Last word on the Big Bang.

[hyksos]

Epistemology is a branch of philosophy that concerns itself with knowledge claims, and what counts as knowledge. Epistemology is in many cases, a set of agreed-upon criteria that set the ground rules for whether a written or verbal claim constitutes a claim of knowledge.

If our epistemic bar is "Does not make sense to me, personally", then the Big Bang theory is wrong coming in the door. One cannot "make sense" of a spacetime singularity, that up-and-decides that being a singularity is boring so better that it transform itself into a universe. That story does more than slightly give off non-physical vibes. Rather it is just flatly un-physical. That story is an affront to metaphysical sensibilities of all stripes.

ON THE OTHER HAND, if our epistemic bar line is "Accurately predicts the results of telescope observations" then the Big Bang is resoundingly successful. In 40 years of various telescopes measuring various things , from white dwarf cooling times , Thorium-90 abundances in galaxies , globular cluster cut-off ages , redshift Hubble constant measurements , and the CMBR, the evidence that the universe "began" in a Big Bang is piling up to the ceiling and beyond.

Hate the big bang theory with all your might. Hate it to your bones. Speak negatively of it in public. Chastise it on the internet. But do not deny what is honestly measured and innocently observed.

[edy420]

The Big Bang theory is flawed, in the sense that most of our information is based on what we see with the technology at hand.

Our observations may only provide speculation, towards the beginning of the big bang. But we can not speculate before the big bang, based on our observations.

However, Sir Roger Penrose, is working on a Big Bang model, where the universe cycles through Big Bangs, expansions, a freezing period, then back to a new Big Bang. He has a few mathematical problems to resolve with the black holes swallowing the universe again, but it's hard to calculate without observing it in action.

[curiosity]

GR is an incomplete theory, because unless gravitons are actually discovered gravitation remains a mystery!
Dark matter is no more than a fudge factor introduced in an attempt to explain why observations don't match predictions.
The only thing we really know, is that our universe was once much smaller than it is today, but a theory of everything is not likely to be published anytime soon.
Hubris is no substitute for facts!!!

[bangstrom]

Hate the big bang theory with all your might. Hate it to your bones. Speak negatively of it in public. Chastise it on the internet. But do not deny what is honestly measured and innocently observed.

Denying a human interpretation for a set of observations is not the same as denying the observations.
Trustworthy observations and measurements do not guarantee the correctness of our interpretations. There may be better interpretations than those that are the most popular or metaphysically satisfying. Even the best appearing interpretations should be considered suspect if they fail to explain some well-supported observation.

However, Sir Roger Penrose, is working on a Big Bang model, where the universe cycles through Big Bangs, expansions, a freezing period, then back to a new Big Bang. He has a few mathematical problems to resolve with the black holes swallowing the universe again, but it's hard to calculate without observing it in action.

If black holes swallow bits and pieces of our universe and small black holes coalesce into larger black holes until the whole "shebang" is one enormous black hole, we would be back in a full-blown universe again except one where everything is turned inside out. That is, space and time would swap axes.

GR is an incomplete theory, because unless gravitons are actually discovered gravitation remains a mystery!
Dark matter is no more than a fudge factor introduced in an attempt to explain why observations don't match predictions.

GR works perfectly well as a geometry- curved spacetime. I see no need for gravitons.

Dark matter is a fudge factor and dark energy is an even greater fudge factor. That makes the mass of our universe 96 percent fudge factors.

[hyksos]

There may be better interpretations than those that are the most popular or metaphysically satisfying.

My first question would be : what in the world do you find "metaphysically satisfying" about the Big Bang?

I ask because BB is the most metaphysically un-satisfying theory in all of science, as far as I'm concerned. If metaphysical satisfaction is the motivation and goal here, then Steady State wins hands down by a landslide.

My second question is, do you believe that theories in science prevail because of popularity? Are you aware of any other metric or metrics that are used to validate a theory? What would those be?

[hyksos]

The Big Bang theory is flawed, in the sense that most of our information is based on what we see with the technology at hand.

edy420, yeah I've seen this one before. "While the theory accurately and precisely predicts the results of observations, we should forego drawing any conclusions because we haven't measured everything yet." What you have called the limited "technology at hand".

This argument has been made since the very beginnings of science. Galileo built a telescope and used to it identify some of the larger moons of Saturn. Some philosophers doubted that what was being observed were actually satellite moons going around the planet. Philosophers complained that the telescope itself could be introducing artifacts that merely look like moons.

