Dark Matter Revisited

[shellyhe]

Hello folks, After a short hiatus, but always reading new commentary from respected astrophysicists and space jounalists, I proudly remain in the camp that Dark Matter is nothing more than gravity behaving differently at long distances and closely resembles the Modified Dynamics (MOND) theory line. The only discrepancy is that the equations for MOND do not emulate gravity exactly. Other forces in the universe also are affecting the appearance of the galaxies by JWST and other telescopes. This holds true in the cases of Bullet Clusters and Gravitational Lensing examples where MOND is getting so much ridicule. The research for the right answers is continuing, but right now, I am holding form that Dark Matter is not a real substance. And for those other believers that Dark Matter can be something from another universe or dimension that pops in and out of our universe, that will forever remain a mythical event.

 

[Ed Stauffer]

I believe that dark matter is what makes up the fabric of spacetime and we won’t find it until we figure out how to look outside of spacetime. If in the early universe the dark matter all condensed at the same time this would have resulted in black holes appearing much larger and gravity wells much deeper. In these wells time would pass more slowly relative to use which would match the slower pulsars and to us faster galaxy developement. Pulsar timing also shows a possible phase transition in the early universe. Over time as the ratio of liquid to gaseous dark matter dropped which reduced the time differential across the universe. Not taking into account the redshift due to climbing out of those gravity wells biases our distance calculations making us think the universe is expanding. It would be interesting to calculate the neutrino mass without the assumption of an expanding universe.

 

[amateur astronomer Jeff]

Trying to understand Dark Matter

I am not an astrophysics but consider myself relatively intelligent. I am finding it very difficult to understand the concept of dark matter.

In simplistic terms, as I understand it, astrophysics currently believe that there is far more mass in the universe than can be explained by the visually observable universe (visible, infrared, x-ray and gamma ray light). The observed effects of gravity in distant galaxies is claimed to show far more rotational speed that would be based on the visually observed mass. Based on these assumptions it is stated that 85% of this calculated mass is something we cannot see or indirectly detect. “Dark Matter” is the placeholder name for this “unknown excess” mass that cannot or has not been observed or explained.

It is also my understanding that there are many things of mass that we expect exist which we cannot visually observe. Rogue moons, planets, failed stars, brown dwarfs, interstellar asteroids are just being found within our Milky-way galaxy. Scientists say there are likely millions of stellar-mass black holes in our galaxy. Multiply that by the billons of galaxies, along with the speculated microscopic blackholes and many other possible not yet know items of mass in the universe. Voyager 1 has detected a faint, monotonous hum from plasma (ionized gas) in interstellar space. Therefore, it could be said that all of space contains plasma which has mass.

All of the above could account for the assumed mass within the current known universe.

I must therefore question the 85% estimated Dark Matter hypothesis.

Would someone please address this issue providing a detailed explanation which a non-astrophysicist/quantum physicist could understand.

 

[Jim Franklin]

Trying to understand Dark Matter

I am not an astrophysics but consider myself relatively intelligent. I am finding it very difficult to understand the concept of dark matter.

In simplistic terms, as I understand it, astrophysics currently believe that there is far more mass in the universe than can be explained by the visually observable universe (visible, infrared, x-ray and gamma ray light). The observed effects of gravity in distant galaxies is claimed to show far more rotational speed that would be based on the visually observed mass. Based on these assumptions it is stated that 85% of this calculated mass is something we cannot see or indirectly detect. “Dark Matter” is the placeholder name for this “unknown excess” mass that cannot or has not been observed or explained.

It is also my understanding that there are many things of mass that we expect exist which we cannot visually observe. Rogue moons, planets, failed stars, brown dwarfs, interstellar asteroids are just being found within our Milky-way galaxy. Scientists say there are likely millions of stellar-mass black holes in our galaxy. Multiply that by the billons of galaxies, along with the speculated microscopic blackholes and many other possible not yet know items of mass in the universe. Voyager 1 has detected a faint, monotonous hum from plasma (ionized gas) in interstellar space. Therefore, it could be said that all of space contains plasma which has mass.

All of the above could account for the assumed mass within the current known universe.

