We often hear of the term ‘Universe’. What is known as the Universe? Can we measure its size? What is it composed of? Read here to know all the interesting facts about the universe.
The Universe includes all that we can see, hear, feel, detect, and measure. It consists of time, light, galaxies, dust clouds, stars, and planets. Matter, space, and time were non-existent before the creation of the universe.
There are countless millions of galaxies in the universe. There are millions of stars in each of these galaxies.
We still don’t know how big the universe is, thus we can’t see the edge. There is neither a center nor an edge to the universe.
The universe’s creation is explained by the Big Bang Theory. A massive explosion occurred in the universe when it was only 10-34 of a second old or older, and it caused the universe to expand. Its expansion proceeded more quickly than the speed of light. The size of the universe doubled at least 90 times over this period.
- Initial Singularity: The universe began as an infinitely hot and dense singularity, a point with zero volume and infinite energy.
- This singularity underwent a rapid expansion, often described as an explosion, causing the universe to expand and cool.
- As the universe expanded and cooled, particles and matter formed. Initially, the universe was composed of elementary particles like protons, neutrons, and electrons.
- As the universe continued to cool, atoms formed from these particles. This is an important phase because it allows for the formation of stable structures.
- Gravity played a crucial role in the formation of galaxies, stars, and other cosmic structures. The gravitational attraction between particles led to the clumping of matter, ultimately forming galaxies and stars.
- The universe has been expanding since the moment of the Big Bang and continues to do so. This expansion is supported by various observational evidence, including the redshift of galaxies and the cosmic microwave background radiation.
The light elements were created within the first three minutes after the Big Bang when the Big Bang nucleosynthesis took place. Our solar system was born roughly 9 billion years after the Big Bang. It took seven days to create the universe as we know it today.
However, the theory does not address what caused the Big Bang or what, if anything, existed before it. These questions about the origin of the singularity and the nature of the pre-Big Bang state remain open and subject to ongoing scientific exploration and theoretical speculation.
What is Space?
Nobody can hear your screams in outer space. This is because space is a vacuum and devoid of any air. A vacuum cannot be entered by sound waves.
About 100 kilometers above the Earth, where the atmosphere that surrounds our planet vanishes, the term “outer space” first arises. Space looks to be a black blanket with stars scattered across it because there is no air to reflect sunlight and create a blue sky.
Typically, space is thought of as being empty. However, this is incorrect. Huge amounts of thinly distributed gas and dust occupy the immense spaces between the stars and planets. There are at least a few hundred atoms or molecules per cubic meter in even the most empty areas of space.
Additionally, other radiation types in space are harmful to astronauts. The Sun is primarily responsible for this infrared and ultraviolet energy. Cosmic rays, gamma rays, and high energy X-rays—particles moving at nearly the speed of light—arrive from far-off star systems.
Structure of the Universe
The universe has a hierarchical and interconnected structure that spans from the smallest scales to the largest. It can be described in the following way:
- Cosmic Web: At the largest scales, the universe appears to have a cosmic web structure, characterized by vast filaments of galaxies separated by voids. This structure is the result of the gravitational interactions of dark matter and dark energy.
- Galaxies: Galaxies are the building blocks of the universe. They come in various shapes and sizes, from spiral galaxies like the Milky Way to elliptical and irregular galaxies. Galaxies contain stars, gas, dust, and dark matter.
- Star Systems: Within galaxies, stars form into systems like our solar system. Stars are the fundamental celestial objects that emit light and heat through nuclear fusion reactions in their cores.
- Planets and Moons: Planets orbit stars, and some may have moons. Our solar system, for example, consists of the Sun, planets like Earth, and their respective moons.
- Asteroids, Comets, and Other Objects: The universe is also populated with smaller objects like asteroids, comets, and meteoroids, which can impact planets and moons.
- Cosmic Dust and Gas: The interstellar medium contains cosmic dust and gas, which provide the raw materials for star formation and planetary systems.
All the energy and matter are present in the universe. As the simplest atomic element with simply a proton and an electron, hydrogen makes up a large portion of the universe’s observable matter (if the atom also contains a neutron, it is instead called deuterium).
- A molecule is made up of two or more atoms sharing electrons. An aggregate of several trillions of atoms is a dust particle.
- An asteroid is created by mixing a few tonnes of carbon, silica, oxygen, ice, and a few metals. Or create a Sun-like star by combining 333,000 Earth masses of hydrogen and helium.
In addition, there appears to be a lot of matter and energy in the universe that we cannot directly observe.
- Less than 5% of the universe’s matter is made up of stars, planets, comets, sea otters, black holes, and dung beetles all combined.
- The remaining substance is made up of around 68 percent dark energy and about 27 percent dark matter, neither of which is even vaguely known.
Dark matter and dark energy, which are referred to as “dark” because they are difficult for scientists to directly witness, are necessary for the functioning of the universe as we currently understand it. At least not yet.
- Ordinary Matter (Baryonic Matter): This is the matter we are most familiar with and can directly observe. It includes atoms, molecules, planets, stars, and galaxies. Ordinary matter constitutes a relatively small portion of the universe, estimated at around 5% of the total mass-energy content.
- Dark Matter: Dark matter is a mysterious and invisible form of matter that does not emit, absorb, or interact with electromagnetic radiation (light). It exerts gravitational forces and is thought to make up about 27% of the universe’s mass-energy content. Its nature is one of the major mysteries in astrophysics.
- Dark Energy: Dark energy is an even more mysterious component that makes up about 68% of the universe. It is believed to be responsible for the observed accelerated expansion of the universe. The nature of dark energy is a topic of ongoing research and debate.
- Radiation: Various forms of radiation, such as cosmic microwave background radiation (CMB), X-rays, and gamma rays, exist throughout the universe. They play a crucial role in understanding its history and evolution.
The size of the universe has changed over time. According to scientists, the Big Bang, which occurred almost 14 billion years ago, is where it all started. Since that time, the Universe has been rapidly expanding.
Therefore, compared to when the Universe was extremely young, the amount of space that we can see today is billions of times larger. As the distance between them widens, the galaxies are also getting farther away.
Humans continue to reveal the mysteries of the cosmos thanks to ever-improving technology, knowledge, and creativity. This endeavor is aided by and results in fresh insights and creative ideas.
There are billions upon billions of other stars in the galaxy, yet we haven’t even sent a space probe to the nearest one yet. Even the planets in our solar system have not been fully discovered by humans. In other words, the majority of the cosmos is yet unknown.
Also Read: Fast Radio Bursts
Article written by: Krishnapriya JR