What is a parsec? Definition and calculation

One arcsecond angular size at one parsec distance from Earth also = one AU in diameter. Thus, a telescope that resolves to one arcsecond angular size in the eyepiece, viewing an object 10 pc distance means the linear size or diameter of the object is 10 AU or astronomical units. Applying this to observing binary stars at 10 pc with one arcsecond angular size split, the distance between the two stars is 10 AU. The parsec is a great unit of measurement in astronomy.
 
Jul 30, 2022
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The term parsec is NOT misused in Star Wars.
The point of the Kessel Run mentioned by Han is to find the shortest route by DISTANCE. Less time in hyperspace = less fuel and more profit.
It's the viewers who get it wrong, not the movie.
 
The term parsec is NOT misused in Star Wars.
The point of the Kessel Run mentioned by Han is to find the shortest route by DISTANCE. Less time in hyperspace = less fuel and more profit.
It's the viewers who get it wrong, not the movie.

Um, just how does an "intelligent being" in a galaxy "far-far away" at a time "long ago" know what a parsec is? Did they visit Earth and calculate it for themselves, long before humans invented telescopes?

Or, is it based on the parallax of some other planet orbiting some other star in that other galaxy, so that it has no known relationship to what we call a parsec?

Heck, even a light year would not match unless they happen to have come from a planet that also has a year that is 31,556,952 seconds long.

Wait, what are those alien guys calling a "second"? Maybe one 24th of one 3600th of the length of the day on their home planet? o_O

Just a reminder of how Earth-centric all of our cosmological thinking is.
 
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Um, just how does an "intelligent being" in a galaxy "far-far away" at a time "long ago" know what a parsec is? Did they visit Earth and calculate it for themselves, long before humans invented telescopes?

Or, is it based on the parallax of some other planet orbiting some other star in that other galaxy, so that it has no known relationship to what we call a parsec?

Heck, even a light year would not match unless they happen to have come from a planet that also has a year that is 31,556,952 seconds long.

Wait, what are those alien guys calling a "second"? Maybe one 24th of one 3600th of the length of the day on their home planet? o_O

Just a reminder of how Earth-centric all of our cosmological thinking is.
The "universal translater" accounted for that...Wait, that was the Star Trek universe. Never mind. o_O
 
Here is a site stating the parsec error was addressed shortly after the movie’s release in 1977. It was corrected (ad hoc) 40 years later in the Solo movie.

It makes little sense to outrun your enemy by taking a sorter distance path that takes longer time. Your enemy will be happy to await your arrival.

iPhone.
 
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It always amuses me when somebody screws-up and then tries to redefine the words in our language to make themselves seem correct. That just always seems to compound the screw-up. And then we are supposed to be "polite" and not notice? People get a lot more respect when they admit an error and fix it, compared to never admitting an error.
 
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I went back and reviewed my copy of Allen's Astrophysical Quantities, Fourth Edition, c. 2000. On page 12, "2.3 General Astronomical Constants", the parsec is defined as 206264.806 AU (astronomical units). In meters defined as 3.0856776 x 10^16 m.

Defining H0 as 67 km/s/Mpc, space expands at 2.17131 x 10^-18 cm/s/cm. What happens to the value of the parsec now? :)
 
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I went back and reviewed my copy of Allen's Astrophysical Quantities, Fourth Edition, c. 2000. On page 12, "2.3 General Astronomical Constants", the parsec is defined as 206264.806 AU (astronomical units). In meters defined as 3.0856776 x 10^16 m.

Defining H0 as 67 km/s/Mpc, space expands at 2.17131 x 10^-18 cm/s/cm. What happens to the value of the parsec now? :)

That depends on how space-time actually expands (if there really is "Inflation"). If all of space is expanding the same everywhere, that is just the same problem of how to measure expansion with a meter stick that is also expanding - you can't. So, a parsec will always be a parsec, and a cm will always be a cm, as far as we can determine by measuring dimensions.

Since this thread started with a whimsical topic (Star Wars script not getting astronomy jargon right), I feel at liberty to drift it back to cosmology and what that may or may not be getting right.

So, there is also time involved in space-time. Thus, if one postulates that "Inflation" affects the physical dimensions, why not the time dimension? In fact, how could it not affect the time dimension if it pulls matter farther apart, since there is clearly an effect (actual observations) on time with proximity to large amounts of matter.

And , how about the effect of "Inflation" on the "laws" of physics, or just the parameters of things like the ionization potential of specific atoms of specific elements.

