The expansion of the Universe

The expansion of the Universe

The discovery of the expansion of the Universe begins in 1912, with the works of the American astronomer Vesto M. Slipher.

While studying the spectra of the galaxies, he observed that, except in the nearest ones, the spectrum lines shift towards red.

This means that most galaxies move away from the Milky Way since, correcting this effect in the spectra of galaxies, it is shown that the stars that integrate them are composed of known chemical elements. This redshift is due to the Doppler effect.

If we measure the shifting of the spectrum of a star, we can know if it approaches or moves away from us. In the majority this displacement is towards the red one, which indicates that the focus of the radiation moves away. This is interpreted as a confirmation of the expansion of the Universe.

In principle it seems that galaxies are moving away from the Milky Way in all directions, giving the feeling that our galaxy is the center of the Universe. This effect is a consequence of the way in which the Universe expands. It is as if the Milky Way and the other galaxies were points located on the surface of a globe. When you inflate the balloon, all the points move away from us. If we changed our position to any of the other points and performed the same operation, we would observe exactly the same.

Hubble's Law

The American astronomer Edwin Powell Hubble related, in 1929, the redshift observed in the spectra of the galaxies with the expansion of the Universe. He suggested that this redshift, called cosmological redshift, is caused by the Doppler effect and, as a consequence, indicates the recoil speed of galaxies.

Hubble also observed that the speed of recession of the galaxies was greater the farther they were. This discovery led him to state his law of the recession velocity of galaxies, known as the "Hubble Law," which states that the speed of a galaxy is proportional to its distance.

The Hubble constant or proportionality is the ratio between the distance of a galaxy to Earth and the speed with which it moves away from it. It is estimated that this constant is between 50 and 100 km / s per megaparsec.

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Forces and movements