“One finds that the Planck value is disfavoured at 99.9999999999994% confidence level or ∼ 7.8σ.” This sentence is hilarious.

BTW dear researchers, I believe there is one huge missed opportunity here!

quasars (QSOs) are standardisable through a non-linear UV, X-ray flux relation popularised by Risal- iti & Lusso [70]. This begets an anomaly, whereby the re- sulting QSO data set [71, 72] favours smaller luminosity dis- tances than Planck-ΛCDM [57],

This new extremely promising cosmological probe needs Xrays and as explain the original author(s) of the concept: “A few thousands SDSS quasars already have serendipitous X-ray observations with Chandra or XMM-Newton, and at least 100,000 quasars with UV and X-ray data will be available from the eROSITA all-sky survey in a few years.”

This recent 2024 paper still uses a low quality and 100 times smaller Xray sample via chandra (2022) despite eROSITA DR1 being released since 4 months!! It appears nobody has yet rebuilt the Hubble diagram of quasars with eROSITA! The closest thing I can find is a pre-analysis a week before the data release https://arxiv.org/abs/2401.12860

(you can see a list of most eROSITA related papers here https://erosita.mpe.mpg.de/publications/ ) As such if any of you could do such an analysis, you would automatically produce a high value, highly cited paper with record high constraints on LCDM, however there probably is someone else working on it at the moment (but it has been 4 months) Personally I won’t do it since I am not technically a researcher. Note that there is also the related ART-XC telescope (that is often forgotten despite being useful) about that one, probably no one is working on its data for an augmented hubble diagram (because it is russian/politics) https://arxiv.org/abs/2405.09184 there is also https://www.srg.cosmos.ru/publications/155/show https://www.srg.cosmos.ru/publications/

Note: I do not understand what takes JWST so long, the high redshift candidates were almost all, already discovered photometrically in 2022, many at Z=16, and even one at Z=20!!

I can think of a couple reasons.

A. Exoplanet research - there is as much interest in exoplanets/ETs as there is in the early universe B. Spectroscopic confirmation is difficult/impossible for the highest redshifts using NIRSpec. I made this little graph to show where the visible range of the spectrum is at different redshifts:

https://mikehelland.github.io/hubbles-law/other/jwstir.htm

Between z=11 and z=12 the visible spectrum is out of NIRSpec’s range. They’re using the break in the UV range (in the rest frame) to make the determination of redshift.

If you look at the spectrum of GS-z14 in the paper (2nd one in the original post), Fig 1:

That’s what they are working with. it’s creeping away from reliable information. In my spectrum/redshift graph, the Lyman-α 121.6 nm (dashed line) is still detectable by NIRSpec out to z=40, but the amount of information you’re getting out of it is probably highly degraded.

NOTE, I’m a layman, so this is just my working knowledge of what they do and how they do it. I’m quite open to corrections on these points.

The scientific community… is in the process of rewriting the astronomy textbooks.

Which is to say the theorists are (once again) rejiggering their model to fit new data that the model (once again) failed to predict. As has been said, cosmologists are often wrong but never in doubt.

You have to appreciate too the way they spread the blame for this mess to the “scientific community” as if biologists and chemists, etc. have a hand in it.

The maximally possible redshift in the observable universe is 28.5, according to (my version of) the Variable Mass Theory. I’m breathlessly awaiting.

Related, excess of early quiescent galaxies https://arxiv.org/abs/2406.02664

We report the detection of seven new galaxy candidates with redshift z > 11 (not spectroscopically though) https://arxiv.org/abs/2406.05306

Not galaxies, but release of optical and infrared spectroscopy for 45 of the highest redshift quasars (6.5 to 7.6)

This work presents the largest medium/moderate-resolution sample of quasars at z>6.5 from ground-based instruments. proves that the same spectral features are preserved in quasars at different redshift ranges. https://arxiv.org/abs/2406.07612

I wonder why no one has made a tolman test or distance duality test based on quasars?

I wonder why no one has made a tolman test or distance duality test based on quasars?