I must therefore question the 85% estimated Dark Matter hypothesis.

Would someone please address this issue providing a detailed explanation which a non-astrophysicist/quantum physicist could understand.

Jeff, you have a basic misunderstanding here, we can account for around 15% of all energy in the observable Universe, this includes all baryonic matter as mass and energy are interchangeable.

The 85% you mentioned is not all Dark Matter - take a look at this graphic.

Now, as you can see, in this graphic, Dark Matter only makes up around 26% of the matter in the Observable Universe, some 63% is believed to be Dark Energy, however, this assumptions has been called into question lately due to the publication in The Monthly Notices of the Royal Astronomical Society, of a paper by Antonia Seifert, Zachary G Lane, Marco Galoppo, Ryan Ridden-Harper, David L Wiltshire called Supernovae evidence for foundational change to cosmological models.

The new evidence supports the "timescape" model of cosmic expansion, which doesn't have a need for dark energy because the differences in stretching light aren't the result of an accelerating Universe but instead a consequence of how we calibrate time and distance. It takes into account that gravity slows time, so an ideal clock in empty space ticks faster than inside a galaxy.

The model suggests that a clock in the Milky Way would be about 35 per cent slower than the same one at an average position in large cosmic voids, meaning billions more years would have passed in voids. This would in turn allow more expansion of space, making it seem like the expansion is getting faster when such vast empty voids grow to dominate the Universe.

With regards Dark Matter, despite being invisible, its presence is inferred through its gravitational effects on visible matter, radiation, and the large-scale structure of the Universe.

So what is dark matter?
Dark Matter refers to a form of matter that does not emit, absorb, or reflect light, making it undetectable through electromagnetic radiation. It interacts primarily through gravity, and its existence is postulated to explain several astronomical observations that cannot be accounted for by visible matter alone.
How Do We Know Dark Matter Exists?
1. Galaxy Rotation Curves:

• Observations of spiral galaxies show that stars at their edges orbit faster than predicted by the visible mass (stars, gas, and dust). This discrepancy implies the presence of unseen mass extending beyond the visible galaxy.

2. Gravitational Lensing

• Massive objects, such as galaxy clusters, bend light from background objects. The amount of bending often exceeds what can be attributed to visible matter, suggesting the presence of additional invisible mass.

3. Cosmic Microwave Background (CMB) Radiation

• The CMB, a relic of the Big Bang, shows patterns that can only be explained if there is much more matter than we can see, with Dark Matter being a significant contributor.

4. Large-Scale Structure of the Universe

• The distribution and formation of galaxies and galaxy clusters over time require a gravitational framework provided by Dark Matter to clump and form structures.

5. Galaxy Clusters and Missing Mass

• Measurements of galaxy cluster masses via the motion of galaxies, hot gas observed in X-rays, and gravitational lensing reveal far more mass than visible matter accounts for.

Effects of Dark Matter on Normal Matter
Dark Matter affects the Universe in several profound ways:

• Gravitational Binding - It provides the gravitational "scaffolding" that holds galaxies and galaxy clusters together. Without it, galaxies would disperse.
• Formation of Structures - During the early Universe, Dark Matter clumped under gravity, forming the seeds for galaxies and larger structures.
• Motion of Stars and Gas - It influences the dynamics within galaxies, explaining their flat rotation curves.
• Cosmological Evolution - It impacts the expansion rate and structure of the Universe, interacting indirectly with normal matter through gravity.

What Might Dark Matter Be?
The nature of Dark Matter remains unknown, but several hypotheses exist:

1. WIMPs (Weakly Interacting Massive Particles)

• Hypothetical particles that interact only via gravity and weak nuclear forces. They are a popular candidate and are sought through particle physics experiments.

2. Axions

• Ultralight particles predicted by extensions of quantum field theory. They might form a diffuse field that permeates the Universe.

3. Sterile Neutrinos

• Hypothetical heavier versions of neutrinos that do not interact via normal weak nuclear forces, only through gravity.

4. MACHOs (Massive Compact Halo Objects)

• These include objects like black holes, neutron stars, or brown dwarfs. However, they are not sufficient to explain the observed effects.

