Now, in this context the astronomer Edwin Powell Hubble observed several celestial bodies, and when obtaining the spectra of distant galaxies he observed the spectral lines were displaced towards the red (red shift), whereas the nearby stars showed a spectrum displaced to the blue.

From there, Hubble deduced that the farther the galaxy is, the more redshifted it is in its spectrum, and noted that all galaxies are "moving away from each other with a speed that increases with distance", and enunciated the now called Hubble–Lemaître Law.

This means in the past the distance between two galaxies was smaller than at present, being this the proof that the universe is expanding (like a balloon expands when it is filled with air or another gas).

At this poitn it is important to stay clear that the redshift is not produced by the relative movement of the galaxies with each other. This effect is in fact, due to the own expansion of the space among the galaxies.

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3 years ago