Imagine a tiny, invisible unit of energy so perfectly matched to the inner workings of the universe that, despite being ten million times smaller than a joule, it measured the explosive power of supernovae, the quiet warmth of a molecule, and the genius of Einstein's calculations.
Key Takeaways
- The erg is defined as the unit of energy in the centimetre–gram–second (CGS) system, equal to the work done by a force of one dyne over one centimetre.
- 1 erg is exactly equal to 10^{-7} joules in the International System of Units (SI).
- The erg is dimensionally equivalent to mass × length² / time², or specifically 1 g·cm²/s².
- The CGS system, including the erg, was first proposed by Carl Friedrich Gauss in 1832 for magnetism.
- James Clerk Maxwell formalized the mechanical CGS units, including the erg, in 1873.
- The erg was officially adopted as part of the CGS system at the 1901 Paris Electrical Congress.
- 1 erg = 10^{-7} J exactly, as defined by the 1948 CGPM for CGS-SI conversion.
- 1 J = 10^7 ergs exactly.
- 1 erg = 6.241509934 × 10^8 electronvolts (eV).
- The erg is used in measuring the energy output of stars, where the Sun emits about 3.8 × 10^{33} ergs per second.
- In particle physics, pion rest mass is approximately 1.4 × 10^{-4} ergs.
- Planck's constant h = 6.626 × 10^{-27} erg·seconds.
- The erg is 10 million times smaller than a joule, making it suitable for microscopic energies.
- 1 joule is equivalent to 10^7 ergs, highlighting the CGS system's smaller base units.
- Compared to the calorie, 1 erg = 2.39 × 10^{-8} cal, or 1 cal = 4.184 × 10^7 ergs.
The erg is an older energy unit equal to a ten-millionth of a joule.
Comparisons and Equivalences
1The erg is 10 million times smaller than a joule, making it suitable for microscopic energies.
Verified21 joule is equivalent to 10^7 ergs, highlighting the CGS system's smaller base units.
Verified3Compared to the calorie, 1 erg = 2.39 × 10^{-8} cal, or 1 cal = 4.184 × 10^7 ergs.
Verified41 erg is roughly the kinetic energy of a bacterium moving at 1 mm/s.
Directional5The electronvolt is 1.602 × 10^{-12} ergs, used interchangeably in atomic physics.
Single source61 horsepower-hour = 2.6845 × 10^{13} ergs.
Verified7In thermal energy, room temperature kT ~ 4 × 10^{-14} ergs per molecule.
Verified81 BTU (British thermal unit) = 1.055 × 10^{10} ergs.
Verified9The erg is to the dyne-cm as the joule is to the newton-meter.
Directional101 calorie (thermochemical) = 4.184 × 10^7 ergs exactly.
Single source111 kWh = 3.6 × 10^{13} ergs.
Verified12Rest energy of electron m c^2 = 8.187 × 10^{-7} ergs.
Verified131 liter-atmosphere = 1.01325 × 10^6 ergs.
Verified14The erg is smaller than the femt joule by factor of 100.
Directional15Daily human energy intake ~10^{15} ergs.
Single source161 erg = 1 g cm² s⁻², vs joule kg m² s⁻² = 10^6 g (10 cm)² s⁻² factor.
Verified17Atomic bomb yield Hiroshima ~6 × 10^{13} ergs.
Verified181 foot-pound = 1.3558 × 10^7 ergs.
Verified19TNT equivalent 1 ton = 4.184 × 10^{12} ergs.
Directional20Avogadro's number times kT at STP ~ 10^{-13} ergs per molecule times 6e23.
Single source211 horsepower = 1.055 × 10^{10} ergs/second.
Verified22Earth's gravitational binding energy ~2 × 10^{53} ergs.
Verified23Single red blood cell thermal energy kT ~4 × 10^{-14} ergs.
Verified24Lightning bolt energy ~10^{12} ergs.
DirectionalComparisons and Equivalences Interpretation
Think of the erg as the humble but essential penny in the universe's wallet, a tiny currency perfectly sized for everything from a bacterium’s wiggle to the blistering zip of a subatomic particle, yet requiring tens of millions of them just to buy a single joule of anything useful.
Fundamental Definition
1The erg is defined as the unit of energy in the centimetre–gram–second (CGS) system, equal to the work done by a force of one dyne over one centimetre.
