Michael Faraday

Michael Faraday received little formal education, but went on to become one of the most influential experimental physicists of the nineteenth century. His studies of electricity and magnetism laid the foundation for the scientific understanding of the principle of electromagnetic induction as well as the relationship between chemistry and electromagnetism, also known as electrochemistry.

Basic Information

Birthdate: September 22, 1791

Birthplace: Newington Butts, Surrey, England

Married: Sarah Barnard, June 12, 1821

Died: August 25, 1867

Early Exposure to Science

As a youth, the lower-class Michael Faraday was apprenticed to a bookbinder. During the seven years of his apprenticeship, he developed a love of scientific concepts from reading books on the subject.

Starting in 1812, at the end of his apprenticeship, Faraday began attending scientific lectures, notably given by a prominent English scientist of the day, Humphry Davy (who invented the first electric lamp), though he attended lectures given by other scientists as well. Faraday took careful notes on these lectures and compiled them into a 300-page book, which was able to give to Davy. Despite the differences in their station, Davy is reputed to have responded favorably to the book. When Davy was injured in 1813, with his eyesight damaged due to a chemical accident, he hired Faraday as his assistant, and also got him a position at the Royal Society as a Chemical Assistant.

Davy traveled on a lecture tour from 1813-15, and Faraday served as both his scientific assistant and valet on the trip. This trip allowed Faraday, despite the social position he had come from and remained in, to become familiar with the greatest European scientific minds of the age and to become intimately familiar with the scientific concepts they discussed.

Major Scientific Insights

Michael Faraday was one of the most influential experimental physicists of the nineteenth century, but is most widely recognized for achievements in two fields: electrochemistry and electromagnetism.

His early work with Davy focused on chemistry, and his earliest experiments were related to simple chemical batteries. In studying chemical compounds discovered by Davy, he formulated laws governing the chemical process of electrolysis (not to be confused with the hair removal treatment), published in 1834.

Faraday also explored the concept of electromagnetism more directly. Danish physicist Hans Christian Orsted had already discovered in 1821 that electric fields induced a magnetic field, but it was Faraday’s work that is largely recognized as revealing that magnetic fields could also induce electric fields and thus more fully exploring the concept of electromagnetic induction. Faraday’s work at the time sparked some controversies related to whether or not he was properly crediting colleagues with whom he collaborated. In his later years, Faraday’s collaboration with James Clerk Maxwell provided the foundation for Maxwell’s Equations describing the key physical relationships of electromagnetism, some of which were direct reformulations of Faraday’s experimental insights.

A cage made of conductive metal mesh is today known as a Faraday cage, and has the property that any objects inside the cage are protected from electromagnetic fields or electric discharges coming from outside of the cage. The Faraday cage gets its name from an 1843 experiment conducted by Faraday, called the “ice pail experiment,” which showed that electromagnetic induction on a conductor results in an electric charge on the outer shell of the conductor.

Religious Convictions

Throughout his lifetime, Michael Faraday was a devout Christian who strongly felt that his scientific discoveries helped to illuminate a fundamental unity between God and nature. He was a member of the Sandemanian church, an offshoot of the Church of Scotland.

James Clerk Maxwell

 - Public Domain
James Clerk Maxwell – from Popular Science Monthly Volume 17, 1880.  Public Domain

James Clerk Maxwell is a Scottish theoretical physicist who is best known for formulating what became known as Maxwell’s equations, the series of equations that codifies the relationships between electricity and magnetism within electromagnetism.  

Basic Information

Birthdate: June 13, 1831

Birth location: Edinburgh, Scotland

Date of death: November 5, 1879

Early Life, Education, & Career

James Clerk Maxwell studied first at the University of Edinburgh (1847-1850) and then on the University of Cambridge (1850-1856).

He graduated from the University of Cambridge in 1854 with a degree in mathematics, but remained at the university for two additional years on a fellowship. In 1856, he obtained a professorship at Marischal College in Aberdeen, where he remained until 1860, at which point he moved on to King’s College, London. He retired from King’s College in 1965, though he remained academically active and wrote a number of books. He returned to Cambridge in 1871 as the first Cavendish Professor of Physics, where his duties included overseeing the creation of the Cavendish Laboratory (a research laboratory that, as of the time of this writing in summer 2015, has resulted in a total of 29 Nobel Prizes in Physics).

