Penzias and Wilson's Cosmic Microwave Background

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The discovery of the cosmic microwave background (CMB) by Arno Penzias and Robert Wilson in 1964 marked a pivotal moment in modern cosmology. Using the Holmdel Horn Antenna at Bell Labs, they detected a persistent, uniform microwave radiation coming from all directions in the sky. Initially, they sought to eliminate potential sources of interference, including pigeon droppings in the antenna, but the signal remained constant. This discovery provided crucial evidence for the Big Bang theory, which posits that the universe began in a hot, dense state and has been expanding ever since. The CMB is a remnant of the early universe, dating back to about 380,000 years after the Big Bang, when electrons and protons first combined into neutral atoms, allowing photons to travel freely. The CMB's uniform temperature, approximately 2.73 K, supports the Big Bang theory and challenges steady-state models. Penzias and Wilson's findings were recognized with the Nobel Prize in Physics in 1978. The CMB has since been extensively studied, revealing subtle fluctuations that are key to understanding the universe's structure and evolution.