Janez Strnad (March 4, 1934 – November 28, 2015) was a Slovene

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate ca ...

and popularizer of natural science.

Life and work

Strnad was born in

Ljubljana Ljubljana (also known by other historical names) is the capital and largest city of Slovenia. It is the country's cultural, educational, economic, political and administrative center. During antiquity, a Roman city called Emona stood in the a ...

Kingdom of Yugoslavia The Kingdom of Yugoslavia ( sh-Latn-Cyrl, separator=" / ", Kraljevina Jugoslavija, Краљевина Југославија; sl, Kraljevina Jugoslavija) was a state in Southeast and Central Europe that existed from 1918 until 1941. From 1918 ...

(now

Slovenia Slovenia ( ; sl, Slovenija ), officially the Republic of Slovenia (Slovene: , abbr.: ''RS''), is a country in Central Europe. It is bordered by Italy to the west, Austria to the north, Hungary to the northeast, Croatia to the southeast, and ...

). He received a degree at the University of Ljubljana in

technical physics Engineering physics, or engineering science, refers to the study of the combined disciplines of physics, mathematics, chemistry, biology, and engineering, particularly computer, nuclear, electrical, electronic, aerospace, materials or mechanical ...

in 1957, and got his

Ph.D. A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is a ...

in 1963. His main research work was carried out at the Jožef Stefan Institute. He taught for many years beginning in 1961 at the

University of Ljubljana The University of Ljubljana ( sl, Univerza v Ljubljani, , la, Universitas Labacensis), often referred to as UL, is the oldest and largest university in Slovenia. It has approximately 39,000 enrolled students. History Beginnings Although certain ...

, Faculty for natural science and

technology Technology is the application of knowledge to reach practical goals in a specifiable and reproducible way. The word ''technology'' may also mean the product of such an endeavor. The use of technology is widely prevalent in medicine, scie ...

on the Department of physics introductory courses and topics from

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which rel ...

. In 1974 he became a full professor. In 1990 he wrote a book about

fundamental particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include electrons, the fundamental fermions ( quarks, leptons, a ...

s physics entitled ''Iz take so snovi kot sanje'' (''We are such stuff as

dream A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, al ...

s are made of''). With his short and long articles he had deepened the knowledge about Stefan's

scientific Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence ...

work. His thick booklet in the series of monographs, ''Zbirka Sigma'' (the Sigma Collection), entitled ''Kvantna fizika'' (''

Quantum Physics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, q ...

''), (DZS, Ljubljana 1974) contains a definition and introduction to the understanding of

Heisenberg Werner Karl Heisenberg () (5 December 1901 – 1 February 1976) was a German theoretical physicist and one of the main pioneers of the theory of quantum mechanics. He published his work in 1925 in a Über quantentheoretische Umdeutung kinematis ...

uncertainty principle In quantum mechanics, the uncertainty principle (also known as Heisenberg's uncertainty principle) is any of a variety of mathematical inequalities asserting a fundamental limit to the accuracy with which the values for certain pairs of physic ...

for the graduate beginner. He wrote over 1000 works. Strnad's works also includes topics of physics which are not exactly related at first glance to it, for instance as in this his article ''Znanost in politika v vinjetah'' (''Science and politics in vignettes'')].Znanost in politika v vinjetah by Dr. Janez Strnad
/ref>

Selected works

University textbooks

# Janez Strnad, ''Atlas klasične in moderne fizike'' (''Atlas of classical and modern physics''), translation and adaptation of Hans Breuer, ''dtv-Atlas zur Physik'', (Deutscher Taschenbuch Verlag, München 1987, 1988), DZS, Ljubljana 1993, pp 400, . # Janez Strnad, ''Fizika, 1. del, Mehanika, Toplota'' (''Physics, 1st part,

Mechanics Mechanics (from Ancient Greek: μηχανική, ''mēkhanikḗ'', "of machines") is the area of mathematics and physics concerned with the relationships between force, matter, and motion among physical objects. Forces applied to objects ...

Heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...

''), (DZS, Ljubljana 1977, pp 1 – 284. # Janez Strnad, ''Fizika, 2. del, Elektrika, Optika'' (''Physics, 2nd part,

Electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describ ...

Optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultra ...

''), (DZS, Ljubljana 1978, pp 285 – 564). # Janez Strnad, ''Fizika, 3. del, Posebna teorija relativnosti, Atomi'' (''Physics, 3rd part,

Special Theory of relativity In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates: # The laws o ...

Atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas ...

s''), (DZS, Ljubljana 1980, pp 320). # Janez Strnad, ''Fizika, 4. del, Molekule, kristali, jedra, delci'' (''Physics, 4th part,

Molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...

Crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macr ...

s, Nuclei, Particles''), (DZS, Ljubljana 1982, pp 283). # Janez Strnad, Mladen Gros, Marjan Hribar,

Alojz Kodre Alojzij Franc 'Alojz' Kodre (born 22 February 1944 in Villach, Austria) is a Slovenian physicist and translator. Kodre was a professor at the Faculty of Mathematics and Physics in Ljubljana, where he lectured Mathematical Physics and Model An ...

, ''Naloge iz fizike'' (''Exercises from Physics''), (DMFA SRS, Ljubljana 1981, pp 108).

Selected chapters from physics and postgraduate seminars

# Janez Strnad, ''Fazna, skupinska, signalna hitrost'' (''Phase, Group, Signal

Velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

''), (DMFA SRS, Ljubljana 1975, pp 31). # Janez Strnad, ''Poskusi v posebni in splošni teoriji relativnosti'' (''Experiments in Special and

General Theory of Relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. ...

''), (DMFA SRS, Ljubljana 1977, pp 44). #Janez Strnad, ''Na pot v kvantno elektrodinamiko'' (''On the way to the

Quantum Electrodynamics In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and spec ...

''), (DMFA SRS, Ljubljana 1986, pp 176). #Janez Strnad, ''Na pot k Schwarzschildu'' (''On the way to

Schwarzschild Schwarzschild () is a German surnameIt is likely to be misspelled and/or mispronounced by native English speakers, particularly involving failure to grasp that * German ''sch'' (at the beginning of ''each'' of the two syllables) is pronounced as E ...

''), (DMFA S, Ljubljana 1991, pp 52). #Janez Strnad, ''Homogeno gravitacijsko polje: med posebno in splošno teorijo relativnosti'' (''Homogeneous Gravitational Field: Between Special and General Theory of relativity''), (DMFA S, Ljubljana 1994, pp 44). #Janez Strnad, ''Začetki kvantne statistične mehanike'' (''The Beginnings of Quantum Statistical Mechanics''), (DMFA S, Ljubljana 1997, pp 31). #Janez Strnad, ''Odkritje razcepa'' (''Discovery of the split''), (DMFA S, Ljubljana 2000, pp 39).

Books

# Janez Strnad, ''Jožef Stefan, Ob stopetdesetletnici rojstva'' (''Jožef Stefan, By his 150th anniversary of birth''), (DMFA SRS, Ljubljana 1985). #Janez Strnad, ''Prapok Prasnov požene v dir'' (''Primordial Bang drives Primordial Substance into a Gallop''), (DZS, Ljubljana 1988, pp 81). # Janez Strnad, ''Zgodbe iz fizike'' (''Stories from Physics''), (Slovenska matica, Ljubljana 1990). # Janez Strnad, ''Fiziki 1'' (''Physicists 1''), (Mihelač in Nešović, Ljubljana 1995, pp 159). # Janez Strnad, ''Razvoj fizike'' (''The Development of Physics''), (DZS Ljubljana 1996, pp 400). # Janez Strnad, ''Fiziki 2'' (''Physicists 2''), (Modrijan, Ljubljana 1999, pp 199). # Janez Strnad, ''Fiziki 3'' (''Physicists 3''), (Modrijan, Ljubljana 2000, pp 227). # Janez Strnad, ''Svet merjenj: o razvoju fizike in merjenju osnovnih fizikalnih količin'' (''The World of Measurements: About the Development of Physics and Measuring of Fundamental

Physical Quantities A physical quantity is a physical property of a material or system that can be quantified by measurement. A physical quantity can be expressed as a ''value'', which is the algebraic multiplication of a ' Numerical value ' and a ' Unit '. For examp ...

''), (DZS, Ljubljana 2001, pp 139). #Janez Strnad, Sto let fizike: od 1900 do 2000 (''A Hundred Years of Physics: from 1900 to 2000''), (DMFA S, Ljubljana 2001, pp 233).

Scientific articles

# Janez Strnad, ''Sto let Stefanovega zakona'' (''Hundred years of Stefan's law''), (Obzornik mat, fiz. 26 (1979) 3). # Janez Strnad, A. Vengar, ''Stefanova meritev toplotne prevodnosti zraka'' (''Stefan's measurements of the

thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...