As I said, quasars have a large “intrinsic redshift”, so the “distance redshift” is unreliable and a Tolman test is not possible (despite what everybody else thinks… https://github.com/orgs/a-cosmology-group/discussions/215#discussioncomment-9727719)

@RedshiftDrift, how large is the intrinsic redshift?

There’s this example quasar I’ve been using:

https://en.wikipedia.org/wiki/3C_273

It has a redshift of 0.1583. If the intrinsic redshift was something like a gravitational redshift from the quasar’s surface, I would think it would be somewhat universal. All quasars have an intrinsic redshift that’s a function of their mass, not their distance. So at most, it would have to be less than what’s reasonable for 3C 273. Maybe something like 0.05?

But to answer @LifeIsStrange ’s question, quasars are quasi-stellar, point-like. Not much surface area to a point. At least that’s my understanding.

@mikehelland the scatter is huge. At a given luminosity the redshift is scattered over $\Delta z > \pm 1$! (e.g. at $10^{33}$ erg/s/Hz in the radio bands, the redshifts are scattered over $0.5 < z < 3$. See sample image below)

despite what everybody else thinks

If you’re slant writing about me, please reread what I wrote in that thread you linked that tags me. My point about quasar distance was that it is known with near-certainty that the quasars are very very far away, way beyond the local supercluster.

At a given luminosity

How reliable is the chart’s “given luminosity”? The chart caption says, “To obtain the [luminosity], we use the luminosity distance obtained from the redshift and the standard cosmology and the standard K-correction.” It doesn’t seem reliable to base a luminosity distance on a quasar redshift.

A better chart would plot [quasar distance as estimated by the quasar’s associated galaxy’s redshift] vs the quasar’s redshift. Also, a better chart would replace ‘z’ with the freq_obs/freq_emit, or λ_emit/λ_obs.

Assuming that quasars evolve from higher to lower intrinsic redshift and from RL to RQ then the large scatter in the RL quasars will be greatly reduced when their intrinsic redshift is accounted for. It also follows that since the RQ-lower intrinsic redshift galaxies have overestimated luminosities also the lower bound line should be lower overall and perhaps flatten somewhat?

It’s interesting that the paper mentions quasar evolution:

… we have found that the radio luminosity evolves at a different rate than the optical luminosity, with the consequence that their ratio is a function of redshift.

Additionally, the luminosity evolution found for the optical only dataset matches that found for the combined radio-optical dataset…

So the data shows quasar evolution but they interpret it as epochal population evolution of course.

From the arxiv article:

This mass is comparable to the inferred stellar mass of its host galaxy, in contrast to what is found in the local Universe wherein the BH mass is ∼0.1% of the host galaxy’s stellar mass.

Can you find anywhere the size of the galaxy is estimated? As in arcseconds?

The big bang and its singularity require something very odd, that the size of objects as they appear on the sky start to get bigger after z=1.6. This is the angular diameter turnaround.

This assumption is why all high redshift galaxies are perplexingly compact. They don’t look as big as the theory says, so they must be tiny.

If you figure out their actual size without that bizarre assumption, they’re actually probably exactly like they are at z~0. If the size is being underestimated by orders of magnitude, then so are the masses (usually derived from SED fitting).

Sorry I don’t know the size of this galaxy. IIRC the size and estimated mass of JADES-GS-z14-0 is published in https://arxiv.org/pdf/2405.18485 ? (figure 3 maybe) Nobody has yet done a tolman test and distance duality test based on those record high Z galaxies hence it seems like a low hanging fruit to further obviously rule out LCDM. https://arxiv.org/abs/2212.06575 see figure 5 the study is from 2022 so they is clearly better data nowadays, but their scale isn’t clear, it seems they go up to z=15~ so I suppose they didn’t require spectroscopic redshift to measure the angular distance, if so there are photometrics redshifts above z=20 they could use, otherwise z=14.32 is a major advance. Since the deviation increase with redshift, the higher we go the more, non linearly, LCDM is falsified, this will also allow to falsify Gupta’s hybrid (the last expandist bastion along with maybe, rh=ct).

