Hey everybody, you guys definitely have heard about the JWST findings of massive galaxies and clusters of galaxies, early supernovae and monster stars, early spiral galaxies way before expected, etc., with the taglines “It defies the standard cosmological model, i.e., ΛCDM”. There is a need for new theories to explain these phenomena. It made me curious to explore more, and the Kurzgesagt video discussing this topic as a beginning of a revolution increased my interest in this discussion.

I am sure you have heard about the James Webb Space Telescope; there is no need to explain it. But have you guys heard about the ΛCDM (Lambda–Cold Dark Matter) model? This is the standard model of our Universe. It is one of the most fascinating theories about our entire Universe. Let me explain.

What is ΛCDM?

Since 1998, ΛCDM has been the most efficient cosmological model, explaining the Universe better than any other theory. The acronyms of this name are Λ (Lambda), which stands for dark energy, and CDM, which stands for cold dark matter. This theory does not only deal with dark energy and dark matter; it also explains baryonic matter. There are some of the craziest discussions on dark energy and dark matter. Dark matter is not a dark particle; it is an invisible particle and barely interacts except through gravity. Dark energy is a phenomenon that stretches the Universe, increasing the gap between galaxies and galaxy clusters. These are wonderful phenomena of the Universe. I will definitely explain them in one of our future posts on Formulon.

The ΛCDM model is not just an idea that discusses phenomena or talks about the age or evolution of the Universe. It is a mathematical model that gives an idea of our Universe, and it is based on general relativity.

One of the well-known parameters we use in the Lambda–CDM model is the Hubble constant, the expansion rate of the Universe. Recent calculations show that the value of the Hubble constant is approximately

H₀ = 73 km/s/Mpc,

which means a galaxy 100 megaparsecs away is moving away with a velocity of 7300 km/s. The Hubble constant is not actually constant when we look into the history of the Universe. It is better to call it the “Hubble parameter.”

Another parameter we use for our standard model is the curvature parameter. This discusses the geometry of a homogeneous Universe. Physicist Alexander Friedmann solved Einstein’s equations for a homogeneous Universe. His results give three possible universes. One is a flat 3D Universe—not a flat sheet like 2D space. This is similar to Euclidean space: if you shoot two lasers parallel, they do not meet, and the sum of the angles of a triangle is equal to 180°. In this space, the curvature parameter is equal to 0.

The second possibility is a closed Universe, just like a higher-dimensional sphere. When you shoot two parallel lasers, they will meet at least at two points, and the sum of the angles of a triangle is more than 180°. In this space, the curvature parameter is greater than 0.

The third possibility gives negative curvature. This makes the Universe open, just like Pringles chips. The sum of the angles of a triangle is less than 180°, and the parallel lasers meet at one point. The curvature parameter of this space is less than 0.

The third important parameter is the density parameter. How much stuff is packed inside the Universe? This parameter gives the answer. It also includes the energy distributed in the Universe. As per calculations, it is about

9.4 × 10⁻²⁷ kg/m³,

which is 10²⁹ times less dense than water. It is equivalent to about four hydrogen atoms per cubic meter of space.

One important thing I like about the Lambda–CDM model is that it discusses the history and future of our Universe. It gives ideas from the Big Bang to the cold death of the Universe.

The Big Bang theory tells us that the Universe, 13.8 billion years ago, was infinitely small and hot, and expansion started. This event is called the Big Bang. It is a nice term. The first time I heard about it, I thought of it as a planet-sized sphere that suddenly burst like an atom bomb because of internal pressure, and that we are particles of that big planet. Recently, I have heard much about relativity and started thinking about singularity and other stuff. Now I have a good understanding of the Big Bang theory.

According to Lambda–CDM, the Universe began as a hot, dense, compact space, followed by a sudden hyper-expansion of space called inflation. Before that, our physics breaks down, and we do not know about the Universe before inflation. The theory also says that after inflation, particles formed like quarks and photons, and the entire Universe was filled with quark–gluon plasma. As the Universe expanded, quarks coupled up and formed protons and neutrons. Other fundamental particles like electrons, positrons, neutrinos, etc., also formed. Multiple interactions happened, such as protons interacting with neutrinos to form neutrons and positrons. Expansion of the Universe made it friendly for complex particles, then atoms and molecules, by reducing the temperature and energy density of the Universe.

