Rosalind Franklin

Today we recognize Rosalind Franklin as a significant woman in the history of physics because of her pioneering work in the area of X-ray diffraction. She is well-known for being the first person to produce a clear diffraction image of DNA, but she is slightly less well-known for her imaging of the tobacco mosaic virus and the micro-crystal structure of coal. Some might argue that her contributions make her a woman in the history of biology, which I do not deny. However, we learn how to do X-ray diffraction in solid state physics and her mentor and supervisor W. Lawrence Bragg won his Nobel Prize in the field of Physics for this technique. Her methods are the methods of physics although she applied them to biological structures. 

Regarding DNA, Franklin made a significant discovery, that DNA takes two crystal forms, one for the wet orientation and another for the dry. It is the wet DNA that appears in the famous Photograph 51 on which James Watson and Francis Crick based their molecular model of DNA (without her permission) and later won their Nobel Prize. Having particular knowledge of Franklin’s unpublished work, the famous pair Watson and Crick was able to take more credit than they deserved for what appeared to be scientific intuition. In 1962, Watson, Crick, and Maurice Wilkins (Franklin’s team member) received the Nobel Prize in Physiology or Medicine. Franklin deserved the Nobel Prize for her work. Franklin certainly should have been the third person on the Nobel Prize Award; however, she had passed away four years earlier. 

Many of the women on our list of significant women in the history of physics worked in Modern Physics concepts that are difficult to grasp (for high school students). However, Rosalind Franklin represents a good example of a woman physicist who you can easily discuss her achievements in her classroom. Her work on diffraction is something that high school students can understand, because diffraction of light is easy to demonstrate in your classroom and most people can understand the idea that since X-rays have much smaller wavelengths, they will make diffraction images of much smaller objects. I have produced a video on this topic—see below:

Female students in particular are interested in the applications and the usefulness of the ideas we learn in physics. To image the genetic blueprint of life is certainly a useful application of both X-rays and diffraction. When we understand the structure of a molecule or a virus, we have taken the most important step to understanding and curing diseases that affect human life.  

What Was the Experiment Like?

Franklin and her lab assistant collected a small quantity of DNA and set it in the path of an X-ray beam. The beam was created by accelerating electrons through a high voltage and having them slam into a copper plate. This produced a nearly “monochromatic” beam of X-rays.  After passing through the DNA, the X-ray beam was split or diffracted into fringes upon a photographic plate. The center of this plate was obstructed by a small piece of lead to block out the large amount of X-rays that would pass right through the DNA. This enabled the diffracted rays to show up with greater contrast. 

X-ray diffraction photo of DNA: Photograph 51
Photo credit: 

http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/cells/dnarev3.shtml

The best photograph she took was Photograph 51. Clearly visible in this photograph: the blank spot in the middle (the lead shield) and three diffraction spots on each leg of the X. These spots tell us how tightly wound the DNA helix is and the missing spot indicates the thickness of the DNA helix. Just by looking at this picture, Watson and Crick were able to inform their model of DNA with the appropriate scale and pitch (twistiness). They would not have been able to build such a model without this most important clue provided by Rosalind Franklin.

Biographies about Rosalind Franklin

The impact of biographies about Rosalind Franklin is powerful; they affect how we remember her and the importance of her work. New York Times reporter Robert McG. Thomas, Jr., wrote about the influence of the first definitive biography of Frank, entitled Rosalind Franklin and DNA, written by Anne Sayre and first published in 1975. The article noted: “Until Mrs. Sayre's book was published by Norton in 1975, Rosalind Franklin had been little more than a footnote to the history of the discovery of the double helix, the form taken by deoxyribonucleic acid, the stuff of heredity.” The biography also touched on the perceptions and struggles of women in science: “Mrs. Sayre's book has been widely cited in feminist circles for helping to expose rampant sexism in science.” 