Though he is best known for his work studying electromagnetism and light, he also contributed insights into the field of thermodynamics, including a study of the kinetic theory of gases.

Developing Maxwell’s Equations

Maxwell studied intently the insights into electromagnetism developed by Michael Faraday, including his concept of lines of force.

With his more rigorous mathematical approach to the field, Maxwell was able to solidify this intuitive concept into a series of 20 equations with 20 variables, which he published in 1861. Over the following decade, he would refine his understanding, ultimately writing his Maxwell’s equations as four partial differential equations in his 1873 book A Treatise on Electricity and Magnetism. (They have been refined a bit in the years since then.)

In the course of this work, Maxwell realized that both electricity and magnetism moved at approximately the speed of light. This suggested to him that light itself was electromagnetic in nature, setting the groundwork for the concept of the electromagnetic spectrum of light. Indeed, he extensively studied the field of optics, specifically as it related to colors (and the perception of color by humans) in the visible spectrum of light.

Consequences of Maxwell’s Equations

Maxwell’s key insight was that light could be described as waves moving through space at the speed of light. This seemed to definitively establish that light behaved as a wave, confirming the explanation that most readily explained Thomas Young’s double-slit experiment. The problem with this wave explanation of light, however, was that the common understanding of waves at the time was that it required a medium to pass through (something had to “do the waving”). This led to the search for the luminiferous ether as a medium for light to travel through. A search that ultimately failed to discover the luminiferous ether.

When Albert Einstein looked at Maxwell’s equations, he realized that a key feature of them was that the light moved at the speed of light. If light indeed moved through a medium, it would move at speeds relative to the medium rather than at a single speed. He assumed that the light moved at a single fixed speed, and this became one of the core postulates of his theory of relativity.

1995 Nobel Prize In Physics

 - Fermilab
The Standard Model of Elementary Particles. 

The 1995 Nobel Prize in Physics was awarded “for pioneering contributions to lepton physics,” with the award split jointly and evenly between Martin L. Perl “for the discovery of the tau lepton” and Frederick Reines “for the detection of the neutrino.”

The Science: Leptons

Throughout the twentieth centuries, physicists discovered much about the fundamental particles that compose matter in our universe.

The electron was discovered early on (theorized in 1874 and discovered in 1897), but it took a while longer for physicists to realize that there existed heavier particles that were similar the electron. These particles are collectively called leptons.

In addition to the electron there is a heavier lepton called the muon, which has a mass about 200 times heavier than the mass of the electron. The muon was discovered by Carl Anderson in 1936, while researching cosmic rays. With this discovery, it was said that the electron (and its related electron-neutrino) were the first “family” of leptons, while the muon (and its related muon-neutrino) were the second “family” of leptons.

The third “family” of leptons was discovered in a series of experiments at the Stanford Linear Accelerator Center (SLAC) between 1974 and 1977, with the discovery of the tau lepton (sometimes called just “tau”). This research was conducted by Martin L. Perl and his colleagues, and is the reason for the awarding of this prize.

The existence of this particle helped explain charge and parity violation (see: CP symmetry) and complete the Standard Model of particle physics.

The Science: Neutrinos

Neutrinos were proposed by Wolfgang Pauli in 1930, in trying to explain radioactive decay without violating conservation laws. His approach required the creation of very light, very fast-moving particles (later dubbed neutrinos by Enrico Fermi, who added refinements to the concept).

During the 1950’s, Frederick Reines and Clyde L. Cowan, Jr., were able to experimentally demonstrate the existence of the electron’s antineutrino. This is very difficult, because of how weakly neutrinos interact with atoms (when they bother to interact at all). Their original neutrino detector used only about half of a cubic meter of water, setting the stage for modern neutrino detectors that fill vast underground chambers with thousands of cubic meters of water to detect the neutrinos from cosmic rays that bombard our planet constantly.

Martin L. Perl

Martin L. Perl was born on June 24, 1927, in New York City. His parents immigrated to the United States from Russia as children, their families fleeing the poverty and antisemitism. His father founded a printing company and worked the family into the middle class. Martin went to college for chemical engineering, with delays for participating in the war in the U.S. Merchant Marines, he completed his undergraduate study and earned his degree in 1948 from Polytechnic University in Brooklyn. (He had skipped some years in school.)