During Galileo's lifetime, optics and the reaction of light with curved glass pieces was not understood well enough to remove this as a plausible source of error. The doubting-Thomas philosophers won that round of debate.

This point is understood in science, and science differs from engineering to the extent that you must include precise descriptions of sources of error. Science always adopts a skeptical position and this is the reason why we need corroboration. We cannot and should not date the earth based off of a single rock pulled off the coast of Ireland in 1984, published in a single paper by a single author. Nor should we base the age of the universe off of a single white dwarf seen in a single galaxy , written about in one paper by one author. We need corroboration both in repeated experiments. We should demand corroboration in get matching estimates from other techniques, or even corroboration across disciplinary lines.

With the Big Bang theory, in 2020 we have this corroboration. The various techniques of aging mentioned in my leader post all cluster around an interval that runs from 10 bya ( globular clusters) to 18.6 bya (radiometric techniques). All the other dating techniques fall inside of this interval. It is not a coincidence that 13.7 bya fits neatly inside that interval.

You have mentioned that we only have observations from our limited "technology at hand" and that we should not jump to conclusions until more data that comes in that will soon upset the applecart (allegedly). This situation with the universe and its beginning is different. I would have to ask you how you define the word "universe"?

This question seems stupid but matters in this context, since "universe" referred to the Milky Way galaxy alone in 1907. Say I decide to define the word "universe" as a box of space with a 23 billion light-year edge, centered around our galaxy. I am allowed to do this, as you are allowed to choose your own definition, as long as you tell us what you mean. It is now impossible to claim that nothing unusual happened to that volume of space in that box circa 14 billion years ago. Something obviously happened, as there are no atoms found in the box which are seen to be older than 18.6 billion years. ( Again, this is not a one-off estimate from a single guy. That estimate is corroborated with 4 other different sets of data and 4 other dating techniques.)

In any case, everyone on this entire forum is under an obligation to put forth an explanation or theory as to WHAT HAPPENED in our local box of the universe 14 billion years ago. Something obviously happened as the data clearly shows. In some sense, the academics and scientists do not need us. They already have mathematically-consistent theory called the Big Bang as the description of what happened. The Big Bang Theory is not flawed -- if by "flawed" we mean it is not matching what is observed.

[bangstrom]

My first question would be : what in the world do you find "metaphysically satisfying" about the Big Bang?

I ask because BB is the most metaphysically un-satisfying theory in all of science, as far as I'm concerned. If metaphysical satisfaction is the motivation and goal here, then Steady State wins hands down by a landslide.

The Big Bang may be less satisfying than the Steady State but it beats out most rivals such as Hoyle’s Continuous Creation version of SS, Divine Creation, or Multiverses. A naive version of the BBT is easy to visualize because everyone knows what an explosion looks like.

Edgar Allen Poe explained in the mid 1850s that Newton’s theory of gravity favors a dynamic universe over a steady state. If massive bodies attract, the entire universe should be drawn to a central point by its own gravity. The only way the universe could exist as anything other than a solid lump is if some powerful event caused the masses of the universe to disperse and eventually slow and be drawn back together by gravity so the only way the universe can exist if it is either expanding or contracting or briefly poised between the two.

My second question is, do you believe that theories in science prevail because of popularity? Are you aware of any other metric or metrics that are used to validate a theory? What would those be?

Some theories prevail because of popularity. Lee Smolin complains in his book “The Trouble With Physics” that a “herd mentality” favors some theories over others because of their popularity rather than their merit. His prime example is string theory which has led to no new discoveries or understandings despite its popularity. String theory has attracted an inordinate amount of talent and funding to the determent of all other areas of physics. Smolin also complains that string theory adherents have bullied many doubters into silence.

The metrics we have can be used to verify any theory including such theories as Intelligent Design or the Flat Earth. The real test of a theory is not in its verifiability or popularity but in its internal consistency and most importantly, as Thomas Kuhn says, its falsifiability.

The Big Bang Theory is not flawed -- if by "flawed" we mean it is not matching what is observed.

The trouble is the BBT does not match what is observed as well as should be expected. The universe appears to be older and larger than expected after just 14 billion years of expansion. Also, expansion should be slowed by gravity- not accelerating. Guth’s inflationary period and dark energy are two explanations invented ad-hoc to explain away the discrepancies between what is predicted and what is observed.

[Faradave]

Gravity is lightlike. Gravitational waves propagate at speed limit c.

An instance of a gravitational field describes a light cone. The earth now feels the attraction of the sun about 8.5 minutes ago and vice versa.