5. Modified Gravity

• Some theories suggest modifying our understanding of gravity (e.g., MOND—Modified Newtonian Dynamics) to explain the observations without invoking Dark Matter. However, these fail to account for all evidence. This has been largely disproved in recent months with one of its biggest proponents now actively speaking out against the theory. I have included it for completeness.

How Might We Detect Dark Matter?
1. Direct Detection

• Experiments aim to observe rare interactions between Dark Matter particles and normal matter. Facilities like LUX-ZEPLIN (LZ) and XENON use ultra-sensitive detectors to look for WIMP interactions.

2. Indirect Detection

• Dark Matter annihilations or decays might produce high-energy gamma rays, neutrinos, or other particles. Observatories like the Fermi Gamma-ray Space Telescope search for these signals.

3. Collider Experiments

• High-energy particle colliders, like the Large Hadron Collider (LHC), may produce Dark Matter particles that escape detection, inferred through missing energy in particle collisions.

4. Astrophysical Observations

• Improved telescopes and gravitational wave detectors might provide additional indirect evidence by studying the effects of Dark Matter on cosmic structures.

5. Axion Detection

• Experiments like ADMX (Axion Dark Matter Experiment) use resonant cavities to search for the conversion of axions into photons in a magnetic field.

The search for Dark Matter is challenging due to its weak interactions. However, upcoming projects, such as the Vera C. Rubin Observatory, Euclid mission, and advanced particle detectors, aim to unravel its nature. Breakthroughs in theoretical physics, including quantum gravity and supersymmetry, may also provide clues.

In essence, Dark Matter remains one of the Universe's greatest mysteries, with its discovery promising to revolutionize our understanding of physics and cosmology.

I hope this helps you get a better understanding of Dark Matter and do not confuse it with Dark Energy.

 

[shellyhe]

Trying to understand Dark Matter

I am not an astrophysics but consider myself relatively intelligent. I am finding it very difficult to understand the concept of dark matter.

In simplistic terms, as I understand it, astrophysics currently believe that there is far more mass in the universe than can be explained by the visually observable universe (visible, infrared, x-ray and gamma ray light). The observed effects of gravity in distant galaxies is claimed to show far more rotational speed that would be based on the visually observed mass. Based on these assumptions it is stated that 85% of this calculated mass is something we cannot see or indirectly detect. “Dark Matter” is the placeholder name for this “unknown excess” mass that cannot or has not been observed or explained.

It is also my understanding that there are many things of mass that we expect exist which we cannot visually observe. Rogue moons, planets, failed stars, brown dwarfs, interstellar asteroids are just being found within our Milky-way galaxy. Scientists say there are likely millions of stellar-mass black holes in our galaxy. Multiply that by the billons of galaxies, along with the speculated microscopic blackholes and many other possible not yet know items of mass in the universe. Voyager 1 has detected a faint, monotonous hum from plasma (ionized gas) in interstellar space. Therefore, it could be said that all of space contains plasma which has mass.

All of the above could account for the assumed mass within the current known universe.

I must therefore question the 85% estimated Dark Matter hypothesis.

Would someone please address this issue providing a detailed explanation which a non-astrophysicist/quantum physicist could understand.

I like your answer but just don't think that the objects mentioned is enough to keep any particular galaxy from falling apart. For example, if there were many black holes near a large visible galaxy, there would be some visible evidence. Maybe it could be a combination of unseen matter, as you mentioned, plus the MOND gravity adjustment and some other unseen forces in the universe. Just no pure dark matter.

 

[amateur astronomer Jeff]

01-11-25

Jim, I greatly appreciate the information in your response.

I found your reference to the "timescape" model very intriguing. It provides an explanation that does not rely on inventing new/unknowns to account for observable interactions.

Concerning the “Dark Matter,” I’m still not sure why the items I postulated could not account for at least the matter portion of the discussion.

You provided a graphic showing that Dark Matter makes up around 26% of the matter in the observable Universe. For sack of this discussion, I will accept that number. Hopefully we can address Dark Energy issue in the future.

For now, however, in your explanation “How Do We Know Dark Matter Exists?” you at least partly supported my postulation.