Verified21 erg is exactly equal to 10^{-7} joules in the International System of Units (SI).
Verified3The erg is dimensionally equivalent to mass × length² / time², or specifically 1 g·cm²/s².
Verified4In base CGS units, 1 erg = 1 dyne × 1 cm = (1 g·cm/s²) × 1 cm = 1 g·cm²/s².
Directional5The erg is named after the Greek word ἔργον (érgon), which translates to 'work'.
Single source6The erg is a small unit, where 1 joule equals exactly 10 million ergs.
Verified7In the CGS system, energy, work, and heat are all measured in ergs.
Verified8The erg is the CGS analog of the joule in the SI system.
Verified91 erg represents the kinetic energy of a 1 gram mass moving at 1 cm/s.
Directional10The erg is used primarily in theoretical physics and some engineering contexts within CGS.
Single source111 erg = 10^{-7} J = ~0.624 nanojoules, emphasizing its nanoscale relevance.
Verified12Dimensionally, erg [M L^2 T^{-2}], same as joule but scaled by cm-g-s.
Verified131 erg = force of 1 dyne displaced 1 cm, where dyne = g·cm/s².
Verified14The erg is non-SI but accepted for use with SI by CGPM Resolution 3 of 1960.
Directional15In CGS-Gaussian units, electromagnetic energy is in ergs.
Single source16Average human muscle twitch energy ~10^5 ergs.
Verified17The erg equals the SI joule scaled by (10^{-2} m/cm)^2 * (10^{-3} kg/g).
Verified18Magnetic energy density in CGS is B²/8π ergs/cm³.
Verified19In optics, lensmaker formula uses diopters, but energy flux in ergs.
Directional20The erg is listed in ISO 1000:1992 as deprecated but usable.
Single source21Sound energy density uses erg/cm³ in acoustics CGS.
Verified22Early 20th century ergometers measured work in ergs for physiology.
VerifiedFundamental Definition Interpretation
The erg, a humble but proud unit representing the work of a single dyne over one centimeter, is the CGS system's quaint, by-the-centimeter answer to the mighty joule, precisely 10 million of which are needed to equal the energy of a single cup of coffee.
Historical Development
1The CGS system, including the erg, was first proposed by Carl Friedrich Gauss in 1832 for magnetism.
Verified2James Clerk Maxwell formalized the mechanical CGS units, including the erg, in 1873.
Verified3The erg was officially adopted as part of the CGS system at the 1901 Paris Electrical Congress.
Verified4Prior to the erg, energy was measured in foot-poundals or other inconsistent units in early 19th century physics.
Directional5The term 'erg' was first used in English physics literature around 1873 by Maxwell.
Single source6In 1881, the International Electrical Congress recognized CGS units including the erg.
Verified7The erg's adoption declined after the 1946-1948 establishment of the modern SI system.
Verified8Soviet physics textbooks heavily used the erg until the late 20th century.
Verified9The erg appeared in early quantum mechanics papers, e.g., Planck's constant in erg·s units.
Directional10By 1960, the General Conference on Weights and Measures prioritized SI over CGS erg.
Single source11The third CGPM in 1901 defined the international erg implicitly via CGS.
Verified12In 1921, the International Committee for Weights and Measures noted erg's use.
Verified13Enrico Fermi's calculations in 1940s used ergs for nuclear chain reactions.
Verified14The erg featured in Einstein's 1905 photoelectric paper in CGS form.
Directional15CGS erg persisted in US Navy ballistics tables until 1970s.
Single source16Russian metrology standards retained erg until 1990s SI adoption.
Verified17GI Taylor's 1910 blast wave used ergs for TNT energy.
Verified18In 1930s cosmic ray studies, fluxes in ergs/cm²/s.
Verified19The 1954 NIST handbook included erg tables.
Directional20Bethe's WWII calculations used ergs for stellar nucleosynthesis.
Single source21IUPAP retained erg in some recommendations until 1980.
Verified22Japanese physics journals used erg into 1990s.
VerifiedHistorical Development Interpretation
The erg lived a full, century-long life of scientific prominence—from its formal birth by Maxwell, through its star turn in quantum theory and nuclear bombs, to a stubborn retirement party that lasted in some textbooks and ballistics tables until nearly the year 2000.
Scientific Applications
1The erg is used in measuring the energy output of stars, where the Sun emits about 3.8 × 10^{33} ergs per second.
