March 17 marks the passing of Austrian physicist Christian Doppler, best known for the Doppler effect.
Doppler wrote in a paper titled “On the Colored Light of Double Stars and Certain Other Stars of the Heavens” an explanation for the apparent color change of the frequencies of light from stars. He explained how the change in frequency was due to the relative motion of the source and the observer.
The easiest demonstration of the Doppler effect uses sound waves. When a noise approaches a stationary observer, the pitch of the sound (the frequency) increases. As the source passes, the pitch decreases as it speeds away from the observer. This effect applies to all forms of waves, including light. Stars are all made up of mostly hydrogen and spectral analysis shows this to be true, but the spectral lines are moved uniformly towards the red end of the spectrum or lower frequencies. This suggests the stars are moving away from our solar system and is part of the evidence that the universe is expanding.
Notable Science History Events for March 17
1983 – Haldan Keffer Hartline died.
Harline was an American physiologist who shares the 1967 Nobel Prize in Medicine with George Wald and Ragnar Granit for their research into the neurological mechanics of vision. He investigated the electrical activity of the retinas of mollusks and arthropods. He found the photoreceptor cells are linked and suppress signals by their neighbors so they can work together and refine the contrast and clarity of the image.
1958 – NASA launches Vanguard 1 satellite.
NASA launched the Vanguard 1 satellite into orbit. Vanguard 1 was the second US satellite and first solar-powered satellite.
It has the distinction of being the oldest man-made object in space along with the upper stage of the rocket which brought Vanguard to its orbit. It still orbits the Earth, although communications were lost in 1964. Vanguard’s expected orbit lifetime is 240 years when it will re-enter the atmosphere in 2198.
The 16.5 cm sphere was dubbed the “grapefruit satellite” by the Soviet Premier, Nikita Khrushchev.
1956 – Irène Joliot-Curie died.
Joliot-Curie was a French chemist who shared the 1935 Nobel Prize in Chemistry for the synthesis of new radioactive isotopes with her husband Frédéric. They bombarded stable atoms with alpha particles to transmute them into different radioactive elements. They created nitrogen from boron, phosphorus from aluminum and silicon from magnesium.
She was the daughter of Marie and Pierre Curie.
1950 – Californium discovery announced.
Scientists at the California Radiation Laboratory in Berkeley announced the discovery of element 98. They had produced the first atoms of element 98 by accelerating alpha particles into a sample of curium-242. They named their new element californium after the state of California.
1881 – Walter Rudolf Hess was born.
Credit: Nobel Foundation
Hess was a Swiss physiologist who was awarded half the 1949 Nobel Prize in Medicine. He identified the parts of the brain that controlled internal organs.
Hess used a technique of electrical stimulation to conduct a repeating signal directly into areas of the brain. He found different parts of the brain, when stimulated, produced emotional responses as well as physical responses. He managed to cause hunger, thirst, slow respiration, lower blood pressure, urination, and defecation.
1853 – Christian Andreas Doppler died.
1846 – Friedrich Wilhelm Bessel died.
Bessel was a German astronomer and mathematician who is credited as the first to determine the distance to a star using parallax of the Earth’s orbit. Parallax is measured by charting the position of a star at two different times, half a year apart. The difference in the angle and the diameter of the Earth’s orbit gives a measure of the distance to the star.
He also charted the positions of over 50,000 starts during his tenure as director of the Königsberg Observatory.
1803 – Carl Jacob Löwig was born.
Löwig was a German chemist who discovered bromine independently of Antoine Balard. He made his discovery while adding chlorine and ether to spring water and found a red colored substance. While he investigated this substance, Balard published his discovery which had similar properties to Löwig’s substance.
1782 – Daniel Bernoulli died.
Daniel Bernoulli was one of the famous Bernoulli family of mathematicians and the Bernoulli of fluid mechanics fame. He showed a fluid’s pressure per area is a constant and directly proportional to the velocity and density of the fluid. He also made contributions to the mathematics of mechanics and statistics.
1771 – Chester Moor Hall died.
Hall was an English mathematician who developed the achromatic lens. Glass lenses would refract light by different amounts for different color light, resulting in blurry images in the telescope. The achromatic lens would correct the color distortion problem and greatly improve telescopes.
1741 – William Withering was born.
Withering was an English physician who discovered digitalis from foxglove and its use as a treatment for heart conditions.
He identified digitalis as the active ingredient from an herbal remedy given to people with “cardiac dropsy” or congestive heart failure. He conducted several studies to identify the toxicity and effects of digitalis.