Edwin Hubble's Redshift Observation

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Edwin Hubble's redshift observation was a pivotal moment in modern astronomy. In 1929, Hubble demonstrated that the redshift of galaxies—measured by the shift of spectral lines towards the red end of the spectrum—was directly proportional to their distance from Earth. This meant that galaxies farther away were moving away faster, indicating an expanding universe. Hubble's discovery built upon the work of Vesto Slipher, who first observed the redshift in spiral nebulae, and Henrietta Leavitt, whose period-luminosity scale for variable stars allowed Hubble to calculate galaxy distances. Hubble's findings supported the Big Bang theory and transformed our understanding of the cosmos. The observation showed that the universe is not static but expanding uniformly in all directions. This led to the formulation of Hubble's Law, which relates a galaxy's recessional velocity to its distance. While initial estimates of the Hubble constant were refined over time, the fundamental principle remains unchanged. Hubble's work laid the foundation for modern cosmology, providing crucial evidence for the expanding universe and its finite age, supporting theories like the Big Bang.