Physical Constant

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Physical constant, sometimes called fundamental physical constant or universal constant, is a physical quantity that is generally believed to be both universal in nature and have constant value in time. It is contrasted with a mathematical constant, which has a fixed numerical value, but does not directly involve any physical measurement.

There are many physical constants, some of the most widely recognized being the speed of light in vacuum c, the gravitational constant G, Planck’s constant h, the electric constant ε0, and the elementary charge e. Physical constants can take many dimensional forms: the speed-of-light signifies a maximum speed for any object 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. — Wikipedia

Physical Constant (Encyclopædia Britannica)

Fundamental Physical Constants (NIST)
CODATA Internationally Recommended Values of Fundamental Physical Constants (NIST)
CODATA Internationally Recommended Values of Fundamental Physical Constants, Universal (NIST)

Physical Constants (Eric Weisstein’s World of Physics, Wolfram Research)
Physical Constants (Wolfram Alpha)




There’s a Glitch At The Edge of The Universe That Could Remake Physics (Michael Brooks, New Scientist)
Humankind’s Existentially Lucky Numbers (George Johnson, New York Times)
A Brief History of the Grand Unified Theory of Physics (Lawrence M. Krauss, Nautilus)

Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO, European Southern Observatory)
ESPRESSO (Wikipedia)

Fine-structure Constant (NIST)
Fine-structure Constant (Wikipedia)



Physical Constant Gifts (Zazzle)




Subatomic Stories (Fermilab, YouTube Channel)

Planck Length, Minimal Length? (Don Lincoln, Fermilab Today)
Possible Connection Between Gravitation and Fundamental Length (Alden Mead, Physical Review)
On Absolute Units, III: Absolutely Not? (Frank Wilczek, Physics Today)

Max Planck (Encyclopædia Britannica)
Planck’s constant (Encyclopædia Britannica)

Fundamental Physical Constants: Introduction to the Constants for Nonexperts (NIST)


Library of Congress # QC Physics (UPenn Online Books)

WorldCat, Library of Congress, UPenn Online Books, Open Library


MERLOT: Multimedia Educational Resource for Learning and Online Teaching
OER Commons: Open Educational Resources



Physicists (CareerOneStop, U.S. Department of Labor, Employment and Training Administration)
Careers in Physical Sciences (Physics World)


American Physical Society (APS)
European Physical Society (EPS)
American Institute of Physics (AIP)


Physical Constants (



Physical Constants (



Here are links to pages about closely related subjects.

Knowledge Realm


Law (Constant) Relativity
Force Gravity, Electromagnetism (Light, Color)
Matter (Microscope) Molecule, Atom (Periodic Table), Particle

Universe (Astronomical Instrument)
Galaxy Milky Way, Andromeda
Planetary System Star, Brown Dwarf, Planet, Moon

Our Neighborhood
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Trans-Neptunian Object
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid


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