Through the centuries, physics has had thousands of heroes — people who furthered the field in some way or another. In this chapter, you take a look at ten physics heroes who’ve done their bits to make physics what it is today. And just because age has its privileges, these are arranged in chronological order by birth date.
Galileo Galilei (1564–1642) was an Italian physicist, mathematician, astronomer, and philosopher. He was an important person in the Scientific Revolution — at various times, people called him the father of modern observational astronomy, the father of modern physics, and even the father of science. He was the first to employ a pendulum as a timekeeping device, and he laid the groundwork for both Newton’s three laws of motion and Einstein’s theories of relativity. He also studied the motion of objects undergoing constant acceleration.
Galilei is perhaps best known for his improvements to the telescopes and the consequent observations he was able to make. Among his other achievements were the confirmation of the phases of Venus, the discovery of the four largest satellites of Jupiter (now named the Galilean moons), and the observation and analysis of sunspots.
Famously, Galilei supported the heliocentric view of the solar system, which says the planets orbit around the sun, not Earth. That was a tough stance to take in 1610, and he got into trouble for it with the Catholic Church, which in 1616 declared it “false and contrary to Scripture.” In 1632, he was tried by the Roman Inquisition, found guilty of heresy, and forced to recant. He spent the rest of his life under house arrest. Modern physicists can be glad that kind of thing doesn’t go on much anymore.
Like many early physicists, Robert Hooke (1635–1703) had his finger in many pies — he was a scientist, architect, investor, and so on. He’s best known for his law of elasticity, Hooke’s law, which says that the restoring force on an object undergoing an elastic pull is proportional to the displacement of the object and a constant, often called the spring constant.
Hooke experimented in many different fields, however — in fact, he was the first person to use the term cell to refer to the basic unit of life. Originally very poor, he grew quite wealthy through his investments. He was very active after the Great Fire of London, surveying the ruins in organized maps. He was also a well-known architect, and buildings he designed still survive in England.
Sir Isaac Newton
Sir Isaac Newton (1643–1726) was an exceptional genius. He was an English physicist, mathematician, astronomer, natural philosopher, and theologian. His accomplishments include the following:
Laying the groundwork for most of classical mechanics
Formulating the law of universal gravitation
Formulating the three laws of motion
Building the first practical reflecting telescope
Developing a theory of color based on prisms
Discovering an empirical law of cooling
Studying the speed of sound
Sharing the credit with Gottfried Leibniz for the development of differential and integral calculus
Demonstrating the generalized binomial theorem, an ancient mathematical problem of the expansion of the sum of two terms into a series
Developing Newton’s method for approximating the roots of a function
Adding to the study of power series
Newton greatly influenced three centuries of physicists. In 2005, the members of Britain’s Royal Society were asked who had the bigger effect on the history of science and made the greater contribution to humankind — Sir Isaac Newton or Albert Einstein. The Royal Society chose Newton.
Benjamin Franklin (1706–1790) is familiar to most people as one of the Founding Fathers of the United States. He was an author, printer, political theorist, politician, postmaster, scientist, inventor, statesman, and diplomat. He invented the following:
The lightning rod
The Franklin stove
A carriage odometer
The glass “armonica” (a popular musical instrument of the day)
The first public lending library in America
Franklin even created the first fire department in Pennsylvania. He was also a leading newspaperman and printer in Philadelphia (the major city of the colonies at that time). He became wealthy publishing Poor Richard’s Almanack and The Pennsylvania Gazette. He played a large role in the creation of the University of Pennsylvania and was elected the first president of the American Philosophical Society. He became a national hero when he headed the effort to have Parliament repeal the unpopular Stamp Act.
As a scientist, Franklin is famous for his work with electricity. The idea that lightning is electricity may seem pretty clear today, but in Franklin’s day, the largest manmade sparks were only an inch or so long. No one knows whether he really performed his most famous experiment — tying a key to a kite string and flying it during a thunderstorm to see whether it could draw sparks from the key, indicating that lightning was electricity. However, Franklin did write about how someone could carry out such an experiment, saying that flying the kite before the storm actually started would be important, or else you’d risk getting electrocuted.
Charles-Augustin de Coulomb
Charles-Augustin de Coulomb (1736–1806) is best known for developing Coulomb’s law, which defines the electrostatic force of attraction or repulsion between charges. In fact, the MKS unit of charge, the coulomb (C), was named after him.