It seems to me that "Inflation" has a definition that translates to "It does everything we need it to do to make the BBT plausible, but does nothing to disturb the plausibility of the BBT."

Redshift is certainly an observable effect, but can have several causes that we know about so far. If we start to question some basic assumptions that are accepted as "principles" but have no proof they are actually true everywhere for all times, then there are lots of things that one could imagine as we try to interpret what we see in astronomy. But, people are looking for "order" and "simplicity" to understand things that we observe, and tend to have a strong bias against things that seem to detract from those goals and in favor of things that seem to achieve those goals.

So, mind bending things like questioning whether time is operating at the same speed in all that we see is usually rejected by citing things like the "uniformity principle", even thought we have no way of proving that physical parameters (and time) are uniform at every point in space-time that we can observe in astronomy.

I am waiting for some of the initial Webb Telescope findings to be verified before getting into questioning the apparent disparity between the supposed age of the cosmic background radiation and the age of some distant galaxies that have been claimed in analyses of the initial deep field pictures. As with Hubble, it looks like the "history book" for the universe is going to need a new time line to accommodate new observations. But, I am waiting for some of those claims to be checked and accepted before getting into discussions about what they mean.

Getting back to red shift - I am wondering about the interpretation that expansion is accelerating. What I see presented is 3 graphs that each use a straight line to relate distance to recession speed, with different slopes for the straight lines. Because those 3 graphs use different techniques for "measuring" (actually, trying to estimate) distances, I am not surprised that they have somewhat different results. Yes, people keep checking their math and reducing uncertainties to the point that they think that the differences between the slopes of their lines are statistically significant - but my experience has been that uncertainties are most often underestimated. What strikes me about the conclusion that expansion is accelerating is that I have not seen anybody put those 3 lines together and shown a curved line fits all 3 better than 3 separate straight lines in different time periods. To me, that is necessary to reach a conclusion that they are all accurately measuring the same parameters of distance and redshift such that we can conclude that expansion is accelerating with time.
 
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I went back and reviewed my copy of Allen's Astrophysical Quantities, Fourth Edition, c. 2000. On page 12, "2.3 General Astronomical Constants", the parsec is defined as 206264.806 AU (astronomical units). In meters defined as 3.0856776 x 10^16 m.
Is this based on the semi- major axis, or a fixed value like150E6 km. If the former, does the parsec get tweaked with better and better values for a?

Defining H0 as 67 km/s/Mpc, space expands at 2.17131 x 10^-18 cm/s/cm. What happens to the value of the parsec now? :)
Local expansion, even for the parsec may take a long time before needing tweaked, I think. But I’m not convinced expansion overpowers any of the four forces, so nothin will change much in our galaxy until acceleration rates cause distance problems fir galaxies.

iPhone
 
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That depends on how space-time actually expands (if there really is "Inflation"). If all of space is expanding the same everywhere, that is just the same problem of how to measure expansion with a meter stick that is also expanding - you can't. So, a parsec will always be a parsec, and a cm will always be a cm, as far as we can determine by measuring dimensions.
I’m one who can’t seem to imagine how expanding space will overcome anything other than intergalactic space,when the force of gravity is very feeble relative to the expansion.

The CMBR space was about 1200x “denser”. So if the electrons were 1200x closer to the atom during this time, then the values for the redshift we observe today make little sense to me.

The expansion (Hubble Flow) is a river that flows in all directions away from any boat, but boats don’t get stretched by it much at all, IMO.

I would assume this view is mainstream, but perhaps not.
 
I guess the way people think about it is dependent on how they think about "space". Is it empty "nothing"? Is it filled with "fields"? Do those fields interact - if so how? Etc. And then there is the time part. Does it get stretched by inflation, or not?

But trying to think about it logically, if gravity can overcome inflation, then wouldn't the reason for "inflation" be lost for making the BBT work? Clearly, the whole universe must have been a black hole early on, and probably still, based on current estimates of density and radius. So, "inflation" was invented to make matter disperse at more than the speed of light while being attracted by gravity to huge accelerations that would promptly exceed the speed of light in collapse.

So, how do you suppose that "space" can expand nonuniformly such that it does not change the spacing in atomic nuclei, electron orbitals, molecular bonds, orbiting planets, etc. but still can make all those things fly apart without going through "space"? Remember, this is not the same as two forces pulling matter in opposite directions through space. There is an assumption that one force ("dark energy") works on space itself, changing its dimensions, while the other forces act on matter, but not space, and try to move matter through space.