“Galaxy Rotation Curves … stars at their edges orbit faster than predicted by the visible mass … This discrepancy implies the presence of unseen mass extending beyond the visible galaxy.

Gravitational Lensing … Massive objects … bend light from background objects. The amount of bending often exceeds what can be attributed to visible matter, suggesting the presence of additional invisible mass.

Cosmic Microwave Background (CMB) Radiation … The CMB … shows patterns that can only be explained if there is much more matter than we can see …

Galaxy Clusters and Missing Mass … Measurements of galaxy cluster masses via the motion of galaxies, hot gas observed in X-rays, and gravitational lensing reveal far more mass than visible matter accounts for.

Effects of Dark Matter on Normal Matter … It impacts the expansion rate and structure of the Universe, interacting indirectly with normal matter through gravity.”

Why is it necessary to say Dark Matter is not normal matter. Most of your explanation implies that what the term Dark Matter is used to describe what is simply matter which as of yet is not visibly observable.

I again ask the question why do we need “Dark Matter”? It still appears that the effects of Dark Matter could be explained by normal matter that just has not yet been visually observed.

 

[Jim Franklin]

Jim, I greatly appreciate the information in your response.

Glad to be useful.

I found your reference to the "timescape" model very intriguing. It provides an explanation that does not rely on inventing new/unknowns to account for observable interactions.

It is an intriguing concept and theory, I have read the paper and run the numbers, it checks out - but that may not make it true or even all of the answer, nature has a habit of combining "solutions" to create confusion until we realise we need to take off the blinkers and join ideas together, just like Eintein did to create The Special Theory of Relativity.

Concerning the “Dark Matter,” I’m still not sure why the items I postulated could not account for at least the matter portion of the discussion.

It is believed that that the Universe is critically balanced between being open and closed. We derive this fact from the observation of the large scale structure of the Universe. It requires a certain amount of matter to accomplish this result. Call it M.

We can estimate the total baryonic matter of the universe by studying Big Bang nucleosynthesis. This is done by connecting the observed He/H ratio of the Universe today to the amount of baryonic matter present during the early hot phase when most of the helium was produced.

Once the temperature of the Universe dropped below the neutron-proton mass difference, neutrons began decaying into protons. If the early baryon density was low, then it was hard for a proton to find a neutron with which to make helium before too many of the neutrons decayed away to account for the amount of helium we see today. So by measuring the He/H ratio today, we can estimate the necessary baryon density shortly after the Big Bang, and, consequently, the total number of baryons today.

It turns out that you need about 0.05 M total baryonic matter to account for the known ratio of light isotopes. So only 1/20 of the total mass of the Universe is baryonic matter.

You provided a graphic showing that Dark Matter makes up around 26% of the matter in the observable Universe. For sack of this discussion, I will accept that number. Hopefully we can address Dark Energy issue in the future.

It is up to you to either accept or dimiss the 26%, but it is a science fact based on current knowledge. This may change in the future, it may reduce or increase, personally I think there are flaws in the methodology I described above, but we must start somewhere, and we can only go on the information we have.

For now, however, in your explanation “How Do We Know Dark Matter Exists?” you at least partly supported my postulation.

I did not support your postulation about planets etc because they are baryonic matter that is accounted for in the 26% of the Universe. However, Yes, we know, or the evidence strongly suggests that there is some form of matter that interacts only by gravity and we see the vidence for this across the universe - except for some galaxies that appear to be DM poor!

“Galaxy Rotation Curves … stars at their edges orbit faster than predicted by the visible mass … This discrepancy implies the presence of unseen mass extending beyond the visible galaxy.

That is correct, that is the primary way we know there is material out there that interacts via gravity but in all other respects is "dark" to our current technology. But of you think about it, IR was once "dark" because although we could feel it and see its effects, we had no idea what it was until we developed technology that could capture IR radiation - the same is true for all parts of the electromagnetic spectrum outside of visible light - afterall, UV lamps are still caled "black lamps". It may be dark now, but once discovered properly it will not longer be dark.

Gravitational Lensing … Massive objects … bend light from background objects. The amount of bending often exceeds what can be attributed to visible matter, suggesting the presence of additional invisible mass.

