The Big Bang model as a theory of the origin of the Universe is accepted by most cosmologists, because there are substantial indications that allow us to think that this model is correct.
In the cover image you can see a picture of how the cosmos came into existence. Credit: web “quo.es/ciencia”
What does the Big Bang theory say?
The Big Bang is often described as the instant in which a concentrated ball of energy exploded, turning into matter and expanding at enormous speed.
It is postulated that this happened about 15 billion years ago, and that at that time the temperature reached gigantic values: 1028 degrees of temperature and perhaps 10 billion degrees (1010 degrees) just a few minutes later.
You have to know that on the edge of a temperature of 1032 degrees, all kinds of formulas and definitions of current physics stop making sense.
Therefore, nothing can be affirmed with mathematical certainty about that zero moment of the universe. The volume of the cosmos was minimal and the density tended to infinity.
If it is accepted that, from this situation, the universe began to expand and cool down; we can speak of the fact that at that moment the beginning of the current universe took place.
I will mention four scientific indications by which the scientific community accepts the Big Bang theory as valid.
First argument in favor of the big bang
A first argument for thinking that the Big Bang theory is correct is based on the proven fact that galaxies are moving away from each other.
Currently, everything seems to indicate that the universe, including the space between galaxies, is expanding at an increasing speed, at tens of thousands of kilometers per second.
This statement is based on the fact that it has been repeatedly verified that the light from galaxies moves towards the red end of the spectrum, which indicates that the wavelengths of the detected light are longer.
This redshift, which is called the “Doppler effect“, indicates that the galaxies are moving away from us, and at increasing speeds.
The receding of the galaxies was first discovered in 1929 by Edwin Hubble. No blue shift has ever been seen in the more distant galaxies.
This discovery, the expansion of the universe, produced the most important intellectual revolution of the 20th century, and implies that, as the galaxies escape, the universe becomes emptier and, therefore, cools.
The current temperature of the cosmos is about three degrees absolute (3 ° K), that is, 270 degrees Celsius below zero. The cooling progresses since the expansion of the universe began.
Second argument in favor of the big bang
A second argument in support of the Big Bang theory is the amount of hydrogen and helium present in the cosmos.
The Big Bang theory states that at the beginning of everything, due to the enormous heat, with temperatures of 1032 degrees, the hydrogen nuclei collided with each other at such great speeds that they began to fuse two by two and form helium nuclei.
Based on this postulate, the theory predicts that in the Universe the proportion of hydrogen compared to that of helium must be 3 to 1.
The observational results confirm that indeed in the Universe there is 25% helium compared to 75% hydrogen.
Third argument in favor of the big bang
A third argument in support of the Big Bang theory is somewhat more complicated and lengthy to explain.
It refers to the fossil radiation (of photons) or background radiation in the Universe.
This discovery has been the most spectacular scientific confirmation of the Big Bang theory. Go for it.
All hot bodies radiate. The hotter they are, the more they radiate.
The human body, for example, emits infrared rays that our eye cannot detect, but that with a night viewer it is possible to do so.
Snakes do not need an artificial night viewer as they have a third eye that detects infrared on their foreheads.
Very hot bodies emit shorter wave radiation, so they appear blue and purple.
As they cool down, the radiation wave gets longer and the perceived color changes from blue to green, yellow, orange, red, until it reaches infrared.
This light emitted by a hot body is called “thermal light“.
Shortly after the Big Bang, when the early universe was at temperatures of millions of degrees Kelvin, thermal agitation caused matter to be totally dissociated, electrons were unable to bind to protons and form atoms.
The matter was in the form of an electric plasma opaque to light, as no photons were generated. That universe was absolutely dark. However, it began to expand.
The initial universe was completely disorganized, it had no galaxies, no stars, no molecules, no atoms, not even nuclei of atoms. It was just a broth of formless matter, at a temperature of billions of degrees.
When about 380,000 years had passed after the Big Bang, the Universe had undergone an expansion that, in turn, had produced a strong cooling.
When the temperature dropped below 3,000ºK, the electromagnetic interaction was already able to make the electrons start to bond with the protons.
Hydrogen and helium atoms were generated, photons were able to escape and this is how the universe became transparent to light.
At such a high initial temperature, physical processes accelerated incredibly.
More processes occurred in a second than would occur in millions of years in a colder world.
The Ukrainian physicist and astronomer George Gamow (1904-1968) made the following reasoning: if the current universe presents a picture of cooling due to expansion, it means that it was initially very hot and therefore emitted radiation.
Gamow wondered what happened to that glowing radiation that existed at the beginning of the universe?
Where have the photons that were generated gone?
He assumed that the expansion of space had lengthened the wavelength of the primordial photons.
His calculations led him to deduce that the temperature of the original radiation had already dropped to about 8º K (8º above absolute zero).
In 1948, shortly after the end of the Second World War, he predicted that there had to be a trace of this primitive radiation and that it would be of a millimeter wavelength, that is, they must be microwaves.
