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Hubble's Law basically states that the greater the distance of a galaxy from ours, the faster it recedes. It was proof that the Universe is expanding. It was also the first observational support for a new theory on the origin of the Universe proposed by Georges Lemaitre: the Big Bang.

Using Hubble's Law enables the crucial determination of Hubble distances to galaxies and quasars (Hubble distances are those derived from Hubble's Law using the observed velocity of the object; these distances represent the true cosmic distance plus a small peculiar motion component).Mar 17, 2015

This is the distance of an object based on the Hubble flow. It is the speed of light, c times the Hubble time, t_H (or equivalently c divided by the Hubble constant H₀) and is called the Hubble distance D_H.

3 The Hubble parameter, H, is the characteristic expansion rate and is of the order of the inverse of the age of the universe. The particular form of equation (1) assumes, as appears to be the case, that the energy density u is equal to the critical value so that the space-time is flat.

The Big Bang: the birth of the universe

Around 13.7 billion years ago, everything in the entire universe was condensed in an infinitesimally small singularity, a point of infinite denseness and heat.Nov 5, 2021

Scientists' best estimate is that the universe is about 13.8 billion years old. But, like so many of the largest-scale properties of the universe, we are not entirely sure about its age.

So essentially, the Hubble constant reflects the rate at which the universe is expanding. So to determine an object's distance, we only need to know its velocity. ... Most astronomers believe that Hubble's Law does, however, hold true for a large range of distances in the universe.

Hubble's brilliant observation was that the red shift of galaxies was directly proportional to the distance of the galaxy from earth. That meant that things farther away from Earth were moving away faster. In other words, the universe must be expanding. He announced his finding in 1929.

What is 'red shift'? ... The term can be understood literally - the wavelength of the light is stretched, so the light is seen as 'shifted' towards the red part of the spectrum. Something similar happens to sound waves when a source of sound moves relative to an observer.