April 15 in Physics History
Physics history will help you to develop a better understanding of the physics world!
birthdays & deaths
Explore all birthdays & deaths of physicists occurred on this day with their short biography!
physics Events
Know all important discoveries made by physicists & events happened on this day with complete information!
April 15 in Physics History - Births – Physicists born on April 15
Samuel K. Hoffman (15 Apr 1902 - 26 Jun 1995)
Samuel Kurtz Hoffman was an American engineer who led the development of the liquid-fuel rocket engines used in America’s early space programs. His career began as an aeronautical design engineer (1932-45) and then he spent 4 years teaching in that field. By 1949, he joined the Propulsion Section of North American Aviation which he later headed as its president (1960-70). (That division, renamed Rocketdyne, later became part of Rockwell International Corp.) He supervised the development of the first-stage Redstone propulsion system, which launched Explorer I, America’s first satellite (31 Jan 1958). His work continued with the high-thrust engines used for the Mercury rockets that propelled the first U.S. astronauts into space, and the F-1 rocket engines used in the first stage of the Saturn V rockets of the Apollo moonshot program.
Robert L. Mills (15 Apr 1927 - 27 Oct 1999)
American physicist who shared the 1980 Rumford Premium Prize with his colleague Chen Ning Yang for their “development of a generalized gauge invariant field theory” in 1954. They proposed a tensor equation for what is now called Yang-Mills fields. Their mathematical work was aimed at understanding the strong interaction holding together nucleons in atomic nuclei. They constructed a more generalized view of electromagnetism, thus Maxwell’s Equations can be derived as a special case from their tensor equation. Quantum Yang-Mills theory is now the foundation of most elementary particle theory, and its predictions have been tested at many experimental laboratories.
Johannes Stark (15 Apr 1874 - 21 Jun 1957)
German physicist who won the 1919 Nobel Prize for Physics for his discovery in 1913 that an electric field would cause splitting of the lines in the spectrum of light emitted by a luminous substance; the phenomenon is called the Stark effect.
Emory Leon Chaffee (15 Apr 1885 - 8 Mar 1975)
He was an American physicist who in his Ph.D. thesis research, invented the “Chaffee Gap” spark type method to produce continuous high-frequency electrical oscillations for radio transmission. The spark gap was between the end faces of metal rods in an atmosphere of moist hydrogen in a sealed chamber. The rods were cooled by external radiating fins. He also specialized in the field of thermionic vacuum tubes and test measurements. Later, he worked with William T. Bovie on the electrical response of the retina, which he amplified with a vacuum tube circuit.
Friedrich Georg Wilhelm von Struve (15 Apr 1793 -23 Nov 1864)
German-Russian astronomer, one of the greatest 19th-century astronomers and the first in a line of four generations of distinguished astronomers. He founded the modern study of binary (double) stars. In 1817, he became director of the Dorpat Observatory, which he equipped with a 9.5-inch (24-cm) refractor that he used in a massive survey of binary stars from the north celestial pole to 15°S. He measured 3112 binaries—discovering well over 2000—and cataloged his results in Stellarum Duplicium Mensurae Micrometricae(1837). In 1835, Czar Nicholas I persuaded Struve to set up a new observatory at Pulkovo, near St. Petersburg. There in 1840 Struve became, with Friedrich Bessel and Thomas Henderson, one of the first astronomers to detect parallax. Astronomer Otto Struve was his great-grandson.
Leonhard Euler (15 Apr 1707 - 18 Sep 1783)
Leonhard Paul Euler was a Swiss mathematician and physicist, one of the founders of pure mathematics. He not only made decisive and formative contributions to the subjects of geometry, calculus, mechanics, and number theory but also developed methods for solving problems in observational astronomy and demonstrated useful applications of mathematics in technology. At age 28, he blinded one eye by staring at the sun while working to invent a new way of measuring time.
April 15 in Physics History - Deaths – Physicists died on April 15
Christopher Hansteen (26 Sep 1784 - 15 Apr 1873)
Norwegian astronomer and physicist who is noted for his research in geomagnetism. In 1701, Edmond Halley had already published a map of magnetic declinations, and the subject was studied by Humboldt, de Borda, and Gay-Lussac, among others. Hansteen collected available data and also mounted an expedition to Siberia, where he took many measurements for an atlas of magnetic strength and declination.
John Houghton (30 Dec 1931 - 15 Apr 2020)
Welsh meteorologist who began in the late 1960s drawing attention to the buildup of carbon dioxide in the earth’s atmosphere and its result of global warming, now known as the greenhouse effect. As director-general (1983) of the British Meteorological Office, he began tracking changing climate patterns. In 1990, he co-chaired a team of scientists working for the United Nations that produced the first comprehensive report on the science of climate change. This led to the 1997 U.N. Conference on Climate Change, in Kyoto, Japan. The Kyoto Protocol that resulted there was a treaty among industrialized and developed nations to combat global warming by voluntarily adhering to progressively stiffening emissions-reduction standards.
April 15 in Physics History - Events – Physics Events of April 15
Isaac Newton's Apple
In 1726, writer William Stukeley held a conversation with Isaac Newton in Kensington during which Newton recalled: “when formerly, the notion of gravitation came into his mind.” Later, Stukeley writing in his Memoirs of Sir Isaac Newton’s Life, recorded that Newton said, “It was occasioned by the fall of an apple, as he sat in a contemplative mood. Why should that apple always descend perpendicularly to the ground, thought he to himself. Why should it not go sideways or upwards, but constantly to the earth’s center.”
Balmer series
In 1895, a mathematical relationship between the frequencies of the hydrogen light spectrum was reported by a Swiss school teacher, Johann Balmer, in Annalen der Physik. Its significance was overlooked until Niels Bohr realized this showed a structure of energy levels of the electron in the hydrogen atom.
