Charles Townes was the experimental physicist who invented the laser – now indispensable in science, technology, and medicine. Townes received the 1964 Nobel Prize in Physics for his work. More than a dozen subsequent Nobel Prizes have depended on the existence of lasers.
If you’re reading this on the internet, it’s likely the words you’re reading were encoded in a laser beam traveling through a fiber optic cable for most of the journey from our server to your screen.
Later in his career, Townes established that the Milky Way has a supermassive black hole at its center.
A profoundly religious man, he was awarded the Templeton Prize in 2005.
Beginnings
Charles Hard Townes was born into a prosperous family on July 28, 1915 in Greenville, South Carolina, USA. His father, Henry Townes, was a lawyer and newspaper editor. His mother, Ellen Hard, was a college graduate. Charles had two brothers and three sisters, and the family lived on a 20-acre farm.
Charles’s father was an enthusiastic amateur biologist. He passed his interest in the natural world to his children. Charles’s older brother Henry became an entomologist – a biologist specializing in insects.
All the children did chores on the farm and were fairly self-sufficient. Charles’s favorite fiction books had self-sufficiency themes: The Swiss Family Robinson, and Two Little Savages.
Education
Both parents encouraged their children to work hard at school. In the evenings, they would check the youngsters’ homework. Their home was filled with reference books and encyclopedias to help the children find any information they needed.
From an early age, with his love of nature, Charles decided to learn about science.
He was educated in Greenville’s public schools. He went as far as possible at Greenville High School, finishing eleventh grade at age 15.
He spent the following four years at Furman University, Greenville’s small Baptist university. He joined the Furman swimming team, became a writer for the college newspaper, and was curator of Furman’s natural history museum. He graduated Summa cum laude (with highest honor) in 1931, age 19, with a Bachelor of Science degree in Physics and a Bachelor of Arts degree in Modern Languages.
Leaving home for the first time, Townes spent the following year at Duke University in Durham, North Carolina. He graduated with a Master’s degree in Physics.
In 1936, age 21, he headed west to study for a Ph.D. at the California Institute of Technology. He got his doctorate in 1939 with a dissertation entitled: Concentration of the heavy isotope of carbon and measurement of its nuclear spin.
Inventing the Maser/Laser
Townes with the world’s first maser at Columbia University. Image from Radio-Electronic Engineering Magazine.
In the spring of 1952, while seated on a park bench between meetings in Washington D.C., Townes had a scientific revelation. His scribbles on the back of an envelope recorded the birth of the maser concept – microwave amplification by stimulated emission of radiation.
With colleagues at Columbia he built the world’s first maser in 1953. It began operating in 1954.
Ignoring the Experts
The working maser astonished the founder of quantum mechanics, Niels Bohr, and the Nobel Laureate physicist Isador Rabi, who was Townes’s boss at Columbia. Both had told Townes his idea would never work. Rabi actually requested Townes end his maser research program, but Townes, convinced he was right, had pressed on with it.
The maser found instant use in astronomy, where it was utilized to determine the surface temperature of Venus.
Townes then wondered if he could take the maser concept further to develop a way of amplifying visible light to create a laser – light amplification by stimulated emission of radiation. After all, light and microwaves were both part of the electromagnetic spectrum and were governed by the same scientific laws.
He and his brother-in-law Arthur Schawlow described how a laser could work in their paper Infrared and Optical Masers in December 1958’s Physical Review. They also patented the concept. Their paper enabled Ted Maiman to build the first operating laser device in 1960.
“Maiman’s laser had several aspects not considered in our theoretical paper…”
Townes received the 1964 Nobel Prize in Physics “for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle.” He was awarded half of the prize. Nicolay Basov and Aleksandr Prokhorov, who independently carried out similar work to Townes, were each awarded quarter of the prize.
The Science of the Maser & Laser – Rough Guide
You’ve most likely heated food in a microwave oven. These ovens work because microwaves can penetrate into the middle of food, carrying the energy needed to cook it quickly and evenly. Each individual microwave photon gives its energy to a water molecule in the food, which makes the molecule rotate. Rotating molecules pass their energy to other molecules, raising the food’s temperature.
The reverse principle also works: rotating molecules have excess energy and, under the right circumstances, they can lose this energy by emitting microwaves.
The maser concept says that molecules can be stimulated to release their excess energy of rotation as microwave radiation.
- In a sample of gas molecules, some have excess energy of rotation. These high energy molecules are said to be excited.