Perl went to work for the General Electric Company, ultimately working in the Electron Tube Division and living in Schenectady, New York. Though a chemical engineer, he wanted to learn how electron vacuum tubes worked, so began taking courses at Union College, where he was encouraged by a professor to take up the study of physics.

Perl entered Columbia University’s doctoral physics program in 1950, where he studied under the 1944 Nobel Prize laureate, I.I. Rabi. Perl earned his doctorate in 1955, and then went on to the University of Michigan to conduct the research involving bubble chambers and spark chambers to study the physics of strong interactions. In 1963, Perl joined the staff at Stanford University working at the Stanford Linear Accelerator Center (SLAC), where he conducted the research that led to the discovery of the tau particle.

Martin Perl died September 30, 2014, in Palo Alto, California.

Frederick Reines

Frederick Reines was born on March 16, 1918, in Paterson, NJ. Like Perl, his parents were Jewish immigrants from Russia. Reines attended college at the Stevens Institute of Technology, studying engineering for a bachelor’s degree in 1939 and then obtaining his M.S. degree in mathematical physics in 1941. He then proceeded to New York University for his doctoral work, which he completed in 1944. During this time he began working at Los Alamos on the Manhattan Project, under the direction of Richard Feynman. During his time conducting research with Clyde Cowan, and the two of them were able to discover the electron antineutrino (for which this award is given to Reines alone, as Cowan was deceased by 1995). In 1959, he left Los Alamos for a position as the Professor and Head of the Physics Department at Case Institute of Technology in Cleveland, Ohio. He then went on to the University of California, Irvine, in 1966, having a number of administrative, research, and teaching positions within the physics department.

Frederick Reines died on August 26, 1998, in Orange, California.

1994 Nobel Prize in Physics

The 1994 Nobel Prize in Physics was awarded “for pioneering contributions to the development of neutron scattering techniques for studies of condensed matter.” The award was split jointly between Bertram N. Brockhouse “for the development of neutron spectroscopy” and Clifford G. Shull “for the development of the neutron diffraction technique.”

The Science: Neutron Scattering

Creating methods for studying small objects in detail has long been an interest in science, and new advances in these technologies have helped drive the scientific endeavor forward.

Microscopes allow for the enhancement of visual light images, and these can be modified to include X-Ray techniques that magnify at a range greater than what can be seen in visible light.

The science recognized in this Nobel Prize was developed after World War II, using the nuclear reactors that were available at that time to harness the emitted neutrons and use them to study the behavior of atoms, by measuring how the neutrons deflect off of the atoms (a process called neutron scattering). This method is useful because neutrons are electrically neutral, so do not have any electromagnetic interactions with the protons or electrons of an atom. The official 1994 Nobel Prize of Physics press release has a particularly useful and concise description of this process:

When the neutrons bounce against (are scattered by) atoms in the sample being investigated, their directions change, depending on the atoms’ relative positions. This shows how the atoms are arranged in relation to each other, that is, the structure of the sample. Changes in the neutrons’ velocity, however, give information on the atoms’ movements, e.g. their individual and collective oscillations, that is their dynamics. In simple terms, Clifford G. Shull has helped answer the question of where atoms “are” and Bertram N. Brockhouse the question of what atoms “do”.

Bertram N. Brockhouse

Bertram N. Brockhouse was born on July 15, 1918, in Lethbridge, in the province of Alberta, Canada, though his family moved to Vancouver, British Columbia, in 1926 and that’s where he grew up (except for a brief stint in Chicago from 1935 to 1938). After some time in the military during World War II, Brockhouse proceeded to study Physics and Mathematics at the University of British Columbia. During this time he worked as a government scientist at the Chalk River Laboratory. He completed his PhD work in fall of 1950, and he performed the neutron scattering work that would earn him the Nobel Prize throughout the early 1950’s. Brockhouse joined the faculty of McMaster University, in Hamilton, Ontario, as a Professor of Physics in 1962.

Bertram Brockhouse died on October 13, 2003, in Hamilton, Ontario.

Clifford G. Shull

Clifford G. Shull was born on September 23, 1915, in the Glenwood section of the city of Pittsburgh, in the state of Pennsylvania, United States of America. For college, he attended the Carnegie Institute of Technology (later renamed to Carnegie Mellon University) for his undergraduate degree, then went on to graduate school at New York University in 1937. He completed his work to earn his doctorate in physics in June 1941. 

