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DID YOU KNOW, July 2023

July 10th - Dr. Cohen, Dr. Anderle, & the Pear-Shaped Earth

Over 73 years ago Dr. Charles Cohen and Dr. Richard Anderle confirmed that the gravity field around the Earth was pear-shaped as shown in the picture. The gravity bulges and wells were confirmed, but understanding what caused them continued to be studied. Scientists think they have discovered what causes the 300-foot gravity well near India. The article states "... they found the hole was likely shaped by plumes of low-density magma." ( The legacy of the work performed at Dahlgren years ago continues to influence the research of today.

Come to the museum to see the featured exhibit model built in the early '60s by these early Dahlgren Pioneers that shows the effects of the gravity hole on mean sea level, and learn the incredible story of the life and times of Dr. Charles Cohen.

July 17th - Captain Parsons, Dr. Ramsey, & A Piece of the Manhattan Project

A new movie will open later this week about theoretical physicist J. Robert Oppenheimer, a man who led a team that created a weapon that would change the world. Did you know that, as part of the Manhattan Project, bits and pieces of the work were assigned to various people who knew that they were working on something important but were not told the overall scope

of the work? As one piece of that work, in 1943 Captain William S. “Deak” Parsons and Dr. Norman Ramsey first tested the ballistic qualities of the Thin Man gun assembly atomic bomb design at Dahlgren using scale, sewer-pipe-shaped models dropped from 20,000 feet.


Captain William S. Parsons, USN, in 1945 as a technical member of the atomic bomb project at an advanced base. (Naval History and Heritage Command)

July 24th - Manhattan Project Pieces: Barometric Fuses & RF Proximity Initiators

As we mentioned last week, during 1943, Naval Proving Ground Dahlgren was the site for testing the ballistic qualities of the “Thin Man” plutonium atomic bomb. It was also a site for small scale testing of barometric fuses being developed to trigger the bomb and for developing an RF proximity initiator for the bomb based on the projectile RF proximity fuse for anti-air rounds.

Caption: Proximity fuze MK53 removed from shell. (U. S. Navy Photo)

July 31st - Manhattan Project Pieces: Armor Plate

In addition to people transferring from Naval Proving Ground Dahlgren to Los Alamos to support the Manhattan Project and the testing we have mentioned in the last two weeks’ “Did You Know” facts, Dahlgren filled Los Alamos’ orders for various sizes of armor plate and almost certainly proof tested numerous experimental guns sent to Los Alamos that were manufactured at the Washington Navy Yard. More connections may be uncovered as documents are declassified and examined in support of the Los Alamos National Laboratory historical park efforts. This year happens to be the lab’s 80th anniversary (

There is more to share about Dahlgren’s related work after World War II. We hope that you will check out August’s featured “Now You Know” article to read more about the Atomic Energy Commission’s task for Dahlgren. Visit this Friday to read the first segment.

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