- The excited molecules can be separated from non-excited molecules, using, for example, a nonuniform electric field.
- The excited gas molecules can be sent to a resonant cavity.
- The resonant cavity could be a metal box with dimensions chosen to allow input microwaves to resonate back and forth repeatedly so they are not lost from the box. When an input microwave hits an excited gas molecule two things happen. The molecule re-emits the input microwave and is also stimulated to lose its own excess energy by emitting a further microwave identical in energy and frequency to the input microwave. The result is a chain reaction producing many more microwaves than originally entered the cavity.
- All the microwaves produced by a maser have identical energy/wavelengths.
- In a laser, which involves visible light rather than microwaves, and therefore higher energies, the photons of light emitted by the laser all have the same wavelength, so the light is monochromatic – a single color. This is unlike familiar white light, which is a jumble of all the colors of the rainbow.
- Lasers can amplify light into very powerful beams carrying enough energy to, for example, cut through metal.
Lasers emit monochromatic light. Image by Pang Kakit.
Discovery of the Milky Way’s Supermassive Black Hole
In 1967, Townes became a professor at the University of California, Berkeley. He stayed at Berkeley for the rest of his career.
In 1971, Sir Martin Rees and Donald Lynden-Bell theorized that a very massive black hole lies at the center of the Milky Way. In 1974, Rees went further, saying that “a black hole might lurk in the centers of most normal galaxies.”
In 1976, Townes and his team at Berkeley published infrared observations of the Milky Way’s center in Astrophysical Journal. They calculated that a stupendous mass – as much as 4 million of our suns – was present at the center of the galaxy.
By 1980, they found that the mass was pointlike. In other words, there was an object with enormous mass and no volume at the center of our galaxy, suggesting it was a black hole. Later work by the team and other astronomers confirmed the existence of a supermassive black hole, whose estimated mass, at 4.1 million solar masses, is little changed from Townes’s original estimate.
Hubble Space Telescope observations later established that all spiral galaxies have a supermassive black hole at their centers. It may be that spiral galaxies can only develop around supermassive black holes.
“I sometimes say that most of my successes have come out of failures. A failure makes you try to do something else.”
Townes and Religion
Townes was born into a rather devout Baptist family. His religion was very important to him throughout his life.
In 2005, he was awarded the $1.5 million Templeton Prize for Progress Toward Research or Discoveries about Spiritual Realities.
He donated half the money to Furman University and half to church charities. He wrote:
“I myself have always thought that science and religion are not unrelated, and should be honestly and openly interacting.”
In fact, his religious views were sometimes unpopular with other scientists.
“…when I was a graduate student at the California Institute of Technology, even my professor who was directing my research jumped on me for being religiously oriented.”
Some Personal Details and the End
Matterhorn
At the age of 40, a lover of the great outdoors, Townes climbed the infamous Matterhorn on the border between Switzerland and Italy. He took the challenge seriously, first climbing some smaller mountains in Austria to prepare himself for the big one.
He officially retired from his Berkeley professorship in 1986, age 71, but actually continued working there until a year before his death.
Charles Townes died at age 99 on January 27, 2015 in Oakland, California. He was survived by his wife and four daughters.
Author of this page: The Doc
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Further Reading
Spectral and spatial resolution of the 12.8 micron NE II emission from the galactic center
E. R. Wollman, T. R. Geballe, J. H. Lacy, C. H. Townes, D. M. Rank
Astrophysical Journal, vol. 205, Lett. L5-L9, Apr. 1, 1976, pt. 2
Observations of the motion and distribution of the ionized gas in the central parsec of the Galaxy. II
J. H. Lacy, C. H. Townes, T. R. Geballe, D. J. Hollenbach
Astrophysical Journal, vol. 241, pp. 132-146, Oct. 1, 1980, pt. 1
Mass distribution in the galactic centre
M. K. Crawford, R. Genzel, A. I. Harris, D. T. Jaffe, J. H. Lacy*, J. B. Lugten, E. Serabyn & C. H. Townes
Nature, vol. 315, no. 6019, pp. 467-470, 6 June 1985
Genius Talk
Denis Brian
Plenum Press, New York, 1995
How the Laser Happened: Adventures of a Scientist
Charles H. Townes
OUP USA, 1 Jul 1999
Creative Commons
The laser beams image courtesy of Pang Kakit under the Creative Commons Attribution-Share Alike 3.0 Unported license.