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What does Hubble’s law say about the distance and recession speed of galaxies?

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Hubble’s law describes the relationship between the distance of a galaxy and the speed at which it is moving away from Earth. The law states that a galaxy's recessional velocity is directly proportional to its distance from us, expressed by the formula:

$velocity = H_{0} \times distance$

In this equation, $H_{0}$ represents the Hubble constant, which serves as the constant of proportionality and indicates the rate at which the universe is expanding.1

According to this principle, the greater the distance of a galaxy, the faster it recedes. This motion causes the light from these galaxies to undergo a cosmological redshift, where the light's spectrum is shifted toward longer, redder wavelengths. Hubble’s law provided the first observational evidence for the expansion of the universe, demonstrating that space itself is expanding rather than galaxies simply moving through static space.123