Having earned his doctorate, he proceeded to Beacon, NY, for a research laboratory job with The Texas Company. His company would not release him for work on the Manhattan Project during World War II. After the war was over, Shull and his family moved to the Clinton Laboratory in Tennessee, where he performed a great deal of neutron diffraction research along with his colleague Ernest Wollan. He left Tennessee in 1944 to join the faculty at the Massachusetts Institute of Technology (MIT), where he remained until his 1986 retirement.

Clifford Shull died on March 21, 2001, in Medford, Massachusetts.

Film Review: The Theory of Everything

Cosmologist Stephen Hawking is one of the most intriguing figures of the twentieth century, not only for his deep and impressive contributions to theoretical physics, but also for the profound personal challenges he faced in order to offer those contributions. Diagnosed with the debilitating neurological disorder amyotrophic lateral sclerosis (also called ALS or Lou Gehrig’s disease) while in graduate school, Hawking was originally diagnosed with only two years of life yet regardless went on to become on of the most successful scientists of all time.

As the film depicts things, his initial reaction was to push away the woman he was in the midst of dating, Jane Wilde, but she wouldn’t allow it. The feeling from the film is that her determination and dedication to him likely went very far toward helping him deal with the debilitating conditions of the disease, including the loss of all voluntary muscle control. However, the sacrifices she had to make to support Stephen through his extreme health problems took a heavy toll on her emotionally and ultimately the relationship could not survive the twin challenges of his disease and his fame.

Portraying the film primarily through the eyes of Jane Hawking is also a useful tool for offering the relevant physics to the viewing audience. Jane herself has a doctorate in Romance languages, so is clearly an extremely intelligent woman, but since she is not a physicist, the explanations of Stephen Hawking’s scientific work are often offered and translated through the eyes of the non-physicist. This makes many of the more abstract concepts still accessible to those without strong scientific backgrounds.

One intriguing aspect of the film is the tension between Jane Hawking’s belief in God and Stephen Hawking’s firm naturalistic, atheist stance. This comes across early in their meeting and continues throughout the film, either explicitly or as subtext.

Hawking’s own memoir, My Brief History, discusses this period of his life, but somewhat downplays the personal aspects. While his scientific work is covered with a charm and wit, the details of his family life, including the details surrounding his first divorce, are offered almost in passing. This film, however, is based on the memoir of his first wife, Jane Hawking, entitled Travelling to Infinity. (This is the 2007 edition, which is a heavily updated edition of her original 1999 book, Music to Move the Stars.) I haven’t read Jane Hawking’s book, so can’t speak to the degree to which the film remains true to her account.

The Academy Award for Best Actor went to Eddie Redmayne for his portrayal of Dr. Stephen Hawking. This was an intensely physical role, as Redmayne had to simulate the effects of the debilitating ALS condition. In a November 20, 2014, interview with The Daily Show with Jon Stewart, Eddie Redmayne discussed preparing for the role. It is certainly a well-deserved Oscar, but the portrayal of Jane Hawking by actress Felicity Jones was also equally challenging and compelling, though on an emotional rather than a physical level.


Though Hawking’s life is an amazing success story, as a love story the film is a bittersweet tragedy. It provides a little of something for everyone. For those who are already familiar with Hawking’s scientific achievements, it provides a glimpse into a personal aspect of his life that he has often been reluctant to discuss (even in his own memoir). For those who are not familiar with Hawking, it offers a deeply compelling dramatic account of his first marriage, while also providing the context in which to become exposed to his scientific insights about the nature of physics and black holes. In short, the film has a little of something for everyone.

1993 Nobel Prize in Physics

The 1993 Nobel Prize in Physics was awarded jointly to Russell A. Hulse and Joseph H. Taylor, Jr., “for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation.”

The Science: Pulsars and Gravitation

In 1974, the two winners of the 1993 Nobel Prize in Physics used the the 300 meter radiotelescope at Arecibo, Puerto Rico, to search space for pulsars.

Pulsars had been discovered in 1967 (an achievement recognized with the 1974 Nobel Prize in Physics, in fact), but Taylor and his research student Hulse discovered something new: a pair of binary pulsars.

