"The Formation of Particles: Exploring the Early Universe and the Emergence of Fundamental Forces"

In this blog, we will delve deeper into this transformative phase and explore how the changing conditions during this critical time period played a vital role in the formation of various particles. The evolving universe presented a dynamic environment that facilitated the birth of new particles and shaped the foundations of the cosmos as we know it today.

By understanding the intricate processes that unfolded during this era, we can gain invaluable insights into the origins of matter and the fundamental particles that make up our universe. From the interactions of particles to the complex interplay of forces, we will unravel the fascinating story of how the changing conditions allowed for the emergence and organization of particles.

Mass Energy Equivalence :

Have you ever come across the famous equation E=mc^2 and wondered what it means and how it came about? This equation, introduced by Albert Einstein in 1905 during what is known as his "miracle year", revolutionized modern physics and provided insights into the formation of particles after the Big Bang, as suggested by Stephen Hawking. Now let's dive deeper into the significance of this equation and its implications in the world of physics.

In his fourth paper of 1905, Einstein explained that if a body emits radiation, its mass would diminish by {Energy/c^2} where c is the speed of light, which is approximately 300000000 m/s. This led him to conclude that mass and energy are two different names for the same thing. In other words, Einstein's paper suggests that conservation of mass and conservation of energy are equivalent, an idea that had already been introduced by Sir Isaac Newton in 1717, who proposed that light and matter particles were interconvertible.

This theory was experimentally verified by Cockroft and Wailtin in 1932. This interconversion of mass and energy is responsible for the energy produced in very exothermic reactions. In these reactions, the mass that gets converted into energy is so small that it cannot be detected easily. The change in mass in these reactions is generally of the order of 0.00000000000055 grams.

To understand the scale of energy-mass equivalence, consider that if you convert 0.000000002 grams of mass into energy, the energy produced is equivalent to the energy of the Sun's core.

Pair Production:

Pair production is a process where a photon with sufficient energy can spontaneously transform into a pair of particle and antiparticle (The antiparticle have exactly opposite behavior's of it's associated particle it is similar to mathematical sign '+' and '-'). This process is possible due to the energy-mass equivalence principle given by Einstein's famous equation E=mc^2. According to this equation, energy and mass are interconvertible, and in pair production, the photon's energy is transformed into the mass of the particle and antiparticle produced. The energy of the photon must be greater than or equal to twice the rest mass of the particle-antiparticle pair to allow for pair production to occur. This process plays a crucial role in the early universe's formation, where it led to the production of quarks, leptons, and X-bosons, among other fundamental particles.

Annihilation:

Annihilation is a process in which a particle and its antiparticle collide, resulting in their mutual destruction and the production of energy in the form of photons or other particles. This process plays a crucial role in the early universe and in particle physics.

Unification and Spontaneous Breaking of Forces:

The idea that the fundamental forces of nature were once unified into a single Theory of Everything is a widely accepted concept among physicists. It is believed that before the Plank time, which occurred approximately 10^-43 seconds after the Big Bang, the gravitational force, the electromagnetic force, and the strong and weak nuclear forces existed as a single, all-encompassing force. As the universe began to cool and expand, this force spontaneously separated into different fundamental forces in a process known as spontaneous symmetry breaking.

The Entire timeline of spontaneous breaking as temperature of universe decreases 

At 10^-45 seconds after the Big Bang, the single Theory of Everything force broke into the gravitational force. The unification of the remaining three forces was described by grand unified theories, which predicted that the strong and weak nuclear forces and the electromagnetic force would remain unified until the temperature of the universe had fallen to about 10^25 Kelvin and the universe was approximately 10^-35 seconds old. At this point, another episode of spontaneous symmetry breaking occurred, and the strong nuclear force separated from the electroweak force.

As the temperature of the universe continued to fall, the electroweak force eventually broke into the electromagnetic and weak forces when the temperature dropped below 10^15 Kelvin. This process of spontaneous symmetry breaking played a critical role in the formation of the different fundamental particles and forces in the early universe.

Formation of Particle in Early Universe:

Formation of the Quarks and the leptons :

After the big bang, the universe began as a singularity with an infinite density of matter and radiation concentrated at a single point. During the Plank Era, all known fundamental forces were unified, including the strong and electroweak interactions. However, gravity separated from these forces at the end of the Plank Era. The temperature of the universe during this period was incredibly high, around 10^28 electron volt (electron volt is an unit to measure the Energy in Astrophysics we often refer temperature and Energy as similar entity as temperature and energies are interconvertible). The temperature was too high for any atoms to exist, and there was formation of quarks, leptons, X bosons, and their antimatters through pair production. Due to the presence of matter and antimatter, they both annihilated to give out photons. As a result, the universe was opaque during this period, and we could not see through it. The universe was only a few millimeters across 

During 10^-43 to 10^-35 seconds,  the universe had cooled down to around 10^25 Kelvin, which resulted to insufficient energy for the pair production of X bosons.  During this period the strong and electroweak interactions had separated from each other. As a result, X bosons started to decay into antileptons and neutrinos, which resulted in an asymmetry in a slight excess of matter over antimatter. As time progressed, the matter and antimatter annihilated, and only one in a billion matter survived through this era.

After 10^-35 seconds, At this point, the universe was a Quarks and Lepton Plasma, which means there was a high density of charged particles. Scientists also refer to the plasma state as a fourth matter state. This is how the early fundamental particles got into the existence in the universe.