Coulomb originally came to prominence with his long-titled work Recherches théoriques et expérimentales sur la force de torsion et sur l’élasticité des fils de métal (“Theoretical and experimental research on the force of torsion and the elasticity of metal wire”).
Throughout his life, Coulomb conducted research in many fields, but his work in electrostatics was what brought him true fame. He showed that electrostatic attraction and repulsion varied inversely as the square of the distance between the charges. There was still a lot of work to be done, though — Coulomb thought electric “fluids” were responsible for the charges.
Amedeo Avogadro (1776–1856) is best known for Avogadro’s number, approximately 6.022 × 1023 — the number of molecules contained within a mole. He started practicing as a lawyer after getting his doctorate. In 1800, he started studying mathematics and physics and became so interested (who wouldn’t be?) that he turned to it as his new career.
Avogadro was a pioneer of physics on the microscopic level with Avogadro’s hypothesis, which says that “equal volumes of all gases under the same conditions of temperature contain the same number of molecules.” Unfortunately, acceptance of the hypothesis was slow because of opposition from other scientists and a general confusion between molecules and atoms.
Fifty years later in the Karlsruhe Congress, Stanislao Cannizzaro was able to get general agreement on Avogadro’s hypothesis. When Johann Josef Loschmidt calculated Avogadro’s number for the first time in 1865, Loschmidt happily called it Loschmidt’s number. But the general scientific community, in deference to the guy who first suggested that such a number existed, renamed it Avogadro’s number.
Nicolas Léonard Sadi Carnot
Nicolas Léonard Sadi Carnot (1796–1832) was a French physicist and military engineer. In 1824, he published his work Reflections on the Motive Power of Fire, which gave the theoretical description of heat engines, now called the Carnot cycle. That work laid the theoretical foundations for the second law of thermodynamics.
Some people call Carnot the father of thermodynamics because he came up with concepts such as Carnot efficiency, the Carnot theorem, the Carnot heat engine, and others.
William Thomson (Lord Kelvin)
William Thomson (1824–1907) did important work in analyzing electricity mathematically and formulating the first and second laws of thermodynamics. Like many physicists of his day, he had many interests, starting off as an electric telegraph engineer and inventor, which made him famous — and rich. With enough money to do what he wanted, Thomson turned to physics, naturally.
Physicists remember Thomson for developing the absolute zero scale of temperature, which bears his name to this day — the Kelvin scale. Already a knight, he became a nobleman in recognition of his achievements in thermodynamics. He’s also almost as well known for his work on developing a maritime compass as on the laws of thermodynamics. Queen Victoria knighted him as Lord Kelvin for his work on the transatlantic telegraph.
Perhaps the most well-known physicist in the popular mind is Albert Einstein (1879–1955). Einstein, whose name has become synonymous with genius, made many contributions to physics, including the following:
The special and general theories of relativity
The founding of relativistic cosmology
The explanation of the perihelion precession of Mercury, which is the gradual rotation of the axis of the elliptical orbit of the planet
The prediction of the deflection of light by gravity (gravitational lensing)
The first fluctuation dissipation theorem, which explained the Brownian motion of molecules, which is the random jittery motion of small particles suspended in a fluid, which is caused by collisions with the molecules of the fluid
The photon theory
The quantum theory of atomic motion in solids
Einstein was the scientist who, on the eve of World War II, alerted President Franklin D. Roosevelt that Germany could be creating an atomic bomb. As a result of that warning, Roosevelt created the top-secret Manhattan Project, which led to the development of the atomic bomb.
In 1921, Einstein won the big one, the Nobel Prize, “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect.”
Einstein was affected by that absent-mindedness that scientists who habitually spend all their time thinking about their studies can suffer from. He’s said to have painted his front door red so he could tell which house was his. People joke that he once asked a child, “Little girl, do you know where I live?” And the little girl answered, “Yes, Daddy. I’ll take you home.”
Amalie Emmy Noether
Amalie Emmy Noether (1882–1935) was a German mathematician and physicist. She was certified to teach English and French but decided to study mathematics. She became interested in physics when the famous mathematicians David Hilbert and Felix Klein asked for her help in understanding Albert Einstein’s theory of general relativity.
Noether’s most important contribution to physics was Noether’s theorem, which says that for every (continuous) symmetry, there’s an associated conserved quantity. Noether’s theorem reveals surprising relationships between seemingly unrelated concepts, like time and energy. Because you’ll get the same result if you do your favorite physics experiment today, tomorrow, or 97 years from now, Noether’s theorem says that energy is conserved.