Binary stars are a pair of stars that orbit around each other. This binary system of pulsars allowed for a study of the behavior of gravitation between them, which greatly advanced physicists’ understanding of the general theory of relativity developed by Albert Einstein. Specifically, these systems seem to indicate a loss of energy which is consistent with the gravity waves predicted by Einstein’s theory. This is partly because the “pulse period” between sweeps of the pulsar’s beacon of light is incredibly stable, seeming to increase by no more than 5% during 1 million years (assuming the time we’ve been looking at it is representative, of course). In essence, this means that this binary pulsar can be used as a very precise cosmological clock.

It is important to recognize that this observed loss of energy is only an indirect indication of the existence of gravity waves, and hardly a smoking gun that confirms the existence of gravity waves.

Scientists continue to search for them today with experiments such as the Laser Interferometer Gravitational-Wave Observatory (LIGO), consisting of 4-kilometer-long detectors located in Hanford, Washington, and Livingston, Louisiana.

Russell A. Hulse

Russell A. Hulse was born on November 28, 1950, in New York City. He attended the Bronx High School of Science and then attended Cooper Union for his undergraduate degree, which he earned in 1970. He proceeded to the University of Massachusetts in Amherst for his doctorate, completed in 1975. It was while working on his thesis that he conducted the radio astronomy research that resulted in this Nobel Prize.

The National Radio Astronomy Observatory in Charlottesville, Virginia, provided post-doctoral work from 1975 to 1977. He began work at the Princeton University Plasma Physics Laboratory (PPPL) in 1977, where he remained for many years. In 2003, Hulse became Founding Director of the University of Texas at Dallas Science and Engineering Education Center (SEEC). 

Joseph H. Taylor Jr.

Joseph H. Taylor Jr. was born on March 29, 1941, in the city of Philadelphia in the state of Pennsylvania, United States. Taylor attended Haverford College (which he describes as a “Quaker institution” in his own biography) before going on for graduate studies in physics at Harvard University. Following his graduate work, he proceeded to positions at the University of Massachusetts (where he worked with Hulse on the research that earned him the Nobel Prize) and then ultimately he, too, went on to work at Princeton University in 1980. At Princeton University, Taylor was the James S. McDonnell Distinguished Professor in Physics. He retired in 2006.

1992 Nobel Prize in Physics

The 1992 Nobel Prize in Physics was awarded to Georges Charpak “for his invention and development of particle detectors, in particular the multiware proportion chamber.”

The Science: Particle Detectors

As physics progressed to more refined level of experimental analysis, particle accelerators and the detectors connected to them needed to look for ever more rare particle interactions, and the particles that resulted from them.

Early bubble chamber detectors could be photographed and analyzed to identify the properties of the elementary particles that resulted from particle interactions. This often required a careful accounting of every single resulting particle trajectory. As the energy level increased within these accelerators, the resulting particle collisions created more and more particles, and it became impractical (if not impossible) for physicists to analyze film visually to identify each resulting particle trajectory.

Charpak’s work in developing the multiwire proportional chamber was focused on the idea of connecting the detector directly to a computer, allowing for the direct computational analysis of the data by the machine, rather than through visual analysis by physicists. This used modern advanced electronics to upgrade the previous design known as the proportional counter. Charpak’s innovative design reduced the scale of precision from approximately a centimeter to less than a millimeter.

This advance in particle detector technology, published in 1968, was utilized in a variety of new detector advancements, resulting in a variety of discoveries …

many of which had been recognized with Nobel Prize awards in the years preceding and following this reward for the detector design itself.

Georges Charpak

Georges Charpak was born on August 1, 1924, in Dabrovica, Poland. Charpak’s family relocated to Paris when he was 7 years old. During World War II, Charpak served in the resistance and ultimately ended up relocated to a Nazi concentration camp.

After being liberated from the camp in 1945, he returned to his academic studies. He attended a mining school, the Ecoles des Mines, in Paris, earning a bachelor’s in science degree in Mining Engineering. He then went on to the College de France, culminating in a Ph.D. in experimental physics in 1954. His thesis was on the subject of low-level radiation from the disintegration of nuclei. From 1948 through 1959, he worked with the French governmental research organization the Centre Nationale de la Recherche Scientifique (NCRS) while working on his doctorate. He also got married in 1953 to Dominique Vidal.