This assumption is why all high redshift galaxies are perplexingly compact. They don’t look as big as the theory says, so they must be tiny.

Honestly I have always wondered about this, I am aware of the differing angular distance bias based on an expanding universe, but still there are other biases that might makes the corrected galactic size and mass evolve with redshift, basically the time since the universe start (if it had a start) as the first objects have gradually grown in size, conversely at late time in some aging models, size should decrease I suppose as matter in a non homeostatic universe, would be gradually ireversibly converted into light. Moreover regardless of thoses, biases including malmquist and increasing cosmic dust opacification would alter the angular distance even in a static universe. Actually if we make the assumption that the universe is static and that the real size of galaxies is constant over redshift then this assumption might allow to better empirically constrain the degree of opacity of the universe, which is currently one of the biggest open questions (and has implications for e.g. the CMB)

So I’m not sure how consistently in the litterature, the size of galaxies falsely is said to be smaller over redshift because of the expanding effect, is this effect systematically applied? Since it is empirically refuted since decades I’m not sure how consistently the zoom factor is applied. If you could prove the size and mass appears constant over redshift, that would be a huge result. I speculate that distant objects truly appears smaller than their local counterparts, because of dust opacification. If so, could the tolman test and distance duality tests truly be considered refutations of the big bang? Couldn’t they simply assume there is more dust opacification than expected? Tolman is also constrained by the luminosity distance in addition to the angular distance so maybe it is possible to do better inferences than I do.

While as I said, going with higher Z galaxies is key to solve the conundrum, orthogonally, few people seems to know that the most accurate angular distance measurements are currently made by the Cherenkov telescopes. https://arxiv.org/abs/1904.06324 Cherenkov telescopes are very bad optical telescopes but they are also the largest optical telescopes to exists, which seems (layman) to be the single most important limiting factor for angular distance measurements. This use is even more useful IMHO than their classical use for transient astronomy/gamma rays detection. While the VERITAS has paved the way, the soon to be operational CTA telescope should considerably increase the amount of SOTA angular size measurements. https://en.wikipedia.org/wiki/Cherenkov_Telescope_Array We should be able to get even better measurements via the soon to be operational E-ELT. The veritas paper says:

direct measurement of the occulted stars’ angular diameter at the ≤0.1 milliarcsecond scale. This is a resolution never achieved before with optical measurements and represents an order of magnitude improvement over the equivalent lunar occultation method. We compare the resulting stellar radius with empirically derived estimates from temperature and brightness measurements, confirming the latter can be biased for stars with ambiguous stellar classifications.

See figure 4, the angular size measured seems considerably smaller than usually assessed (I would have expected the opposite) I’m not sure those measurements allow a tolman/distance duality test since those are stars, not galaxies and at relatively short distances, but it should at least inform us that our models to infer angular distances clearly artificially inflate the real size.

regarding JADES-GS-z14-0 (figure 3 top row) I don’t really understand how to interpret the data, the size isn’t given as a number but as a function, between normalized surface brightness and arcseconds, where the radius goes from 0 to 0.4 arcseconds (or 1.25 kiloparsecs). Regardless google says:

Most galaxies are 1,000 to 100,000 parsecs in diameter

so the upper? bound of 1250 parsecs puts JADES-GS-z14-0 within the minimum value (but one, I am probably badly understanding the data, and two I have not corrected for the expandist zoom factor I suppose (not sure) they have applied. I hope you will compute its proper size.

Here’s an example:

https://iopscience.iop.org/article/1…7#apjlacfe07t1

Both UNCOVER-z12 and UNCOVER-z13 are clearly resolved with measured half-light radii of 4.35 pixels and 3.95 pixels, respectively, with a pixel scale of 0’’.04 per pixel.

If, hypothetically, z12 and z13 were the same physical size, z13 should appear larger than z12; farther objects should appear larger due to the angular diameter turnaround.

With an angular diameter distance of 2.37 Gly, a galaxy at z=13.07 should appear the same size on the sky as a similarly sized galaxy at z=0.21.

