Geertruida Luberta "Berta" de Haas-Lorentz (20 November 1885 – 1973) was a Dutch
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 cau ...
and a professor at the
Technical University of Delft
The Delft University of Technology (TU Delft; ) is the oldest and largest Dutch public technical university, located in Delft, Netherlands. It specializes in engineering, technology, computing, design, and natural sciences.
It is considered one o ...
. She was the first to theoretically study
thermal fluctuations
In statistical mechanics, thermal fluctuations are random deviations of an atomic system from its average state, that occur in a system at equilibrium.In statistical mechanics they are often simply referred to as fluctuations. All thermal fluctu ...
in
electric circuit
An electrical network is an interconnection of electrical components (e.g., battery (electricity), batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e. ...
s, treating
electrons
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
as
Brownian particles. Consequently she is considered one of the pioneers of
electrical noise
In electronics, noise is an unwanted disturbance in an electrical signal.
Noise generated by electronic devices varies greatly as it is produced by several different effects.
In particular, noise is inherent in physics and central to therm ...
theory. She was the daughter and doctoral student of
Hendrik Lorentz
Hendrik Antoon Lorentz ( ; ; 18 July 1853 – 4 February 1928) was a Dutch theoretical physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for their discovery and theoretical explanation of the Zeeman effect. He derive ...
. She went by the name Berta, or Ber.
Life
Berta Lorentz was born in Leiden, Netherlands, the eldest daughter of the physicist and 1902
Nobel Prize in Physics
The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
winner
Hendrik Lorentz
Hendrik Antoon Lorentz ( ; ; 18 July 1853 – 4 February 1928) was a Dutch theoretical physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for their discovery and theoretical explanation of the Zeeman effect. He derive ...
and . Berta was the eldest of four children. Her siblings were Johanna Wilhelmina (born 1889), Gerrit (born 1893, died 1894), and Rudolf (born 1895). At that time of her birth, her father was Professor of Theoretical Physics at the
University of Leiden
Leiden University (abbreviated as ''LEI''; ) is a public research university in Leiden, Netherlands. Established in 1575 by William, Prince of Orange as a Protestant institution, it holds the distinction of being the oldest university in the Neth ...
.
Her mother, Aletta Kaiser, took care of the children and household, did charity work, and was heavily involved with the local women's suffrage movement.
On 22 December 1910, Berta Lorentz married
Wander Johannes de Haas
Wander Johannes de Haas (2 March 1878 – 26 April 1960) was a Dutch physicist and mathematician. He is best known for the Shubnikov–de Haas effect, the De Haas–Van Alphen effect and the Einstein–de Haas effect.
Personal life
Wander de Ha ...
, who would become professor of experimental physics in Leiden, and they went on to have two sons and two daughters. Some of their children changed their last name to "Lorentz de Haas."
She studied physics at the
University of Leiden
Leiden University (abbreviated as ''LEI''; ) is a public research university in Leiden, Netherlands. Established in 1575 by William, Prince of Orange as a Protestant institution, it holds the distinction of being the oldest university in the Neth ...
with her father as dissertation advisor and earned her doctor's degree in 1912 on a thesis entitled "On the theory of
Brownian motion
Brownian motion is the random motion of particles suspended in a medium (a liquid or a gas). The traditional mathematical formulation of Brownian motion is that of the Wiener process, which is often called Brownian motion, even in mathematical ...
and related phenomena" ().
After defending her doctoral dissertation in Leiden, De Haas-Lorentz taught physics at the
Technical University of Delft
The Delft University of Technology (TU Delft; ) is the oldest and largest Dutch public technical university, located in Delft, Netherlands. It specializes in engineering, technology, computing, design, and natural sciences.
It is considered one o ...
and translated some of her father's works into German.
She also wrote a biography of her father.
Berta de Haas-Lorentz died on 2 January 1973 in Leiden.
Research
De Haas-Lorentz was one the first to apply
Albert Einstein
Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
's theory of
Brownian motion
Brownian motion is the random motion of particles suspended in a medium (a liquid or a gas). The traditional mathematical formulation of Brownian motion is that of the Wiener process, which is often called Brownian motion, even in mathematical ...
to other domains.
During her thesis work, she was the first to carry out a theoretical analysis of thermal fluctuation of electrons in electrical circuits, predating the experimental discovery of the
Johnson–Nyquist noise
Johnson–Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the voltage or current noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happe ...
. She considered that a circuit with resistance ''R'' and inductance ''L'' should store an energy , where ''I'' is the current. If there was a fluctuating thermal current, by the
equipartition theorem
In classical physics, classical statistical mechanics, the equipartition theorem relates the temperature of a system to its average energy, energies. The equipartition theorem is also known as the law of equipartition, equipartition of energy, ...
the energy would be related to the thermal energy
''kT'' where ''k'' is the
Boltzmann constant
The Boltzmann constant ( or ) is the proportionality factor that relates the average relative thermal energy of particles in a ideal gas, gas with the thermodynamic temperature of the gas. It occurs in the definitions of the kelvin (K) and the ...
and ''T'' is the temperature. De Haas-Lorentz obtained,
:
,
where the angle brackets denote the thermal average.
She was also the first to propose thermal fluctuations limit the detection of
electromagnetic radiation
In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength ...
.
In collaboration with her husband, the De Haas couple showed that experiments carried by
James Clerk Maxwell
James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish physicist and mathematician who was responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism an ...
failed to prove the hypothesis of
André-Marie Ampère
André-Marie Ampère (, ; ; 20 January 177510 June 1836) was a French physicist and mathematician who was one of the founders of the science of classical electromagnetism, which he referred to as ''electrodynamics''. He is also the inventor of ...
, that magnetism in matter is caused by microscopic
current loop
In electrical signalling an analog current loop is used where a device must be monitored or controlled remotely over a pair of conductors. Only one current level can be present at any time.
A major application of current loops is the industry ...
s.

She also predicted the
London penetration depth
In superconductors, the London penetration depth (usually denoted as \lambda or \lambda_L) characterizes the distance to which a magnetic field penetrates into a superconductor and becomes equal to e^ times that of the magnetic field at the surface ...
for
superconductivity
Superconductivity is a set of physical properties observed in superconductors: materials where Electrical resistance and conductance, electrical resistance vanishes and Magnetic field, magnetic fields are expelled from the material. Unlike an ord ...
in 1925, before the development of the
London equations
The London equations, developed by brothers Fritz and Heinz London in 1935, are constitutive relations for a superconductor relating its superconducting current to electromagnetic fields in and around it. Whereas Ohm's law is the simplest con ...
in 1935.
Selected works
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* contributing author
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Notes
References
*
External links
Ph.D. students of H.A. Lorentz: 1881-1921Photo of De Haas-Lorentz*
{{DEFAULTSORT:Haas Lorentz, Geertruida Luberta De
1885 births
1973 deaths
20th-century Dutch physicists
Dutch women physicists
Leiden University alumni
Scientists from Leiden
20th-century Dutch women scientists
20th-century women physicists