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The cosmic microwave background (CMB) supports the Big Bang Theory by providing evidence of the universe's hot, dense origin.
The CMB is a faint glow of microwave radiation that fills the entire universe and can be detected in every direction. This radiation is a remnant from an early stage of the universe, just 380,000 years after the Big Bang, when the universe had cooled enough for protons and electrons to combine into neutral hydrogen atoms. Before this recombination, the universe was a hot, dense plasma that was opaque to radiation. As the universe expanded and cooled, it became transparent, allowing this radiation to travel freely through space.
The Big Bang Theory predicts that this radiation should still be observable today, but it would have cooled to just a few degrees above absolute zero due to the expansion of the universe. In 1965, Arno Penzias and Robert Wilson accidentally discovered this background radiation, which matched the predicted temperature of about 2.7 Kelvin. This discovery provided strong evidence for the Big Bang Theory, as it confirmed that the universe had indeed expanded from a hot, dense state.
Furthermore, detailed measurements of the CMB, such as those made by the COBE, WMAP, and Planck satellites, have revealed tiny fluctuations in temperature. These fluctuations correspond to the seeds of all current structure in the universe, such as galaxies and clusters of galaxies. The patterns of these fluctuations match the predictions made by the Big Bang Theory and provide a snapshot of the universe at a very young age.
In summary, the CMB is a crucial piece of evidence for the Big Bang Theory, as it confirms the universe's hot, dense origin and provides insights into its early development and subsequent expansion.
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