Rosalind Franklin and DNA

By Anne Sayre

Rosalind Franklin: The Dark Lady of DNA

By Brenda Maddox

Links and Resources Consulted

“How Rosalind Franklin Discovered the Helical Structureof DNA: Experiments in Diffraction” by Gregory Braun, Dennis Tierney, and Heidrun Schmitzer. The Physics Teacher. Vol. 49, March 2011 DOI: 10.1119/1.3555496

NOVA Film: The Secret of Photo 51  http://www.pbs.org/wgbh/nova/photo51/

DNA Learning Center: http://www.dnalc.org/view/16439-Biography-19-Rosalind-Elsie-Franklin-1920-1958-.html

Nobel Prize website: http://www.nobelprize.org/

Thomas, Robert McG. (1998) “Anne Sayre, 74, Whose Book Credited a DNA Scientist, Dies” New York Times. Published March 18, 1998. Retrieved from http://www.nytimes.com/1998/03/18/nyregion/anne-sayre-74-whose-book-credited-a-dna-scientist-dies.html. 29 January 2015.

Energy Stick

One of my videos was posted in Arbor Scientific's CoolStuff Newsletter. You can learn about fun and engaging activities to perform with the Energy Stick.

Read the article here

Emmy Noether's 133rd Birthday Featured on Google

 Today Google featured physicist Emmy Noether on the homepage!

https://www.google.com/doodles/emmy-noethers-133rd-birthday

Read our blog about Emmy Noether, one of the top women in physics that we selected.

http://lincolnphysics.blogspot.com/2014/03/emmy-noether-mathematician-theorist.html

Marie Curie: Notable Nobel Prize Winner and Contributor to Women in Physics

 Marie Curie: 

Notable Nobel Prize Winner 

and Contributor to Women in Physics

You may think you already know all there is to know about Marie Curie, but we hope this article detailing why she made our list of important women physicists will shed new light on her contributions to the fields of chemistry and physics.

The Nobel Prizes

Did you know that Marie Curie was the first woman to win a Nobel Prize and the only woman to win the prize in two different fields of science? She won the Nobel Prize in Physics (1903) and the Nobel Prize in Chemistry (1911). While others have won two Nobel prizes, no one else, man or woman, has won the prize in both physics and chemistry. The Nobel Prize in Physics in 1903  was shared with Pierre Curie and Henri Becquerel and awarded for their work on radioactivity. Her Nobel Prize in Chemistry in 1911 was awarded to Marie Curie alone, for her discovery of radium and polonium and the isolation of radium and study of this element’s intriguing properties.

Long-Lasting Impact on Women in Physics

Marie Curie’s accomplishments were unprecedented in the history of science, but her contributions to women in the field of physics reaches further than admiration for her Nobel Prizes. Curie is notable for starting the Curie Institutes (one located in Paris and one in Warsaw), also known as the Radium Institutes, funded by the Curie Foundation.

Curie travelled to the United States in search of funding for her research, and she successfully funded the Warsaw Branch of the Radium Institute in 1929; later she appointed her sister, Bronya, as director of the Warsaw institute.  In the following decades, the Curie Foundation became an important player in the treatment of cancer. In a 1900 research paper, Pierre and Marie were the first to suggest and research the use of radiation therapy to treat cancer.

“It may be easily understood how deeply I appreciated the privilege of realizing that our discovery had become a benefit to mankind, not only through its great scientific importance, but also by its power of efficient action against human suffering and terrible disease. This was indeed a splendid reward for our years of hard toil.” –from Autobiographical Notes, pp. 199-200, quoted on this website 

 The institutes focused on research in physical chemistry and the majority of employees were women physicists. Curie’s daughter Irene became a researcher there, and later went on to win the Nobel Prize in 1935 (jointly with her husband, Frederic Joliot, a chemical engineer) for their work on artificial radioactivity and the synthesis of new radioactive elements.

Irene Joliot-Curie and husband Frederic

 Another colleague, Marguerite Perey, who was employed by Madame Curie, discovered the element Francium.

