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The Big Bang Theory Proposed by Georges Lemaître in the 1920s and later confirmed by Edwin Hubble, the Big Bang Theory suggests that the universe originated from an incredibly dense and hot singularity approximately 13.8 billion years ago.
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Cosmic Microwave Background (CMB) In the 1960s, astronomers Arno Penzias and Robert Wilson discovered the cosmic microwave background radiation, which is considered the afterglow of the Big Bang.
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Expansion of the Universe In the 1920s, Edwin Hubble observed that galaxies were moving away from each other, indicating that the universe is expanding. This idea revolutionized our understanding of the cosmos.
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Formation of Elements The theory of nucleosynthesis, developed by George Gamow in the 1940s, explains how the first elements like hydrogen and helium formed shortly after the Big Bang. Heavier elements formed later in stars.
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Dark Matter Hypothesis In the 1930s, astronomer Fritz Zwicky proposed the existence of dark matter to explain discrepancies in the gravitational behavior of galaxies. Dark matter is believed to make up a significant portion of the universe's mass.
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Friedmann-Lemaître-Robertson-Walker Metric In the 1920s and 1930s, various scientists contributed to the development of the FLRW metric, which describes the expanding universe's geometry within Einstein's theory of general relativity.
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Steady State Theory In contrast to the Big Bang Theory, the Steady State Theory, proposed by Fred Hoyle and others in the 1940s, suggested that the universe had no beginning or end.
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Age of the Universe In the mid-20th century, estimates of the universe's age varied widely. It was only in the late 20th century that improved measurements narrowed down the age to approximately 13.8 billion years.
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Inflation Theory Proposed by physicist Alan Guth in the 1980s, inflation theory suggests that the universe underwent a rapid and exponential expansion in the moments following the Big Bang, explaining certain aspects of the universe's structure.
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Observable Universe The observable universe is limited by the speed of light and the universe's age. It extends about 93 billion light-years in diameter, providing us with a glimpse into the vast cosmic history.
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