Gravity, as any force, has a forward temporal component. As objects attract (or repel) they are also drawn forward in time. With a curved-space, radial-time model that means the gravity of both pulls outward to concentrically expanded future space. (That is to a bigger balloon.)

[hyksos]

Gravity is lightlike. Gravitational waves propagate at speed limit c.

Gravity, as any force, has a forward temporal component. As objects attract (or repel) they are also drawn forward in time. With a curved-space, radial-time model that means the gravity of both pulls outward to concentrically expanded future space. (That is to a bigger balloon.)

"With a curved-space,"

Yes. But I think this was done already.

https://uncw.edu/phy/documents/thefriedmannequations.pdf

[hyksos]

The Big Bang may be less satisfying than the Steady State but it beats out most rivals such as Hoyle’s Continuous Creation version of SS, Divine Creation, or Multiverses. A naive version of the BBT is easy to visualize because everyone knows what an explosion looks like.

You have appealled here to metaphysical satistifaction being measured by folk psychology and ease of visualization by the populace. This is an appeal to popularity -- which is strange for a guy who rails against popularity.

Rest assured the Big Bang was not an explosion in an existing empty space. The Big Bang theory is claiming something quite different than that. You have voiced a misunderstanding about the BBT that is made by high school kids, and you did it on this forum, inside a thread that I created. That's an insult.

Edgar Allen Poe explained in the mid 1850s that Newton’s theory of gravity favors a dynamic universe over a steady state. If massive bodies attract, the entire universe should be drawn to a central point by its own gravity. The only way the universe could exist as anything other than a solid lump is if some powerful event caused the masses of the universe to disperse and eventually slow and be drawn back together by gravity so the only way the universe can exist if it is either expanding or contracting or briefly poised between the two.

Yes. Looks good. This is one of the reasons our recent theories have Dark Energy. ( maybe Dark Energy is not as ad-hoc as you claimed...?)

Some theories prevail because of popularity. Lee Smolin complains in his book “The Trouble With Physics” that a “herd mentality” favors some theories over others because of their popularity rather than their merit.

In precise terms, can you explain what you mean when you say a theory prevails over another on merit?

The metrics we have can be used to verify any theory including such theories as Intelligent Design or the Flat Earth.

Who is "we" here?

What metrics that verify Intelligent Design and Flat earth?

The real test of a theory is not in its verifiability or popularity but in its internal consistency and most importantly, as Thomas Kuhn says, its falsifiability.

Is it your stated position that the Big Bang theory is internally inconsistent and unfalsifiable?

The trouble is the BBT does not match what is observed as well as should be expected. The universe appears to be older and larger than expected after just 14 billion years of expansion.

You have claimed that you are in possession of evidence that contradicts the Big Bang. Do you have any citations which someone could use to verify your claim?

[Dave_C]

I've recently (in the past year) heard that the "infinite universe" couldn't have arisen from a singularity, that an infinite universe was already infinitely large at the time of the big bang. The theory holds that the big bang still occurred, but it occurred to an already infinitely large universe.

Is this a recent development? Any good references?

[Faradave]

But I think [curved-space] was done already.

Well, the balloon analogy has been given but usually comes with an absurd disclaimer, specifically denying the radial-time of my model.
"This [balloon] analogy is potentially confusing since it wrongly suggests that the big bang took place at the center of the balloon. In fact points off the surface of the balloon have no meaning, even if they were occupied by the balloon at an earlier time."

Note their use of "earlier time" to deny that the radius is temporal. Ha! Corresponding points on nested concentric spheres describe the radius, which happens to elongate with 3-sphere expansion over time.

However, my main point is that gravity, as with all force, is lightlike. Whether objects are seen to accelerate or not, forces have a futureward component which is expansional! This conflicts with the prevailing, incorrect notion that gravity opposes expansion (urging a "Big Crunch"), and giving rise to theories of dark energy to overcome this.
"The cosmological constant was first proposed by Einstein as a mechanism to obtain a solution of the gravitational field equation that would lead to a static universe, effectively using dark energy to balance gravity." - Wikipedia

"Cosmologists estimate that the acceleration began roughly 5 billion years ago. Before that, it is thought that the expansion was decelerating, due to the attractive influence of matter." - Wikipedia

[hyksos]

Faradave,

Your ease in embracing theory is both parts refreshing, and very rare on the internet.

"This [balloon] analogy is potentially confusing since it wrongly suggests that the big bang took place at the center of the balloon. In fact points off the surface of the balloon have no meaning, even if they were occupied by the balloon at an earlier time."

