5. James Watt
Few researchers affected modern engineering as profoundly as James Watt. A chemist and inventor, Watt pioneered the use of steam power. He perfected and patented his first condenser in 1769, and within the decade, the first practical Watt steam-driven engines were pumping water out of English mines. Later steam engines found use in agriculture and finally aboard ships and locomotives. Studies of the net efficiency of Watt’s engines not only proved to be the catalyst for the Industrial Revolution, but led to insight by James Maxwell and others into that most central of ideas in physics; the Laws of Thermodynamics. The unit of power known as a watt, which can be defined as a rate of energy conversion equal to one joule per second, is named in his honor. Watt also led development of several other mechanical concepts we’re familiar with today, including the concept of horsepower and multi-cylinder engines.
4. Alessandro Volta
Born in Como, Italy in 1745, Count Alessandro Volta became fascinated with the study of static electricity and the chemistry of gases, particularly methane marsh gas. Electricity was considered to be a novelty at the time, and very crude experiments were conducted across Europe to study its animating effects as a motive force for life. Volta’s study led to the first ideas of charge and capacitance, and he constructed the first modern battery, complete with zinc/copper electrodes submerged in a brine mixture electrolyte. Anyone who has made a “lemon battery” in high school chemistry class has constructed a voltaic pile similar to Volta’s. The term “volt” as a unit of electromotive force and such terms as “photovoltaic” bear his name.
3. Daniel Gabriel Fahrenheit
Three scales of measurement for temperature are in widespread use, all bearing the names of their developers; the Kelvin scale, the Celsius scale, and the Fahrenheit scale proposed in 1724 by physicist Daniel Gabriel Fahrenheit. Fahrenheit invented alcohol- and mercury-based thermometers, which were an improvement on the water-filled Galileo-style thermometers of the day. Fahrenheit based his scale on three fixed points easily available to him; 0 degrees he based on a mixture of water, ice, and ammonium chloride salts at thermal equilibrium; the freezing point of water was assigned to 32 degrees. Finally, normal body temperature was stated to be 96 degrees, slightly lower than the 98.6 degrees Fahrenheit we’re familiar with today. This is because the Fahrenheit scale was later refined by a fourth fixed point of 212 degrees for the boiling point of water at sea level, making an even 180 degrees from freezing to boiling. This system found widespread adoption in English-speaking countries right up until the 1960s; the United States and Belize remain the only Fahrenheit holdouts.
2. Christian Doppler
All of us are inadvertently familiar with the physics first codified by Christian Doppler every time we note the rising and falling pitch of a passing siren. First proposed in 1842 while the Austrian physicist was based in Prague, the Doppler effect simply states that a wave changes in frequency as the generating source moves relative to a stationary observer. This phenomenon holds true for any wave propagation, namely sound. Although Doppler first erroneously evoked the effect that now bears his name to explain the color of certain double stars, the shift later found an astronomical application in the field of cosmology in the 20th century to explain redshift and the expansion of the universe. Doppler’s studies were the first inkling that something strange was at the heart of the nature of light.
Doppler’s theory helped set the foundation for the development of both radar and sonar. Most people today are familiar with Doppler’s name through the use of Doppler radar by meteorologists. The Doppler effect has also been used to develop GPS and military applications.
1. Isaac Newton
Sir Isaac Newton may well have been the most influential mind of a millennium. Concepts of calculus, theories of light, and ideas about physical motion all bear the mark of his fertile mind. Today, his famous three laws of motion are a bulwark of classical physics, and stood unchallenged until Einstein demonstrated in the 20th century that Newtonian physics was in need of a modification under extreme circumstances. When NASA sends a probe on a distant mission, Newton’s laws tell us that it will arrive where and when it is supposed to be. Less well known are Newton’s dabblings in biblical numerology or his flirtations in alchemy, which may have led to arsenic and mercury poisoning that caused his ultimate mental decline.
Newton’s design for a reflecting telescope, known as a Newtonian reflector, still bears his name. A Newtonian is simply a reflecting telescope with a parabolic primary mirror that focuses light up to a secondary mirror that then directs light to an eyepiece. These are simple to construct and allow for telescopes of a large aperture to be built. The SI unit of force known as a newton also bears Newton’s name.