Light from distant objects has been seen to divert or refract in ways that cannot be accounted for by the observable mass, but when the motion of the stars on the outer edge of the galaxy are observed the mass of unseen material is calculated, the gravitational force of this is added and the gravitational lensing is accounted for - but not in all cases.

Cosmic Microwave Background (CMB) Radiation … The CMB … shows patterns that can only be explained if there is much more matter than we can see …

Fluctuations in the cosmic microwave background (CMB) are caused by a number of factors, including:

• Inflation
  A brief period of rapid expansion in the universe a fraction of a second after the Big Bang. This caused points in space that were far apart to become neighbors, resulting in similar temperatures in the CMB. LINK
  
  
• Density fluctuations
  The CMB's temperature fluctuations are thought to be a reflection of density fluctuations in the early universe. Photons that were in denser regions of space lost energy to gravity, making them colder than average. LINK
  
  
• Interaction with matter
  Some CMB photons interact with matter on their way from the surface of last scattering to the rest of the universe. This is known as the Sunyaev-Zeldovich effect. It is not connected to Dark Matter.
  LINK
• Dust and gas in the Milky Way
  These are known as foregrounds, and are a source of tertiary fluctuations. This is covered in the link above from Cambridge University.

Galaxy Clusters and Missing Mass … Measurements of galaxy cluster masses via the motion of galaxies, hot gas observed in X-rays, and gravitational lensing reveal far more mass than visible matter accounts for.

It has been observed in clusters of galaxies that the motion of galaxies within a cluster suggests that they are bound by a total gravitational force due to about 5-10 times as much matter as can be accounted for from luminous matter in said galaxies. And within an individual galaxy, you can measure the rate of rotation of the stars about the galactic center of rotation. The resultant "rotation curve" is simply related to the distribution of matter in the galaxy. The outer stars in galaxies seem to rotate too fast for the amount of matter that we see in the galaxy. Again, we need about 5 times more matter than we can see via electromagnetic radiation. These results can be explained by assuming that there is a "dark matter halo" surrounding every galaxy.

Effects of Dark Matter on Normal Matter … It impacts the expansion rate and structure of the Universe, interacting indirectly with normal matter through gravity.”

Yes, that is not in dispute.

Why is it necessary to say Dark Matter is not normal matter. Most of your explanation implies that what the term Dark Matter is used to describe what is simply matter which as of yet is not visibly observable.

Dark Matter, as I said above and have said in other posts, is simply material we are unable to detect, therefore it is dark to our current technology, thus is is not Baryonic matter and thus not normal matter as we know it. That is not to say it is something super exotic, but just material, likely of various types, that we cannot see. For all we know, beings who live on planets in the dark matter universe may see out baryonic Universe as the "dark" or missing matter - unlikely, but nothing is impossible until conclusively rulled out.

I again ask the question why do we need “Dark Matter”? It still appears that the effects of Dark Matter could be explained by normal matter that just has not yet been visually observed.

We need Dark Matter to explain the motion of stars on the outer fringes of galaxies that orbit too fast based on both Newtonian and Einsteinian gravity, even MOND has been ruled out now. Further, the motions of whole galaxies in clusters cannot be accounted for the detectable mass we can see and account for. Galaxy clusters cause lensing that exceeds what their visible/detectable mass can account for, and this gets worse the larger the galaxy cluster, so it is clear there is something in the Universe that appears to only interact via gravity and we cannot otherwise detect - so we need Dark Matter to explain observations or the entire standard model and Relativity is flawed - and thousands of experiments have proved both to be correct in many ways although it is accepted that there are flaws in all our major theories.

 

[Jzz]

Now, as you can see, in this graphic, Dark Matter only makes up around 26% of the matter in the Observable Universe, some 63% is believed to be Dark Energy, however, this assumptions has been called into question lately due to the publication in The Monthly Notices of the Royal Astronomical Society, of a paper by Antonia Seifert, Zachary G Lane, Marco Galoppo, Ryan Ridden-Harper, David L Wiltshire called Supernovae evidence for foundational change to cosmological models.