I don't know who wrote this, but this is just wrong. Points outside the balloon absolutely have a meaning. Our universe could be embedded in a higher dimension, and the choice to do this is perfectly meaningful, even mathematically consistent.

(I would ask the writer to just google Kaluza–Klein)

[TheVat]

M-theorists call it "the bulk. " You could have an eternal Bulk, with big bangs eternally popping in it in a purely random way. Not really a testable idea, at this point, unfortunately.

[Faradave]

It's possible to have a balloon analogy in 4D hyperspace (four spatial dimensions) but I advise against it.

1. Such a model leaves time conspicuously out. We could say there's a clock ruing elsewhere and timelines are just not shown but why?

2. The volume of the cosmos is represented by the expanding balloon (a 3-sphere). The cosmos expands as it ages. So, one way or another, the radius of the 3-sphere relates to cosmic age, which is invariant time (all observers can agree on it, even as their on aging varies).

3. If we adapt a familiar Minkowski space-time diagram to the balloon analogy, it clearly yields curved-space, radial-time.

Let blue dot = event (here,now) in both diagrams. Red dot = big bang event, most simply represented on the right.

A fourth spatial dimension seems to me an extravagance. Literally a waste of space.

[bangstrom]

Yes. Looks good. This is one of the reasons our recent theories have Dark Energy. ( maybe Dark Energy is not as ad-hoc as you claimed...?)

I prefer theories that don’t require the invention of some mysterious “dark” force to make them work.

In precise terms, can you explain what you mean when you say a theory prevails over another on merit?

A theory has “merit” when it is internally consistent, explained the known laws of physics, consistent with observation, and falsifiable but lacking in contrary evidence. That is too much to expect from any complex theory but some are better than others.

Who is "we" here?

What metrics that verify Intelligent Design and Flat earth?

The “we” is anyone who has looked into the topic.

If you look into some of the fringe theories such as ID or the Flat Earth, you will discover that they use the same observations to support their theories as do those who support the opposite. The difference is that different individuals look at the same evidence but from different points of view.

The cautionary take-away from this is an awareness of how influential one’s personal point of view can be to their interpretation of a body of evidence and the error in looking at a complex problem from a single point of view and excluding all others. Looking at an issue from more than a single point of view gives us a greater perspective by using one point of view to test the correctness of another.

Is it your stated position that the Big Bang theory is internally inconsistent and unfalsifiable?

Inconsistent and unfalsifiable” are mutually exclusive conditions. My position is that I am not sold on the entirety of the theory.

You have claimed that you are in possession of evidence that contradicts the Big Bang. Do you have any citations which someone could use to verify your claim?

Are you suggesting there is NO publicly known, credible evidence contradicting the Big Bang?

My personal source of doubt about the Big Bang mainly involves the theory’s heavy reliance on the distant galactic redshifts as indicators for the age and extent of the universe. My doubts began long ago with an article by Edward Harrison in “Physical Review Letters.” I don’t have the citation handy but I still have a copy of the article somewhere in my piles of papers.

Briefly, Harrison decided to test the correctness of the BB density value for the universe. He reverse-engineered the math by guessing different density values and then crunching the numbers to see which set of values coincided best with observations.

This is a summary of Harrison’s conclusions from “Sky and Telescope” September 1993.

“With the enormous successes of Big Bang cosmology and inflationary-universe theory, the ‘standard model of the universe’ goes almost unquestioned by cosmologists these days. In this picture...the Big Bang happened around 10 or 15 billion years ago, and, very early in the Big Bang, inflation gave the cosmos precisely the right density to balance it forever between rapid expansion and recollapse.…

“Or maybe not. As an exercise, cosmologist Edward Harrison (University of Massachusetts,
Amherst) tried to devise a radically different universe [and] succeeded surprisingly well. In Harrison’s most extreme model...the expansion is very slow [and] the density of the universe today is about 10 times greater than needed to halt the expansion....Harrison’s universe is 35 billion years old. ...The universe will cease expanding in another 22 billion years, then begin recollapsing toward a Big Crunch 79 billion years in the future.”

Harrison’s cooked-up model passed all the major observational tests — without the need to invoke unknown types of dark matter.”

[curiosity]

I prefer theories that don’t require the invention of some mysterious “dark” force to make them work.

So Do I... However, there isn't actually anything mysterious about the energy which drives the expansion of our universe, it is a form of energy which certainly doesn't warrant the prefix "dark". Neither does it need to be "invented", as its existence can easily be explained and its effect measured.

[bangstrom]

Since when has dark energy become a known and why wasn't I informed? I am still in the dark.

