What phenomenon describes the observation that more distant galaxies move away faster?

The observation that more distant galaxies move away faster is described by Hubble's law. This law states that the recessional velocity of galaxies is proportional to their distance from Earth. The farther a galaxy is, the faster it appears to move away from us. This relationship suggests that the universe is expanding, and it provides critical evidence supporting the Big Bang theory.

Hubble's law is mathematically represented as v = H₀ × d, where v is the recessional velocity, H₀ is the Hubble constant, and d is the distance to the galaxy. This law has been validated through observations of galaxies across different distances, demonstrating a uniform expansion of the universe.

In context, while redshift is a related concept that describes the shift of light towards longer wavelengths as objects move away, Hubble's law specifically captures the relationship between distance and recessional velocity. Gravitational lensing refers to the bending of light due to gravity, and quantum fluctuations pertain to uncertainties at a quantum scale, which are not directly related to the movement of galaxies in the expansion of the universe.