THE PANORAMIC UNIVERSE - Edition I

In the endless night sky, countless stars twinkle, distant galaxies whirl, and black holes shroud themselves in cosmic mystery. The universe, with its majestic expanse and limitless wonders, has captured the collective imagination of humanity for millennia. Today, with the strides in technology and the broadening of scientific knowledge, we are closer than ever before to the cosmic canvas that envelops us. It is an era of great discovery, exploration, and awe-inspiring understanding.

We start the series with this article. In the series that we will discuss piece by piece, we will introduce you to the depths of the universe.

In the first part of the article, which is a continuation, you will have knowledge and insight on the following topics:

• Beginning of the universe?
• The Big Bang Theory?
• Singularity - Origin of The Theory
• Types Of Singularity
• Dark Energy?
• Dark Matter?
• Gravity
• General Relativity
• Gravitational Waves

Introduction

The Universe, or Cosmos, is all of space and time, including planets, stars, galaxies, and all other matter and energy structures. This article gives the reader short and clear information about the universe and the unknowns of the universe and includes the formation stages of the universe, many important names who contributed to the world of science and their theories.

Beginning of The Universe

The?universe?is all of?space?and?time and their contents, including?planets,?stars,?galaxies, and all other forms of?matter?and?energy . Much of the observable matter in the universe takes the form of individual atoms of hydrogen, which is the simplest atomic element, made of only a proton and an electron. Around 68% of the total energy in the universe is composed of?dark energy, a hypothetical form of energy that appears to reside in the vacuum of?space-time?itself.

In the early years, everything was made of gas. This gas, mostly hydrogen and helium, expanded and cooled. Over billions of years, gravity caused gas and dust to form galaxies, stars, planets, and more.

In the 1920s in California, astronomer?Edwin Hubble?observed distant galaxies using?an extremely powerful?telescope. Hubble figured out that the?Milky Way isn’t the only Galaxy and discovered that?the galaxies are constantly?moving away from each other.?In other words, the?universe?is expanding.?A few years later,?Belgian astronomer Georges Lema?tre used Hubble‘s amazing discoveries to suggest?an answer to a big astronomy question:?How did the universe begin? This breakthrough idea later became known as the?Big Bang!

The Big Bang Theory

Around 13.7 billion years ago, everything in the entire universe was condensed in a small singularity, a point of infinite deseness and heat. Suddenly, an explosive expansion began, ballooning our universe outwards faster than the speed of light. Some scientist believe that the Big Bang (aka “singularity”) was not an explosion, but an expansion of space that continues today. The first galaxies and stars formed less than a 1/2 billion years after the Big Bang.

Stages of the Big Bang Theory

The Big Bang theory states that everything was simply energy at the beginning. This energy was transformed into tiny particles (like photons). These early photos were dispersed by early electrons because there were earlier free electrons. Subsequently, atoms were generated when electrons were mixed with protons and neutrons (atomic nuclei). The Big Bang Theory is divided into four stages:

• Heavy Particle Era
• Light Particle Era
• Radiation Era
• Matter Era

Singularity

There are places in the universe where our laws of physics simply break down. To understand what a singularity is, imagine the force of?gravity?compressing you down into an infinitely tiny point, so that you occupy literally no volume. That sounds impossible … and it is. These "singularities" are found in the centers of black holes and at the beginning of the?Big Bang.?Singularities were first predicated as a result of Einstein’s Theory of General Relativity, which resulted In the theoretical existence of black holes. In essence, the theory predicted that any star reaching beyond a certain point in its mass (aka. The Schwarzschild Radius) would exert a gravitational force so intense that it collapse. There are different types of singularities, each with different physical features which have characteristics relevant to the theories from which they originally emerged, such as the different shape of the singularities,?conical and curved. They have also been hypothesized to occur without event horizons, structures which delineate one spacetime section from another in which events cannot affect past the horizon; these are called?naked.

• Curvature Singularity : Curvature singularity is the best exemplified by a black hole. At the center of a black hole, space-time becomes a one-dimensional point which contains a huge mass. As a result, gravity become infinite and space-time curves infinitely, and the laws of physics as we know them cease to function.?
• Conical Singularity : Conical Singularity occur when there is a point where the limit of every general covariance quantity is finite. In this case, space-time looks like a cone around this point, where the singularity is located at the tip of the cone. An example of such a conical singularity is a cosmic string, a type of hypothetical one-dimensional point that is believed to have formed during the early universe.
• Naked Singularity : Naked Singularity is a type of singularity which is not hidden behind an event horizon. These were first discovered in 1991 by Shapiro and Teukolsky using computer simulations of a rotating plane of dust that indicated that General Relativity might allow for ‘naked’ singularities.

Some basic features of the singularity in the scientific community have been determined:

• Zero volume, infinite density.
• Laws of physics are no longer valid.
• Light?emitted from?beyond the event horizon (Schwarzschild radius) cannot escape the singularity.
• There is an escape mechanism from the event horizon, however, related to quantum effects. This process is known as Hawking radiation or simply as Black Hole evaporation.
• Objects sent towards an event horizon never appear to cross it from the sender observer’s point of view
• To the sender the clocks on the spaceship sent towards an event horizon appear to slow down and finally stop at the event horizon
• The General Relativity theory is inadequate to describe the spacetime singularity. We need a theory of quantum gravity for a better understanding of the event horizons.
• “What is beyond the event horizon ?” is a legitimate question for physics.

