his home planet.

[jeffreyH]

I have some bad news for you bc. Your friend Zog died. About 9 point something billion years ago.

[Bored chemist]

I have some bad news for you bc. Your friend Zog died. About 9 point something billion years ago.

Why do you say that?
His race is rather long-lived by our standards.

[Bill S]

Maybe our understanding of the speed of light as the ultimate speed limit is wrong.

It might be worth looking at the work of João Magueijo, who believes the speed of light was greater in the early Universe.

Some have hypothesized that the universe has parts that are made of matter, and parts made of antimatter, but we should be able to see the boundary between those regions as random bits of dust and antidust meet

Could it be that these boundaries are so far away that light from them has not reached us, and probably never will?

[petelamana (OP)]

I suppose it is possible that light from these boundary objects will never reach us, considering that Sol only has 7,600,000,000 years until it swallows the Earth. 

[Bill S]

This also echoes what bill said:  And so is everything/everywhere else in the Universe.

There was no intention of invoking quantum entanglement here.

At risk of trying to teach my grandmother to suck eggs, I’ll use the balloon analogy to show how I understand the situation. 

Imagine an uninflated balloon on which you mark a small dot.  As you inflate the balloon, the dot grows.  Now, ask yourself where, within that enlarged patch, you might find your original mark.  Obviously, the answer must be “everywhere”.  The same can be said of the Big Bang.  At the instant of “creation” it encompassed the entire Universe, and as the Universe has expanded it has continued to do that; it has not left behind some original Big Bang site. 

Having said, and perhaps accepted, all this; if we return to the balloon analogy, there must always be a feeling that because the mark expanded evenly in every direction from the centre, that must be its spreading centre.  I suspect that it is this feeling, rather than an inability to accept that the Big Bang happened everywhere, that is the hitch-hiker’s chief difficulty.  Obviously your original dot has expanded, but has it spread across the balloon?  The answer has to be “no”, because the material of the balloon has expanded, carrying your mark with it.  It is tempting to think that your spot was made in the centre of the extended mark, but such is not the reality, either in the case of your dot, or the Universe.

[Bill S]

I suppose it is possible that light from these boundary objects will never reach us, considering that Sol only has 7,600,000,000 years until it swallows the Earth.

They might also fail to reach us if the distance between them and us is increasing at superluminal speed.

[petelamana (OP)]

Thank you. That is a truism that I failed to mention.

[jeffreyH]

Maybe our understanding of the speed of light as the ultimate speed limit is wrong.

It might be worth looking at the work of João Magueijo, who believes the speed of light was greater in the early Universe.

Some have hypothesized that the universe has parts that are made of matter, and parts made of antimatter, but we should be able to see the boundary between those regions as random bits of dust and antidust meet

Could it be that these boundaries are so far away that light from them has not reached us, and probably never will?

The answer may lie in s channel scattering.