"Unveiling the Cosmic Microwave Background: A Window into the Big Bang"

Have you ever wondered over how the widely accepted Big Bang theory gained its prominence in the scientific community? The answer lies in a remarkable discovery that provided crucial evidence supporting this groundbreaking theory. In our latest blog post, we /explored the Cosmic Microwave Background (CMB). In this blog let's delve deeper into the Cosmic Microwave Background and understand its connection to the Big Bang Theory.

Before Exploring the Cosmic Microwave Background let's explore few backgrounds which led Scientists to think something like CMB 

The Space Time : 

Before Einstein the scientific community believed that the Time is absolute and they were also sure that the Space and Time were independent of each other here space refers to the three co-ordinates that we use for defining position.

Einstein suggested that the space and time are no 2 different independent term, but how one can relate time and spacial co-ordinates together? Let's explore how it is even possible.

In Einstein's General Theory of Relativity he mentioned that the speed of the light is absolute in this universe which is 300000000 m/s on this basis of this postulate Einstein developed his General Relativity, using his postulate Einstein proposed that we can calculate distance by measuring the time taken by light to travel from Point 'A' to point 'B', now we can 1 meter length as distance traveled by light in 0.000000003335640952 which led to the new unit of length called light-second which basically means distance travelled by light in one second.

The Imaginary Space time Fabric as it is impossible to visualize a 4 dimensional Structure 

Extending this idea Einstein suggested that the entire universe is placed on a fabric of space an time and he stated that the light travels through this space time fabric to reach us from all distant objects in order to verify this theory Einstein stated that whenever there exist a heavy object such as stars in the universe it will give a curvature to this space time fabric which eventually bend the direction of the light coming from an distant object behind the Star 

The curvature produced in space time fabric due to heavy object 

Einstein in his paper published in 1915, predicted that if we observe distant stars in the presence of Sun than what we observe is that the positions of these distant stars will be shifted by a certain amount which can be calculated the mathematics and formulas of GTR.  

This Is what Einstein Predicted in his Theory 

In 1919, Arthur Eddington, an English astronomer, seized the opportunity to test Einstein's prediction of light bending near massive objects. He recognized that during a total solar eclipse, star positions near the Sun could be compared to images taken when the Sun was in a different part of the sky. However, World War I delayed the verification process. Finally, in 1919, a total solar eclipse occurred, visible from northern Brazil to the African coast, near the Hyades star cluster. Eddington led an expedition to Príncipe, and Andrew Crommelin led another to Sobral, Brazil. By comparing the photographs from both expeditions to reference images of the Hyades, Eddington confirmed that starlight had indeed been deflected by approximately 1.75 seconds of arc, in agreement with Einstein's general theory of relativity. This historic experiment provided strong evidence supporting Einstein's groundbreaking theory.

The Original image Captured by Arthur Eddington during 1919 Total solar eclipse the circled spots are the exact spots of the stars observed and the small white lines within that shows the amount of fluctuation in position of stars 

Better image recreated to understand the shift 

The Red Shift :

Redshift refers to the phenomenon where light or electromagnetic radiation from distant objects appears shifted towards longer wavelengths, typically towards the red end of the spectrum. This shift provides valuable information about the motion and properties of celestial objects.

This Spectrum is observed over different sources and the laboratory reference is the ideal observation and all other sources are giving spectrum which is shifted towards the red side of the spectrum this observation will give vital information of the source of the light 

Gravitational Redshift :

Gravitational redshift is a consequence of Einstein's general theory of relativity, which describes how gravity affects the curvature of spacetime. According to this theory, the presence of a massive object, such as a star or a black hole, creates a gravitational field that influences the path of light passing through it. As light travels away from the gravitational source, it loses energy due to the gravitational pull. This energy loss causes a shift in the frequency or wavelength of the light towards the red end of the spectrum. This effect has been observed and confirmed through experiments and observations of light from massive objects, such as the bending of starlight around the Sun during a solar eclipse.

Cosmological Redshift :

Cosmological redshift, on the other hand, arises from the expansion of the universe. It was Edwin Hubble's observations in the 1920s that revealed that galaxies are moving away from us, and this motion is not due to their individual velocities but rather the expansion of space itself. As the universe expands, the space between galaxies (or any other objects) stretches, causing the wavelengths of light traveling through this expanding space to also stretch. This stretching of light waves results in a redshift, where the light is shifted towards longer wavelengths. The degree of redshift is directly proportional to the distance between the observer and the light source, providing a valuable tool for measuring cosmic distances. The cosmological redshift is considered a key piece of evidence supporting the Big Bang theory, as it suggests that the universe has been expanding since its early stages.

Both gravitational redshift and cosmological redshift play crucial roles in our understanding of the universe. Gravitational redshift provides insights into the behavior of light in strong gravitational fields and contributes to our knowledge of black holes, while cosmological redshift enables us to study the large-scale structure and expansion of the universe. These phenomena have been extensively studied and confirmed through observations and experiments, contributing to our understanding of the fundamental principles that govern the cosmos.