If it’s ~4 pixels, and 0.04 arcseconds per pixel, then that’s 0.16 arcseconds, or 7.757e-7 radians.

If we’re talking z=13 and 2.37 Gly, that’s 726.645 Mpc.

Diameter D = distance d * angle, so, in LCDM, the z13 galaxy has an effective radius of 0.56 kpc.

In a nonexpanding universe, and no angular diameter turnaround, the distance is d = 3.9 Gpc, d * a = 3.05 kpc.

That’s pretty close to the Milky Way:

Because of uncertainty in the current measurement of the Milky Way’s size (Methods), we adopt a range of effective radii of 3.4–6.7 kpc

https://www.nature.com/articles/s41550-023-01977-z

Maybe this will clarify the topic:

If you’re talking about angular size, that’s just an empirical measurement that’s model independent. If an object takes up 1 arcsecond of the sky in our telescope, that’s how much of the sky it takes up. Angular diameter doesn’t care if you’re talking about LCDM or static models.

It’s converting the angular size to physical size (ie, 1 arcsecond vs 1 kpc) that requires the model, and that’s not based on anything fancy, except the estimated distance. Diameter D = distance d * angle. Technically it should be tan(angle), but when the angles are small enough it doesn’t matter.

https://astronomy.stackexchange.com/questions/7720/diameter-of-any-galaxy

The difference between the models is the distance each predicts for z. In the case of LCDM, distance increases with z until 1.6, then decreases.

Does that help?

@LifeIsStrange

From your link:

We assume throughout the analysis a cosmology with H0 = 67.7 km/s/Mpc and Ωm = 0.31. Under these assumptions, 1 SW pixel (0.02′′) corresponds to 83.7 pc at z = 10.2.

Here’s a notebook that gets that value (in kpc) from the parameters:

https://github.com/mikehelland/hubbles-law/blob/master/other/python/angularsize.ipynb

Thanks a lot for your help

FWIW, That only gives the LCDM prediction. I was going to add a nonexpanding estimate, but it’d be interesting if proponents here of alternative models gave their angular diameter distance (d_A) estimates for z=10.2. We can compare the results of the models with that.

The rest of the formula is the same.

arcsec = 0.02    
radians = 2 * math.pi * arcsec / (360 * 3600)
diameter = d_A * radians * 1000

Any takers? @HanDeBruijn @ExpEarth, @RedshiftDrift ?

@mikehelland With $H_0 = 74 \ {\rm km/s/Mpc}$, $z = 10.2$ in a Static Cosmology with STz calculator, the angular distance is $d_A = 9.8 \ {\rm Gpc}$ and a scale $47.4 \ {\rm kpc/‘’}$. $0.02 {\rm ‘’}$ would be $948 \ {\rm pc}$. (About ten times larger because $z \simeq 10$.)

But there is some additional gravitational lensing magnification to consider, which won’t be correctly calculated if an LCDM distance $d_A = 866 \ {\rm Mpc}$ is used!

Good point. Ignoring the gravitational lensing $z=10.2$ for various distances:

$$d = \frac{c}{H} \frac{z}{1+z}$$

$$d = \frac{c}{H} \log(1 + z)$$

$$d = \frac{c}{H} z$$

Gives (in kpc):

ΛCDM
0.083

z/(1+z)
0.378

log(1+z)
1.003

z
4.235

I updated the notebook to include these.

https://github.com/mikehelland/hubbles-law/blob/master/other/python/angularsize.ipynb

@RedshiftDrift writes something that I do not understand: >About ten times larger because $z \simeq 10$

???? Please explain, Louis!