[hyksos]

My personal source of doubt about the Big Bang mainly involves the theory’s heavy reliance on the distant galactic redshifts as indicators for the age and extent of the universe.

This person has just claimed a "heavily reliance" on redshift as indicators of age. This only means one thing.

This person hasn't even tried to read a single link in my lead post. For your convenience, I will repeat them all here again.

• white dwarf cooling times
  
• Thorium-90 abundances in galaxies
  
• globular cluster cut-off ages
  
• redshift Hubble constant measurements
  
• and the CMBR

[bangstrom]

My personal source of doubt about the Big Bang mainly involves the theory’s heavy reliance on the distant galactic redshifts as indicators for the age and extent of the universe.

This person has just claimed a "heavily reliance" on redshift as indicators of age. This only means one thing.

This person hasn't even tried to read a single link in my lead post.

So I read a few cherry-picked articles posted on the internet about a single cosmological theory that I find dubious in its origin and evolution and suddenly I am to become a believer. I don’t think so.

And the citations don’t really address my complaint about the interpretations of distant redshifts.

Distant galactic redshifts were once thought to represent recessional velocities in a 3D universe that was expanding like ejecta from a giant explosion. Later they were interpreted as resulting from the expansion of space itself. The latter interpretation makes more sense but the two are quite different effects. If the redshifts are the result of the expansion of space, then they are telling us how fast space is expanding but space can’t expand without changing our perception of time. This is where things begin to get complicated and the solutions to this complication involve too many assumptions, too many circular interpretations, and too many conclusions contrary to observations for my satisfaction.

Halton Arp discusses some of his complaints about redshifts here:
https://www.haltonarp.com/articles/is_physics_changing

And Geoff Haselhurst has compiled a number of criticisms of the BB cosmology here:
https://www.spaceandmotion.com/Cosmolog ... Theory.htm

[hyksos]

For those of you who are too busy, I will give a synopsis of the articles I have linked -- with the aim of emphasizing how bangstrom is not acting in good faith. bangstrom is not making any attempt to engage with evidence. He is making every excuse to avoid having to interact with a giant pile of observational evidence that supports the Big Bang. The observations , measurements , estimates dovetail neatly with the predictions of the theory.


White Dwarf cooling times.

• title : White dwarfs and the age of the universe
• link : https://www.slac.stanford.edu/econf/C0307073/papers/JI.pdf
• grant agencies : European Union FEDER funds. Generalitat de Catalunya . Spanish Ministry of Science and Innovation.
• no. of authors : 2
• times the paper was cited : 3
• physics : white dwarf cooling times.
• conclusion : Science has never observed a white dwarf older than 12 billion years. Authors write these estimates place an "extreme constraint to the age of the universe."

Radioactive dating.

• title : The age of the universe from nuclear chronometers
• link : https://www.pnas.org/content/95/1/18.long
• sponsor : National Academy of Sciences
• no. of authors : 1
• times the paper was cited : 8
• physics : Cosmic clocks from nuclear half-lives. nuclear chronometers.
• conclusion : The Milky Way galaxy contains no atoms in it older than 15.8 billion years, (w/ mean 12.3 Gyr). The oldest star ever observed with this technique is halo star CS22892– 052. It must be younger than 20 Gyrs, with mean 15.2 Gyr. Abstract states these findings are consistent with all other known dating techniques.

Globular clusters

• title : The Age of the Universe from Globular Clusters
• links : Lohfink's abstract. https://www.astro.umd.edu/~peel/ASTR622/abstracts/lohfink.pdf AAAS Science paper https://scholar.google.com/scholar?cluster=15767443588923219974&hl=en&as_sdt=0,30
• sponsor : American Academy for the Advancement of Science.
• no. of authors : 2
• times the paper was cited : 398
• physics : globular cluster temp/luminosity scatterplots.
• conclusion : verbatim quote : "Despite the numerous uncertainties, all three methods for age determination are in agreement with each other and the current cosmological model." The mean age of the oldest GCs is 12.6 billion years. 16 Gyr for an upper bound with 95% confidence.

Expanding universe

• title : The Velocity-Distance Relation among Extra-Galactic Nebulae
• links : Richard Pogge course website http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/expand.html . American Astronomical Society https://scholar.google.com/scholar?cluster=14244672573336387399&hl=en&as_sdt=0,30
• sponsors : American Astronomical Society. NASA. Carnegie Institute of Washington.
• no. of authors : 2
• times the paper was cited : 725
• physics : metric expansion of the universe.
• conclusion : The recessional velocity of galaxies scales with their distance. The coefficient on this is relation between distance and velocity is the HUbble Constant, H_0.
  
