What observation is Hubble known for regarding the universe?

Hubble is renowned for his groundbreaking observation that the universe is expanding. This conclusion was primarily based on his study of the light from distant galaxies, which he found to be redshifted, indicating that these galaxies are moving away from us. This redshift is a direct consequence of the Doppler effect, which occurs when an object emitting light is moving away from an observer, causing the light's wavelength to stretch into the red part of the spectrum.

Hubble's findings led to the formulation of Hubble's Law, which states that the velocity at which a galaxy recedes from us is proportional to its distance from us. This relationship provided compelling evidence for the expansion of the universe and supported the Big Bang theory, suggesting that the universe has been expanding since its inception. The implications of this observation were profound, fundamentally altering our understanding of the cosmos and leading to further exploration into questions of the universe's origin, structure, and ultimate fate.

In contrast, the idea that the universe is static does not align with Hubble's findings. The notion of contraction suggests that the universe might be shrinking, which contradicts the evidence gathered by Hubble. While gravity does play a significant role in the dynamics of the universe, Hubble's primary contribution was