The most widely accepted theory about the origin and development of the universe is the Big Bang, which refers to a big explosion that created everything in the universe.
Yes, scientists agree that everything we know, including space and time, came about 13.8 billion years ago from a single point, the thickness of a needle’s head. The explosion resulted in enormous release of energy and the formation of the first chemical elements.
Hard to believe? But there is evidence that was exactly what it happened.
Step by step to understand the Big Bang
1. The starting point
This cosmic embryo, as we said, was the thickness of a needle head, with absolutely extraordinary density and temperature. Imagine that the entire universe we know today, made up of countless galaxie with up to hundreds of billions of stars each, was once concentrated in a single, extremely hot spot. This is what the Big Bang theory says.
2. The Big Burst
Then there was the great release of energy: the Great Explosion. But if at first there was only concentrated energy, how did matter form? After all, the universe is made up of matter, isn’t it?
To answer this question, which is not at all simple, we have to resort to what is perhaps the most famous formula of modern physics: the equivalence between energy and matter (E = m.c²). Its author is none other than the German physicist Albert Einstein (1879-1955). Einstein’s formula allows us to explain how energy could become matter.
Albert Einstein developed the theory of general relativity, one of the pillars of modern physics.
3. The origin of the first chemical elements
The expanding universe gradually cooled and formed matter. Then the first chemical elements were formed: hydrogen and helium. In the beginning, all that existed was huge clouds formed of hydrogen. What existed was darkness and nothing more.
4. The first stars: condition for the origin of life
After some hundred million years, the first stars appear. They “ignited” due to the aggregation of gaseous hydrogen, initiating nuclear reactions between hydrogen atoms. It was, therefore, throughout a slow process that stars such as the sun emerged, absolutely indispensable to human life.
But what was before the Big Bang?
Here we face an intriguing question. As intriguing as asking a religious person, “If God created everything, then what was before God? Or who created God?”
Was the zero point of the universe preceded by anything?
Shortly before his death, British physicist Stephen Hawking (1942-2018), answering this question posed by astrophysicist Neil deGrasse Tyson on a television channel, said there was nothing before the Big Bang. There was no time and space before the Big Bang. There was nothing we know today and nothing that can be accessed by the scientific theories we have.
Although the Big Bang model is widely accepted and there is evidence to support it, this does not mean that there are no riddles. And they are many. Incidentally, what is not lacking are doubts about this which is the main subject that has been populating the thinking of human beings since the beginning: the origin of the universe.
How scientists came to the Big Bang theory
All scientific discovery involves observing reality, formulating a hypothesis, and conducting tests that prove the validity of that hypothesis. This is how you get to a scientific theory: a well-tested and well-founded explanation of a particular phenomenon.
From the “primordial atom” to the expanding universe
In the case of the Big Bang theory, it all began in the 1920s, with the mathematician Alexander Friedmann (1888-1925) and the physicist Georges Lemaître (1894-1966), who put forward the hypothesis that everything would have developed from a single point. They called this idea the “primordial atom hypothesis.”
Physicist Georges Lemaître, who was a priest, was one of the creators of the Big Bang theory.
The Big Bang theory includes the idea that the universe is expanding, today a theory widely accepted by the scientific community. But, as we said above, a hypothesis is a speculation, a provisional formulation. It is not enough to explain a phenomenon, whatever it may be. That will say a phenomenon as complex as the origin of the universe.
Therefore, someone would have to confirm this hypothesis. And that someone is the American astronomer Edwin Hubble (1889-1953). In 1929, from observing the movement of galaxies through telescopes, he could see that the galaxies were moving away from Earth. Hubble’s Law says that galaxies are not only moving away from Earth, but the more distant galaxies are moving even faster than those closest to them.
Edwin Hubble proved the expansion of the universe from telescopic observations.
A very easy experience to understand the law of the expanding universe
In an article entitled “The Origin of the Universe”, João E. Steiner, professor at USP’s Institute of Astronomy, Geophysics and Atmospheric Sciences, suggests a very simple experiment to understand how Hubble’s Law works.
To understand why the galaxies move away and why those farther away from us move even faster, draw small dots on an empty bladder. The bladder represents the universe (albeit two-dimensional), and the dots represent the galaxies. Use a different color to draw our galaxy, the Milky Way, of which the Solar System is part.
When you fill your bladder, you will notice that the galaxies closest to ours move farther apart than the farthest ones. This is how the terrestrial observer sees the phenomenon happening before his own eyes. Here’s Hubble’s Law in operation!
What if we empty the bladder? If we do that, we will see that the dots will approach each other again.
What are the conclusions?
-The universe is not stationary but expanding.
-Formerly it was smaller than it is today.
-In the future, the universe will be larger than it is today or was in the past.
-There was someday an origin, a starting point from which the whole universe arose.
-It is called the Big Bang the explosion that gave rise to the universe 13.8 billion years ago.
-Since then, the universe has not stopped expanding according to Hubble’s Law.
-The theory of the inflationary universe
-But has the universe always followed a pattern or pace of expansion? American cosmologist Alan Harvey Guth states that the universe, soon after the original boom, underwent a period of faster than normal expansion. This period, which would have lasted very little time, is known as the inflationary scenario of the universe.
This model proposed by Guth would complement certain limitations of the Big Bang theory, such as the problem of the curvature of the universe. Have you ever thought about the shape of the universe? Was he flat? Or is the universe round?
According to Guth, the universe is flat. And this is explained by the inflationary scenario, that is, the idea that initially the expansion took place frighteningly fast.
To explain this theory, Dartmouth College physics professor Marcelo Gleiser gives the example of a ball that inflates rapidly. When we observe any region of this ball during filling, we will see that this curvature decreases. That is, it becomes increasingly flat. The same thing happened with the universe.
Origin of the universe: a riddle that accompanies humanity
Although the Big Bang theory is recent, the desire to know the origin of the universe is very old. Thus, for thousands of years, cultures have been making attempts to answer this important and enigmatic question.
Anthropological studies reveal these stories of how the world began and developed and how humanity arose: cosmogonies. Origin myths are common to many different religions, which try to explain how everything we know was created. As we know, the belief that the universe arose out of the will of a supernatural being (God) is still very present.
If we think about the history of mankind, science is very recent. And so scientific explanations for phenomena of the physical universe arose very recently. Just to have an idea, until the publication of Copernicus’s famous heliocentric theory in 1543, we thought that the earth was at the center of the universe.
Thus, as science evolved, new theories emerged. And as far as the origin of the universe is concerned, the Big Bang is not the only one.
The biggest rival to Big Bang theory at the time it emerged was the steady state theory of Hermann Bondi (1919-2005), Thomas Gold (1920-2004) and Fred Hoyle (1915-2001). This theory says that the universe is what it always has been. The universe is constant in time; so it does not evolve or expand as evidenced by Hubble’s observations.
What do you think about all this theory? Live your comment below.