The study of how the universe is expanding has been central to modern cosmology for decades. In its framework, the main pillar is the Hubble constant, a parameter that describes the way in which this expansion occurs. This is a factor established by a famous astronomer Edwin Hubble in the 19th century, representing the apparent rate at which distant galaxies are receding as a result expansion: It is a very important piece when it comes to measuring and quantifying the expansion rate of the universe.
Over the years, however, the precise measurement of the Hubble constant has evolved with technological advances and new observational techniques. This allowed us to have much more accurate data that shows certain contradiction in determining the constant according to the method used to calculate it. This contradiction is known as “Hubble voltage” and sparked a huge debate in the scientific community, posing a major challenge to understanding the processes that drive the expansion of the universe.
Edwin Hubble, father of observational cosmology
HUBBLE’S CONSTANT
The approach of a single constant that represented the degree of expansion of the universe was an idea that began to take shape in the minds of the scientific community from the first decade of the 20th century. During this period, the understanding of the universe was undergoing a major transformation as pioneering observations were made of distant galaxies showing the first signs of expansion and changed the view of the universe as static.
In 1920, Edwin Hubble was the one who gave the starting signal to this cosmological revolution and suggested existence relationship between the speed of movement of the galaxy – the radial speed – and its distance, which became the conceptual basis of the galaxy Hubble’s constant. This was a direct link between galaxy redshift and the expansion of the universe. And although it was a somewhat rudimentary and imprecise calculation at first (assuming it required measuring extremely large astronomical distances), over the years the measurement techniques were refined.
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1931 portrait of Edwin Hubble
Among them, the method Type Ia supernovae, which uses the luminosity emitted by this type of explosion to estimate the distance at which they are located. On the other hand, through measurement Cosmic radiation background – the echo of the big bang – it is possible to infer the rate of expansion of the universe in the early stages.
Redshift: A powerful tool to understand the big bang theory
Also through nearby galaxies using methods with it cepheids (variable stars) it is possible to establish reference points for the calibration of these distances. Still, whether due to extrapolations or the need to establish certain models, they all show some misalignment in terms of accuracy.
INEQUALITY AND TENSION
As a disagreement between these estimates of the Hubble constant, the Hubble tension was born. In fact, during recent years when observation and measurement have reached great sophistication, this problematic became more and more apparent. On the one hand, observations of supernovae and cosmic background radiation suggest a lower value for the constant, while measurements based directly on nearby galaxies suggest a much higher value.
This disagreement raises big questions that concern reliability in methodsas well as possible existence hitherto undiscovered physical phenomena or assimilated. Will it be necessary to create new physics or will it be a consideration of systematic errors?
In this way, in addition to being one of the most current problems in astronomy, so is the Hubble tension decisive to understand not only cosmic expansion, but also to understand the constraints of the fundamental physics and evolution of the universe.
Resolving this contradiction is expected to improve the measurement of cosmic distances and even influence understanding dark energy, which is not ruled out to be involved in the problem. This is research that undoubtedly opens up new perspectives on cosmic knowledge.
