Joseph Stefan
Encyclopedia
Joseph Stefan (24 March 1835 – 7 January 1893) was a physicist
, mathematician
, and poet
of Slovene mother tongue and Austrian
citizenship.
(Slovene Žrelec) (today a district of Klagenfurt
) (Celovec) in the Austrian Empire
(now in Austria
) to father Aleš (Aleksander) Stefan, born in 1805 and mother Marija Startinik, born 1815. His parents, both ethnic Slovenes, were married when Jožef was eleven. The Stefans were a modest family. His father was a milling assistant and mother served as a maidservant. Stefan's father died in 1872 while his mother died almost ten years earlier in 1863.
Stefan attended elementary school in Klagenfurt, where he showed his talent. They recommended that he continue his schooling, so in 1845 he went to Klagenfurt gymnasium. He experienced the revolutionary year of 1848, as a thirteen-year-old boy, which inspired him to be sympathetic toward Slovene literary production.
After having graduated top of his class in high school he briefly considered joining the Benedictine
order but his great interest in physics prevailed. He left for Vienna in 1853 to study mathematics
and physics
. His professor of physics in gymnasium was Karel Robida who wrote the first Slovene physics textbook. Stefan then graduated in mathematics and physics at the University of Vienna
in 1857. During his student years, he also wrote and published a number of poems in Slovene. He taught physics at the University of Vienna, was Director of the Physical Institute from 1866, Vice-President of the Vienna Academy of Sciences and member of several scientific institutions in Europe
.
He published nearly 80 scientific articles, mostly in the Bulletins of the Vienna Academy of Sciences, and he is best known for originating a physical
power law
in 1879 stating that the total radiation
from a black body
j* is proportional to the fourth power of its thermodynamic temperature
T:
This law was mathematically derived from the measurements of French physicists Dulong and Petit. As both incident radiation and blackbody emission are always equal, this equation applies equally to the temperature of any ideal body subject to incident radiation across its surface. In 1884 the law was extended to apply to grey-body emissions by Stefan's student Ludwig Boltzmann
and hence is known as the Stefan–Boltzmann law. Boltzmann treated a heat engine
with light
as a working matter. This law is the only physical law of nature named after a Slovene physicist. Today we derive the law from Planck's law of black body radiation
:
With his law Stefan determined the temperature of the Sun
's surface and he calculated a value of 5430 °C
. This was the first sensible value for the temperature of the Sun.
Stefan provided the first measurements of the thermal conductivity
of gas
es, treated evaporation
, and among others studied diffusion
, heat conduction
in fluid
s. For his treatise on optics
he received the Richard Lieben award from the University of Vienna. Flow from a droplet or particle that is induced by evaporation or sublimation at the surface is now called Stefan flow
because of his early work in calculating evaporation and diffusion rates.
Very important are also his electromagnetic equations, defined in vector notation, and works in the kinetic theory
of heat
. He was among the first physicists in Europe who fully understood Maxwell's
electromagnetic theory
and one of the few outside of England who expanded on it. He calculated inductivity
of a coil
with a quadratic cross-section, and he corrected Maxwell's miscalculation. He also researched a phenomenon called the skin effect
, where high-frequency electric current
is greater on the surface of a conductor than in its interior.
In mathematics the Stefan problem
s or Stefan's tasks with movable boundary are well known. The problem was first studied by Lamé
and Clapeyron
in 1831. Stefan solved the problem when he was calculating how quickly a layer of ice
on water grows.
He died in Vienna
, Austria-Hungary.
His life and work is extensively studied by the physicist Janez Strnad
.
The Jožef Stefan Institute
was also named after him.
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
, mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
, and poet
Poet
A poet is a person who writes poetry. A poet's work can be literal, meaning that his work is derived from a specific event, or metaphorical, meaning that his work can take on many meanings and forms. Poets have existed since antiquity, in nearly all languages, and have produced works that vary...
of Slovene mother tongue and Austrian
Austrian Empire
The Austrian Empire was a modern era successor empire, which was centered on what is today's Austria and which officially lasted from 1804 to 1867. It was followed by the Empire of Austria-Hungary, whose proclamation was a diplomatic move that elevated Hungary's status within the Austrian Empire...
citizenship.
Life and work
Stefan was born in an outskirt village St Peter (Slovene Sveti Peter) near EbenthalEbenthal
Ebenthal is a town in the district of Klagenfurt-Land in Carinthia in Austria.According to the 2001 census 4.2% of the population are Carinthian Slovenes....
(Slovene Žrelec) (today a district of Klagenfurt
Klagenfurt
-Name:Carinthia's eminent linguists Primus Lessiak and Eberhard Kranzmayer assumed that the city's name, which literally translates as "ford of lament" or "ford of complaints", had something to do with the superstitious thought that fateful fairies or demons tend to live around treacherous waters...