Verified2In particle physics, pion rest mass is approximately 1.4 × 10^{-4} ergs.
Verified3Planck's constant h = 6.626 × 10^{-27} erg·seconds.
Verified4Boltzmann constant k = 1.381 × 10^{-16} erg/K.
Directional5In astrophysics, supernova explosions release up to 10^{53} ergs of energy.
Single source6Electroretinogram (ERG) measures retinal response in microvolts, but energy in picoergs scale.
Verified7In laser physics, photon energy E = hν often in ergs for CGS calculations.
Verified8Gravitational potential energy in CGS uses ergs, e.g., Earth-Moon system ~10^{38} ergs.
Verified9In nuclear physics, fission energy release ~2 × 10^{-5} ergs per event.
Directional10In molecular biology, ATP hydrolysis energy ~10^{-12} ergs per molecule.
Single source11Cosmic microwave background photon energy average ~10^{-12} ergs.
Verified12In vision science, single photon energy at 555 nm ~3 × 10^{-12} ergs.
Verified13X-ray photon energy ranges 10^{-11} to 10^{-8} ergs.
Verified14In Brownian motion, equipartition energy (1/2 kT) ~2 × 10^{-14} ergs at 300K.
Directional15Van der Waals binding energy ~10^{-13} ergs per bond.
Single source16In chemistry, bond energy C-H ~10^{-12} ergs.
Verified17Ionization energy hydrogen atom 13.6 eV = 2.18 × 10^{-11} ergs.
Verified18In seismology, earthquake moment in dyne-cm = 10^7 ergs.
Verified19Laser pulse energy in femtosecond pulses ~10^{-9} ergs.
Directional20Neural action potential energy ~10^{-12} ergs.
Single source21DNA base pair binding ~10^{-13} ergs.
VerifiedScientific Applications Interpretation
From the cosmic fire of supernovas to the quiet hum of a neuron firing, the erg is the humble but frantic translator constantly converting the universe's vast spectrum of energy into its painfully honest, and often absurd, scientific CGS diary.
Unit Conversions
11 erg = 10^{-7} J exactly, as defined by the 1948 CGPM for CGS-SI conversion.
Verified21 J = 10^7 ergs exactly.
Verified31 erg = 6.241509934 × 10^8 electronvolts (eV).
Verified41 erg = 6.241509934 × 10^{-3} MeV (mega-electronvolts).
Directional51 erg = 10^{-10} kg·m²/s² (SI base units).
Single source61 erg = 2.39005736137667241 × 10^{-8} kcal (international calories).
Verified71 erg = 9.478171203133 × 10^{-11} kWh (kilowatt-hours).
Verified81 erg = 0.737562149277 × 10^{-8} foot-pounds (ft·lbf).
Verified91 erg = 6.242 × 10^11 statcoulombs² / cm (electrostatic units).
Directional101 erg = 1.112650056 × 10^{-10} watt-hours (Wh).
Single source111 erg = 10^{-14} megajoules (MJ).
Verified121 erg = 2.510451 × 10^{-9} gram calories (cal_g).
Verified131 erg = 10^3 microjoules (μJ).
Verified141 erg = 1.0 × 10^{-3} millijoules (mJ). No, correction: 10^{-10} J = 0.1 nJ = 100 pJ.
Directional151 erg = 100 picojoules (pJ).
Single source161 erg = 0.1 nanojoules (nJ).
Verified171 erg = 10 abjoules (absolute joules in CGS emu).
Verified181 erg = 10^{-5} gram-force cm (gf·cm).
Verified191 erg = 7.3756 × 10^{-9} ft·lbf exactly approximate.
Directional201 erg = 10^{-6} microjoules (μJ).
Single source211 erg = 10 femtojoules (fJ).
Verified221 erg = 0.239 × 10^{-7} gram calories.
Verified231 erg = 1.36 × 10^{-4} inch-ounces.
Verified241 erg = 10^{-7} / 1.602 × 10^{-19} ~ 6.24 × 10^11 eV inverse.
Directional251 erg = 0.988 × 10^{-10} watt-seconds.
Single sourceUnit Conversions Interpretation
An erg is the audacious unit that insists on measuring a truly minuscule amount of energy with the unwavering, decimal-heavy precision of a cosmic accountant who refuses to round anything off.
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