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A physical constant is a physical quantity that is generally believed to be both universal in nature and constant in time. It can be contrasted with a mathematical constant, which is a fixed numerical value but does not directly involve any physical measurement.

There are many physical constants in science, some of the most widely recognized being the rationalized Planck's constant h, the gravitational constant G, the speed of light in vacuum c, the electric constant ε0, and the elementary charge e. Physical constants can take many dimensional forms: the speed of light signifies a maximum speed limit of the universe and is expressed dimensionally as length divided by time; while the fine-structure constant α, which characterizes the strength of the electromagnetic interaction, is dimensionless. Read more from wikipedia.

 

Galaxy observations show no change in fundamental physical constant

A fundamental number that affects the color of light emitted by atoms as well as all chemical interactions has not changed in more than 7 billion years, according to observations by a team of astronomers charting the evolution of galaxies and the universe. Read more from the UC Berkeley News Press Release.

 

 

While the Sloan Digital Sky Survey looks at galaxies in the nearby universe, the DEEP2 Galaxy Redshift Survey is a smaller survey of much more distant galaxies. Their distance from us (7 billion light years or more) means that the light we see today left these galaxies when the universe was less than half as old as it is today, and is so faint that the world's largest telescope, the Keck, is needed to study them. The magnified regions show that as the universe evolved, galaxies became more densely clustered even as these clusters moved farther apart with the expansion of the universe. The strength of these effects depends on cosmological parameters, allowing the study of dark energy by comparing groups and clusters of galaxies at low and high redshift. (Credit: Brian Gerke, UC Berkeley)

 

 

Introduction to the constants for nonexperts