Big Bang Theory Science: Fascinating Facts For Kids

Among others, the Big Bang is one of the leading theories on the universe's birth.

The term 'Big Bang' was coined by the British astronomer Fred Boyle in an attempt to deride the explanation. Till his death, Fred Boyle remained a faithful exponent of the Steady State Model and endorsed the explanation that the universe regenerates itself and has no beginning or end.

So, what is this Big Bang theory? Simply put, the theory suggests that our universe began at one single point in time approximately 13.8 billion years ago.

Back then there were no stars or planets, rather the whole universe was compacted into a small ball with infinite density and heat, like black holes.

It was at this moment that this small ball started inflating and stretching. Over the next thousands of years, the early universe continued to expand and cool down, and then it constructed the universe that we see and know today.

Even though it seems intriguing when we visualize the whole thing, most of this explanation takes place on paper using numbers and mathematical formulae. However, through a phenomenon called cosmic microwave background, astronomers can perceive the echo of an expanding universe.

The explanation of an expanding universe was first introduced to the world of science by Alexander Friedmann, a Russian Cosmologist. Friedmann's equation showed that the universe was in a state of expansion.

A few years later, Edwin Hubble's extensive research managed to discover the existence of other galaxies.

And finally, Georges Lemaitre proposes that the constant expansion of the universe means that the more we go back in time the smaller the universe will get. And at one point there will be nothing but a 'Primeval atom' comprising the whole universe.

Even though most astronomical communities accept and endorse the Big Bang theory, some theorists still refuse to agree with this explanation and support other theories, such as Steady State theory, the Milne Model, or the Oscillatory Universe model.

Read on to find more such interesting facts about the Big Bang theory.

Cosmological Model For The Big Bang Theory

With the universe, the Big Bang theory itself has expanded since it was introduced. New theories were penned based on this one, along with new instruments to probe into this mystery.

The story of the Big Bang theory begins at the dawn of the 20th century with Vestro Slipher, an American astronomer, conducting multiple observations of spiral nebulae and measuring their large redshifts (will be discussed later in the article).

In 1922, Alexander Friedmann developed his own equation based on Einstein's equations of general relativity that claimed that the universe was in a state of inflation. This theory is known as the Friedmann equations.

Later, the Belgian physicist and Roman Catholic priest Georges Lemaitre used these equations to build his own theory on the creation and evolution of the universe.

In 1924, Edwin Hubble started measuring the distance between the Earth and the nearest spiral nebulae. And by doing so he discovered that those nebulae were actually distant galaxies floating in space and receding far aware from us.

In 1929, after a lot of research on distance indicators, he discovered a correlation between recession velocity and distance, which we now call Hubble's law.

In 1927 and 1931, Georges Lemaitre proposed two theories based on the creation of the universe. The first one, in 1927, was much similar to the Friedmann equation where Lemaitre infers that the recession of the galaxies is a consequence of the expansion of the universe.

However, in 1931, he went a little further to claim that if the universe had been expanding, then going back in time would shrink it until it becomes a tiny point with infinite density. He called this tiny point the 'primeval atom'.

Eventually, the Big Bang theory gained much popularity after Second World War. During this period the only model that stood against this one was Fred Boyle's Steady-State Model, which claimed that the universe did not have any beginning or end.

In 1965, cosmic microwave background radiation was discovered, and the observational evidence that it brought out began to favor Big Bang over Steady State theory.

With more technological inventions and factual discoveries coming out every day, scientists started relying more on this theory, and soon it secured its place as the most relevant theory regarding the creation of the universe.

Till then to the '90s the exponents of the Big Bang amended most of the issues raised by the theory and made it even more accurate.

In the '90s, Dark Energy was introduced to the world of science for resolving some very important issues in cosmology. It provided an explanation for the missing mass of the universe, along with an answer to the question regarding the universe's acceleration.

Satellites, telescopes, and computer simulations have assisted cosmologists and scientists to make significant progress by allowing them to observe the universe in a better and subtler way. With the help of these instruments gaining a better understanding of the universe and its actual age became possible.

Telescopes such as the Hubble Space Telescope, Cosmic Background Explorer (COBE), Planck Observatory, and Wilkinson Microwave Anisotropy Probe (WMAP) changed the way the universe was perceived by cosmologists and scientists.

Evidence Of Big Bang Theory Science

Much about the history of the universe was subjected to speculation until the discovery of the cosmic microwave background.

Over the years Wilkinson Microwave Anisotropy Probe (WMAP) and Plank Observatory have proved the existence of dark energy and dark matter. Not only that, but their reports have also specified that dark energy and dark matter fill most of the universe.

No one really knows what dark matter is made of but the evidence of its existence can be seen by observing galaxy rotation curves, galaxy motions in clusters, the phenomenon of gravitational lensing, and hot gas in elliptical galaxies and clusters.

Many researchers have been working on the dark matter for many years. But nothing substantial has yet been discovered.

And all we know about dark energy is that it might be the reason why the universe expands, and it has offered a resolution to the Cosmological Constant (Einstein). All in all these strange primordial elements of the universe support the Big Bang hypothesis.

In 1912, astronomers observed large redshifts in the spectra of spiral nebulae, giant clouds going outwards from the core in the shape of a spiral. Later it was discovered by the Doppler effect that these large redshifts signify nothing but large recession velocity from the Earth.

And when Hubble and his colleagues estimated the distance of these spiral nebulae from Earth it became clearer that these objects are constantly receding.

Then in the '20s, it was discovered that the spiral nebulae are actually external distant galaxies situated on the scale of the Milky Way Galaxy.