Wow, what a fabulous answer, I don't know how I missed it before, thank you Jim Franklin.
The "Timescape" theory of cosmic expansion, originating from Oxford University, offers an alternative and compelling explanation for the observed acceleration of the universe's expansion. Unlike other models that rely on the presence of an undetectable and mysterious substance, such as "Dark Energy," the Timescape theory posits that cosmic expansion is a result of variations in the way time behaves in different gravitational environments. Specifically, time moves more slowly in stronger gravitational fields (such as within galaxies) and faster in weaker gravitational fields (such as in the vast spaces between galaxies).

The theory rests on well-established empirical observations that time is influenced by gravity: in regions of strong gravitational pull, time slows down, and in regions of weaker gravity, time moves more quickly. This leads to a key insight of the Timescape model: time flows more slowly within galaxies, where gravitational forces are strong, than it does in the nearly empty intergalactic spaces, where gravitational forces are minimal. Consequently, time moves faster in the intergalactic voids, and thus, cosmic expansion appears more pronounced in these areas. This difference in the passage of time explains why the universe's expansion is observed to accelerate in the vast, empty spaces between galaxies, but not within galaxies themselves.

The beauty of the Timescape theory lies in its simplicity and its grounding in observable phenomena. It does not rely on hypothetical, exotic concepts like dark energy or modifications to Newtonian dynamics (as in the MOND theory), but instead explains the acceleration of cosmic expansion through fundamental differences in how time behaves in various gravitational environments. This makes the theory more grounded in empirical evidence, without invoking speculative or elusive concepts.

An equally important implication of the Timescape theory is its potential effect on our understanding of dark matter. If dark energy is no longer necessary to explain cosmic acceleration, as suggested by the Timescape model, it would significantly alter our current understanding of the universe’s composition. Given that dark energy was previously assumed to make up around 68% of the universe's energy density, its removal would require a major revision of the proportion of other components, particularly dark matter.

Dark matter, which has been empirically detected through its gravitational effects (such as influencing the rotational speeds of galaxies), would likely constitute a much larger share of the universe’s mass. Where dark matter was previously estimated to make up about 27% of the universe’s mass, it could, under the Timescape model, account for as much as 90%—a dramatic shift that would fundamentally alter the way we understand the composition of the cosmos.

In summary, the Timescape theory offers a novel and empirical approach to understanding cosmic expansion, based on how time behaves in different gravitational fields. It provides a more coherent and observationally grounded explanation than models involving dark energy, and also opens up new avenues for exploring the true nature and quantity of dark matter in the universe. This new understanding would reshape the current framework of cosmology, bringing dark matter into an even more prominent role in explaining the dynamics of the universe.

 

[contrarian]

So the Timescape Model suggests that the postulation of dark energy (DE) is based on observations which might be defined as a 'Relativistic Mirage'. If true. one wonders what else falls into this category on a cosmic scale. Could the CMB and/or its interpretation be distorted in ways we could never know?

This really should not come as a big surprise that there is one or more reasonable explanations for our expanding Universe. The current widely accepted version of the cosmos is that we don't know what 95% of the Universe is composed of, except that it has mass or mass equivalence (DE is presumed to have mass equivalence).

If we really don't know what 95% of the Universe is, or, ditching DE, even if it is something much more than all the baryonic matter, it begs the question of what else we do not know about. Sounds like there will be tension in cosmology for quite some time to come.

 

[Jzz]

If we really don't know what 95% of the Universe is, or, ditching DE, even if it is something much more than all the baryonic matter, it begs the question of what else we do not know about. Sounds like there will be tension in cosmology for quite some time to come.

One of the prime reasons for adopting the theory of cosmic expansion, is that of Olber’s paradox. Olbers’ Paradox questions why the night sky is dark if the universe contains an infinite number of stars. Traditional solutions involve cosmic expansion, redshift, and the finite age of stars. But just consider for a second the 95% of the unknown Universe that you referred to, were in fact Dark matter and dark matter was the medium through which all electromagnetic radiation propagated? I am aware that this might be a boring ‘been there done that’ scenario, but consider for a moment, what an amazing effect this would have on astronomy. What if light, just like every other wave, were dependent on the amount and time, over which power was applied to its creation. For instance, drop a small pebble in a pond and the wave created by this action would travel a certain distance and only that distance before becoming indistinguishable from the ambient surroundings (i.e., dying out). Or light from a candle appears to travel so far and only so far, no matter for how long it burns it can’t send the beam any further out. The same holds good in our experience with radio transmissions. The role of power in transmission is often downplayed because modern radio communication relies heavily on frequency selection, antenna design, and propagation techniques rather than brute-force power. However, power remains fundamental—higher power increases the probability of signal detection over long distances, especially in noisy environments. Just as a radio signal weakens over distance due to the inverse square law, starlight loses intensity over vast cosmic scales. Even with an infinite number of stars, their power output would be insufficient to make the sky uniformly bright.