  

Cosmic Microwave Background

• title : Lambda-CDM model , ( Cosmic Black-Body Radiation.(1965))
• links : wikipedia https://en.wikipedia.org/wiki/Lambda-CDM_model . Original 1965 paper on the discovery of the CMBR. https://scholar.google.com/scholar?cluster=10107349462129263630&hl=en&as_sdt=0,30
• sponsors : American Astronomical Society. NASA. Carnegie Institute of Washington.
• no. of authors : 4
• times the paper was cited : 1319
• physics : relic radiation from a denser, hotter time in the universe.
• conclusion : The CMBR exists !! It is radiation , a kind of radio static, from a time when the universe was hotter and denser, and its light has been red-shifted into the microwave range.
  

Putting it all together.
The Big Bang Theory is a scientific theory that predicts the universe is expanding and that it had a beginning.

Have we actually seen expansion? Yes. Expansion is observed.

When we measure the ages of various objects in the sky do they have an age? Yes.

Do age estimates use various techniques to cross-check each other? Yes.

Do those estimates agree with one another? They do. They corroborate, as repeatedly stated by the articles above.

The Big Bang Theory suggests that the universe was hotter and denser in the past. Has this been observed? Yes. It is the CMBR.

[hyksos]

Distant galactic redshifts were once thought to represent recessional velocities in a 3D universe that was expanding like ejecta from a giant explosion.

They still think this. This is still in our current theory and cosmologists call it the inertial component. Nobody "changed their minds" , if that's where you're going with this.

Later they were interpreted as resulting from the expansion of space itself.

There was no change or move of any scientific goalposts. Read the Hubble article linked.

The latter interpretation makes more sense but the two are quite different effects.

Yep. They are different effects. Both of them are considered.

If the redshifts are the result of the expansion of space, then they are telling us how fast space is expanding but space can’t expand without changing our perception of time.

(linguistic confusion)

This is where things begin to get complicated and the solutions to this complication involve too many assumptions, too many circular interpretations, and too many conclusions contrary to observations for my satisfaction.

Science does not concern itself with your satisfaction. It concerns itself with theories that accurately predict observation. The Big Bang Theory does that.

[hyksos]

(To concede..the BBT is highly unsatisfying for a laundry list of various metaphysical reasons. But that is an issue for Philosophy of Science. )

[bangstrom]

For those of you who are too busy, I will give a synopsis of the articles I have linked -- with the aim of emphasizing how bangstrom is not acting in good faith. bangstrom is not making any attempt to engage with evidence. He is making every excuse to avoid having to interact with a giant pile of observational evidence that supports the Big Bang. The observations , measurements , estimates dovetail neatly with the predictions of the theory.

My own views are strongly influenced by neo-Machian physics which tries to draw a sharp line between conjecture and observation. Here are two examples where the two are confused in explanations of the Big Bang theory.

The Big Bang Theory is a scientific theory that predicts the universe is expanding and that it had a beginning.

Have we actually seen expansion? Yes. Expansion is observed.

We have not observed expansion. We have only observed redshifting and redshifting is not necessarily caused by expansion. The expansion we “see” is a calculation based on the assumptions within the model but it is not an observation.

There are several cosmological models other than the Big Bang based on different dimensional changes as an explanation for cosmological redshifting.

When we measure the ages of various objects in the sky do they have an age? Yes.

Do age estimates use various techniques to cross-check each other? Yes.

Do those estimates agree with one another? They do. They corroborate, as repeatedly stated by the articles above.

The estimates you cited may agree with one another but they indicate the origin of objects found in a universe at an advanced state of evolution not so different from the present. That is stars, globular clusters, thorium, extra-galactic nebulae, or white dwarfs.

The estimates point to the time of the origin of these objects but not to the origin of the Big Bang which must have been a few billion years older. The estimated age for the universe is 13.8 billion years old and I find it difficult to see how the ages for the objects cited fit within that time frame.

The Big Bang Theory suggests that the universe was hotter and denser in the past. Has this been observed? Yes. It is the CMBR.

The observed temperature of the CMBR is 2.37K which is far from hot. The hot CMBR is a conjecture derived from the theory but a mighty cold CMBR is what we observe.

You may recall that you posted a perfectly good cosmology by Christof Wetterich, a physicist at Heidelberg University, who proposed a cold origin of the universe where the CMBR was and still is, 2.73 K. His theory appeals to me because it describes our universe as we observe it and with fewer assumptions than does the Big Bang.