@mikehelland . OK, I’ll bite too. According to this reply: In a flat and static cosmology, the radial distance $d$ is equal to the angular distance $d_A$. And in (my version of) the Variable Mass Theory we have the same relationship between redshift and distance as in tired light models:

$$ d = \frac{c}{H}\ln(1+z) $$

Calculation:

ArcSec := 0.02;
radians := 2*Pi*ArcSec/(360*3600);
Mpc := 3.08567758*10^22;
H := 73.4; # Riess
H := H*1000/Mpc;
c := 299792458;
z := 10.2;
d_A := c/H*ln(1+z);
diameter := evalf(d_A*radians);
diameter := diameter/Mpc*1000*1000; # parsec

                       diameter := 956.7774609

That is $\approx 957\mbox{ pc}$. Ah, now I understand the factor (*1000) in your formula for the diameter.

FWIW, using the LCDM best for $H_0$ to the supernovae data is not the best fit for Hubble’s constant in a static model. Here’s H = 74:

The best fit (using sum of squared errors) is 70.5 km/s/Mpc. You can see for yourself using these tools:

https://mikehelland.github.io/hubbles-law/other/supernovae.htm https://mikehelland.github.io/hubbles-law/other/sse.htm https://github.com/mikehelland/hubbles-law/blob/master/other/python/sse.ipynb

Yeah, the *1000 just converts Mpc to kpc.

About ten times larger because $z \simeq 10$

???? Please explain, Louis!

@HanDeBruijn the ratio between the $\Lambda\mbox{CDM}$ equation and the STz equation for angular distance is about $(1+z)$. This makes Big Bang cosmologists hallucinate and see objects (1+z) times smaller than they really are.

The facts of the matter with regard to the Cosmos are straightforward:

1. The maximum speed of light in the Cosmos is to the best of our knowledge @ 3x10^8 meters per second.

2. The radius of our observational range of the Cosmos is now in excess of 10 billion lightyears, while the nearest observed galaxy is 2.5 million lightyears away.

3. Therefore, it follows that we do not have and cannot have any knowledge of the current state of any of the galactic systems we observe nor can we have or do we have any knowledge of their aggregate state. The very concept of that aggregate state is entirely metaphysical - it has no scientific meaning, in that the existence of such a state cannot be scientifically verified.

In other words, the commonly held belief that the Cosmos we observe constitutes a simultaneously existing “universe” is entirely metaphysical in nature. The facts listed above are both well known and widely acknowledged but their unavoidable consequence is papered over with a convenient mathematical model (FLRW) that axiomatically assumes a “universe”.

The Universe of that model or any variant that shares the “universe” assumption, cannot and does not exist in physical reality; it only exists in the minds of those who choose to believe in it. The Cosmos is not a Universe and the concept of a simultaneously existing universe is metaphysics not science.

I do not understand what you mean and your reasoning at all @budrap00 The only main consequence of the speed of light here is that we cannot observe the present state of distant objects, we only observe the status of a distant object at the time it’s light was emitted, which is function of the speed of light (+universe expansion for expandists) It’s true it’s a fundamental limitation to our understanding of the evolution of the universe but I don’t think this time ignorance allows for much new physics. I don’t understand the point of whether things exists simultaneously at all.

1. there is a high coherence of the objects we observes, with their age and their evolution. So we mostly truly observe the universe as it was before (minus some IGM/ISM alterations of light e.g dust attenuation) And we can know the current state of the universe by looking at the local universe physics, e.g. the Milky Way has stars that are estimated to be 13 billion years old.

The universe even of distant objects we observe, is not static at all, we observe its age advance in real time (albeit extremely slowly) and this is what allows the field of transient astronomy (supernova variable luminosity cycles, etc). The time resolution of current sky surveys is booming. We see coherent causal chains spanning the whole observable history of the universe, which require distant sources to have existed durably.

You might believe distant objects no longer exists at present time and we would only gets to know that in billions of light years, but this spontaneous disparition is an extremely unparcimonous idea that require high finetuning given coherent observations at multiple redshifts. A zone cannot start to exists because you look at it, such a reversal of causality cannot make sense. So I don’t see the point your are making, things must necessarily coexist simultaneously. At best you might believe there are “time lags” (e.g as in Minecraft taking time to load chunks) but a global resynchronization of the causal chains must regularly happen to match our observations.

