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Since the first light of our existence, the human mind has wondered about the origin of our Universe, about the genesis of this immense and complex cosmos that surrounds us. How could this grandiose spectacle arise from nothing?? If our ancestors found the answer to this question by turning towards the immaterial and deification, the Big Bang theory began to take shape in the 1920s and 1930s thanks to the work of several scientists.
Alexander Friedmann, Georges Lemaître, Edwin Hubble, all contributed to developing this new theoretical model. The latter was actually established and accepted in 1964, after the work of Arno Penzias and Robert Wilson. So let's go back to the past to understand a little better where we came from.
A misleading name for a complex phenomenon
The Big Bang was not an explosion, contrary to what its name might suggest. Imagine that the Universe was a small balloon, so small that it was just a tiny dot. Suddenly, it began to swell and increase in size: this is what scientists call the Big Bang. It is a continuing expansion of space-time itself, beginning about 13.8 billion years ago .
Since then, this expansion has continued, shaping the Universe that we know today, with its billions of galaxies, its stars, its holes black and its infinity of celestial bodies. Before the Big Bang, nothing that we understand today in terms of matter, space and even time existed. A completely dizzying thought, but definitely real.
The term originally comes from Fred Hoyle , a British astronomer who popularized the term “Big Bang” in the 1950s. Himself skeptical of this theory, he wanted to denigrate it and make fun of it during a radio show with this derogatory term. The imagination of the general public was then captivated by the term, and the name has stuck ever since. Rather funny!
David Louapre is a doctor of physics and videographer known as ScienceEtonnante on the YouTube platform. Two years ago, he posted a very qualitative video (see below) explaining the Big Bang theory in detail. This certainly remains to this day the best French video popularizing this theory and has accumulated no less than 1.6 million views.
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Evidence supporting the Big Bang
Two major discoveriessupported the Big Bang theory and revolutionized our understanding of the Universe and cosmology. The first, carried out by Edwin Hubble in 1929, was the observation of the red shift of galaxies. By measuring light from distant galaxies, Hubble found that its wavelengths were stretched, or “shifted.” towards the longer, redder wavelengths of the spectrum. This crucial observation indicated that these galaxies were moving away from us at a speed proportional to their distance.
While the Universe was believed to be static, Hubble's discovery overturned this paradigm and helped us understand that it was in fact in expansion. Another key element of understanding: the Universe must have been much smaller and denser in the distant past, potentially converging towards a single point of origin, a point that we names singularity. According to the definition of Astropolis, a singularity is: “ a “point”, dimensionless and containing all of the energy of the Universe. A point where all virtual matter and energy in the universe are condensed into a state of infinite density, along with all dimensions of space and time“.
The other key piece of the cosmic puzzle that the Big Bang represents was the discovery of fossil radiation from the cosmic microwave background (CMB)in the years in 1964 by Arno Penzias and Robert Wilson. The CMB is radiation, a form of residual thermal light constituting a distant echo of the original explosion of the Big Bang. This second discovery changed everything.
It was irrefutable proof that the Universe had indeed had an extremely hot and dense beginning. The CMB offers a glimpse of the Universe as it was just 380,000 years after the Big Bang, before the formation stars and galaxies. On a cosmic scale, this represents only a very brief moment. Considering that the Universe is 13.8 billion years old, these 380,000 years only represent about 0.003% of the entire universe. ;cosmic history.
These two discoveries are the major pillars supporting the Big Bang theory, which allowed us to trace its evolution to the immensity observable today.
In reality, the Big Bang is much more than a scientific theory; it also constitutes an essential conceptual framework for exploring the origin and evolution of the Universe. Understanding the Big Bang means being able to situate our existence in a broader temporal and cosmic context. However, the Big Bang is not an end in itself; rather, it should be seen as a starting point towards an endless intellectual journey. Many questions still remain unanswered to this day: the nature of dark matter or dark energy, the possible existence of parallel worlds or extraterrestrial life. We haven't finished wondering !
- The Big Bang is a theory that describes the origin of the universe from a singularity, confirmed by Edwin Hubble in 1929.
- The discovery of the CMB in 1964 by Arno Penzias and Robert Wilson provided direct evidence of the initial state of the Universe.
- These discoveries revolutionized cosmology and established a theoretical framework explaining our existence.
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