''), (European Journal of Physics, 1984). # Janez Strnad, ''Kako je Jožef Stefan odkril zakon o sevanju'' (''How Jožef Stefan discovered the law of

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, vi ...

''), (Zbornik za zgodovino naravoslovja in tehnike 8, Ljubljana 1985). # Janez Strnad, ''Stefanov tok'' (''Stefan's current''), (Obzornik mat, fiz. 32 (1985). # Janez Strnad, ''Stefanova naloga'' (''Stefan's task''), (Obzornik mat, fiz. 34 (1987). # Janez Strnad, ''Stefanove elektodinamične enačbe'' (''Stefan's equations of electrodynamics''), (European Journal of Physics, 1989). # Janez Strnad, ''Ernst Mach kot fizik'' (''Ernst Mach as physicist''), (Zbornik za zgodovino naravoslovja in tehnike 10, Ljubljana 1989). # Janez Strnad, ''Dvigajoči se mehurčki'' (''Rising bubbles''), (Obzornik mat, fiz. 39 (1992) 4, pp 85 – 89). # Janez Strnad, ''Oslabitev Brownovega gibanja'' (''Squeezing

Brownian motion Brownian motion, or pedesis (from grc, πήδησις "leaping"), is the random motion of particles suspended in a medium (a liquid or a gas). This pattern of motion typically consists of random fluctuations in a particle's position insi ...

''), (Obzornik mat, fiz. 39 (1992) 2, pp 49 – 54). # Janez Strnad, ''Opazovanje in teorija'' (''

Observation Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data via the use of scientific instruments. Th ...

and

theory A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may ...

''), (Obzornik mat, fiz. 39 (1992) 5, pp 141 – 150). # Janez Strnad, ''J. Stefana 'Longitudinalna nihanja palic' '' (''J. Stefan's 'Longitudal

oscillation Oscillation is the repetitive or Periodic function, periodic variation, typically in time, of some measure about a central value (often a point of Mechanical equilibrium, equilibrium) or between two or more different states. Familiar examples o ...

s of rods' ''), (Obzornik mat, fiz. 40 (1993) 1, pp 17 – 19). # Janez Strnad, ''Ali mora znati, kdor uči?'' (''Should he who teaches know?''), (Obzornik mat, fiz. 40 (1993) 1, pp 23 – 31). # Janez Strnad, ''Superprevodnost'' (''

Superconductivity Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlik ...

''), (Obzornik mat, fiz. 40 (1993) 4, pp 110 – 120). # Janez Strnad, ''Nenavadni interferenčni poskusi I. Interferenčni poskus s sevanjema v nasprotnih smereh'' (''Unusual

interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extra ...

experiments I. Interference experiment with radiations in opposite directions''), (Obzornik mat, fiz. 40 (1993) 5, pp 135 – 136). # Janez Strnad, ''Supertekočnost'' (''

Superfluidity Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two i ...

''), (Obzornik mat, fiz. 40 (1993) 6, pp 183 – 191). # Janez Strnad, ''Fizika iz Karlsruheja: O novostih v poučevanju fizike'' (''The

Karlsruhe Karlsruhe ( , , ; South Franconian German, South Franconian: ''Kallsruh'') is the List of cities in Baden-Württemberg by population, third-largest city of the German States of Germany, state (''Land'') of Baden-Württemberg after its capital o ...

physics course: On new approaches in physics teaching''), (Obzornik mat, fiz. 41 (1994) 4, pp 122 – 128). # Janez Strnad, ''Nenavadni interferenčni poskusi I. Youngov poskus z ionoma'' (''Unusual interference experiments I. Young's experiment with two

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s''), (Obzornik mat, fiz. 41 (1994) 5, pp 119 – 153). # Janez Strnad, ''Nenavadni interferenčni poskusi, Interferenčni poskus z laserjema'' (''Unusual interference experiments, Interference experiment with two

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The firs ...

s''), (Obzornik mat, fiz. 41 (1994) 6, pp 187 – 190) (PACS 42.50.-p.) # Janez Strnad, ''Premo centralno gibanje J. Vege'' ('' J. Vega's linear central

motion In physics, motion is the phenomenon in which an object changes its position with respect to time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed and frame of reference to an observer and mea ...