Women at Work in the Curie Lab: Sonia Cotelle and Marguerite Perey

More Discoveries

Marie and Pierre, commons.wikimedia.org 

Curie also discovered uranium, which was extracted from a black ore called “pitchblende.” She even influences the way we talk about radioactivity. She invented the terms “radioactive” and “isotope.” Later, Pierre and Marie would apply their work with radioactivity to the treatment of cancerous tumors. There is a myth that Marie was an assistant to Pierre in his work, however, that is not true; Pierre was working on crystals at a time when Marie’s work appeared more promising, and so he joined her in her research. The element “curium” is named after Pierre and Marie Curie and radioactivity is measured in “curies.”

Pierre Curie is known for some discoveries in his own right, as well, including the Curie Effect—when you heat a piece of metal and it loses its magnetism. He is also known for Piezo electricity—when you put pressure on a crystal, it generates a voltage. Not every crystal does this, but this is still used today, like in ultrasonic speakers.

Education and Early Influences

Marie Curie as a Child:

 image credit http://www.fromquarkstoquasars.com/wp-content/uploads/2013/03/marie-curie-as-a-child.jpg

  

Marie Curie was born Maria Sklodowska in Warsaw, Poland in 1867. Both of her parents were teachers and her father taught her some science. She attended local schools and later, in 1891, she moved to Paris to study math and physics at the Sorbonne. She earned her Doctor of Science degree in 1903, and when her husband Pierre passed away, she became the first woman to hold the position of Professor of General Physics in the Faculty of Sciences.  

The Importance of Encouraging Parents, Teachers, Mentors, and Colleagues

It is worth mentioning that many of the women physicists in our series had parents who strongly supported their daughters' educations. Without this early and ongoing parental support (all the more important in time periods and societies that were not encouraging toward educating women), these young women would not have achieved their later, great accomplishments. 

Teachers, mentors, and supportive colleagues are also very important, as much now as in the past. In the case of Maria Goeppert-Mayer, a teacher, like Max Born encouraged her interest in physics and colleague Enrico Fermi supported her research. For Marie Curie, her colleague was her husband, Pierre Curie, who put some of his research aside to support her promising work. 

Later, Marie used her success to support other women in physics through raising funding and hiring women to work in her research institutes. These women proved that her investments were worthwhile as they went on to discover an element or win a Nobel Prize. 

If you are a teacher, think of yourself as a mentor and encourage a young woman to pursue physics. If you have a colleague or acquaintance who is trying to make her way as a woman in physics, think about how you can be a more supportive colleague. 

Marie Curie with daughters Eve and Irene

Read the rest of our series about top ten important women in physics:

1. Maria Goeppert-Mayer
2. Lise Meitner
3. Emmy Noether
4. Sally Ride
5. C.S. Wu

New Physics Teacher Workshop on Electricity and Magnetism

This Saturday, January 17, SCAAPT held the New Physics Teacher Workshop (NPTW) at Santa Monica College.

The science building (below)

The topic for today was Electricity and Magnetism for New Teachers, with a focus on hands-on demos and labs. Teachers received handouts about everything from circuits to magnetostatics.

Teachers received one of our best "goodie bags" ever. Leiden Jars, powerful magnets, and more (see photo above).

Participants received many free lab and demo materials, as well as helpful handouts. Breakfast and lunch were provided as well. If you want to attend our next workshop, join our email list by writing to LincolnPhysics at gmail dot com. It is likely that the workshop will be scheduled in April or May.

Special thanks to Xump for once again donating bags for the workshop!

Maria Goeppert Mayer: Nobel Prize Winner, 1963

Maria Goeppert Mayer won a Nobel Prize in Nuclear Physics in 1963. She developed the nuclear shell model of atomic nuclei. She is an important woman in physics for her model of perseverance and her research discoveries. Even during times when universities would not employ her as a professor or physicist, she continued to learn, conduct research, write textbooks, pursue physics, and persevere, until she met more enlightened colleagues to collaborate on her research.