Dark Energy

The universe is full of matter and the attractive force of gravity pulls all matter together. Then came 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the universe was actually expanding more slowly than it is today. So the expansion of the universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it. But something was causing it. Theorists still don't know what the correct explanation is, but they have given the solution a name. It is called dark energy.

Some notes to keep in mind are listed below:

• Dark energy is an unknown form of energy that affects the universe on the largest scales.
• The first observational evidence for its existence came from measurements of supernovae, which showed that the universe does not expand at a constant rate; rather, the expansion of the universe is accelerating.
• Prior to these observations, it was thought that all forms of matter and energy in the universe would only cause the expansion to slow down over time.
• Measurements of the cosmic microwave background suggest the universe began in a hot Big Bang, from which general relativity explains its evolution and the subsequent large-scale motion.
• Without introducing a new form of energy, there was no way to explain how an accelerating universe could be measured.

Dark Matter

Dark matter is?composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation. Dark matter is material that cannot be seen directly. We know that dark matter exists because of the effect it has on objects that we can observe directly.

????????????Dark matter appears to be spread across the cosmos in a net-like pattern, with galaxy clusters forming at the nodes where fibers intersect. By verifying that gravity acts the same both inside and outside our solar system, researchers provide additional evidence for the existence of dark matter. (Things are even more complicated as in addition to dark matter there also appears to be?dark energy, an invisible force responsible for the expansion of the universe that acts against gravity.)

Galaxy clusters?are particularly important for dark matter studies since their masses can be estimated in three independent ways:

• From the scatter in radial velocities of the galaxies within clusters
• From?X-rays?emitted by hot gas in the clusters. From the X-ray energy spectrum and flux, the gas temperature and density can be estimated, hence giving the pressure; assuming pressure and gravity balance determines the cluster's mass profile.
• Gravitational lensing?(usually of more distant galaxies) can measure cluster masses without relying on observations of dynamics (e.g., velocity).

Scientists can't see dark matter directly, they have found other ways to investigate it. We can use indirect ways to study things, like looking at a shadow and making an educated guess about what's casting the shadow. One way scientists indirectly study dark matter is by using gravitational lensing.

The similarities and distinctions of the two "dark" concepts are briefly given below, respectively.

Dark Energy?68.3%

• The single largest constituent of the universe
• Tends to drive universe part
• No interaction with normal matter
• Can be thought as 5th fundamental force

Dark Matter 26.8%

• Second largest constituent of the universe
• Tends to drive universe together
• Interacts with normal matter by Gravity (gravitational lenses)
• Dark Matter is not Antimatter or black holes.

Gravity

Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038?times weaker than the?strong interaction, 1036?times weaker than the?electromagnetic force?and 1029?times weaker than the?weak interaction.?Isaac Newton?was the first to develop a quantitative theory of gravity, holding that the force of attraction between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them.?Albert Einstein?proposed a whole new concept of gravity, involving the four-dimensional continuum of?space-time, which is curved by the presence of matter. In his general theory of?relativity, he showed that a body undergoing uniform acceleration is indistinguishable from one that is stationary in a gravitational field.

Isaac Newton?said it did almost three and a half centuries ago: a force that tells massive objects how to move. Newton’s law of gravitation, statement that any particle of matter in the universe attracts any other with a?force?varying directly as the product of the masses and inversely as the square of the distance between them. In symbols, the magnitude of the attractive force?F?is equal to?G?(the?gravitational constant, a number the size of which depends on the system of units used and which is a universal constant) multiplied by the product of the masses (m1?and?m2) and divided by the square of the distance.

General Relativity

Einstein's theory of gravity, is the?geometric?theory?of?gravitation?published by?Albert Einstein?in 1915 and is the current description of gravitation in?modern physics. General?relativity?generalizes?special relativity?and refines?Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of?space?and?time?or?four-dimensional?spacetime. In particular, the?curvature?of spacetime?is directly related to the?energy?and?momentum?of whatever?matter?and?radiation?are present. The relation is specified by the?Einstein field equations, a system of second order?partial differential equations. Newton's law of universal gravitation, which describes classical gravity, can be seen as a prediction of general relativity for the almost flat spacetime geometry around stationary mass distributions.

This curvature is caused by the presence of?mass. Generally, the more mass that is contained within a given volume of space, the greater the curvature of spacetime will be at the boundary of its volume.?As objects with mass move around in spacetime, the curvature changes to reflect the changed locations of those objects. In?certain circumstances, accelerating objects generate changes in this curvature which propagate outwards at the?speed of light?in a wave-like manner. These propagating phenomena are known as gravitational waves.

Gravitational Waves

Gravitational waves?are waves of the intensity of?gravity?generated by the accelerated masses of an orbital binary system that?propagate as waves?outward from their source at the?speed of light. Gravitational waves were later?predicted in 1916?by?Albert Einstein?on the basis of his?general theory of relativity?as ripples in?spacetime.?Later he refused to accept gravitational waves. Gravitational waves transport energy as?gravitational radiation, a form of?radiant energy?similar to?electromagnetic radiation.

The most powerful gravitational waves are created when objects move at very high speeds. Some examples of events that could cause a gravitational wave are:

• when a star explodes asymmetrically (called a?supernova)
• when two big stars orbit each other
• when two?black holes?orbit each other and merge

We thank ?pek Seyito?lu, the founder, researcher and content creator of LUX Space Science & Technology - LSS , who wrote this article.

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