When it comes to the rate of expansion, observations of a distant supernova along with closer Cepheid variable stars made by the Hubble space telescope determine the rate as 163296 mph (262799.5 kph). But the observations made by WMAP and Planck of the cosmic microwave background radiation determine the rate as 149,868 mph (241,189.2 kph).

This difference of the two rates can point to important modifications of the Big Bang theory and to new physics.

Another instrument that provides evidence of the Big Bang is the Hertzsprung–Russell diagram or the HRD. Plots of color and luminosity of stars, given in this diagram, allow astronomers to determine the evolutionary state and age of a star or a bunch of stars.

And the reports of this diagram confirm that the oldest stars in the universe are more than 13 billion years old, meaning they were formed right after the Big Bang.

When the universe began with the Big Bang, it created the cosmic microwave background radiation along with a background noise made of gravitational waves. These gravitational waves do exist in our universe and have been detected a few times by several astronomers.

In 2014, astronomers claimed that they had detected B-modes (one kind of gravitational wave) using Background Imaging of Cosmic Extragalactic Polarization (BICEP2).

However, in 2015 it was revealed that the waves were mostly from stardust. Still, Laser Interferometer Gravitational-Wave Observatory is known for detecting many gravitational waves created by the collisions of black holes.

Big Bang Theory Explosion

Even though the name 'Big Bang' instinctively suggests an image of the universe exploding like a volcano, it was more of an expansion like the tectonic plates of our planet.

The scientific theory on the Big Bang suggests that before its disintegration, our observable universe was just a tiny point called a singularity. This tiny point had infinite mass density and unimaginable heat. However, a point came when this singularity suddenly started to expand.

And this is called the Big Bang. The expansion of the universe did not break Einstein's equations of general relativity. And more interestingly the universe is still expanding according to certain scientific theories.

After this initial expansion, the denser regions of the early universe began to pull each other using their gravitational forces. Thus they became more clustered and started forming gas clouds, galaxies, stars, and all other astronomical structures that we see every day.

This period is known as the Structure epoch; for during this time, the universe started taking its modern shape with all its structures and elements, such as planets, moons, and galaxy clusters.

13.7 billion years ago and fractions of a second later the Big Bang, the cooling process of the Universe started. It is believed that with the temperature and density the energies of all the articles also decreased until the elementary particles and the fundamental forces of physics transformed into their present form.

Similarly, it was claimed by the scientists that at 10^-11 seconds particle energies dropped significantly.

When protons, neutrons, and their antiparticles were formed (10^-6 seconds), a little number of extra quarks led to the formation of a few more baryons than antibaryons.

The temperature by then was not high enough for the formation of new proton-antiproton pairs, and that led to an inevitable mass annihilation resulting in the eradication of most of the proton particles and all of their antiparticles.

A similar process happened with positrons and electrons just after one second of the Big Bang.

Expansion Of The Big Bang Theory Science

The Big Bang was an explosive expansion that marked the beginning of the currently visible universe.

The first stage of the model of Big Bang cosmology is Planck Epoch. The stage is named after the German physicist Max Planck.

The time period that this epoch marks is 10^-43 seconds after the Big Bang happened. Modern science with all its technology still cannot figure out what happened before this point, as the physical laws that govern the present universe hadn't yet come to existence.

So this is the earliest insanely dense and physically describable existence of the universe.

Though Einstien's relativity theory predicts that before this point the universe was an infinitely dense singularity, the Planck epoch focuses more on the quantum-mechanical interpretation of gravitation, meaning a state where all four forces of nature were unified (though it is yet to be fully articulated).

The next one is the Grand Unification epoch. Here we can see the partial disintegration of the four unified natural forces: Gravitation, strong, weak, and electromagnetic.

This epoch begins at 10^-36 seconds after the Big Bang when gravitation split off from the rest of the forces. At around 10^-32 seconds electroweak (weak and electromagnetic) and electrostrong (strong and electromagnetic) separated from each other; in physics this phenomenon is known as symmetry breaking.

Between 10^-33-10^-32 seconds after the Big Bang, it is said that the universe began expanding suddenly, and its size increased on the order of 10^26 times.

This period of expanding universe is known as the Inflation epoch, and the theories that describe this transformation of the universe are known as Inflation models or theories. Alan Guth, an American physicist, was the first person to propose this theory based on cosmic inflation in 1980.

After that, it was widely developed to resolve key issues in the theory of the Big Bang, such as the flatness problem, the horizon problem, and the magnetic monopole problem.

At about 10^-12 seconds after the Big Bang, most of the contents of the universe were in a state known as a quark-gluon plasma due to the extreme heat and pressure.

In this state, the elementary or fundamental particles called quarks are not yet ready to bind with the gluons to create the composite particles called hadrons (protons and neutrons).

This period is called the Quark Epoch. The Hardron Collider at CERN can achieve the sufficient energy required to transform a matter into its primordial quark-gluon state.

At 10^-6 seconds, the universe cooled enough for hadrons to form. It is theoretically proven that after its formation there should have been equal amounts of antimatter and matter in the universe.

Antimatter is similar to matter with opposite properties of quantum number and charge. But antimatter could not survive due to a slight asymmetry between these substances. This asymmetry has been the subject of much research, and neither the standard model of particle physics nor the Big Bang theory could describe its nature.

However, some small and insufficient asymmetry between antimatter and matter has been discovered, and researchers continue to probe into this issue. We can hope to hear more about this asymmetry if their experimentations go right.

More details of the expansion of the universe are dependent on the type and amount of warm dark matter, cold dark matter, baryonic matter, and hot dark matter present in the universe.

However, it was proposed by the Lambda-Cold Dark Matter model that the particles of dark matter move slower than the speed of light, and it is also considered to be the standard Big Bang model to describe the universe and the cosmic evolution because it best fits the available data.