Personally, I have my own doubts about the existence of "inflation" in the sense that the BBT requires it to work via "dark energy".

On the other hand, I do think about how space behaves under intense gravitation, such as in the vicinity of a black hole. As I have asked here several times with no discussion in response: Does space just "warp" like a static lattice that can stretch but not shift in bulk, or does space "flow" more like a compressible fluid?

I have an easier time envisioning the behavior of light photons in the vicinity of an event horizon if I think in terms of flow, rather than warp. If "space" is continuously flowing into a black hole, then it is easy to see the boat-in-the-current analogy of the light particles going "out" at only light speed while "space" is flowing "in" at greater than light speed. But, if space is static, just warped, then a photon emitted "outward' into space right at the event horizon would seem to need to be able to rise through space to "infinity" above the horizon as it loses energy as a particle and goes to longer wavelength as a wave, at increasing distances outside the event horizon.

If we could make a probe that could approach an event horizon, maybe we could tell which was happening. But, we can't do that.
 
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... And then there is the time part. Does it get stretched by inflation, or not?
I wish I had time to answer this. *wink*. Perhaps if we learn more about time we can answer your good question,

But trying to think about it logically, if gravity can overcome inflation, then wouldn't the reason for "inflation" be lost for making the BBT work?
I think there is no problem for the earliest moments of “pure” (Spock) energy. .

So, how do you suppose that "space" can expand nonuniformly such that it does not change the spacing in atomic nuclei, electron orbitals, molecular bonds, orbiting planets, etc. but still can make all those things fly apart without going through "space"?
The atoms formed after 380k years, so the expansion speed at the atomic level was likely too wimpy to effect proton-electron orbits, IMO.

Remember, this is not the same as two forces pulling matter in opposite directions through space. There is an assumption that one force ("dark energy") works on space itself, changing its dimensions, while the other forces act on matter, but not space, and try to move matter through space.
Nicely put.

Personally, I have my own doubts about the existence of "inflation" in the sense that the BBT requires it to work via "dark energy".
There may be a correlation there, but Guth’s original hypothesis used a different mechanism for Inflation. DE was introduced to address the acceleration of expansion.

On the other hand, I do think about how space behaves under intense gravitation, such as in the vicinity of a black hole. As I have asked here several times with no discussion in response: Does space just "warp" like a static lattice that can stretch but not shift in bulk, or does space "flow" more like a compressible fluid?
I had read one account suggesting space flows into a black hole, but Dr. Joe said otherwise, and his view is likely mainstream.

If we could make a probe that could approach an event horizon, maybe we could tell which was happening. But, we can't do that.
Ironically,SMBHs have a somewhat weak grav gradient that might allow close approaches in the distant future.

iPhone
 
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I think there is no problem for the earliest moments of “pure” (Spock) energy. .

The atoms formed after 380k years, so the expansion speed at the atomic level was likely too wimpy to effect proton-electron orbits, IMO.

Even for atoms that formed 380,000 years after the BB, there has still supposedly been a factor of 1080 inflation of space since then. Surely, if that also expanded atoms and affected their electron energy levels, there is a problem with looking at redshifted hydrogen lines. And, well before that, protons and neutrons were formed, and supposedly some alpha particles (helium nuclei). Wouldn't space dimensional differences affect the strong and weak nuclear forces' abilities to create stable nuclei and the energies involved?

At this point, even the 380K years looks questionable, given that some astronomers think they are seeing older galaxies in the new Webb deep field picture. And, there is also that "Methuselah star" that looks older than the 13.8 billion years that the universe has been thought to exist. See https://en.wikipedia.org/wiki/HD_140283 .

So, maybe the cosmologic "dark age" didn't actually end at the age the BBT currently says. Maybe earlier? Maybe timing is off because time is not as constant as being assumed?

It sort of amuses me when theoreticians start making assumptions to make their models fit other assumptions, rather than observations, as is the case with the BBT time line before what is assumed to be 380,000 year old light in the form of the microwave background. True that there is nothing else to fit if you have no actual observations. But, the logic of the interweaving of assumptions seems to be unconstrained attempts to make current thinking seem to be OK, without seriously exploring other potential ramifications of the added assumptions. To me, the concept of "inflation" raises a whole lot of questions about how we are interpreting actual observations. Theorists really can't have their simplifying assumptions without also raising complicating plausibilities.
 
