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In the early Universe, particle physics was supreme.

ESSENTIAL NOTES
Scientists can recreate the circumstances of the early Universe with particle accelerators such as the Large Hadron Collider, providing insights into everything from the Big Bang to the birth of atoms. These investigations provide insight into the early stages of the universe and its development into a complex universe full of galaxies and stars. Our comprehension of the early epochs of the Universe has been significantly improved by this fusion of theoretical and experimental physics.

According to the Big Bang hypothesis, the universe was considerably hotter around 14 billion years ago. But how are we to know for sure what the Universe was like all those years ago? It might be possible to create a time machine, but that technology is undeveloped. The next best thing, therefore, is what scientists do: they utilize particle accelerators to simulate the early Universe’s circumstances in the lab. Data from particle physics experiments can provide a window into the early stages of the universe in this way.

It is vital to comprehend the capabilities and constraints of this methodology, nevertheless. According to the Big Bang hypothesis, there are several epochs, each with a distinct temperature and energy. These eras are not entirely fully understood. For example, the Universe’s early times are still mysterious. They are cloaked in mystery, and what we know about them is based on conjecture. But in an instant, the circumstances of the early Universe changed to ones that could be tested with current technology.

Replicate the early Universe

Protons are accelerated to almost the speed of light and collide head-on in the Large Hadron Collider (LHC), the most potent particle accelerator currently in use in the world. Heat energy from the velocity of the proton is transformed into heat that can reach temperatures 100,000 times hotter than the Sun’s center, which were last experienced by the universe less than a trillionth of a second after it first formed.

Other studies have looked at what happened to matter when the Universe cooled down enough to break the principles of particle physics and enter the nuclear physics era. The composition of the Universe and its governing principles were predetermined even before it existed for a few minutes. Though it would take hundreds of thousands of years for the Universe to cool down sufficiently to produce atomic hydrogen and helium, the nuclei of the primordial hydrogen and helium that comprised the first stars already existed three minutes after the Universe began. Gravitational forces predominated for hundreds of millions of years following the formation of atoms, which resulted in the birth of the earliest stars—a point when nuclear physics was essential once more.

What eras of the early Universe are so studied by particle accelerators? Let’s start the narrative in an era for which there is still plenty to learn about it. Cosmologists think that the Universe had a phase of expansion at speeds faster than light at a very early epoch, about 10-36 to 10-32 seconds after the Universe began. We refer to this as the inflationary period. Although there is a lot of indirect evidence to support this, inflation has not been shown to have happened. Inflation is still a theoretical concept as of this writing.

The universe was hot and dense toward the conclusion of inflation, and it was very different from what it is today. Atoms couldn’t exist since the universe was much too hot. Quarks, the particles that reside within protons and neutrons, and protons themselves all followed the same pattern. It is believed that neither mass nor electric charge ever existed. That means that massless, very energetic particles pervaded the whole universe.

From discoveries from experiments to theoretical physics

It is unclear to scientists what occurred in the universe before around 10^13 seconds. One explanation is that we don’t have the technology to focus our energies in a way that allows us to study those early periods. On the other hand, pairs of protons travelling at almost the speed of light can collide with each other at the LHC. Ten to thirteen seconds after the collision starts, the maximum energy produced in one of those collisions will produce temperatures that are last in the universe.

That skill allows us to have a far better grasp of how the Universe has evolved. The Higgs field is an energy field that was created at a time of around 10^12 seconds. Particles derived their mass from interactions between this field and the universe’s stuff. Electric charge was created at the same moment. Particles with mass began to exist in the universe instead of only massless energy. These were referred to as leptons and quarks. Quarks can only be discovered within protons and neutrons nowadays, and the electron is the most well-known lepton. In 2012, the Higgs boson—a vibration of the Higgs field—was found. (Disclosure: The writer was involved in that finding.)

Quarks, however, were not limited to being in protons and neutrons at that early period. Quarks were free to move about. Since the early Universe was too hot for protons and neutrons to exist, a proton would effectively melt and release its constituent quarks, much like when an ice cube is placed on a heated pavement and the heat melts the ice to let water to flow freely.

As time went on, the universe cooled and expanded even more. After the Universe cooled down to a temperature of one millionth of a second (10-6 s), quarks were no longer free to move about. Protons and neutrons are the result of strong interactions bringing quarks together. There were electrons and there was also this strange particle called a neutrino. Very low mass subatomic particles called neutrinos have very weak interactions with matter. These days, they are produced by nuclear processes and have less impact on the cosmos. Nonetheless, neutrinos interacted quite strongly with the protons, neutrons, and electrons that dominated the Universe at 10-6 seconds due to the Universe’s extreme density.

The Universe became enough less dense by the time it was one second old that neutrinos could not interact with other kinds of matter. In fact, neutrinos, which last interacted with matter a very short time after the Universe began, are abundant in our modern Universe. Within the next ten years, very sensitive instruments should be able to detect these primordial cosmic neutrinos.

The expansion of the universe cooled over the course of the following few minutes to a point where protons and neutrons could start to group together to form atomic nuclei. The nuclei of all known elements may have formed if the universe’s density had remained high. But only the most basic nuclei could develop due to the Universe’s sudden decrease in density. Together with uncommon isotopes of hydrogen (deuterium and tritium), hydrogen nuclei (single protons) and helium nuclei (two protons and two neutrons) had created by the time the universe was three minutes old.

About 75% of the universe was made up of hydrogen and 25% of helium by three minutes. By mass ratio, that is. Helium nuclei weigh four times as much as hydrogen nuclei, so if you only counted them, the ratio would be around 92% hydrogen and 8% helium.) While other chemicals were present in trace amounts, most other elements would not exist until they were synthesized in the center of stars.

This is the tale of how our understanding of the early Universe is shaped by particle accelerators. The first atoms were created when the universe cooled down to a point around 380,000 years after it started, allowing the nuclei of hydrogen and helium to absorb electrons. Furthermore, gravity gradually collected those atoms into heated clusters that eventually developed into stars and galaxies, thus the narrative was undoubtedly not finished.

From the birth of the Universe until a few minutes after it started, we have a fairly advanced knowledge of its nature based on precise observations. More crucially, sophisticated and thorough measurements rather than theoretical conjecture have led to our knowledge. Scientists can really reproduce the circumstances of the early Universe and see how things function by using enormous “atom smashers.”

The first accounts of the quest to discover the origins of our universe may be found in some of humankind’s oldest literature. Astronomical observations along with research carried out within massive particle accelerators are starting to provide a pretty clear picture of how it all started.