) (Celovec) in the Austrian Empire
Austrian Empire
The Austrian Empire was a modern era successor empire, which was centered on what is today's Austria and which officially lasted from 1804 to 1867. It was followed by the Empire of Austria-Hungary, whose proclamation was a diplomatic move that elevated Hungary's status within the Austrian Empire...
(now in Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
) to father Aleš (Aleksander) Stefan, born in 1805 and mother Marija Startinik, born 1815. His parents, both ethnic Slovenes, were married when Jožef was eleven. The Stefans were a modest family. His father was a milling assistant and mother served as a maidservant. Stefan's father died in 1872 while his mother died almost ten years earlier in 1863.
Stefan attended elementary school in Klagenfurt, where he showed his talent. They recommended that he continue his schooling, so in 1845 he went to Klagenfurt gymnasium. He experienced the revolutionary year of 1848, as a thirteen-year-old boy, which inspired him to be sympathetic toward Slovene literary production.
After having graduated top of his class in high school he briefly considered joining the Benedictine
Benedictine
Benedictine refers to the spirituality and consecrated life in accordance with the Rule of St Benedict, written by Benedict of Nursia in the sixth century for the cenobitic communities he founded in central Italy. The most notable of these is Monte Cassino, the first monastery founded by Benedict...
order but his great interest in physics prevailed. He left for Vienna in 1853 to study mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
and physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
. His professor of physics in gymnasium was Karel Robida who wrote the first Slovene physics textbook. Stefan then graduated in mathematics and physics at the University of Vienna
University of Vienna
The University of Vienna is a public university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world...
in 1857. During his student years, he also wrote and published a number of poems in Slovene. He taught physics at the University of Vienna, was Director of the Physical Institute from 1866, Vice-President of the Vienna Academy of Sciences and member of several scientific institutions in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
.
He published nearly 80 scientific articles, mostly in the Bulletins of the Vienna Academy of Sciences, and he is best known for originating a physical
Physical law
A physical law or scientific law is "a theoretical principle deduced from particular facts, applicable to a defined group or class of phenomena, and expressible by the statement that a particular phenomenon always occurs if certain conditions be present." Physical laws are typically conclusions...
power law
Power law
A power law is a special kind of mathematical relationship between two quantities. When the frequency of an event varies as a power of some attribute of that event , the frequency is said to follow a power law. For instance, the number of cities having a certain population size is found to vary...
in 1879 stating that the total radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
from a black body
Black body
A black body is an idealized physical body that absorbs all incident electromagnetic radiation. Because of this perfect absorptivity at all wavelengths, a black body is also the best possible emitter of thermal radiation, which it radiates incandescently in a characteristic, continuous spectrum...
j* is proportional to the fourth power of its thermodynamic temperature
Thermodynamic temperature
Thermodynamic temperature is the absolute measure of temperature and is one of the principal parameters of thermodynamics. Thermodynamic temperature is an "absolute" scale because it is the measure of the fundamental property underlying temperature: its null or zero point, absolute zero, is the...
T:
This law was mathematically derived from the measurements of French physicists Dulong and Petit. As both incident radiation and blackbody emission are always equal, this equation applies equally to the temperature of any ideal body subject to incident radiation across its surface. In 1884 the law was extended to apply to grey-body emissions by Stefan's student Ludwig Boltzmann
Ludwig Boltzmann
Ludwig Eduard Boltzmann was an Austrian physicist famous for his founding contributions in the fields of statistical mechanics and statistical thermodynamics...
and hence is known as the Stefan–Boltzmann law. Boltzmann treated a heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...
with light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
as a working matter. This law is the only physical law of nature named after a Slovene physicist. Today we derive the law from Planck's law of black body radiation
Planck's law of black body radiation
In physics, Planck's law describes the amount of energy emitted by a black body in radiation of a certain wavelength . The law is named after Max Planck, who originally proposed it in 1900. The law was the first to accurately describe black body radiation, and resolved the ultraviolet catastrophe...
:
With his law Stefan determined the temperature of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
's surface and he calculated a value of 5430 °C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
. This was the first sensible value for the temperature of the Sun.
Stefan provided the first measurements of the thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
of gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
es, treated evaporation
Evaporation
Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
, and among others studied diffusion
Diffusion
Molecular diffusion, often called simply diffusion, is the thermal motion of all particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size of the particles...