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Even for atoms that formed 380,000 years after the BB, there has still supposedly been a factor of 1080 inflation of space since then. Surely, if that also expanded atoms and affected their electron energy levels, there is a problem with looking at redshifted hydrogen lines.
Right. Thus expansion of space does not have much affect on the other forces, except weak gravity areas between galaxy clusters.

And, well before that, protons and neutrons were formed, and supposedly some alpha particles (helium nuclei). Wouldn't space dimensional differences affect the strong and weak nuclear forces' abilities to create stable nuclei and the energies involved?
I suspect the strong force in the early microseconds would not be affected by expansion. Your H line example in the CMBR should be evidence enough, IMO.

At this point, even the 380K years looks questionable, given that some astronomers think they are seeing older galaxies in the new Webb deep field picture.
I suspect they are seeing just what was expected, furthering the BBT.

And, there is also that "Methuselah star" that looks older than the 13.8 billion years that the universe has been thought to exist. See https://en.wikipedia.org/wiki/HD_140283 .
IIRC, its age is in the margin of error. If not shouldn’t we have found many others by now. ~100 years ago, many stars were deemed older than the universe but this was due to Cepheid variations.

So, maybe the cosmologic "dark age" didn't actually end at the age the BBT currently says. Maybe earlier? Maybe timing is off because time is not as constant as being assumed?
Perhaps this is so, but multiple lines of evidence supports the current model. Perhaps the best evidence is found in the time dilation effects in SN. The more distant ones will appear to last longer and be dimmer due to the expansion rate, matching the theory.

It sort of amuses me when theoreticians start making assumptions to make their models fit other assumptions, rather than observations, as is the case with the BBT time line before what is assumed to be 380,000 year old light in the form of the microwave background.
I don’t see this as ad hoc. The addition of Inflation theory, however, is sometimes held as ad hoc to fix two problems, including the anisotropy.

True that there is nothing else to fit if you have no actual observations. But, the logic of the interweaving of assumptions seems to be unconstrained attempts to make current thinking seem to be OK, without seriously exploring other potential ramifications of the added assumptions.
The Big Bang Bullets thread presents objective evidence to greatly restrain suppositions.

To me, the concept of "inflation" raises a whole lot of questions about how we are interpreting actual observations. Theorists really can't have their simplifying assumptions without also raising complicating plausibilities.
Yes, you’re hardly alone. Inflation theory looks at events that modern science cannot create in colliders, which are limited to t>1E-12 sec.

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Helio, I did recently read through the BB Bullets thread, again. Not so easy with 7 pages of posts, now. So, no need to refer me to it.

I do have trouble with the media articles that play loose with the language regarding red shift, with z, 1+z and age all being mixed together, and not necessarily properly. So, I tend to focus on estimated age values. Things like the Methuselah star don't fit. True, they keep trying to make it fit, and doing the "uncertainty band" dance, but the "best guess" value still doesn't fit. And, it is a relatively close star, so well studied. There are others farther away that aren't as easy to measure parameters with such small uncertainty.

Similarly, the cosmic background radiation supposedly having a black body temperature of 3000 Kelvins before 1080 times expansion of its wavelength by inflation seems to not match the current temperature where hydrogen ionizes in our sun's atmosphere (7,000 to 10,000 K). So, why did hydrogen not form until the universe had cooled by expansion to 3000 K?

Even if the "big picture" of the Big Band is roughly correct, and inflation really exists, it seems very likely to me that the timing is not as well known as stated in the media articles.

And, the sequence of events does not seem all that certain to me. For example, why could stars not have formed well before hydrogen atoms condensed out of electrons and protons in plasma in free space? Stars are made of plasma. Gravity was already at work on the plasma for substantial period of time (as estimated) and it can condense plasma, especially if it is already thousands of times more dense than what we see now in the local region galaxies. And, with potential for nonuniformities in density during inflation, why could we not already have "primordial" black holes seeding galaxies as soon as there were protons and electrons?

As for:
Inflation theory looks at events that modern science cannot create in colliders, which are limited to t>1E-12 sec.
I don't agree that modern science has created the conditions of the Big Bang after 10^-12 seconds, simply by slamming protons together and looking at the "pieces" that get created at high energies. There is a difference between two protons hitting each other at relative speeds similar to extreme temperatures in the early fractions of a second of the Big Band and the extreme density of such subatomic particles postulated for the condition of the whole universe at that point in time. All of the pressures, particle interactions, etc. are computed on the basis of theories that we can't really check for accuracy in those conditions. The idea that we "know everything there we need to know" about how subatomic particles behaved in the early universe seems not just uncertain, but unlikely to me.

