The theory popularly known as the Big Bang finds support or theoretical backing in the so-called Hubble law.
Hubble's Law is the name of an old postulate in the field of physics that had two great promoters. The first of them was Georges Lemaître , a scientist, professor and priest who in 1927 laid the foundations for this content through a publication in French on a theoretical model of the universe and a study focused on galaxies where the link was discovered. between speed and distance .
The second was Edwin Hubble , an American astronomer who years later disseminated material on the expansion of the universe . To recognize the contributions of both, over time it was decided to cite this law with the surnames of the two specialists, consolidating the name of the Hubble-Lemaître law .
This contribution is valuable since, beyond offering evidence and information about how the universe expands, it supports the theory of the Big Bang (commonly cataloged as the Big Bang ).
Features of Hubble's law
It is interesting to note that Hubble's law marks a connection between redshift and distance, as well as between the latter and the speed of galaxies, but it does not specifically mention how the universe is evolving. There are no tools to establish whether the expansion slows down, remains constant, or accelerates.
In its mathematical expression, this law presents a proportionality constant identified with Edwin 's last name: the Hubble parameter or constant . Certain equations linked to the theory of general relativity are useful as proof of the determining role of the Hubble constant in establishing the age of the universe and, if this information is known, what is the proper radius of the observable universe .
Historical records say that it was Alexander Friedmann , a Russian meteorologist and mathematician who specialized in relativistic cosmology , who, starting from Albert Einstein's field equations, conceived the so-called Friedmann equations . With them he demonstrated that the expansion speed of the universe can be calculated.
It is important to consider that if you want to use Hubble's law to calculate distances, only the speed associated with the expansion of the universe is valid and appropriate. It is appropriate to use the peculiar or relative velocities arising from the interaction and movement of galaxies .
In April 1990, the Hubble Space Telescope was launched into orbit, a revolutionary space observatory that, like a law and a constant, bears the surname of the prominent astronomer Edwin Hubble.
Theoretical foundations
Above we detailed what the Hubble parameter or constant is about, but there is still another theoretical foundation to explore: redshift .
This term in English is interpreted in Spanish as redshift or redshift , expressions typical of the fields of astronomy and physics . This phenomenon occurs when there is evidence, in the final part of the electromagnetic spectrum , of a red shift of the electromagnetic radiation that is emitted or reflected from an object (usually visible light ).
According to Hubble's law , the redshift observed in a galaxy is proportional to the distance at which it is located. According to Edwin 's discovery, each galaxy cluster is moving away from each other and, as the distance between the groups increases, the faster the speed at which they move away.
It is enriching to know that Edwin Hubble 's knowledge was complemented by that of his colleague Milton Humason . The latter made the measurement of the redshift of spiral galaxies . Together, they also examined the Cepheid stars and used them to establish the distance away from what were then called nebulae ( galaxies ). Thus they came to the conclusion that the greater the distance, the more marked the redshift of a certain object.
By observing the redshift of a galaxy it is possible, using Hubble's law, to determine its speed and, with that data, establish the distance between one galaxy and another.
Limitations of Hubble's law
Hubble's law , which still remains an object of scientific interest, despite the controversies and debates about it, continues to inspire research and be applied in multiple areas. Work has been done, within this framework, to improve the precision achieved by the Hubble constant and there has been progress in this regard, but challenges still arise and there are limitations linked to this postulate.
The measurements are made difficult, according to the specialists, due to the movement of the galaxies that influences the speeds that are observed, in addition to requiring advanced tools and knowledge to be able to evolve and achieve increasingly better results.