@LifeIsStrange This statement is correct: >The only main consequence of the speed of light here is that we cannot observe the present state of distant objects…

This statement is just metaphysical handwaving: >So I don’t see the point your are making, things must necessarily coexist simultaneously.

The Cosmos is the way it is. Imagining it to be some other way doesn’t change the hard fact that the simultaneously existing entity you envision is not an observable, measurable, or directly detectable thing. Science is restricted to the study of physical reality, the observable, measurable and directly detectable. When that stricture is abandoned science is reduced to irresolvable metaphysical or philosophical disputes.

Perhaps the easiest way to come to grips with this situation is by looking at a light cone model. On a cosmological scale we humans, our Sun, and our galaxy are at the apex. The labeling of the model is poor with only an observer noted at the apex but observers like ourselves don’t emit the outbound radiation labeled as Future Light Cone. The apex of the cone is the observer’s and emitter’s Here and Now. Here and Now is a local condition for any observer or emitter.

For the purpose of this discussion it is the plane labeled the Hypersurface of the Present that is relevant. The points on that plane represent other observer’s Here and Now but none of those points are causally connected except where their respective light cones intersect and those intersections are always out There and Then in the future and past of any local Here and Now system. The simultaneous universe of the Big Bang and other models is an atavistic cultural conceit. The Hypersurface of the Present does not have any physical meaning; it represents the unknowable.

The HOTP is where the simultaneously existing Universe exists - nowhere. That limitation is absolute. It is inherent in the nature of physical reality. Neither mathematics nor the human imagination can alter that reality - because the Cosmos is unknowably vast and the maximum speed of light is 3x10^8 m/s. Cosmology won’t be a science until it comes to grips with that reality.

@LifeIsStrange I have been interested in these themes also. Here are a few of my takes.

What is considerably underappreciated is that the same argument holds for where we are placed in time, …. Hence it appears from this simple argument, that the idea we exist that early is fringe given how ineptly unlikely statistically, it would be. (unless assumptions about future habitability or about doing statistics in time are wrong)

It is not unlikely if the universe operates on a cycle with period 1/H, with the average lifetime of stars being 1/H. Then it would be likely that life evolved at the start of a stellar period, if it is to be where we are now.

While I believed the universe is eternal or at least older than LCDM, there is one extremely potent argument that makes me consider having a younger universe than LCDM more likely. The argument is simply, where are the others? Where are the aliens? You might alter the drake equation as much as you'd like to make life appearance (Abiogenesis or spermatogenesis) as unlikely as you wish. I do believe life appearance and survival is considerably more unlikely and brittle than we appreciate.

On one hand, the Drake Eqn. has a term for number of inhabitable Earth-like planets and a term for the probability of life originating on such a planet. The first term is probably very low as you say. I have worked on the origins-of-life problem and while I found a general solution https://www.sciencedirect.com/science/article/pii/S0169534797013177 , the devil is in the details and I was unable to make further progress. We need a breakthrough, likely from semiconductor physics. For the second term, however, we now know there are so many planets out there that no matter how the origin probability is, it should be covered in the sheer number of planets. And yet, the basic concept that chemicals can appear on a mineral surface and start coding each other’s synthesis is still mind boggling for me. I think we might be alone.

The only way to beat the basic and absolute certainty that aliens should have made contact with us are: To have a Great Filter, a law that prevent alien exploration of the universe with absolute certainty, a 100% blockade. If it is 99.9% there will be an infinite amount. If it is 100% there will be zero.

It is possible to escape one’s home star, but an extreme longterm view must be taken. It has taken 4.5 billion years for humans to appear on Earth. We have only another few billions before we need to move off of it. If we can get off to a different star, again and again, it could be possible even to move between galaxies, for example when galaxies collide. I did quite a lot of work on these problems, eg: https://sciencex.com/news/2021-08-humans-recolonize-earth-mass-extinctions.html

Therefore either there is an absolute great filter, either there is a periodic great reset (the universe would become globally inhabitable each n time), either aliens always discover that life is meaningless (unlikely given the qualia/knowledge dichotomy), either the earth is much younger than we believe it is (Cf Tesla measurements), either the universe (or our local space) is much younger than we understand.

