Final answer:
The Doppler effect, through observations made by Edwin Hubble, showed that the universe is expanding, with galaxies moving away from us at speeds proportional to their distance, supporting the Big Bang theory.
Step-by-step explanation:
The Doppler effect has been instrumental in teaching us about the universe's expansion, particularly through the work of astronomer Edwin Hubble. In 1929, Hubble observed a red shift in the hydrogen spectra of distant galaxies, which was proportional to their distance from us. He concluded that all galaxies were receding from our own and the further a galaxy was, the faster it was moving away. This implied that the universe's space was expanding, a foundational concept for the Big Bang theory and modern cosmology.
Hubble's findings demonstrate that, consistent with our theories of gravity, the universe must be expanding. If galaxies were initially stationary, they would attract each other due to gravity and eventually collide. The fact that they are moving apart indicates that they started moving away from each other at high velocities. This movement at large scales resembling the scenario of a rocket launched with enough speed to avoid falling back to Earth signifies the universal expansion, as observed through Hubble's law.
This cosmological red shift provides profound implications for understanding the Big Bang and the ongoing evolution of the universe, showing that there is no central point of expansion and that the expansion is uniform. Hubble's discovery revealed a much larger universe than previously conceived, continuously growing in scale and complexity.