, heat conduction
Heat conduction
In heat transfer, conduction is a mode of transfer of energy within and between bodies of matter, due to a temperature gradient. Conduction means collisional and diffusive transfer of kinetic energy of particles of ponderable matter . Conduction takes place in all forms of ponderable matter, viz....
in fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
s. For his treatise on optics
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
he received the Richard Lieben award from the University of Vienna. Flow from a droplet or particle that is induced by evaporation or sublimation at the surface is now called Stefan flow
Stefan flow
Stefan flow, occasionally called Stefan's flow , is a transport phenomenon concerning the movement of a chemical species by a flowing fluid that is induced to flow by the production or removal of the species at an interface...
because of his early work in calculating evaporation and diffusion rates.
Very important are also his electromagnetic equations, defined in vector notation, and works in the kinetic theory
Kinetic theory
The kinetic theory of gases describes a gas as a large number of small particles , all of which are in constant, random motion. The rapidly moving particles constantly collide with each other and with the walls of the container...
of heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
. He was among the first physicists in Europe who fully understood Maxwell's
James Clerk Maxwell
James Clerk Maxwell of Glenlair was a Scottish physicist and mathematician. His most prominent achievement was formulating classical electromagnetic theory. This united all previously unrelated observations, experiments and equations of electricity, magnetism and optics into a consistent theory...
electromagnetic theory
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
and one of the few outside of England who expanded on it. He calculated inductivity
Inductance
In electromagnetism and electronics, inductance is the ability of an inductor to store energy in a magnetic field. Inductors generate an opposing voltage proportional to the rate of change in current in a circuit...
of a coil
Coil
A coil is a series of loops. A coiled coil is a structure in which the coil itself is in turn also looping.-Electromagnetic coils:An electromagnetic coil is formed when a conductor is wound around a core or form to create an inductor or electromagnet...
with a quadratic cross-section, and he corrected Maxwell's miscalculation. He also researched a phenomenon called the skin effect
Skin effect
Skin effect is the tendency of an alternating electric current to distribute itself within a conductor with the current density being largest near the surface of the conductor, decreasing at greater depths. In other words, the electric current flows mainly at the "skin" of the conductor, at an...
, where high-frequency electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
is greater on the surface of a conductor than in its interior.
In mathematics the Stefan problem
Stefan problem
In mathematics and its applications, particularly to phase transitions in matter, a Stefan problem is a particular kind of boundary value problem for a partial differential equation , adapted to the case in which a phase boundary can move with time...
s or Stefan's tasks with movable boundary are well known. The problem was first studied by Lamé
Gabriel Lamé
Gabriel Léon Jean Baptiste Lamé was a French mathematician.-Biography:Lamé was born in Tours, in today's département of Indre-et-Loire....
and Clapeyron
Benoit Paul Émile Clapeyron
Benoît Paul Émile Clapeyron was a French engineer and physicist, one of the founders of thermodynamics.-Life:...
in 1831. Stefan solved the problem when he was calculating how quickly a layer of ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
on water grows.
He died in Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...
, Austria-Hungary.
His life and work is extensively studied by the physicist Janez Strnad
Janez Strnad
Janez Strnad is a Slovene physicist and populariser of natural science.- Life and work :Strnad was born in Ljubljana, Kingdom of Yugoslavia ....
.
Eponymous terms
In physics, several concepts are named after Joseph Stefan. In particular:- Stefan–Boltzmann law
- Stefan–Boltzmann constant σ
- Stefan problemStefan problemIn mathematics and its applications, particularly to phase transitions in matter, a Stefan problem is a particular kind of boundary value problem for a partial differential equation , adapted to the case in which a phase boundary can move with time...
- Stefan's equationStefan's equationIn glaciology and civil engineering, Stefan's equation describes the dependence of ice-cover thickness on the temperature history. It says in particular that the expected ice accretion is proportional to the square root of the number of degree days below freezing...
- Stefan's formulaStefan's formulaIn thermodynamics, Stefan’s formula says that the specific surface energy at a given interface is determined by the respective enthalpy difference \scriptstyle \Delta H^*....
- Stefan flowStefan flowStefan flow, occasionally called Stefan's flow , is a transport phenomenon concerning the movement of a chemical species by a flowing fluid that is induced to flow by the production or removal of the species at an interface...
- Stefan number
- Stefan's force
The Jožef Stefan Institute
Jožef Stefan Institute
The Jožef Stefan Institute , is the largest research institute in Slovenia. The main research areas are physics, chemistry, molecular biology, biotechnology, information technologies, reactor physics, energy and environment...
was also named after him.
External links
- Jožef Stefan, in the Jožef Stefan InstituteJožef Stefan InstituteThe Jožef Stefan Institute , is the largest research institute in Slovenia. The main research areas are physics, chemistry, molecular biology, biotechnology, information technologies, reactor physics, energy and environment...
website - "Josef Stefan: His life and legacy in the thermal sciences," Experimental Thermal and Fluid Science, Volume 31, Issue 7, July 2007, Pages 795-803, by John C. Crepeau
- Extended biography of Josef Stefan, by John C. Crepeau