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Cosmic Microwave Background Radiation: How Does It Prove the Big Bang Theory?
Cosmic Microwave Background (CMB), also known as residual radiation, is microwave radiation that fills every corner of the observable universe. When we use conventional optical telescopes to look into the gaps between stars and galaxies, almost no light is visible. However, when using sensitive radio telescopes, a faint background glow emerges that is almost uniform and not associated with any star or galaxy. This glow is strongest in the microwave region.
The discovery of the cosmic microwave background radiation marks a new stage in our understanding of the origin of the universe, supporting the core view of the Big Bang theory.
In 1965, American radio astronomers Arno Penzias and Robert Wilson accidentally discovered the cosmic microwave background radiation, which also summarized a series of scientific research since the 1940s. Explore. According to the Big Bang model of the universe, in its earliest days, the universe was filled with a dense, hot plasma mist of subatomic particles. As the universe expanded, this plasma cooled to the point where the atoms combined into neutral hydrogen.
Once these atoms are formed, the universe will no longer scatter thermal radiation through Thomson scattering and will become transparent. This process is called the recombination period, and the photons released then completely enter every corner of the universe.
However, due to the continued expansion of the universe, these photons experience a cosmic red shift and become less energetic.
The existence and relative uniformity of the cosmic microwave background radiation have become key evidence supporting the Big Bang model.
From discovery to establishment of theoretical model
The initial discovery of the CMB sparked intense debate, with many scientists proposing other possible explanations, such as energy from within the solar system, radiation from galaxies, and radiation from multiple radio sources in the universe. Scientists need to prove that the relationship between the intensity and frequency of this microwave radiation is consistent with the properties of a heat source or black body. This request was realized in 1968.
In addition, whether the light radiation is uniform in all directions is also one of the key research points. It was finally proved in 1970 that this radiation does have a cosmic origin.
Characteristics of cosmic microwave background radiation
The cosmic microwave background radiation exhibits a blackbody spectrum of approximately 2.725 K, whose uniformity contrasts sharply with the almost point-like structure of stars or galaxies. It has been measured that the CMB exhibits a uniformity of approximately 1/25,000 in all directions, with a root mean square variation of 100 microkelvin. While the tiny differences in the CMB are elusive, many details can be measured with high precision, which is crucial for cosmological theories.
Observational data from the CMB provide us with key information about the physical properties of the early universe.
With further experiments, scientists have measured these temperature non-uniformities using many ground-based and space-based experiments, such as COBE, WMAP and Planck. These measurements reveal characteristic structures in the CMB that are related to the various interactions of matter and photons before recombination, resulting in specific block patterns that vary with angle. The portion of the spectrum of these non-uniformity distributions represents the power spectrum, showing a series of peaks and valleys.
Conclusion: Enlightenment from CMB
The existence of the cosmic microwave background radiation has not only become key evidence to support the Big Bang theory, but also gives us a clearer understanding of the origin and evolution of the universe. It also allows us to understand how the universe evolved from a white-hot state to Today's form. Through continued in-depth research, can we reveal more secrets of the universe in future observations, allowing us to better understand our position and role?