[bangstrom]

Distant galactic redshifts were once thought to represent recessional velocities in a 3D universe that was expanding like ejecta from a giant explosion.

They still think this. This is still in our current theory and cosmologists call it the inertial component. Nobody "changed their minds" , if that's where you're going with this.

My understanding of current cosmology is that “expansion” takes place in a curved, 4D spacetime and it is space itself that is expanding. The galaxies are not moving through space. Instead, it is space between the galaxies that is expanding causing the distances between galaxies to expand.

The view of cosmological expansion as an enormous explosion-like event that resulted in galaxies scattering in all directions through empty space sounds like the understanding of the Big Bang in Lemaitre's time and not the modern view where space is expanding from within.

Are you saying the galaxies are still considered to be moving outward from a common center driven by their own inertia as in an explosion?

Also, relative to ‘What’ is the universe expanding?

If the redshifts are the result of the expansion of space, then they are telling us how fast space is expanding but space can’t expand without changing our perception of time.

(linguistic confusion)

In other words, the distant galaxies are not redshifted because they are moving through space and away from us-the Doppler shift. They are redshifted because the space between galaxies is expanding which causes the light waves between galaxies to be “stretched out”.
The last part says: If c=s/t and c is a constant and space s is an expanding variable, then time t must also be a variable.

So the redshifts indicate how fast space is expanding rather than how fast the galaxies are moving through space and away from us as described by the Doppler effect.

[hyksos]

The view of cosmological expansion as an enormous explosion-like event that resulted in galaxies scattering in all directions through empty space sounds like the understanding of the Big Bang in Lemaitre's time and not the modern view where space is expanding from within.

Spatial expansion was in the theory from the beginning. Check out the Hubble links above. I don't know what history you are reading that says someone backed out on something. They backed out on Steady State, and the history of the the age of the universe was very hotly debated. There were literal divorces over it.

We have not observed expansion. We have only observed redshifting and redshifting is not necessarily caused by expansion. The expansion we “see” is a calculation based on the assumptions within the model but it is not an observation.

You have shown that you are not even trying to read the evidence I have linked you. The recessional velocity scales with distance. That is expansion. The Copernican Principle kicks in here. Either you adopt a position that says the milky way and the earth are in a special privileged center of the universe. Alternatively you admit that all galaxies, even distant ones --if you were sitting inside of them -- would also see recessional velocity scale with distance.

That is expansion however you try to slice it. The articles above already say all this.

The estimated age for the universe is 13.8 billion years old and I find it difficult to see how the ages for the objects cited fit within that time frame.

(I have to wonder if you have tried to ready any of the items I linked) Age estimations run below and above 13.7. THey in fact, range from 10.1 Gyr to as much as 18.6 Gyr depending on the method. What is most embarrassing for you is that these numbers are literally on the screen you are looking at.

You are under an obligation to explain to this forum your pet theory as to why every object ever observed by mankind and his technology is younger than 20 billion years. Every atom, molecule, galaxy, star, globular cluster, and nebula : none older than 20 billion years. You are under an obligation to do this.

The observed temperature of the CMBR is 2.37K which is far from hot. The hot CMBR is a conjecture derived from the theory but a mighty cold CMBR is what we observe.

These temperature considerations mean nothing. The very existence of the CMBR is predicted by the theory. How do you even explain its existence without this concordance model?

Are you saying the galaxies are still considered to be moving outward from a common center driven by their own inertia as in an explosion?

Also, relative to ‘What’ is the universe expanding?

What is with these questions? You're the expert here.

In other words, the distant galaxies are not redshifted because they are moving through space and away from us-the Doppler shift. They are redshifted because the space between galaxies is expanding which causes the light waves between galaxies to be “stretched out”.
The last part says: If c=s/t and c is a constant and space s is an expanding variable, then time t must also be a variable.

This is a good question. I think there was some back-and-forth on this forum regarding this particular issue. At this time, I would say that this issue of a time variable (t versus t') was worked out in Friedmann's original paper. As a general hand-wavy statement about this : THe way time is handled in relativistic theories is often unsatisfying.

https://cosmology.education/documents/f ... n_1922.pdf

So the redshifts indicate how fast space is expanding rather than how fast the galaxies are moving through space and away from us as described by the Doppler effect.

There is expansion, or not?

[Faradave]

The last part says: If c=s/t and c is a constant and space s is an expanding variable, then time t must also be a variable.

This is a good question.