And, then there is the question about the rate of time passage that I keep asking, coming from several concepts that suggest it could well not have been like it is here and now. So ideas like the speed of the inflation needing to be so rapid that subatomic particles only had time to make hydrogen and a smaller amount of helium before the opportunity passed to make heavier elements seems like a real logical stretch to me. Are the supernova explosions that make the heavy elements in the present time "slow"? How fast does time pass in the middle of a stellar mass? How fast does time pass in the universe when it is all the size of a current atom? Does the BBT take all of that into account?
 
Helio, I did recently read through the BB Bullets thread, again. Not so easy with 7 pages of posts, now. So, no need to refer me to it.
Yep. I was hoping each bullet would bring further explanation, but it’s similar to how much we’re now not discussing parsecs. :)

Nevertheless, it’sthe bullets that are important for any cosmological theory

I do have trouble with the media articles that play loose with the language regarding red shift, with z, 1+z and age all being mixed together, and not necessarily properly.
Agreed, and I’m guilty as well, especially when an accurate value is not that important.

So, I tend to focus on estimated age values. Things like the Methuselah star don't fit. True, they keep trying to make it fit, and doing the "uncertainty band" dance, but the "best guess" value still doesn't fit.
That’s not my impression. See this article.

Similarly, the cosmic background radiation supposedly having a black body temperature of 3000 Kelvins before 1080 times expansion of its wavelength by inflation seems to not match the current temperature where hydrogen ionizes in our sun's atmosphere (7,000 to 10,000 K). So, why did hydrogen not form until the universe had cooled by expansion to 3000 K?
The upper photosphere is ~ 5000K, and most of the hydrogen is H+. 3000K is the temp. when the vast majority of H is atomic. You might find this article interesting.


?
Stars are made of plasma.
Right, but they formed from atomic and diatomic hydrogen, plus helium etc. As the cloud collapsed, temperatures soared.

I don't agree that modern science has created the conditions of the Big Bang after 10^-12 seconds, simply by slamming protons together and looking at the "pieces" that get created at high energies. There is a difference between two protons hitting each other at relative speeds similar to extreme temperatures in the early fractions of a second of the Big Band and the extreme density of such subatomic particles postulated for the condition of the whole universe at that point in time.
I think proton-proton impacts aren’t too fussy about pressures.
 
Helio,

First, I did read the article in your link before I made my previous post. It discusses how the age estimates for that star have varied, and the uncertainty of the measurements. It also discusses the various estimates for the age of the universe. If you believe the latest star age estimate, then it is finally less than the 13.8 billion years that people keep bantering around for the age of the universe. But, if you also look at more recent ages for the universe, then some of those are much younger, too, and the star looks older than the universe, again. There seems to be some picking and choosing among estimates to make things "look right" with the theory. I just take that to mean that neither the theoretical estimates of the star's age nor the estimates of the universe's age are accurate enough to make the sweeping conclusions about exactly how things happened in the BBT. This star doesn't have to be just younger than the universe for the BBT to have the details right, it has to be young enough to fit the model between the time the universe was initiated and when the BBT says the first stars formed - and then it would still be the very first star - which seems unlikely to have ended up in our own galaxy. Remember, this is a sample of one, so just putting a reasonable distribution for age range of the first generation of stars on this stars age gets us back earlier in time for the actual first star in the whole universe.

Next, thanks for the link describing the theory about the equilibrium ratios of hydrogen ions to hydrogen atoms using the Saha equation and then some improvements. However, those results seems to be at odds with what is said in another link that I can't find at the moment, which gives values for roughly none to roughly 100% hydrogen ionization between 7,000 K and 10,000 K in our sun's photosphere. I thought I had saved that link, but it is not where I thought I put it, and a quick search has not turned it up again. More later, maybe. Anyway, the link you provided also shows a range for hydrogen ionization changing percentage from none to all. So, picking just one temperature for the "dark body" radiation to have made it through seems to have been made near zero percent ionization. I guess the argument for the it that getting through 13.7 billion light year of space would only happen at extremely low level of free electrons. Anyway, I need to resolve the ionization temperature discrepancy in the values in the different links, because it is about a factor of 2 in temperature. And, there is still the question in my mind about how the factor of 1080 inflation assumed for space could have affected the properties of hydrogen, including its ionization temperature.