Nobody took this prediction seriously and it was thought that it would be an extravagance to try to catch the echo of the Big Bang.
Our eye is sensitive to photons of a little less than a thousandth of a millimeter.
Therefore, if the trace of the primitive radiation has a wavelength somewhat greater than one millimeter, it is invisible to our eyes.
In those years there were no instruments to detect waves of that length.
Arno Penzias, a physicist born in Munich in 1933, was working with Robert Wilson at Bell Laboratories in 1964, experimenting with a 6-meter, supersensitive antenna designed to detect radio waves reflected by probes.
To measure these radio waves, it was necessary to suppress any type of interference that could occur in the vicinity of the antenna.
They managed to eliminate the effects of radars and radio stations.
They even suppressed the interference produced by the antenna itself, cooling it with liquid helium to -269º C (4º Kelvin), very close to absolute zero.
After all those precautions, they kept detecting a noise source that they couldn’t explain.
Initially they thought they were birds that had been installed on the antenna or that it was another type of dirt from it.
Despite careful cleaning and fine-tuning the reception, the noise persisted.
It was a noise that persisted day and night and that came from all sides, wherever in the sky they pointed the antenna.
They both concluded that the noise was coming from beyond our own galaxy.
When some friends and colleagues told them that there was a possibility that it was the radiation predicted by George Gamow from the explosion that caused the Universe, Penzias and Wilson realized that they had made a discovery of enormous importance.
The characteristics of the radiation detected by them, perfectly matched the radiation initially predicted by George Gamow and refined by Robert Dicke and other colleagues at Princeton University.
To avoid possible later conflicts, both colleagues decided to jointly publish the results of their work.
In 1978, Arno Penzias and Robert Wilson were awarded the Nobel Prize for their great discovery.
The detection of these millimeter photons requires instruments that are very sensitive to these wavelengths (similar to those of radars and microwave ovens).
They are old signals, of very weak intensity and that it is necessary to separate them from the tangle of parasitic waves.
The heat from the Earth’s atmosphere creates a strong parasitic noise that makes it difficult to detect fossil microwave radiation.
For this reason, NASA decided to manufacture the COBE (Cosmic Background Explorer) specially built to carry out, outside the Earth’s atmosphere, precision studies that could confirm the postulates of the Big Bang theory.
COBE was launched into space on November 18, 1989 in a circular orbit around the Earth, at an altitude of 900 km and with the axis of rotation tilted at 99º.
The 900 km orbit, combined with the inclination of the axis of rotation, made it possible to keep the Earth and the Sun continuously below the plane of the COBE shell, thus allowing a complete scan of the sky every six months.
The results obtained by COBE showed a perfect match between what was predicted by the Big Bang theory and what was observed in the microwave background.
The image created from nine years of WMAP data, reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies.
Fourth argument in favor of the big bang
The fourth argument in support of the Big Bang theory is that the oldest objects in the universe are between 10 and 15 billion years old.
There is no evidence for objects older than the Big Bang. The oldest stars in the Milky Way date back about 10 billion years.
To the question of whether there was anything before the Big Bang, the answer is that we have no clue that allows us to go back any further in the past.
All astrophysics data stops at the same frontier. The laws that scientists have discovered do not work within these limits and we are left without answers.
Quantum theory is unable to explain the behavior of particles subjected to such an intense field of gravity and such high temperatures.
On the other hand, the theory of relativity states that with such a strong field of gravity, everything would be confined in a very restricted space from which nothing could escape, not even light.
According to the Big Bang model, the early universe was a plasma composed mainly of electrons, quarks, and neutrinos totally dissociated from each other.
Electrons could not bond with protons and other atomic nuclei to form atoms because the average energy of such a plasma was very high, so electrons constantly interacted with photons through a process known as Compton scattering.
As the cosmos cooled, the elementary particles were agglutinating and forming nuclei, atoms, molecules, nebulae, stars, galaxies and planets.
Not everything is explained with the Big Bang Theory
The mathematics underlying this theory are inadequate and powerless to explain what happened at the borders of time and space.
- What was there before time zero?
- What was space before the Big Bang?
- How long before the Big Bang?
Scientifically it is impossible to define a zero time, at which time the temperature would reach an infinite value and the space would have zero volume. That is simply the limit of our knowledge.
If the Big Bang theory is correct, currently all the stellar matter should be distributed on the surface of an immense sphere that is becoming more extensive every second.
In the interior of this universal sphere, there would be only the radiation produced by the stars.
In 2007, the prestigious scientist Stephen Hawking said that, according to calculations, if 1 second after the Big Bang the expansion speed had been less than one part in 100,000 trillion, the Universe would have collapsed back on itself before now , due to the attraction of the force of gravity.
But if the expansion speed 1 second after the Big Bang had been greater than one part in 100,000 trillion, the universe, exceeding the force of gravity, would have expanded so much that it would now be practically empty.
The current situation is a “fluke“.