If we consider light as an emitted pulse of energy, it should follow the same fundamental constraints as any other wave-based transmission: As light moves outward from a star, its intensity decreases with distance as 1/r^². Beyond a certain point, its energy per unit area becomes too weak to be detected or to have any significant effect. If the signal needs to travel further, more power would need to be found. Since each star’s light has a finite effective range, even an infinite number of stars would not make the sky uniformly bright. Distant starlight would fade before reaching us, ensuring that the night sky remains dark.

This explanation makes Olbers' Paradox a question of power and transmission limitations rather than one of infinite accumulation.

 

[billslugg]

Olber said since each star has a finite cross section as seen from Earth and there are an infinite number of stars, why don't we see the surface of a star at every point? The light might be dimmer, as you mention, but there should be no empty sky. There is plenty of it, even looking back to as far as JWST can see, which is 300 million years after the BB.

 

[Claudio Marchesan]

I'd like to join this discussion because I am currently finalizing the latest updates to my work, with the paper titled:

ON THE EXISTENCE OF DARK MATTER AND DARK ENERGY

Dark matter and dark energy are functional to the LCDM model:

1.Dark Energy (Λ): Explaining Cosmic Acceleration Einstein’s Cosmological Constant (Λ): In General Relativity (GR), Λ represents a geometric term acting as a repulsive "vacuum energy.", In ΛCDM, Λ (dark energy) explains the observed cosmic acceleration discovered in 1998 (Type Ia supernovae data). Without dark energy, cosmic expansion would decelerate due to gravity from matter. Observations unambiguously show acceleration.

2.Dark Matter: The Scaffolding of Cosmic Structure (Non-baryonic, non-relativistic ("cold") matter interacting only via gravity. Without dark matter, ordinary (baryonic) matter would lack sufficient time to clump into galaxies within the universe’s age (13.8 billion years). Dark Matter provides the gravitational "seeds" for structure growth. Density fluctuations in the CMB (measured by Planck) require dark matter to evolve into galaxies and galaxy clusters.

I ask whether, outside of this model, but particularly excluding its FLRW metric, they are still necessary to explain physical phenomena.

We question here their very existence.

Key Points: The Einstein Field Equations, the Action Principle, and the Role of Λ.

The Einstein field equations are derived from a variational principle (specifically, the Einstein-Hilbert action).

Λ does not alter the fundamental variational principle itself. Instead, it introduces a constant term into gravitational action.

Physically, Λ represents a vacuum energy density that contributes to spacetime curvature even in the absence of matter. Without Λ, the action would produce the original Einstein equations, with Λ, the equations include an additional term, driving cosmic acceleration.

Historical and Conceptual Implications:

Einstein initially added Λ "by hand" to his equations to achieve a static universe. After Edwin Hubble’s discovery of the universe’s expansion (1929), Einstein dismissed Λ as his "greatest blunder," deeming it unnecessary.

It later became a natural part of the action formalism. In modern physics indeed, Λ is interpreted as dark energy, an intrinsic property of spacetime encoded in the action itself.

Λ is often linked to quantum vacuum energy, but its theoretical value (predicted by quantum field theory) and observed value (from cosmology) differ by 120 orders of magnitude – one of the greatest unsolved mysteries in physics (the "cosmological constant problem").

Key Points: Estimating the Presence of Dark Matter through the Study of Gravitational Lenses.

