Images: from brochure distributed at 1939 Golden Gate International Exposition.
“…in the past it has been impossible to detect certain kinds of imperfection by external appearance alone. Frost damage and granulations in oranges…leave no indications on the surface…”
“This X-ray inspection unit permits the operator to look right through the fruit instead of at its surface only.”
Excerpts from the brochure.
Images: front and detail of 1939 postmark on postcard.
Learn about the Mt. Wilson Observatory at https://www.mtwilson.edu/about-mwo/ .
See some “found film” photos taken on Mt. Wilson in 1939: http://www.foundfilmsociety.com/dt_gallery/mt-wilson-1939/ .
“In 1939, the National Academy of Sciences awarded a grant to the Suicide Squad, a group of three students experimenting with rockets at Caltech, now more formally known as the GALCIT (Guggenheim Aeronautical Laboratory at the California Institute of Technology) Rocket Research Project.
“It came just in time.
“Until then, the group, comprised of Frank Malina, Jack Parsons, and Ed Forman, had no way to fund the rockets they were working on, and was on the verge of disbanding. That first award, $1,000, rescued the group, bringing them back together.”
Excerpt from https://www.theatlantic.com/science/archive/2016/06/the-women-behind-the-jet-propulsion-laboratory/482847/ . Click on the link to learn more, especially about the essential role of the human computers making the mathematical calculations.
An important factor in this award was Frank Jewett (below).
Learn more about Frank Jewett and the National Academy of Sciences at https://www.nap.edu/read/579/chapter/14#383 . Throop Institute later became CalTech (California Institute of Technology).
NASA image via https://commons.wikimedia.org/wiki/File:SE1939Apr19A.png .
On April 19, 1939 there was a partial eclipse of the sun that could be seen in southern California but it wasn’t much. Learn more at http://www.eclipsewise.com/solar/SEprime/1901-2000/SE1939Apr19Aprime.html . The area of totality was in Alaska and the North Pole as shown in the image above.
If one were on the moon and there was an eclipse of the sun by the earth, it might look like this illustration appearing in a 1939 issue of National Geographic magazine.
Image: Albert Einstein and Leó Szilárd from
“The Einstein–Szilárd letter was a letter written by Leó Szilárd and signed by Albert Einstein that was sent to the United States President Franklin D. Roosevelt on August 2, 1939. Written by Szilárd in consultation with fellow Hungarian physicists Edward Teller and Eugene Wigner, the letter warned that Germany might develop atomic bombs and suggested that the United States should start its own nuclear program. It prompted action by Roosevelt, which eventually resulted in the Manhattan Project developing the first atomic bombs.”
Excerpt from https://en.wikipedia.org/wiki/Einstein%E2%80%93Szil%C3%A1rd_letter .
Read the letter here: http://www.atomicheritage.org/key-documents/einstein-szilard-letter .