Universe

The word "universe" is derived from the Latin word "universum,"

which was used by the Romans to describe the globe and cosmos.

The universe is a vast expanse of free space that contains

everything from the tiniest particle to the most massive galaxies.
Age of universe
We measured the position of the galaxies in space but also in time, because the
further away they are, the more we go back in time to a younger and younger
universe,” Arnaud de Mattia, a co-leader of the DESI data interpretation team,
told AFP.
One of the most debated questions in Astronomy is how old our Universe is. Many astronomers
believe that the age of the Universe is 13.8 billion years. According to some, our Universe is
much older, while others believe it is much younger. The age of the Universe is calculated using
various ways. One of the ways of calculating the age of the Universe is to find the most ancient
planet, star, or galaxy in the Universe. Methuselah is the oldest planet discovered so far. It is
around 14.5 billion years old. GN-z11 is the oldest galaxy discovered so far. It is around 13.4
billion years old and about 32 billion light-years away from the Earth.

Composition of the Universe

The Universe is made up of all matter and energy. The mass of the Universe is
composed of baryonic matters, which are galaxies, planets, clusters, and gas clouds.
This mass can be observed. The mass of the Universe that remains invisible is called
dark matter. The Universe also has dark energy. The elements found in the Universe
after half a billion years after it was formed, were helium and hydrogen, and these
particles were not heavy. 0.3% of the Universe is made up of neutrinos. Dark energy
constitutes about 73% mass 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.
Dark matter
DESI is on a mission to shed light on the nature of dark energy — a theoretical
phenomenon thought to make up roughly 70 percent of the universe.
Another 25 percent of the universe is composed of the equally mysterious dark
matter, leaving just five percent of normal matter — such as everything you
can see.
in the late 1990s, astronomers were shocked to discover it has been expanding
at an ever-increasing rate. obviously, something was making the universe
expand at ever-faster speeds, and the name “dark energy” was given to this
force.
But we’re also seeing some potentially interesting differences which could
indicate that dark energy is evolving with time,” Levi said in a statement.
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.

How big the universe is?

the universe is unbelievably huge, the observable universe (part of the
universe that we know exists) spans across 46 billion light years, and it is
predicted that the actual universe can be as big as 95 billion light years. To put
that into perspective, if the entire earth was the size of an atom, the known
universe would be as big as seven suns combined! And if you want to know
how big the sun is, well, the fact that 1.3 million earths can fit inside the sun
will paint a clearer picture of how big the universe is.
Wonders of universe
Black holes
Supernova
Quaser 3C273
Jupitar

Black holes

Big bang theory

 The speed of its expansion was faster than the speed of the light. During this time, the size
of the Universe doubled at least ninety times. During the first three minutes after the
Universe came into existence, the Big Bang nucleosynthesis happened, and the light
elements were born.
 Edwin Hubble demonstrated the expansion of the universe in 1920.
The distance between galaxies is getting longer over time.

 Current cosmology – in the form of the Lambda-CDM model – tells us that the universe began with
a big bang. (Lambda stands for the cosmological constant, also known as ‘dark energy’; CDM stands
for ‘cold dark matter’.)


 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.
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.

The future of the Universe

 The Big Freeze Theory: The observations made so far suggest that our Universe will keep
expanding, and as it expands, it will become cooler. A time will come when the Universe will be too
cold, and then there will be no life. This theory is named the Big Freeze Theory.
 The Big Crunch Theory: Another theory suggests that our Universe will expand in the reverse order.
When this happens, the Universe will collapse again and may lead to another Big Bang. This theory
is called the Big Crunch Theory.
 The Big Rip Theory: According to this hypothesis, everything in the Universe will get torn into shreds.
During this process, the dark energy will be stronger than gravity. It is the Big Rip Theory.

Supporting Evidence:
Redshift of Galaxies: Observations show that galaxies are moving away from
us, with more distant galaxies exhibiting greater redshifts in their light
spectra.
Abundance of Light Elements: The theory accurately predicts the abundances
of light elements like hydrogen and helium in the universe.
Large-Scale Structure: The distribution of galaxies and the cosmic microwave
background match the predictions of the Big Bang Theory.

Lambda CDM-model

Spiral nebulae
Ratio of H and He