Formation of Nucleons (Baryon :- Proton and Neutron)  :

After the Plank era, as the universe continued to evolve, the formation of leptons, quarks, and X bosons occurred. However, during this period, the energy of the quarks was too high for them to combine and form protons or neutrons. The unified force that governed the early universe underwent a spontaneous breaking, leading to the separation of the strong force and the electroweak force.

The strong force is responsible for binding protons and neutrons together within atomic nuclei. However, due to the high temperature and energy of the quarks during this stage, the formation of stable protons and neutrons was not yet possible. The universe, at around 10^-35 seconds old, remained at an incredibly high temperature of approximately 10^25 Kelvin, preventing the quarks from combining and allowing the strong force to hold them together.

From 10^-35 seconds to 10^-12 seconds, no significant events occurred apart from the ongoing annihilation of matter and antimatter, as well as the decay of X bosons into electrons and electron neutrinos. The temperature remained too high for quarks to combine and form stable protons.

However, as the universe reached the critical stage of 10^-11 seconds, following the electroweak symmetry breaking, and by 10^-6 seconds a permanent excess of quarks over antiquarks emerged. At this point, the universe had cooled down enough for the quarks to transition into hadrons, specifically protons and neutrons. The combination of quarks and antiquarks resulted in the production of a significant number of baryons and antibaryons, with a slight excess of baryons over antibaryons.

The subsequent firestorm of particle-antiparticle annihilation ensued, eliminating nearly all of the antimatter and leaving behind only a small excess of baryons. These surviving baryons constitute the visible matter we observe in the universe today. The intense release of photons during the annihilation process has since cooled due to the expansion of the universe, giving rise to the Cosmic Microwave Background (CMB) radiation. Each annihilation event of a baryon and an antibaryon produces two photons, which implies that approximately one baryon survived for every billion baryons formed. These remnants of matter that withstood annihilation are what compose the material world we know today.
The intricate interplay between particle-antiparticle annihilation, the survival of a small fraction of baryons, and the emergence of the Cosmic Microwave Background paints a captivating picture of the early universe's evolution.

Cosmic Microwave Background 

Formation of Nucleus :

As the universe progressed to approximately 10^-6 seconds old, significant developments took place. During this phase, nucleons such as protons and neutrons began to form. However, the temperature of the universe remained incredibly high at around 10^12 Kelvin, which is six billion times hotter than the core of the sun. Under such extreme conditions, the strong force struggled to hold protons and neutrons together to form stable atomic nuclei.

Nevertheless, the universe continued to evolve and gradually cooled down. Around 100 seconds after the Big Bang, the temperature dropped to approximately 10^10 Kelvin. At this stage, the energy of the nucleons became low enough for the strong force to successfully bind them, leading to the formation of the first nuclei.

Initially, protons and neutrons combined to create deuterium, a heavy isotope of hydrogen. However, deuterium is unstable on its own, so two deuterium nuclei fused together, resulting in the formation of helium nuclei. Concurrently, the remaining neutrons decayed into protons, contributing to the abundance of hydrogen nuclei. Consequently, the universe consisted of a mixture of electrons, helium nuclei, and hydrogen nuclei.

Despite the emergence of atomic nuclei, the temperature remained too high for electrons to stably orbit the nuclei and form complete atoms. This mixture of electrons, helium, and hydrogen nuclei effectively trapped photons, preventing their escape from the universe. As a result, the universe remained in an opaque state.

The intricate dance of particle interactions and the gradual cooling of the universe during this epoch laid the foundation for the subsequent formation of stable atoms.

Formation of Stable atoms and The Cosmic Background Radiation:

After the formation of helium nuclei, the universe underwent a transformative period lasting several thousand years. During this time, the universe was a hot mixture of photons, hydrogen and helium nuclei, and electrons. The dynamics of the universe's expansion were dominated by radiation. However, at approximately 10^12 seconds, the universe reached a critical point where its density became diluted, and the influence of massive particles began to govern the expansion. This marked the onset of the Matter era in the universe's history.

Over these thousands of years, the universe gradually cooled down to around 3000 Kelvin, making it cooler than the surface of the sun. This lower temperature provided an ideal environment for the weak force to come into play. The weak force, together with the electromagnetic force, enabled electrons to be captured by nuclei, leading to the formation of the universe's first neutral and stable atoms.

As a result of this electron coupling, the captured photons were no longer trapped, allowing them to move freely. This event marked the universe's newfound transparency as photons could now traverse through space without obstruction. Initially, these photons were emitted as gamma rays. However, due to the continuous expansion and cooling of the universe, these gamma photons underwent a process called redshift, causing them to transform into microwave photons. These microwave photons are now uniformly distributed in all directions within space.

The image of the universe when the initial particles were formed after the big bang obtained by CMB

In 1965, Arno Penzias and Robert Wilson accidentally discovered the Cosmic Microwave Background (CMB), which is the spectrum of the first-ever photons in the universe. This serendipitous observation is considered one of the most compelling pieces of evidence supporting the Big Bang theory. The CMB holds crucial information about the early stages of the universe and will be further explored in an upcoming blog post.

By exploring the transformative phase of the early universe, we gain profound insights into the origins of matter and the fundamental particles that shape our cosmos. Understanding the interplay between forces, particle interactions, and gradual cooling enhances our knowledge of the universe's evolution. Stay tuned for upcoming blogs where we delve into the formation of complex structures that define our universe. Enjoy reading and expanding your understanding of the cosmos.