How was the universe born? This is one of the oldest and most challenging questions in human history.
How Did the Big Bang Theory Come About?
The Big Bang theory posits that the universe began from an incredibly small and dense singularity, followed by a violent explosion that created time, space, and matter, which then expanded and cooled continuously to form stars, galaxies, and other celestial objects.
This theory was first proposed by physicist Georges Lemaître in 1927, who developed a mathematical model describing the origin and evolution of the universe based on Einstein’s general theory of relativity.
Lemaître’s theory was initially not widely accepted and was even mocked by British physicist Fred Hoyle, who coined the term “Big Bang”, meaning “the great explosion.” Hoyle himself advocated for the steady state theory of cosmology, which suggested that the universe is eternal and unchanging, with no beginning or end.
However, after the 1950s, with advancements in observational technology and new discoveries, the Big Bang theory gradually gained substantial evidence and support—most notably, the cosmic microwave background radiation.
The Big Bang theory, often referred to as Big Bang in English, is the prominent cosmological model describing the early stages of the universe’s formation. (Image: Zhihu).
The cosmic microwave background radiation refers to the first light emitted about 380,000 years after the universe’s birth, which still permeates the entire universe after 13.8 billion years. This radiation was accidentally discovered in 1964 by American physicists Arno Penzias and Robert Wilson, who, while using a radio telescope, detected faint noises coming from all directions in the sky.
After ruling out various sources of interference, they realized that the noise might be a type of radiation from the distant past. Around the same time, American physicist Robert Henry Dicke and his collaborators were also preparing to use similar equipment to search for the existence of cosmic microwave background radiation. Upon learning that Penzias and Wilson had discovered this radiation, Dicke contacted them immediately to confirm his own findings.
The Big Bang occurred approximately 13.8 billion years ago, marking the age of the universe. (Image: Sciencealert).
Penzias and Wilson were awarded the Nobel Prize in Physics in 1978 for their discovery of cosmic microwave background radiation, while Dicke and his colleagues missed the honor for not publishing their theory in time.
The discovery of cosmic microwave background radiation is the strongest evidence for the Big Bang theory, as it closely matches the temperature and frequency predicted by the theory and is uniformly distributed across the sky, indicating a high degree of homogeneity in the early universe. However, recent observations from the James Webb Space Telescope have posed some challenges to this theory.
Cosmic microwave background radiation refers to the first light emitted about 380,000 years after the universe’s birth, which still permeates the entire universe after 13.8 billion years. (Image: Zhihu).
What Has the Webb Telescope Observed?
According to the Big Bang theory, the universe was a homogeneous, high-temperature, high-density plasma, devoid of any structure or matter in the first few million years. As the universe cooled and expanded over time, slight density fluctuations began to increase and gradually amplify. These density fluctuations caused matter to accumulate in some areas, while becoming sparse in others.
This created regions where some nuclei and electrons could combine to form neutral hydrogen atoms, known as the reionization phase. During this period, there was no light source, and the universe remained dark and transparent.
The reionization period ended about 13 billion years ago, when the first generations of stars and galaxies began to form and emit intense ultraviolet radiation. During this time, stars and galaxies underwent rapid and complex evolutionary processes.
According to the Big Bang theory, the universe was a homogeneous, high-temperature, high-density plasma, devoid of any structure or matter in the first few million years. (Image: Zhihu)
Theoretically, the protogalaxies should have the following characteristics: first, they are irregular in shape, lacking clear structure or rotation; second, their brightness and density are low due to a lack of heavy elements and dust; finally, they are relatively small due to uneven distribution of matter and unstable gravitational forces.
However, the James Webb Space Telescope has provided us with a completely different picture from what was expected. According to newly published papers in journals including Nature, Science, and Acta Astronomica, the James Webb Space Telescope has found something that contradicts expectations.
First, some galaxies are so bright and dense that they exceed theoretical predictions. For example, the James Webb Space Telescope observed a galaxy approximately 13.2 billion light-years away, shining as brightly as 100 billion Suns and being over 100 times denser than the Milky Way, making it one of the brightest and densest known primordial galaxies.
Second, some galaxies already exhibit spiral structures and smooth disks instead of irregular shapes.
Illustration. Image: Acta Astronomica
Additionally, the James Webb Space Telescope has also discovered over 1,000 primordial galaxies in a region about 13 billion light-years away, whereas theoretical simulations suggested that there should only be a few dozen galaxies in that area.
These galaxies are among the largest and densest known groups of protogalaxies. These findings have amazed and perplexed astronomers as they do not align with what the Big Bang theory predicts.
Theoretically, these primordial galaxies should remain in a primitive and chaotic state rather than developing complex and mature characteristics. So, how did these primordial galaxies form and evolve? Did the Big Bang actually occur?
Big Bang Theory: Revision or Abandonment?
Faced with the new perspectives and challenges presented by the James Webb Space Telescope, astronomers have proposed various viewpoints and interpretations. Some believe that these observations do not mean the Big Bang theory is entirely wrong. They think that these primordial galaxies may have formed and evolved at a faster rate due to the influence of dark matter or dark energy.
Dark matter or dark energy may have played a crucial role in the early universe, driving the accumulation of matter and the formation of structures, leading to the rapid development of primordial galaxies. They also believe that these primordial galaxies might be anomalies caused by certain special environments or conditions, rather than by universal laws.
On the other hand, some believe that these observations could indicate that the Big Bang theory needs to be reconsidered or abandoned. They argue that the universe may not have a single beginning or end, but is rather a cyclical process.
The Webb telescope has presented us with challenges and new opportunities to deepen and broaden our understanding of the universe. It also makes us realize that there are still many gaps and blind spots in our understanding of the origins and evolution of the universe that need to be continually revised and refined. (Image: Zhihu).
In other words, the universe may have undergone multiple big bangs and great contractions, each time creating a new universe. This theory is known as the cyclic universe theory, which posits that our universe is just one of countless universes, each with its own characteristics and laws.
Perhaps these primordial galaxies are remnants of a previous universe rather than our own. Of course, this is just a possibility and lacks compelling evidence. To validate this hypothesis, we need increasingly precise observational data for analysis and comparison.