Speed limit c does not apply to "recessional velocity", being included instead in the class of faster-than-light phenomena.
"Rules that apply to relative velocities in special relativity, such as the rule that relative velocities cannot increase past the speed of light, do not apply to relative velocities in comoving coordinates, which are often described in terms of the 'expansion of space' between galaxies." - Wikipedia

Every object can, in principle, be stationary (with Δx=0) and yet still be receding from distant objects. Thus recessional "speed" is speed only in terms or the units we apply to its magnitude (meters/second) in a particular direction (making it seem like a velocity vector). The fact that it is isotropic suggests expansion of a cosmic spatial 3-sphere (i.e. the "balloon analogy") but that is not strictly required (expanding dough with raisins model).

Observationally apparent "recession" is more accurately characterized as a rate of cosmic volume increase (meters³/sec.), which is clearly not a speed.

[bangstrom]

You have shown that you are not even trying to read the evidence I have linked you. The recessional velocity scales with distance. That is expansion.

You may have read something about expansion theory but your comment about how current theory holds that the universe is expanding like a giant explosion sending ejecta into 3D space does not demonstrate an understanding of the Hubble expansion. Redshifts (not recessional velocities) scale with distance and cosmic redshifts are not Doppler recessional velocities.
Do you understand that distant galactic redshifts, as Faradave explained, mainly indicate cosmic volume increases between galaxies rather than recessional velocities of galaxies moving outward through space?

Faradave explained the current understanding in the previous post and I can’t improve on his explanation or make it any more clear. As he said, “Observationally apparent "recession" is more accurately characterized as a rate of cosmic volume increase (meters³/sec.), which is clearly not a speed.”

The Copernican Principle kicks in here. Either you adopt a position that says the milky way and the earth are in a special privileged center of the universe. Alternatively you admit that all galaxies, even distant ones --if you were sitting inside of them -- would also see recessional velocity scale with distance.

That is expansion however you try to slice it. The articles above already say all this.

I agree that nearly all galaxies appear redshifted and how that does not indicate a privileged position at the center of the universe but I do not consider cosmic redshifts to be Doppler values indicating velocities through space and away from the earth.
Cosmic redshifts are commonly thought of as indicators of space expanding between the galaxies rather than motion outward from a common center and there are even more possible explanations that I think are worth considering.

(I have to wonder if you have tried to ready any of the items I linked) Age estimations run below and above 13.7. THey in fact, range from 10.1 Gyr to as much as 18.6 Gyr depending on the method. What is most embarrassing for you is that these numbers are literally on the screen you are looking at.
You are under an obligation to explain to this forum your pet theory as to why every object ever observed by mankind and his technology is younger than 20 billion years. Every atom, molecule, galaxy, star, globular cluster, and nebula : none older than 20 billion years. You are under an obligation to do this.

Just because galaxies, globular clusters, and the other objects you mentioned are never older than 20 billion years does not mean that atoms, molecules, and the universe itself can not be even older. Possibly, several billion years older. Atoms and galaxies did not appear simultaneously.

These temperature considerations mean nothing. The very existence of the CMBR is predicted by the theory. How do you even explain its existence without this concordance model?

The CMBR was predicted, and measured, as the ambient temperature of intergalactic space prior to its “discovery” by Penzias and Wilson. Radio engineers in the fifties and sixties knew the 7cm band was unusable because of interference which was assumed to be radiation from a cold, non-luminous matter in deep space heated by the innumerable galaxies.

This article summarizes the history.
https://www.researchgate.net/publicatio ... and_Wilson
From the article: “We show that the models based on a Universe in dynamical equilibrium without expansion predicted the 2.7K temperature prior to and better than models based on the Big Bang”

[Positor]

Redshifts (not recessional velocities) scale with distance and cosmic redshifts are not Doppler recessional velocities.
Do you understand that distant galactic redshifts, as Faradave explained, mainly indicate cosmic volume increases between galaxies rather than recessional velocities of galaxies moving outward through space?

Faradave explained the current understanding in the previous post and I can’t improve on his explanation or make it any more clear. As he said, “Observationally apparent "recession" is more accurately characterized as a rate of cosmic volume increase (meters³/sec.), which is clearly not a speed.”

But could the redshifts be due to a combination of cosmic volume increase and recessional velocity through space? How do we know there is no recessional velocity component?

Is there an observational way to distinguish between the two?

[bangstrom]

Yes, there is a combined effect. The Andromeda galaxy is blueshifted indicating that it is moving towards the Earth but the expansion effect becomes dominate with increasing distances. There is no way of distinguishing one kind spectral shift from another at great distances.