This Week in Physics History: July 23 - 29

July 25, 1944 - English physicist and chemist John Dalton dies. Dalton is known for having been an early advocate of atomic theory in modern science, though it would be nearly a century after his work that it was more generally adopted by the scientific community.

July 29, 1957 - The International Atomic Energy Agency is founded with the goal of promoting the peaceful use of nuclear energy.

July 24, 1979 - English physicist Sir James Chadwick dies. Chadwick discovered the existence of the neutrally charged atomic particle, the neutron. The neutron, with a lack of electrical charge, is useful in triggering nuclear fission, or "splitting the atom." He received the 1935 Nobel Prize in Physics for this discovery. Because of this work, Chadwick reputedly gained the nickname "Jimmy Neutron."

July 27, 2005 - NASA grounds the space shuttles after the space shuttle Discovery sheds a piece of foam from its external fuel tank larger than that which caused the destruction of the Columbia in 2003. The Discovery foam did not strike the spacecraft and caused no actual difficulties to the launch or mission.

July 29, 2005 - Astronomers announce the discovery of Eris (called Xena at the time of discovery and for about a year thereafter), a possible "tenth planet" in our solar system. It was in part due to the discovery of Eris that astronomers have chosen to "demote" Pluto to the status of dwarf planet, as more bodies in our solar system were discovered which qualified for conventional "planet" status.