The early Universe provides partial evidence for the Big Bang in the form of low-energy radiation called the cosmic microwave background. It is the fossilized evidence of a dense and hot early Universe. It started as gamma rays and, due to redshift and the gravity of massive bodies, became microwaves in the spectrum. It definitely helps us calculate the expansion of the Universe.

The theory says that dark matter also existed in the background from the beginning of inflation. This dark matter forms structures when attracted by gravity and reaches Jeans instability, known as dark matter halos. These halos form web-like large structures that attract baryonic matter, leading to the formation of cosmic webs. These combinations lead the Universe toward the formation of galaxies and galaxy clusters. Galaxies are built on the foundation of dark matter. This was a new thing I learned. Our theory calculates that early galaxies formed approximately 500 million years after the Big Bang.

The theory also suggests that the end of the Universe could be the Big Chill, Big Crunch, or Big Rip. You may have questions: what are they?

The Big Crunch occurs when dark energy loses its momentum and the Universe collapses into a single point again. The Big Rip happens if dark energy does not lose its momentum but instead increases until spacetime itself tears apart.

The Big Chill is far more acceptable than the other theories. The Universe will continue to expand and lose its energy. The life of stars will end, leaving black holes, neutron stars, and white dwarfs, which will also lose energy. In the end, black holes will be the only survivors, and even they will lose energy through Hawking radiation. Finally, the Universe will contain only radiation and vast empty space.

This theory almost feels like we have cracked the code of the Universe. When I first heard about it, I felt the same—we have a perfect theory. But some results from the James Webb Space Telescope and other recent discoveries scatter our thoughts like cannonballs.

Today (27 December 2025), while writing this article, I read a phys.org article discussing that James Webb detected a supernova explosion from the early Universe when it was only 730 million years old. These are unique and very important discoveries for understanding the structure of the early Universe.

This year in March, James Webb found a wonderful discovery: an ancient galaxy from a Universe that was only 330 million years old. These are significant discoveries that make us rethink our theory, which says early galaxies should form 450 to 500 million years after the Big Bang. Using JWST data, some researchers found that early galaxies can contain heavier elements like carbon and nitrogen, which are forged in the cores of stars by fusion of helium and hydrogen. Previously, scientists also found more lithium in our Universe than predicted by Lambda–CDM. This leads to doubt: does our theory need an upgrade? Yes, it definitely needs one.

This image shows the galaxy JADES GS-z13-1 (the red dot at center), imaged with NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) as part of the JWST Advanced Deep Extragalactic Survey (JADES) program. These data from NIRCam allowed researchers to identify GS-z13-1 as an incredibly distant galaxy, and to put an estimate on its redshift value. Webb’s unique infrared sensitivity is necessary to observe galaxies at this extreme distance, whose light has been shifted into infrared wavelengths during its long journey across the cosmos.

In a NASA article, I found the statement, “Webb has not disproved the Big Bang theory.” When we explore more details, we also feel that way. But there are other things as well.

A few years ago, we found long structures of clusters of galaxies extending more than a few million light-years. Phenomena like dark flow also increase our doubts about the Lambda–CDM model. Our model suggests that on large scales, the Universe is a uniform soup of baryonic matter, dark matter, and dark energy. It predicts only a 0.0003% chance of forming such structures, yet we have three or more large structures present in the Universe. This raises questions about the uniformity and isotropic behavior of our Universe.

Another major problem is the Hubble parameter. Scientists have found two different values for it at the same time. This definitely raises questions: have we confirmed it? CMB data yield a value around 69 km/s/Mpc, while distance ladder calculations yield 73 km/s/Mpc. As technology improves, the separation becomes more precise, and the difference remains. So we are not clear about it. We are analyzing the issue, and we will find it—it may be the theory itself.

Some studies on the CMB suggest that our Universe may not be flat and that there could be variations in the curvature of space, with regions having negative curvature. Scientists also believe that dark energy is continuously changing. So the structure of our Minkowski cone might be irregular and different from predictions.

At this point, I want to mention something from the Kurzgesagt video. Let’s explore more to learn this and see how it turns out—Cosmic Mercury or Cosmic Uranus? The anomalies in the orbit of Uranus were solved by adding an element within the existing theory. But the anomalies in Mercury could not be solved that way; instead, they updated the theory into a new one.

This is not a crisis for science, physics, or the Lambda–CDM model. It is the beginning of a revolution—a change and the birth of new ideas. This is the normal behavior of science throughout history. Let’s see how everything changes.

Cosmic Mercury? Cosmic Uranus?