He went on to join the staff at CERN in 1959, working there until his retirement in 1991. It was during this time that he completed the bulk of his research, including the design of the multiwire proportional chamber, and improvements on the design to include spherical drift chambers, multistage avalanche chambers, and photon counters.

Dr. Georges Charpak died on September 29, 2010, in Paris, France.

1991 Nobel Prize in Physics

The 1991 Nobel Prize in Physics was awarded to Pierre-Gilles de Gennes “for discovering that methods developed for studying order phenomena in simple systems can be generalized to more complex forms of matter, in particular to liquid crystals and polymers.”

The Science: Order in Matter

The physical structure of molecules and molecule chains within physical matter can have consequences on the macroscopic properties of the object, such as during the phase transition of an object from one state of matter to another.

In addition to the state of the matter, other properties can be determined from the physical structure of the atoms, such as by the orientation of the magnetic dipoles created by the atoms.

One of the most obvious examples of this phenomena is in a traditional iron bar magnet. The individual iron atoms each have a magnetic field from their magnetic dipole, and the atoms are physically structured within the magnet so that they are oriented in the same direction. This produces the net magnetic field from the bar magnet. When the iron magnet is heated, however, this ordered structure of the iron atoms degenerates, with the atoms transitioning into a disordered state with each of the individual atoms randomly oriented … and, as a consequence, there is no net magnetic field produced by the piece of metal. (See: How Magnets Work) For magnets, the temperature of this phase transition is known as the Curie temperature.

The physical structure of molecules of various phenomena are complex enough that many physicists had studied them but been unable to determine general rules governing their transition from ordered to disordered states.

French physicist Pierre-Gilles de Gennes, however, determined the mathematical relationships governing these sorts of transitions. Instead of needing a unique approach to each of these sorts of transition, Pierre-Gilles de Gennes showed that the same mathematical principles were applicable as a broad generalization for these transitions. Some examples include:

  • Liquid crystals
  • Transition to superconducting states
  • Geometric arrangement and movement in polymer chains
  • Stability conditions in micro-emulsions

The Science: Liquid Crystals

Liquid crystals had been known about for more than a century. (See images of liquid crystals here, here, and here.) Professor Wilhelm Oseen had begun studying how such crystals flowed as early as the 1920s, but it would take decades for them to come into practical use in electronics such as wristwatches and calculators (and even more decades before they would find use in liquid crystal display, or LCD, screens).

Dr. de Gennes formed a research group to focus on liquid crystal research in the late 1960s, including a combination of theorists and experimenters within the team. This group, led by de Gennes, was able to explain light scattering from liquid crystals and how the liquid crystals transitioned in response to a weak alternating electric field. His 1974 book The Physics of Liquid Crystals helped to define the field.

Pierre-Gilles de Gennes

Pierre-Gilles de Gennes was born in Paris, France, on October 24, 1932. He graduated from the Ecole Normale in 1955, then went on to work with the Atomic Energy Center from 1955 to 1959 (earning his PhD along the way in 1957). After some time at Berkeley and then in the French Navy, he went on to become an assistant professor in Orsay. He started a research group on superconductors initially, but then in 1968 switched his research emphasis to liquid crystals … the beginning of the work for which he is largely recognized with this award.

In 1971, de Gennes became a professor at the College de France in Paris and participated in the STRASACOL research group on polymer physics, where he continued his work in identifying mathematical descriptions of the physical structure of matter.

From 1976 to 2002, de Gennes was director of the Ecole de Physique et Chimie, in Paris, which focused on the education of research engineers in the fields of physics, chemistry, and (later) biology. He proceeded to study a number of unusual physical states of matter, such as gels, porous materials, and other “soft systems,” including a study of the “dynamics of wetting” and the physical chemistry of adhesion. Following the receipt of the Nobel Prize, de Gennes used it as an opportunity to speak to over 200 high schools from 1992 through 1994 on the subject of science, innovation, and common sense, ultimately writing a book (in French) on the subject.

He spent the last years of his life doing interdisciplinary research at the Institut Curie in Paris, which emphasizes cancer research. His work was focused on cellular adhesion and brain function. Dr. Pierre-Gilles de Gennes died on May 18, 2007, in Orsay, France.

Brownian Motion

Brownian motion is the seemingly random motion undergone by particles suspended in a liquid or gas. The name comes from the fact that it was observed by Scottish botanist Robert Brown in 1827. While observing pollen grains in water under a microscope, Brown observed the motion of the particle through the liquid. For decades, the cause of the motion was unknown.

