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There are many physical constants in science, some of the most famous being ; while the Fine-structure Constant α characterizes the interaction between Electron s and Photon s, is Dimensionless . Beginning with Paul Dirac in 1937 , some scientists have speculated that physical constants may actually decrease in proportion to the age of the universe. Scientific experiments have not yet pinpointed any definite evidence that this is the case, although they have placed upper bounds on the maximum possible relative change per year at very small amounts (roughly 10-5 per year for the fine structure constant α and 10-11 for the gravitational constant ''G''). It is currently disputed [http://xxx.lanl.gov/pdf/physics/0110060 that any changes in ''dimensionful'' physical constants such as ''G'', ''c'', ''ħ'', or ε0 are operationally meaningless; however, a change in a dimensionless constant such as α is something that would definitely be noticed. If a measurement indicated that a dimensionful physical constant had changed, this would be the result or ''interpretation'' of a more fundamental dimensionless constant changing, which is the salient metric. Unless the system of Natural Unit s is used, the numerical values of dimensionful physical constants are artifacts of the unit system used, such as SI or Cgs ; that is, they are essentially Conversion Factor s of human construct. While some properties of materials and particles are constant, they do not show up on this page because they are specific to their respective materials or properties alone. Constants that are independent of systems of units are typically Dimensionless Number s, known as Fundamental Physical Constant s, and are truly meaningful parameters of nature, not merely human constructs. The Fine-structure Constant α is probably the most well-known dimensionless fundamental physical constant. The dimensionless ratios of masses (or other like-dimensioned properties) of Fundamental Particles are also fundamental physical constants, as are the measure of these properties in terms of natural units. Some people claim that if the physical constants had slightly different values, our universe would be so radically different that intelligent life would probably not have emerged, and that our universe therefore seems to be Fine-tuned for intelligent life. The weak Anthropic Principle simply states that it's only because these fundamental constants acquired their respective values that there was sufficient order and richness in elemental diversity for life to have formed, which subsequently evolved the necessary intelligence toward observing that these constants have taken on the values they have. TABLE OF UNIVERSAL CONSTANTS TABLE OF ELECTROMAGNETIC CONSTANTS TABLE OF ATOMIC AND NUCLEAR CONSTANTS TABLE OF PHYSICO-CHEMICAL CONSTANTS TABLE OF ADOPTED VALUES NOTES 1The values are given in the so-called ''concise form''; the number in brackets is the '' Standard Uncertainty '', which is the value multiplied by the '' Relative Standard Uncertainty ''. 2This is the value adopted internationally for realizing representations of the Volt using the Josephson Effect . 3This is the value adopted internationally for realizing representations of the Ohm using the Quantum Hall Effect . SEE ALSO
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