The Universe is an enormous place. It consists of clusters of galaxies, and in them are stars, solar systems and even the planets. Only 4% of the Universe is ordinary matter (humans, planets and the stars). Some of it (22%) is an unidentified substance known as dark matter. Dark matter only interacts gravitationally with normal matter. The rest of the Universe (74%) is composed of an unidentified force called dark energy that speeds cosmic expansion. In fact it is so massive that it will take you more than a thousand years to count all the stars in a galaxy, without sleeping or eating. There are about a hundred billion stars in one galaxy and there are trillions of galaxies in the Universe. Carl Sagan is a well known astronomer. He states that the total number of stars in the Universe are more than the grains of sand on all the beaches of planet Earth. This must tell you just how big the Universe is. The main questions for astronomers and cosmologists in the twentieth century are about the origins of the Universe. To answer these questions many scientists came up with different and unique theories
There were two main ideas about the creation of the Universe. The first one proposed that the Universe existed eternally with no start or end. The other idea stated that the Universe was created and will end one day. Although science would like to consider itself removed from outside influences, it can’t help but be affected by the people who worked in the field and by the times they lived in. In the seventeenth and the eighteenth century the world was progressing and developing at a great speed, hence most theories of that time proposed an infinite Universe with an infinite future. This reflected an advancing society. Later on, in the twentieth century the development of the world was halted and World Wars, along with atomic bombs and political assassinations dominated the attention of the society. It is not surprising to see that the ideas and theories of a decaying, finite cosmos were proposed at this point in time.
For the Big Bang idea to take shape, the definition of the boundaries of the Universe had to change. Albert Einstein published the General Relativity theory in the year 1915. A few years after that, he stated that the Universe was a finite, closed four dimensional sphere warped by the forces of gravity predicted in his theory. It was a static and unchanging Universe governed by his elegant equations. Einstein also assumed that the Universe as a whole was homogeneous. That means that all matter is spread smoothly throughout space. His General Relativity theory proposed that, the larger the mass of an object, the more it curves space, but by 1919, there was proof that the Universe was clumpy and not homogeneous. This precedent, allowed for assumptions contrary to observations, with the idea that the assumptions will eventually be proven correct one day, led to that theory being perpetuated down through our cosmology of today.
The next stage in the birth of the big bang was called the “Primeval Atom theory”. The first version of the Big Bang was put forth by a Belgian Catholic priest, named George-Henri Lemaître (1894-1966) in 1931. This theory declared that the Universe started from a point of non-expansion, a single point in time and space called a singularity. When the Primeval Atom exploded, it split into smaller and smaller units known as subatomic particles. These particles later on became galaxies, with some decaying into stars and solar systems. In fact, George-Henri Lemaître proposed this theory with the purpose of explaining the existence of cosmic rays, and therefore cosmic rays proved his theory. Several other scientists disagreed with his ideas. It had too many flaws in its fundamental hypothesis. Thus, the first version of the Big Bang died.
Seeing the atomic bomb explode, George Gamow questioned “ If the atomic bomb can in a hundred-millionth of a second create elements that can be detected years later, why can’t a titanic unfolding at the start of time make all the elements we have today?” If the Universe came from a singularity, using equations from the General Relativity theory, Gamow stated that the nuclear reactions produced during the huge unfolding, would create all the light elements like hydrogen and helium. Eventually, as the Universe cooled, heavier elements would be produced as well.
Cosmologists and astronomers don’t exactly know what came before the Big Bang. Some cosmologists think that nothing existed before the Big Bang, while others think that the Universe goes through a cycle of Big Bangs. Using the laws of physics, astronomer and cosmologists can go back to a fraction of a second after the Big Bang, known as the “Planck Era” but there they must stop.
After all this gradual development, the Big Bang theory we know today finally came into existence. The name “Big Bang” was coined by Fred Hoyle in 1950. He was a British astronomer and a supporter of the Steady State theory. The Big Bang theory proposed that 13.7 billion years ago, a point of space, time, and extreme energy unfolded. Commonly, people mistaken the Big Bang as an explosion, but it actually was an unfolding. This point was excessively dense and astonishingly hot. As the hot Universe expanded and cooled in its first billionth of a second, the four fundamental forces of nature (gravity, electromagnetism and the weak and strong nuclear forces) separated and became distinct. Then, subatomic particles formed and over the next three minutes, protons fused to make helium and a few other nuclei. About 380,000 years later, the Universe cooled enough to allow for electrons to bind with nuclei. When these electrons bonded with the nuclei, the first atoms were formed. Photons flew free to generate the CMB (Cosmic Microwave Background). Get your television signal from an antenna and switch the dial where you find static. 1% of the static seem comes from the radiation caused by the Big Bang. In general, the Big Bang theory describes the constant expansion and gradual cooling of the Cosmos. The Big Bang Universe is finite both in space and time. Time, space and all matter was formed in that unfolding.
