What is the universe made up of?

universe composition

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Over the past centuries, the study of the universe among the people has become more fascinating. Throughout the years, scientists come up with various theories and studies.

 

There are thousands of questions that come in our curios minds whenever we think about the universe. A few such questions like what constitutes the universe? What is it made of? What does it consist of? and much more.

These questions, however, are still a mystery in scientists’ minds as well. Though scientists have gathered much information about this, there is still more to discover.  

After the big bang, the cosmic inflation occurred and the universe expands as the time elapsed. The gravitational force and nuclear forces were responsible for the interaction between atoms and nuclei to form elements. Thus the elements were formed about billions of years ago that we see today.

But the matter is not restricted to this visible ordinary matter. However, there is a presence of an unknown matter called ‘The Dark Matter’ which shows no properties at all. Also, an unknown form of energy is present to oppose the contraction of the universe. Instead, it is responsible for the expansion. 

The composition of the matter can be broadly categorized as follows: 

  1. Ordinary matter (4%) 
  2. The Dark Matter (23%) 
  3. The Dark Energy (73%)

These are homogeneously distributed over the universe. Other constituents are the ‘Antimatter’ and ‘Electromagnetic radiation’.

Ordinary Matter

It includes all the cosmological, living, and non-living components; from us to the air we breathe, the water we drink, the earth on which we live, the stars & moons we see, the observable galaxies, to the universe we are a part of 

The matter can be categorized into the following states: Solids, Liquids, Gases, Plasma, Bose-Einstein Condensate, and Fermionic Condensate.      

The formation of the matter came from the formation of the elementary particles after the big bang. The elementary particles quarks and leptons formed into atoms and hence, contributed 4% of the proportion to the universe.

 

Quarks

Quarks are the fundamental elementary particle which combines to form the composite particles such as ‘Hardons’. It includes ‘Baryons’ that further accounts for the formation of protons and neutrons. Quarks also form into ‘Measons’ which are quite unstable. 

Quarks are the only particles with the experience of our four fundamental forces, that is, the gravitational force, the electromagnetic force, weak and strong nuclear forces.

 

Leptons

These are the elementary particles with half-integral spin. These particles form into composite particles like atoms, electrons, positronium, neutrinos, etc. They do not undergo any strong interaction forces. They can be of two kinds, charged and neutral.

Charged lepton forms the electron, muon, and tau. On the other hand, neutral leptons give rise to the neutrinos.   

Now, we’re going to discuss the overall process of the formation of the matter. When the big bang occurred, cosmic inflation also occurred and gave rise to the elementary particles. Then, as the temperature cooled off, the unified force was distinguished into four independent forces that we call today as the gravitational force of attraction, electromagnetic force, weak and strong nuclear forces.

These forces acted between the elementary particles, giving rise to composite particles such as atoms and molecules were formed. Lighter nuclei were formed as a result of nuclear fusions.

The hydrogen element is almost everywhere. The stars also have plenty of hydrogen as a fuel. Nuclear fusion occurs inside the core of the stars gives rise to nuclei of the different elements.

Thus, the fusion of the nuclei of lighter elements gave rise to nuclei of higher elements. As the temperature further cooled off, the universe expanded. Therefore, the formation of celestial bodies such as galaxies, planets, moons, stars, asteroids, living, and non-living took place. 

But all this stuff only contributed to only 4% portion of the universe, then what else is left to explore? Well, we are going to discuss the remaining portion which covers most of the universe.

 

The Dark Matter: The unseen matter

The Dark Matter, A hypothetical kind of matter that cannot be detected directly but its presence can be determined. It is invisible in the Electromagnetic spectrum but makes up nearly 23% of the universal matter.

It was named so because of its difficulty in detection. The name, ‘Dark Matter’ does not specify its darkness or anything related to this.

It does not emit and absorb the light. Therefore, it can’t be an electromagnetic wave.

Also, it can’t be antimatter because it could have emitted gamma-ray (high energy source) when interacted with the matter. Therefore, it is still a difficult task for scientists and researchers to study this.

 

The Dark Energy: The Unknown Energy 

The dark energy is Form of unknown energy that is responsible for the expansion of the universe. It was first observed during the explosion that causes a supernova. The supernova measurements revealed that the universe is accelerating.

It covers 73% portion of the universe. The two proposed forms are as follows:

  • Cosmological constant: The energy density is considered to be constant.
  • Scalar fields: quintessence or moduli whose energy density can be a time variable.

The studies also revealed that the energy density is estimated to be lower than that of the dark matter. It also exerts negative and repulsive pressure. It also behaves like an opposition to the gravitational force of attraction.

 

Other constituents: Antimatter & Electromagnetic Radiation

Antimatter

It is interesting to know that there is opposition to the matter. Like, the properties shown by it will be opposite to the matter. More precisely, we can say that the particles it is made up of will behave opposite to the normal particles. Therefore, these oppositely behaving particles are known as anti-particles.

For example, let us consider an atom. The atom consists of protons with a positive charge, neutrons with a neutral charge, and electrons with a negative charge. Therefore, the anti-matter of that atom will have anti-protons with a negative charge, anti-neutrons still with a neutral charge, and anti-electrons (also known as positrons) with a positive charge. Hence, the atom will behave the opposite.

It was created along with matter after the big bang, but later on, it was realized that the anti-matter is rare as compared to the matter. The matter and the anti-matter were created in equal amounts in ultra-high-energy collisions, but as soon as the time passed, the proportion of matter was large.

The scientists also do not have any explanation for this. Why matter came to dominate is a question that scientists have yet to discover. One theory suggests that more normal matter was created than antimatter in the beginning, so that even after mutual annihilation there was enough normal matter left to form stars, galaxies and us.

Electromagnetic Radiation

Consider a charged particle, let us say, an electron such that it is accelerated by an electric field. Due to the electric field, the electron will move. The moving electron will produce an electric and a magnetic field perpendicular to each other simultaneously.

It constitutes the wave called Electromagnetic wave whose direction of propagation will be perpendicular to both of them. It travels fastest in the vacuum and the speed with which it travels is known as the speed of light. The energy produce by this wave is known as electromagnetic radiation.

Thus, we can say that Electromagnetic radiation is a form of energy that is present everywhere in the form of radio waves, microwaves, X-rays, UV radiations, visible light, and gamma rays.

Since it is a wave, then it will have some wavelength and a frequency range. This range is known as the electromagnetic spectrum. The EM spectrum is generally divided into seven regions, in order of decreasing wavelength and increasing energy and frequency. The common designations are radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays, and gamma rays.

Sunlight is also an Electromagnetic source. The visible light is only a small portion of the Electromagnetic spectrum, which contains a broad range of wavelengths.

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