''), (Obzornik mat, fiz. 47 (2000) 1, pp 20 – 26). (PACS 01.65.+g, 45.40GJ) # Janez Strnad, ''Nenavadni interferenčni poskusi, Interferenčni poskus z molekulami C₆₀'' (''Unusual interference experiments, An interference experiment with C₆₀ molecules''), (Obzornik mat, fiz. 47 (2000) 2, pp 53 – 56) (PACS 33.80.-b.) # Janez Strnad, ''Precesija enakonočij'' (''The

precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In o ...

of equinoxes''), (Obzornik mat, fiz. 47 (2000) 4, pp 120 – 125). (PACS 01.65.+g) # Janez Strnad, ''Osnovne fizikalne konstante 1998'' (''Fundamental

physical constants A physical constant, sometimes 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, ...

1998''), (Obzornik mat, fiz. 47 (2000) 5, pp 177 – 179). (PACS 06.20.Jr) # Janez Strnad, ''Rubinowicz v Ljubljani'' (''Rubinowics in Ljubljana''), (Obzornik mat, fiz. 47 (2000) 6, pp 144 – 146). (PACS 01.60.+g) # Janez Strnad, ''O gravitacijski konstanti'' (''On the Newtonian gravitational constant''), (Obzornik mat, fiz. 48 (2001) 1, pp 19 – 25). (PACS 04.80.-y) # Janez Strnad, ''Med dvema ognjema?'' (''Between two fires?''), (Obzornik mat, fiz. 48 (2001) 1, pp 92 – 94). (PACS 06.20.Fn) # Janez Strnad, ''Sevalni tlak in P. N. Lebedev'' (''Radiation Pressure and P. N. Lebedev''), (Obzornik mat, fiz. 48 (2001) 1, pp 148 – 153). (PACS 01.65.+g, 45.40GJ) # Janez Strnad, ''Prožni trak kot model vesolja'' (''The elastic ribbon as a model universe''), (Obzornik mat, fiz. 49 (2002) 1, pp 21 – 27). (PACS 98.80.-k) # Janez Strnad, ''Stefanova sila'' (''Stefan's force''), (Obzornik mat, fiz. 49 (2002) 2, pp 58 – 61). (PACS 01.65.+g, 47.15.-x) # Janez Strnad, ''Interferenca elektronov na svetlobi'' (''Interference of

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary partic ...

s on

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

''), (Obzornik mat, fiz. 49 (2002) 5, pp 148 – 150). (PACS 33.80.-b) # Janez Strnad, ''Vega o obliki Zemlje'' (''Vega on the form of the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surf ...

''), (Obzornik mat, fiz. 50 (2003) 1, pp 27 - III). (PACS 01.65.+g, 45.40GJ) # Janez Strnad, ''O elektronih v atomu'' (''On electrons in atom''), (Obzornik mat, fiz. 50 (2003) 3, pp 82 – 85). (PACS 01.40.Ej) # Janez Strnad, ''Kako sem pisal učbenik za fiziko'' (''How I wrote a physics textbook''), (Obzornik mat, fiz. 50 (2003) 5, pp 157 – 160). (PACS 01.40.Gm) # Janez Strnad, ''Bose-Einsteinova kondenzacija cezija'' (''Bose-Einstein condensation of cesium''), (Obzornik mat, fiz. 50 (2003) 6, pp 184 – 191). (PACS 03.75.Fi)

Colloquiums

# Janez Strnad, ''Bose-Einsteinova kondenzacija alkalijskih atomov'' ('' Bose-Einstein's condensation of alkaline atoms''), (FMF, IJS, Ljubljana November 5, 2001). # Janez Strnad, ''Nobelova nagrada za fiziko 2000'' (''

Nobel prize for physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...

2000''), (FMF, IJS, Ljubljana November 6, 2000). # Janez Strnad, Alojz Kodre, ''Profesor Kuščer - In Memoriam'' (''In memory of professor Kuščer''), (FMF, IJS, Ljubljana February 2, 2000).

References

# Sandi Sitar (1993), ''Jožef Stefan, pesnik in fizik, Ob stoletnici smrti'' (''Jožef Stefan, the poet and the physicist, By his 100th anniversary of death''), Založba Park, Ljubljana). {{DEFAULTSORT:Strnad, Janez 1934 births 2015 deaths Scientists from Ljubljana Slovenian physicists University of Ljubljana alumni Academic staff of the University of Ljubljana Levstik Award laureates