To sum up, like you say, the odds of life emerging elsewhere and finding us are both 0 and 100% . Does this help?

I think we might be alone.

I think not. Two references and a picture.

• Stefan Denaerde

• 

• UFO CONTACT FROM PLANET IARGA

Since we don’t see anybody else, this tells us that the value of the Drake equation is very small, i.e. $N \ll 1$. An indefinitly long time duration doesn’t make a difference, the finite lifetime of our civilization is the “filter”.

@RedshiftDrift sorry for the delay

the finite lifetime of our civilization is the “filter”

Since we don’t see anybody else, this tells us that the value of the Drake equation is very small

I disagree, in an eternal universe, the value of the drake equation must necessarily be zero given the old age of earth (5 billion years) The argument is very simple yet irrefutable, The task for the aliens (conquering the universe) is a simple computer science task of exhaustive dynamical graph exploration. At first, (an infinite or trillions of years ago) aliens had a low amount of parallelism (number of spacecrafts sent simultaneously) and discovered planets at a rate slower than planets formed. If their space exploration had remained slower than planetary formation, then either instantaneously or after a long time, an infinite number of new planets would have remained unexplored. However because aliens must necessarily, eventually, have reached a point of steady state where they explore planets on average faster than new planets forms. Once such a threshold in the universe is passed, which is only a matter of time given exponential growth and spacecraft parallelism, it is by design only a matter of time before the total share of unexplored planets in the universe starts to shrink. By design after N time, the number of unexplored old planets becomes zero. Though there is always an influx of new planets being created, this planetary creation rate is ridiculously small over the total number of preexisting planets, meaning that aliens should find new planets exhaustively and have only this task remaining given they already had time to explore all old planets. The time it takes to reach the milky way is ~ a billion years from the local group, the milky way appears to be as old as the observable universe, though except some signals, for a weird reason almost all stars seems to be younger than 13 billion years old (unless they rejuvenate without leaving a chemical abundance signature..) Meaning aliens had at least 13 billions years to reach the milky way, once you’re in the milky way, distances are much smaller, via a nearest neighbor search and gigantic space telescopes it should be trivial to find most earth like planets in the milky way. Reaching them takes orders of magnitudes less than 5 billions years. To assume the age of earth is the filter, require the milky way to be not older than 13 billion years old AND require aliens to be greedy and do a “low” amount of parallelism in terms of spacecrafts (despite having not much observational limits (telescopes)) In that scenario earth could still be left to discover, but in such scenario, aliens must still have massively populated the milky way meaning they would send visible biosignatures (radio waves, etc) and I don’t see why we couldn’t see such signatures. Besides previous aforementioned possible great filters like worldwide extinction events caused by new physics, and greed in terms of exploratory parallelism, the only other explanation that remains would be that planetary formation follow a curve that is always higher than alien exploratory parallelism. Since parallelism is expected to be nearly exponential, it follows that new planets must forms more than exponentially. In such a scenario the percentage of explored planets will always be near 0% but in order to preserve observed matter density, it would require a steady state universe with space expansion and constant matter density, even such a scenario is already highly constrained obseevationally in terms of speed.

The age of a “civilization” is the filter, not the age of Earth.

The limit is imposed by the exponential growth of a population ($e^t$ ) which quickly consumes all available resources within a volume (which cannot grow faster than $t^3$ ). Since $A e^t < B t^3$ and $A$ and $B$ are bound by the laws of physics, the maximum possible value of $t$ is a logarithmic function which never reaches the scales involved in the scenario described above.

Any civilization will eventually suffocate, fight for resources and destroy itself. Even a civilization that is a billion times larger will have a history that is merely 20 times longer. There are many studies (this is a gory one) and there are plenty of natural examples of that on Earth.

@RedshiftDrift writes: >Any civilization will eventually suffocate, fight for resources and destroy itself.

This is a very pessimistic view and it is exremely unwise to agree with it. I urge everybody read the two references given in my above reply, especially the last one.