Regarding "[Stars] formed from atomic and diatomic hydrogen, plus helium etc. As the cloud collapsed, temperatures soared." Yes, that is what people who believe the BBT believe. But, why does it need to be true? What observations make it clear that stars must start from atomic matter, rather than plasma. Is it even necessary for the BBT model to work? How does the BBT show that no initial non-uniformities in the plasma could have caused stars and even galaxies to start forming before expansion to (average) universe temperature of 3000 K?

Finally, your comment that you "think proton-proton impacts aren’t too fussy about pressures," seems to ignore my point about using those impacts to try to produce some sort of equation of state for the extremely early universe. The particles produced by proton-on-proton impacts in the CERN collider are at infinitesimal fractions of their postulated densities in the first tiny fractions of a second following the Big Bang. So, how do you verify the theory about how those particles behave in such extremely dense concentrations? Or, does the BBT ignore that physics question by postulating that some unknown force ("dark energy") produced "inflation" of "space" independently of what was in that space at the time, rather than because of what was in it at the time?
 
I'm finally back from travelling and have a keyboard in lieu of the crazy iPhone to use.

There seems to be some picking and choosing among estimates to make things "look right" with the theory. I just take that to mean that neither the theoretical estimates of the star's age nor the estimates of the universe's age are accurate enough to make the sweeping conclusions about exactly how things happened in the BBT.
No theory can ever be proved, so it is always about the credibility of the theory and the objective evidence that supports it. There doesn't seem to be a lot of debate on a wide range of values for the age of the universe. Indeed, it was tweaked from 13.7 Byrs. to 13.8 Byrs. only a year or so ago due to better data.

There is to your point, however, some debate especially given two fairly clean, but slightly different, values for the expansion rate using different methods.

The CMBR (ie anisotropy), apparently, does allow cosmologists to calculate expansion rates. [Dan Hooper's book addresses this a little.]

Next, thanks for the link describing the theory about the equilibrium ratios of hydrogen ions to hydrogen atoms using the Saha equation and then some improvements. However, those results seems to be at odds with what is said in another link that I can't find at the moment, which gives values for roughly none to roughly 100% hydrogen ionization between 7,000 K and 10,000 K in our sun's photosphere.
That's interesting, especially given the solar upper photosphere is ~ 5000K (per Bhatnagar & Williamson), and I assume with a great deal of H ions, though even negative ions are present.

And, there is still the question in my mind about how the factor of 1080 inflation assumed for space could have affected the properties of hydrogen, including its ionization temperature.
That's a good question. I know that reionization produced more Thomson scattering, and this seems to have occurred at z ~ 7.7

What observations make it clear that stars must start from atomic matter, rather than plasma. Is it even necessary for the BBT model to work?
I think cloud collapse models would struggle in producing progenitor stars from plasma given the need for some cooling, but I don't know.

How does the BBT show that no initial non-uniformities in the plasma could have caused stars and even galaxies to start forming before expansion to (average) universe temperature of 3000 K?
The CMBR is uniform to about 1 part in 100,000, which is why it was so hard to produce the maps. This very little anisotropy was enough to produce stars but not for perhaps at least another 150 million years. These anisotropies, as I understand them, are dynamic, meaning these regions have cycles of contraction then, due to heating, expansion.

Finally, your comment that you "think proton-proton impacts aren’t too fussy about pressures," seems to ignore my point about using those impacts to try to produce some sort of equation of state for the extremely early universe. The particles produced by proton-on-proton impacts in the CERN collider are at infinitesimal fractions of their postulated densities in the first tiny fractions of a second following the Big Bang.
I confess to being very weak in particle physics, so I doubt I can be of much help. Nevertheless, it seems logical to me that what happens on an atomic scale would not require information on how close the neighboring atoms are, so I'm unclear just how density would apply, except on a macro scale.

So, how do you verify the theory about how those particles behave in such extremely dense concentrations?
The claims by particle physicists seem to indicate a very strong understanding of what happened after the first trillionth of second, based on LHC experiments.

Or, does the BBT ignore that physics question by postulating that some unknown force ("dark energy") produced "inflation" of "space" independently of what was in that space at the time, rather than because of what was in it at the time?
They seem confident with knowing what was there beginning not long after quarks formed, partly due to the extreme success of the Standard Model, which predicted a number of new particles that were later discovered.

DE doesn't seem to be part of the Inflation theory model at this point. DM is still being understood and, per Hooper, there is some real head-scratching why the WIMP hypothesis is still such a chase. The behavior of the weak force (which is the only force with bias) has given them the best hope, but no luck so far.
 

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