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The core secret of the steady-state universe: Why did it spark a heated debate in astronomy in the 20th century?
Since the beginning of the 20th century, cosmology has been fraught with controversy and debate, particularly regarding the origin and evolution of the universe. Among them, the opposition between the "Steady State Theory" and the "Big Bang Theory" became the focus of dramatic debate in the scientific community. The steady-state theory states that while the universe continues to expand, the density of interstellar matter remains constant, maintaining this phenomenon through the continuous creation of matter. This idea drives what is known as the "perfect cosmological principle," the idea that the universe has the same appearance and structure at all times and places.
“The steady-state theory states that the universe has no beginning and no end, a view that sparked intense scientific debate in the 20th century.”
The theoretical dispute dates back to the 1940s to the 1960s, when a group of scientists including Hermann Bondi, Thomas Gold and Fred Hoyle were active in this field. . The scientists' reasoning was intended to argue that although the universe is expanding, its overall appearance and structure remain unchanged. This means that the composition and properties of the universe are permanent and unchanging. However, this theory gradually lost supporters in the face of challenges from observational data.
Beginning with Edwin Hubble's observations of the expansion of the universe, the astronomical community gradually realized that the universe is not static. The Big Bang theory, first proposed by Georges Lemaître, states that the universe has a finite age and formed the structure we observe today through cooling, expansion and gravitational collapse. At the same time, the steady-state theory insists that the universe is relatively static and requires continuous creation of matter to maintain constant density. This assumption has encountered many challenges in subsequent observations.
"Observations in the 1950s and 1960s showed that the appearance and structure of the universe changed over time, greatly undermining the steady-state theory."
During this period, statistical surveys of radio sources have found that luminous radio sources (such as quasars and radio galaxies) are concentrated in the distant Universe, a phenomenon that is in sharp contrast to the predictions of the Steady-State theory. Steady-state theory predicts that these objects are ubiquitous throughout the universe, including our own galaxy, the Milky Way. However, actual observations have found that these objects exist almost exclusively in the deep universe. By 1961, statistical tests based on surveys of radio sources provided strong evidence against the steady-state model.
A further challenge comes from exploring the X-ray background. In 1959, Gold and Hoyle proposed that the new matter created would inevitably be concentrated in certain regions of the universe where the density was higher than the average density of the universe. However, later studies showed that the thermal stray radiation produced in this case would exceed the observed amount of X-rays, causing steady-state cosmological models to run into trouble in the formation of large-scale structure.
"The discovery of cosmic microwave background radiation in 1964 further confirmed the validity of the Big Bang theory and posed a strong challenge to the Steady State Theory."
With the discovery of the cosmic microwave background radiation, the steady-state theory was forced to provide an explanation, however this explanation could not reasonably explain the observed uniformity and characteristics of the blackbody spectrum. In 1972, the famous physicist Steven Weinberg pointed out: "The steady-state model obviously does not match the observational data. This is undeniable." As more evidence accumulated, the steady-state universe theory was gradually accepted by the scientific community. rejected, while the Big Bang theory is widely accepted as the best model to explain the origin of the universe.
In the 1990s, Hoyle and other scholars proposed a new "quasi-steady-state universe" model, which tried to retain the core concept of the steady-state universe to a certain extent, but the focus shifted to the creation process that appeared over time. , proposed the concept of a series of small creation events. Despite this, this new model has also been questioned and challenged by mainstream cosmologists, showing the fragility of the steady-state theory in contemporary astronomy.
Overall, although the steady-state theory sparked heated debate in the 20th century, with the advancement of observational technology, this theory has been gradually overturned by evidence. Many scientists agree that the universe has undergone a transition from high density to low density. evolution process. Future cosmology may be based on how to explain and integrate ideas similar to the steady-state model and conduct deeper thinking on the nature of cosmic evolution. In this process, we should perhaps think about: How did the true evolution process of the universe come into being?