Just a quote from chapter 2. It’s about what is needed for a civilization to reach eternal life. Nothing new actually: every major religion on earth (communism included) has preached (approximately) the same, in theory, for centuries. I admit that practice is another matter.

“Just this, that unselfishness makes an intelligent race immortal. But before you can understand this, you will first have to climb the ladder with Us to the misty heights of comic integration.”

tripling the number of spectroscopically confirmed galaxies with a BB (balmer break) at z >7. https://arxiv.org/abs/2407.17410

Anomalous gravitational weak lensing evolution over redshift https://arxiv.org/abs/2407.17552

new charachterization of a Z=12 galaxy by JWST its redshift was already known via ALMA but now we have a better understanding of it, including its remarkable brightness https://iopscience.iop.org/article/10.3847/1538-4357/ad5f88

https://academic.oup.com/mnras/article/534/1/325/7756422?searchresult=1

Paper about how to optimally design a JWST survey to break the Z=15 “barrier” and find the highest possible redshift galaxies (mostly via selective gravitational lenses targeting) Be sure that this will be ignored by the JWST teams.. https://iopscience.iop.org/article/10.3847/1538-4357/ad639d

Btw here are some recent interesting jwst related studies https://arxiv.org/abs/2407.15279 https://arxiv.org/abs/2409.18086 https://arxiv.org/abs/2409.16347 https://arxiv.org/abs/2409.15453 https://arxiv.org/abs/2408.00073 https://arxiv.org/abs/2407.15279

The largest ever JWST survey has been released: PANORAMIC, which is twice as large as the previous best. However it seems to prioritize wideness over depth so its ability to break the redshift barrier is unclear, though it should allows many major discoveries https://arxiv.org/abs/2410.01875 among the stated science goals:

The primary motivation for PANORAMIC are two- fold: to reveal statistical samples of (1) luminous galax- ies at z > 9, and (2) the most massive, red sources at 3 < z < 9. Since the abundances of these populations are critical constraints on galaxy formation models, the pure parallel strategy has a strong advantage in lower- ing the uncertainties due to cosmic variance.

Evidence for the milky way being older than 13 billions years https://www.nature.com/articles/s41550-024-02382-w

Let $H=$ Hubble parameter, $c=$ speed of light, $R_O=$ radius of our Observable universe, $W=3.383634283$ a pure number and the Hubble time $=1/H$ . From the G. de Vaucouleurs section at my webite the following is inferred for the maximal age of stars at the edge of our Observable universe. In the Atomic time frame $t$ we have

$$ H t = -(H/c)R_O = -(H/c)W(c/H) = -W \quad \Longrightarrow \quad \mbox{age}_t \approx {\bf 3.38} \times \mbox{(Hubble time)} $$

According to Narlikar’s Law, in the Orbital time frame $T$ we have

$$ \left[1+\frac{1}{2}H T\right]^2 = e^{H t} $$

And so, for $T = -T_O$ at the rim of our Observable universe

$$ 1-\frac{1}{2}H T_O = \sqrt{e^{-W}} \quad ; \quad T_O = 2\left(1-e^{-W/2}\right)\times\frac{1}{H} \quad \Longrightarrow \quad \mbox{age}_T \approx {\bf 1.63} \times \mbox{(Hubble time)} $$

The age of the “whole” Universe in atomic time $t=-\infty$ is simply eternal. Consequently, in the orbital time frame for $T=-T_U$ :

$$ \left[1-\frac{1}{2}H T_U\right]^2 = e^{H(-\infty)} = 0 \quad \Longrightarrow \quad T_U = \frac{2}{H} $$

With the Variable Mass Theory, the age of the (whole) universe in orbital time is twice the Hubble time. Where it is noticed that the Hubble time is around 14 billion years.

related about anomalous dust transparency https://arxiv.org/abs/2410.19042

https://news.ycombinator.com/item?id=41958593

https://phys.org/news/2024-10-webb-dozens-supernovae-remnants-triangulum.html