What is the universe ? It's one of the most frequently asked questions by scientists throughout history. In reality, the universe is everything, without exception. We can encompass matter, energy, space, time, and everything that exists within the universe. However, when we talk about what the universe is, we usually refer to the outer space beyond planet Earth.
In this article we are going to tell you what the universe is, its characteristics and some theories.
What is the universe
The universe is huge, but it may not be infinite. If so, there would be infinite matter in an infinite star, which is not the case. On the contrary, as regards matter, it is primarily empty space. Some people even claim that the universe we live in is not real, it is a hologram.
The known universe contains galaxies, galaxy clusters , and larger structures called superclusters, as well as intergalactic matter. Despite the advanced technology available today, we still don't know its exact size. Matter is not distributed uniformly but is concentrated in specific locations: galaxies, stars, planets, and so on. However, it is assumed that 90% of existence is dark matter, which we cannot observe. Therefore, dark matter plays a fundamental role in understanding the universe.
The universe has at least four known dimensions: three in space (length, height, and width) and one in time. Due to the dominant force of gravity, it is held together and is constantly in motion. Compared to the vastness of the universe, our planet is very small. We are part of the solar system, nestled in the spiral arms of the Milky Way. The Milky Way contains 100.000 billion stars, but it is only one of the hundreds of billions of galaxies that make up the solar system.
Formation and destruction
The Big Bang theory explains how it was formed. This theory that about 13.700 billion years ago, matter had an infinite density and temperature. There was a violent explosion and the density and temperature of the universe have been decreasing since then.
The Big Bang is a singularity , an exception that cannot be explained by the laws of physics. We can know what happened from the beginning, but there is still no scientific explanation for the moment of zero and the zero size. Until this mystery is solved, scientists will not be able to explain with complete certainty what the universe is.
Currently, there are several theories that, based on a hypothesis, explain how they believe the universe will end. To begin, we can talk about the Big Freeze model, which states that the continued expansion of the universe will cause (within a trillion years) the extinction of all stars, resulting in a cold and dark universe.
We can also mention the Big Rip theory , which proposes that the more the universe expands, the more dark energy is generated, eventually reaching a point where dark energy will overcome gravity, breaking the balance between the two forces and causing the disintegration of all types of matter.
Importance of dark matter
In astrophysics, cosmic components other than baryonic matter (ordinary matter), neutrinos, and dark energy are called dark matter. Its name comes from the fact that it does not emit electromagnetic radiation or interact with electromagnetic radiation in any way, making it invisible throughout the entire spectrum of electromagnetic radiation. However, it should not be confused with antimatter.
Dark matter accounts for 25% of the total mass of the universe , due to the influence of its gravitational pull. There are strong signs of its existence, detectable in the astronomical objects that surround it. In fact, the possibility of its existence was first proposed in 1933, when the Swiss astronomer and physicist Fritz Zwicky noted that this "invisible mass" affects the orbital speed of galaxy clusters. Since then, numerous other observations have consistently indicated that it may exist.
Little is known about dark matter. Its composition is a mystery, but one possibility is that it is composed of ordinary heavy neutrinos or recently proposed elementary particles (such as WIMPs or axons), just to name a few. The clear answer about its composition is one of the main questions of modern cosmology and particle physics.
The existence of dark matter is important for understanding the Big Bang model of the universe's formation and the behavior patterns of celestial objects. Scientific calculations show that there is far more matter in the universe than can be observed. For example, the predicted behavior of galaxies often changes for no apparent reason, unless there is a possibility that unobservable matter exerts a gravitational influence on visible matter.
Antimatter and dark energy in the universe
We must not confuse dark matter with antimatter. The latter is a form of ordinary matter, like the matter that constitutes us, but it is composed of elementary particles with opposite electrical signs: positive / negative.
An antielectron is a particle of antimatter, corresponding to an electron, but with a positive charge instead of a negative one. Antimatter does not exist in a stable form because it annihilates matter (which exists in a greater proportion), and therefore does not organize itself into observable atoms and molecules. Antimatter can only be obtained using particle accelerators. However, its production is complex and expensive.
Dark energy is a form of energy that exists throughout the universe and tends to accelerate its expansion by repelling gravity or force. It is estimated that 68% of the energetic matter in the universe belongs to this type, and it is a very uniform form of energy that does not interact with any other fundamental force in the universe, which is why it is called "dark". But, in principle, it has nothing to do with dark matter.
I hope that with this information you can learn more about what the universe is, its origin and its characteristics.