Early Life and Education

Mayer came from a family of academics. For several generations back, her relatives were professors. She was born in Germany and spent much of her life in Gottingen. At the time, this was a prime location for a person interested in physics. Her father was employed by the university and her parents ensured that she could pursue her education, even when the local school for girls was closed. After graduating from high school, she attended university (starting in 1924) intending to study mathematics, but physics sparked her interest. Mayer was a mathematics student until she attended the physics seminars given by Max Born. In an interview she recalls the seminars: "It was very nice, because usually after the seminars we’d go for a walk with Born — the whole seminar — anyone who wanted to come along, and go somewhere in the hills and have a rustic supper in one of the village inns.” Later, she changed her major to physics.

This was a time when the place to be for studying physics was Germany, and she was near the center of cutting edge ideas in nuclear physics and quantum mechanics.  While at University, she spent a term in Cambridge, England, where she learned English—this would serve her well later, when she immigrated to the United States. In 1930, she earned her Ph.D. in theoretical physics.

During her time at university in Gottingen, she was mentored by other Nobel Laureates, including James Franck and Adolf Windaus.

Her Career

During the Great Depression, Mayer immigrated to America with her husband, chemist Joseph E. Mayer, who became a professor at Johns Hopkins University. James Franck was also at JHU at the time. During this time, the university would not consider employing her. Mayer gave birth to a son and a daughter during their time in Baltimore. However, later her husband transferred to Columbia University and she worked at Sarah Lawrence College as a professor and researcher; her work there focused on the separation of isotopes of uranium with Harold Urey, a Nobel Prize winner in Chemistry. Through her interests and colleagues, she became a “chemical physicist” and worked on the study of the color of organic molecules.

Her career really took off when she moved to Chicago with her husband in 1946. There, she was tmore accepted (although she was still not paid and employed as a full professor) and became a professor of physics and researcher at the Institute for Nuclear Studies. She had a lot to learn about Nuclear Physics, but supportive and stimulating colleagues like Enrico Fermi worked with her. 

Fermi and Mayer 

(image credit

http://www.aps.org/units/fhp/newsletters/spring2010/images/goeppert-mayer.jpg)

Nobel-Worthy Discoveries

In 1948, Mayer began to work with the study of magic numbers; over the next several years, she developed an explanation and began to understand the ramifications of her ideas. Meanwhile, other scientists, Wigner and Jensen, were working on these ideas as well and arrived at similar conclusions as Mayer.

 They decided to write a book together and were later awarded the Nobel Prize jointly. Mayer and Jensen officially shared half the prize for their “discoveries concerning nuclear shell structure.”

Women in Physics

When she won the Nobel Prize, a local newspaper in San Diego ran the following headline “S.D. Mother Wins Nobel Prize.” At the time, she was a paid professor of physics at the University of California in San Diego/La Jolla. However, it is interesting (and perhaps representative of the times and the very real professional and social obstacles she had to overcome to be taken seriously as a professional physicist) that the newspaper characterized her as a mother and not a physicist in the headline.

Our previous selection of an important woman in physics, C.S. Wu, was not honored with the Nobel Prize with her colleagues in 1957. The fact that Mayer was honored for her work in 1963, only a few years later, was definitely a step in the right direction for the progress of women in science.

Resources

Read more about Mayer here 

Read the official Nobel Prize biography, which was consulted for this blog, here 

Download a PDF of the Nobel Lecture 

Read an interview with Mayer at the American Institute of Physics website.

10 Cool Demos with a Liquid Crystal Sheet

Testing out three different light sources for their heat output. 

The sheet is more convincing than a typical thermometer

Have you ever wanted to watch ten cool demos performed using a Liquid Crystal Sheet (also known as a heat sensitive sheet)? 

One of my videos is featured in the Arbor Scientific CoolStuff Newsletter. You can sign up for the newsletter here. Read my article here.