The Idea of Cosmic Microwave Background

What is Cosmic Microwave Background ? : 

The Cosmic Microwave Background (CMB) is a crucial component of our understanding of the universe's origins and evolution. It is a faint radiation that permeates the entire cosmos, and its discovery has provided remarkable insights into the Big Bang theory and the structure of our universe.

The CMB is often described as the "echo" or "flashlight" of the Big Bang. It provides a snapshot of the universe when it was only 380,000 years old. Prior to that point, the universe was a hot plasma of particles and light, making it opaque. However, as the universe expanded and cooled, protons and electrons combined to form neutral atoms, allowing light to travel freely. This ancient light has been stretching and cooling for billions of years, manifesting as microwave radiation that we can detect today.

The CMB appears remarkably uniform in all directions, with tiny temperature fluctuations providing valuable information about the distribution of matter and energy in the early universe. These fluctuations serve as the seeds for the formation of galaxies and large-scale structures we observe today.

The discovery and subsequent study of the Cosmic Microwave Background have revolutionized our understanding of the universe. It has provided strong evidence for the Big Bang theory and has allowed cosmologists to refine their models of the early universe's evolution. The precise measurements of the CMB's temperature and its isotropy have provided valuable insights into the composition, age, and geometry of our universe.

Researchers continue to study the CMB in detail, using sophisticated instruments and space-based telescopes to map its fluctuations and extract valuable cosmological information. The CMB has become a powerful tool for investigating fundamental questions about the nature of dark matter, dark energy, and the overall structure and history of the universe.

As we explore the mysteries of the cosmos, the Cosmic Microwave Background remains an essential piece of the puzzle. It serves as a window into the universe's primordial moments, allowing us to glimpse the formation and evolution of the vast cosmic tapestry we call home.

The Early Predictions and Calculations :

The existence of Cosmic Microwave Background was first predicted by the Russian born American Physicist George Gamow and colleagues during the 1940s, the foundation of these ideas came from the 1927 work of the Belgian physicist and priest Georges Lemaitre who is generally recognized as the "Father" of Big bang cosmology. But it was the American physicist Ralph Alpher and Robert Herman who in 1948, first estimated what the temperature of the cosmic Background ought to be, they based their calculations on three pillars, Einstein's General Relativity, Edwin Hubble's Discovery of the expanding universe and the atomic physics developed in laboratories before and during the Manhattan Project that built the atomic bombs of the World War II 

Herman and Alpher calculated and proposed a temperature of 5 degrees Kelvin for the universe. This Calculation was completely wrong. The precisely measured temperature of these microwaves is 2.725 degrees.   

The Discovery :

In 1965, Arno Penzias and Robert Wilson, were testing a very sensitive microwave detector at the Bell Telephone Laboratories in New Jersey. Penzias and Wilson were worried when they found that their detector was picking up more noise that it should. these noise did not appear to be coming from any particular direction. First they discovered bird droppings in their detector and checked for other possibilities of malfunctions, but all were soon ruled out. If these noise came from within the atmosphere then it should be stronger when the detector was not pointing straight up, because light travels through much more atmosphere when received overhead and it was same whichever direction the detector was pointed, hence they concluded that the rays are coming from somewhere outside the atmosphere. now when observed over night and day it was found that the rays were the same irrespective of the place and the time we observe throughout the year, even though the earth was rotating on the axis and orbiting around the sun. This proved that the rays radiation from must come beyond the solar system and even from beyond the galaxy.

Horn Antenna used to observe the CMB

At roughly the same time two American Physicist at nearby Princeton university, Bob Dicke and Jim Peebles were also taking interest in microwaves. They were working on aa suggestion made by George Gamow that the early universe should have been vert hot and dense, glowing white hot. Dickle and Peebles argued that we should still be able to see the glow of the early universe, because light from very distant parts of it would only just reaching us now. However the expansion of the universe meant that this light should be greatly red-shifted that it would appear to us now as microwave radiation. Dickle and Peebles were preparing to look for this radiation when Penzias and Wilson heard about their work and realized that they had already found the Microwaves that Dickle and Peebles were going on a search for.    

The discovery of the Cosmic Microwave Background (CMB) has played a pivotal role in solidifying the Big Bang theory as the prevailing explanation for the origin of our universe. By tracing the origins of the CMB, from Einstein's General Relativity to the groundbreaking experiments and observations by scientists like Arthur Eddington, Arno Penzias, and Robert Wilson, we have gained remarkable insights into the nature of our cosmos.

The CMB's existence and its properties, such as its uniform distribution and specific temperature, provide strong evidence supporting the idea that the universe began with a massive explosion billions of years ago. This discovery has fundamentally shaped our understanding of the universe's evolution, composition, and age.

As we continue to explore the mysteries of the universe, the Cosmic Microwave Background will undoubtedly remain a crucial area of study. Its intricate connection to the Big Bang theory has paved the way for groundbreaking research in cosmology and astrophysics, pushing the boundaries of human knowledge.

The journey of unraveling the secrets of the CMB has exemplified the brilliance of scientific inquiry and the remarkable achievements that arise from our insatiable curiosity. Through continued exploration, we can unlock even more profound insights into the nature of our universe and our place within it.