In gravitational lensing systems, analogous to classical optics, the lens equation depends on the geometric relationships between the observer, lensing mass, and light source. Specifically:

A). The deflection angle is derived from the relative distances between:

1. The observer and the source plane (where the background star/galaxy resides).
2. the observer and the lens plane (where the foreground mass is located).

B). These distances are typically estimated using redshift data, interpreted through a chosen cosmological metric (e.g., FLRW).

Note that, under extreme conditions, in the lens equation, the smaller the ratio between the distances from the "lens" and from the "source", the more the mass of the "lens" and its distance from us become directly proportional.

Concerning my study performed on the article: arXiv:astro-ph/0701589 – The Sloan Lens ACS Survey. IV. The Mass Density Profile of Early-Type Galaxies out to 100 Effective Radii, a confirmation of 4-Sphere model (my OSF Project) was not achieved: I was unable to obtain the mass of the gravitational lens through an independent observation. This is due to the complexity of the estimation, which requires a model-based refinement, and the difficulty in obtaining the observational data.

Nevertheless the discussion highlights that distance assumptions—tied to recession velocity models—play an underestimated role in mass calculations.

Key Points: Key Points: Estimating the Presence of Dark Matter through the Study of Galaxy Rotation Curves.

When challenging the presence of Dark Matter based on galaxy rotation curves, the discussion becomes more complex:

The rotation curve of galaxies is often traced by observing gas (HI, CO) as well as stars. If present, magnetic fields can influence the motion of gas, altering the observed rotation curve. Additionally, the galaxy’s density may not be uniform.

Certainly, these two factors alone cannot fully account for the observed deviations. However, the assumed model used to theorize the rotation curve might play a crucial role.

Inside galaxies, classical mechanics is typically used, but a more appropriate approach would be applying the Schwarzschild metric for the interior solution of a rotating sphere of fluid, as a first approximation of a mixture of gas, dust, and stars. This brings into play the study published in The European Physical Journal C, Volume 81, Article Number: 186 (2021) — Galactic rotation curve and dark matter according to gravitomagnetism.

This study presents a new approach where, due to the coexistence of stars, gas, and dust in a galaxy, the classical concept of equilibrium between gravitational and centrifugal forces is replaced by a set of equations governing the motion of a perfect fluid in a gravitational field. The approximation used is that of weak fields, employing the analogy known as Gravitoelectromagnetism.

These are the conclusions:

“The effects attributed to dark matter can be simply explained by the gravitomagnetic field produced by the mass currents.”

Key Points: Dark Matter detection.

My goal is not to refute the existence of Dark Matter—since it is not a directly measurable entity, it is up to others to prove its existence.

Direct dark matter detection has made significant progress in recent years, although definitive results have not yet been obtained. Here’s an update on the main ongoing experiments:

1. XENON1T Experiment:

XENON1T was one of the most sensitive detectors for direct dark matter detection. In 2020, it reported an excess of events that sparked interest in the scientific community. However, further analysis suggested that this excess might be due to statistical fluctuations or contamination from cosmic radiation, rather than dark matter signals.

1. LUX-ZEPLIN (LZ) Experiment:

LZ is a next-generation detector designed to be more sensitive than XENON1T. In 2022, it began operations, aiming to detect rare interactions between dark matter particles and atomic nuclei. Preliminary results have not shown any dark matter signals but have contributed to further narrowing down the limits on dark matter candidate parameters.

1. CRESST-III Experiment:

CRESST-III uses scintillating crystals to detect interactions between dark matter particles and atomic nuclei. In 2017, it published results that excluded a wide range of possible dark matter masses, helping to constrain theoretical models.

1. DarkSide-50 Experiment:

DarkSide-50 uses ultra-pure liquid argon to detect dark matter signals. In 2018, it published results that excluded a wide range of possible interactions between dark matter and ordinary matter, contributing to further narrowing theoretical models.

1. CERN Experiments:

At CERN, experiments like SND@LHC and SHiP are designed to search for dark matter particles produced in high-energy collisions. These experiments are either still being prepared or have just begun operations, and definitive results are expected in the coming years.

In summary, while no direct signals of dark matter have been detected yet, the ongoing experiments are helping to narrow the parameters of theoretical models and improve our understanding of the possible interactions of dark matter with ordinary matter.