April 21 is Percy W. Bridgman’s birthday. Bridgman was an American physicist known for his work in high-pressure physics.
Bridgman began his career studying the effects of high pressure on matter as a professor at Harvard. During a repair of his equipment, he came up with an idea to improve the seal around the sample area. His idea proved to be a good one since it greatly improved the efficiency of the device. His press could compress his samples on the order of 10 Gigapascals (≈ 1.5 million PSI).
These pressures opened a whole new avenue of research. He cataloged physical properties like compressibility, thermal conductivity, tensile strength and viscosity of over 100 different compounds. He also discovered when a current passes through a crystal and encounters a different crystal orientation, heat is produced. This effect is known as the Bridgman effect. This discovery and the invention of his press earned him the 1946 Nobel Prize in Physics.
General Electric became interested in his work and hired him as a consultant in their synthetic diamond project. The recipe for diamonds is heat and pressure, and Bridgman had the pressure. Their initial attempts proved to be insufficient and no diamonds were produced. Eventually, they invited another young physicist to the project named Tracy Hall. Hall completely redesigned Bridgman’s press and increased the pressure limits enough to produce the first synthetic diamond on December 16, 1954. Their diamonds were tiny and hardly jewelry quality, but they were great for industrial abrasives. GE got the patent and made a lot of money. Hall was rewarded with a bonus of a $10 savings bond for his contribution to the project.
Bridgman continued his research until he contracted metastatic bone cancer. As his condition deteriorated, he decided to end his life on his own terms. He died from a self-inflicted gunshot and part of his note read “It isn’t decent for society to make a man do this thing himself. Probably this is the last day I will be able to do it myself.” His case is often cited in discussions of assisted suicide.
Notable Science History Events for April 21
1965 – Edward Victor Appleton died.
Appleton was a British physicist who investigated the physics of the upper atmosphere or ionosphere. He found radio signals are reflected off a boundary in the atmosphere and interfere with the same signal traveling along the ground. This reflective layer is called the Appleton layer and was important in the development of radar. This work would earn him the 1947 Nobel Prize in Physics.
1889 – Paul Karrer was born.
Karrer was a Swiss chemist who was awarded half the 1937 Nobel Prize in Chemistry for his research into carotenoids, flavins, and vitamins A and B2. Carotenoids are the organic pigments in plants. His investigations were into beta-carotene, the precursor to vitamin A. Flavins are organic compound sources of riboflavin or vitamin B2.
1882 – Percy Williams Bridgman was born.
1849 – Oskar Hertwig was born.
Hertwig was a German biologist who was the first to determine the fusion of the nuclei of sperm and ovum cells was the beginning point of fertilization. He was investigating the transmission of hereditary information between cells when he made the discovery.
Hertwig is also known for Hertwig’s Rule or the ‘long axis rule’ of cell division. He noted cells divide along their longest axis instead of randomly.
1843 – Walther Flemming was born.
Fleming was a German biologist who founded the study of cytogenetics or the study of the cell’s chromosomes. He was the first to describe the behavior of chromosomes during cell division. He called this process ‘mitosis’ after the Greek word for “thread” which describes the appearance of chromosomes under a microscope.
1838 – John Muir was born.
Muir was a Scottish-American naturalist who is considered the founder of the environmental movement. He actively sought to preserve the Yosemite Valley and Sequoia National Park and formed the Sierra Club, the largest environmental organization in the United States.
Minor Trivia: He appears on the California state quarter released in 2005.
1774 – Jean-Baptiste Biot was born.
Biot was a French physicist whose early works included the relationship between current and magnetism which became to be known as the Biot-Savart law.
He also was the first to determine that mica polarizes light.