The phenomenon is also called pedesis, from the Greek for “leaping.” Indeed, the phenomena was observed in ancient Greece by the philosopher Lucretius, who used it as support of his notion of atomism.

In 1905, Albert Einstein published an explanation of Brownian motion, using the statistical methods related to diffusion that he had developed within his doctoral dissertation. His proposal was that Brownian motion was explained if you viewed the liquid as a collection of moving and vibrating particles. These particles collided with the visible particle, causing the change in movement. 

The kinetic theory of gases was already well established, but most scientists of the day viewed the particles used for that statistical analysis as mathematical tools rather than as real objects. Einstein’s paper on Brownian motion was more difficult to interpret in that way. It took as an assumption that water was physically composed of particles, or molecules. The success of Einstein’s explanation in this regard helped to solidify the idea that liquids (and, indeed, everything else) was made of smaller particles. Like the earlier thinking of Lucretius, this seemed to be evidence for the modern concepts of atoms and molecules and other fundamental particles, particularly based on subsequent work by Jean Perrin (for which Perrin received the 1926 Nobel Prize in Physics).

The statistical methods applied in interpreting the random Brownian motion is useful in other areas that exhibit the “drunkard’s walk,” as it is called, such as trends within the stock market.

SLAC Linear Accelerator Center

The SLAC Linear Accelerator Center is one of the most prominent particle accelerators in the United States of America. It is a key research facility in the field of particle physics, with research from throughout the latter half of the twentieth century that has been recognized multiple times with awards such as the Nobel Prize in Physics.

SLAC is a high-energy linear accelerator, meaning that it is built in a straight line, as opposed to the circular rings used in many particle accelerators, including Fermilab and the Large Hadron Collider.

This linear accelerator is housed in a two-mile-long building, which is the third-longest building in the world and the longest building in America. (And by that, I include both North and South America, not merely the United States of America. The two longer buildings are the Great Wall in China and Pakistan’ Ranikot Fort.)

SLAC was built in 1962 at Stanford University, on ground leased to the United States Department of Energy. At the time it was built, the facility accelerated only electrons, but it was eventually upgraded to also include positrons. Various updates to the apparatus have been performed over the years, including the additions of particle accelerator rings which use the initial linear accelerator as a booster stage before sending the accelerated particles for collisions into the rings.

Origins of SLAC’s Name

The acronym SLAC originally stood for Stanford Linear Accelerator Center. In 2008, this was officially changed by the Department of Energy to “SLAC Linear Accelerator Center.” (Plausibly, as suggested by Sean Carroll, “Stanford didn’t want the Department of Energy to trademark an acronym containing their name.”)

Research at SLAC

In the 1970’s, a joint research effort by physicists from Stanford University and the Massachusetts Institute of Technology (MIT) used the electron beam from SLAC to explore the internal physical structure of the proton. This research resulted in the first direct experimental evidence that confirmed the theory that the proton itself was composed of smaller particles. The theory that protons were composite particles containing more fundamental components, called quarks, was already in circulation, but this evidence helped to advance the conviction among physicists that this theory was a correct model of particles. In addition to confirming the existence of the quarks, this also provided hints at another substance within the protons … the mysterious “glue” that held the quarks together, and ultimately came to be recognized as the gluon. This research resulted in the 1990 Nobel Prize in Physics for Jerome Friedman and Henry Kendall of MIT and Richard Taylor of SLAC.

In 1974, Burton Richter of SLAC announced a discovery of the J/psi particle, consisting of a charm quark paired with an anti-charm quark. This was independently discovered at nearly the same time by Samuel Chao Chung Ting of Brookhaven National Laboratory, and the two experimental physicists shared the 1976 Nobel Prize in Physics for the joint discovery.

SLAC physicist Martin L. Perl discovered the tau lepton in 1975, ultimately resulting in the 1995 Nobel Prize in Physics.

Since the 1970’s, SLAC’s scientific mission has gone from its initial role focused on exploration of particle physics to include research in cosmology, environmental science, biology, chemistry, materials science, and alternative energy research. Physicists from SLAC collaborate with scientists at facilities around the world, and a vast array of scientific disciplines utilize the various experimental apparatuses at SLAC to conduct their research.