Eventually, this ball of bright light grew to the size of a galaxy and still is expanding today. The present size of the observable Universe is about 93 billion light years. Light years are used to measure any distance outside our solar system. Light can travel 5.8 trillion miles in a year. Within our solar system, astronomers and cosmologists use astronomical units to measure distance. One astronomical unit is the distance between Earth and the Sun. Light takes about eight minutes and nineteen seconds to travel this distance. As the Universe continues to expand, all the galaxies are drifting away from each other but they remain the same size as the space between them increases. Every second, the Universe is getting a bigger, causing a reduction in its density. Some astronomers think that the Universe is expanding into another dimension, a part of space that we can’t see. The fundamental force of gravity from all of the galaxies is slowing the expansion of the Universe.
No one knows for certain about the future of the Universe. At present, it’s getting larger and less dense. Most astronomers think that someday, the Universe will stop expanding, but there is a lot of disagreement about what will happen then. Will it live on forever, wither and die, or will it start to contract?
According to the Big Bang theory, the Universe could end in a Big Crunch or a Big Chill. The Universe may end in a Big Crunch, if the gravitational pull of all the galaxies, is strong enough to stop the Universe from expanding. This tremendous force of gravity may make it to contract and then eventually collapse. Even this may not be the end of the immeasurable Universe. There’s a possibility that a second Big Bang may follow the Big Crunch, and the complex cycle could start all over again! The Universe also has a possibility to end in a Big Chill, if it expands forever until all the stars and galaxies have exhausted their supply of energy. Then, there would be no heat left. Everything would be cold.
Scientists predicted that if the Big Bang happened, all of the Cosmos should be bathed in a slight radiation left over from that unique event. They explained that this microwave radiation, coming from every direction in the Universe, is barely detectable, glowing at a mere 2.725 degrees above absolute zero. That’s about -454.495 degrees Fahrenheit or -270 degrees Celsius. Absolute Zero is the coldest possible temperature, at which even molecules stop moving. This diluted afterglow of the Big Bang, known as the CMB (Cosmic Microwave Background) was discovered by Arno Penzias and Robert Wilson at Bell Labs, New Jersey in the year 1965. They received the Nobel Prize for their discovery. With this confirmation, scientists now believed that the Big Bang theory was “the answer”. The WMAP (Wilkinson Microwave Anisotropy Probe) produced some of the most precise picture of the CMB. These photons are traveling through space since electrons and protons first combined into atoms of neutral hydrogen, 380,000 years after the Universe’s birth. When the Cosmos was half it’s size, the density of matter was eight times more and the CMB was two times hotter. The CMB was hundred times hotter when the Universe was one-hundredth its present size. When the size of the Universe was only hundred-millionth of its present size, it’s average temperature was 273 Kelvin(32 degrees Fahrenheit or 0 degrees Celsius) above absolute zero. The density of cosmic matter back then, was comparable to that of air on Earth’s surface.
Even though the Big Bang theory was the best one out there, it definitely was not flawless. It proposed that the Universe is smooth and homogeneous, but that’s certainly not the case. There was enough evidence way back in 1919 to affirm that the Universe was clumpy. It would take at least 100 billion years for the oldest, super clusters of galaxies to form, but the Big Bang theory puts forth that the Universe is only about 13.7 billion years old, give or take 100 million years. This is another flaw in the Big Bang theory. The Big Bang theory also states that no object in the Cosmos should be more than 150 light years across, but that’s not true either. Fluctuations in the Cosmic Microwave Background indicate that there must be approximately hundred times more dark matter than visible matter in order for the galaxies to form. Unfortunately, there is no experimental or observable evidence in the Big Bang theory affirming that dark matter exists. Still, the theory states that, if there’s no dark matter, we can’t have galaxies.
Edwin Hubble’s discovery of the expanding Universe is one the most fundamental in the history of astronomy. In this illustration, six clusters of galaxies in a cube 100 million light years across separate from one another as the cube doubles in size. There is no expansion center. From the perspective of an observer in any galaxy cluster, all the other galaxy clusters appear to be moving away. This creates an illusion that each observer lies in the center of the expansion.
The Steady State theory was as popular as the Big Bang theory is today in the late 1940’s and through the 1950’s. It proposed that the Universe looked the same at any time and any place to any observer. Although it was expanding, the Universe would stay unchanged and in perfect balance. This was because material was being constantly created to maintain the density of the cosmos. Sadly, this theory was abandoned after cosmologists and astronomers found proof for the Big Bang.
An alternative for conventional cosmology is plasma cosmology. In plasma cosmology, the Universe has always existed and evolved and will go on to do the same for eternity. The Big Bang theory sees the Universe in terms of gravity alone, while the plasma Universe is formed and controlled by electricity and magnetism, not just gravitation.
Generally speaking, the Universe is flying apart at ever increasing speeds. The 100 billion galaxies we can now see using telescopes will go out of range one by one. Of course, this would take billions of years, but it shall happen one day. Tens of billions of years later, the Milky-Way will be the one and only galaxy we can see. At that point in time, our Sun will have shrunk to a white dwarf(a highly compact star near the end of its life and which emits white light) that will be providing barely any light or heat to who or whatever that is left on Earth. In cosmological time, billions of years is very small. The Universe will advance to exist. Eventually, each of the stars and suns in all of the galaxies will slowly burn out. By the time the Universe is several trillion years old, all the dead matter will collapse into black holes. These black holes will gradually disintegrate into stray particles which will often run into one another. So what was once, a Universe lit up by countless numbers of stars and galaxies will end up being a vast, empty, dark and unimaginably lonely place.