J. Robert Oppenheimer and his student Hartland Snyder publish the Oppenheimer–Snyder model, proving for the first time in contemporary physics how black holes could develop.

J. Robert Oppenheimer was an American theoretical physicist and one of the key figures in the development of the atomic bomb during World War II. He was born on April 22, 1904, and he passed away on February 18, 1967. Oppenheimer is often referred to as the “father of the atomic bomb” due to his leadership of the Manhattan Project, which ultimately led to the successful creation of the first atomic bombs.

Oppenheimer’s contributions to physics extended beyond his work on nuclear weapons. He made significant contributions to various fields, including quantum mechanics, quantum field theory, and astrophysics. In fact, his interests also extended to the study of black holes, which are fascinating and mysterious objects in the universe.

Black holes are regions in space where the gravitational pull is so strong that nothing, not even light, can escape from them. The concept of black holes emerged from Albert Einstein’s theory of general relativity. However, it was Oppenheimer and his collaborator, Hartland Snyder, who made a crucial contribution to the understanding of black holes.

In 1939, Oppenheimer and Snyder published a paper titled “On Continued Gravitational Contraction,” in which they explored the gravitational collapse of massive stars. They showed that if a massive star’s core exhausts its nuclear fuel, the core would collapse under its own gravitational pull, leading to the formation of a singularity—a point of infinite density—and an event horizon—the boundary beyond which nothing can escape. This theoretical prediction laid the groundwork for our modern understanding of black holes.

Oppenheimer’s work on black holes, while not as widely known as his contributions to nuclear physics, significantly impacted the field of astrophysics and led to further exploration and research into these enigmatic cosmic objects. His insights into the gravitational collapse of massive stars and the formation of black holes have been instrumental in advancing our understanding of the universe’s most extreme and fascinating phenomena.

Over 400 people die in the Great Hinckley Fire, a forest fire in Hinckley, Minnesota.

The Eritrean War of Independence officially begins with the shooting of Ethiopian police by Hamid Idris Awate.

A joint American–French expedition locates the wreckage of the RMS Titanic.
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The last known passenger pigeon, Martha, dies in the Cincinnati Zoo.

Martha  1885 – September 1, 1914 was the last known living passenger pigeon; she was named “Martha” in honor of the first First Lady Martha Washington.

The history of the Cincinnati Zoo‘s passenger pigeons has been described by Arlie William Schorger in his monograph on the species as “hopelessly confused,” and he also said that it is “difficult to find a more garbled history” than that of Martha. The generally accepted version is that, by the turn of the 20th century, the last known group of passenger pigeons was kept by Professor Charles Otis Whitmanat the University of Chicago. Whitman originally acquired his passenger pigeons from David Whittaker of Wisconsin, who sent him six birds, two of which later bred and hatched Martha in about 1885. Martha was named in honor of Martha Washington. Whitman kept these pigeons to study their behavior, along with rock doves and Eurasian collared-doves. Whitman and the Cincinnati Zoo, recognizing the decline of the wild populations, attempted to consistently breed the surviving birds, including attempts at making a rock dove foster passenger pigeon eggs. These attempts were unsuccessful, and Whitman sent Martha to the Cincinnati Zoo in 1902.

However, other sources argue that Martha was instead the descendant of three pairs of passenger pigeons purchased by the Cincinnati Zoo in 1877. Another source claimed that when the Cincinnati Zoo opened in 1875, it already had 22 birds in its collection. These sources claim that Martha was hatched at the Cincinnati Zoo in 1885, and that the passenger pigeons were originally kept not because of the rarity of the species, but to enable guests to have a closer look at a native species.

By November 1907, Martha and her two male companions at the Cincinnati Zoo were the only known surviving passenger pigeons after four captive males in Milwaukee died during the winter. One of the Cincinnati males died in April 1909, followed by the remaining male on July 10, 1910. Martha soon became a celebrity due to her status as an endling, and offers of a $1000 reward for finding a mate for Martha brought even more visitors to see her. Several years before her death Martha suffered an apoplectic stroke, leaving her weakened; the zoo built a lower roost for her as she could no longer reach her old one. Martha died at 1 p.m. on September 1, 1914 of old age. Her body was found lifeless on her cage’s floor. Depending on the source, Martha was between 17–29 years old at the time of her death, although 29 is the generally accepted figure.

After her death, Martha was quickly brought to the Cincinnati Ice Company, where she was held by her feet and frozen into a 300-pound block of ice. She was then sent by express train to the Smithsonian, where she arrived on September 4, 1914, and was photographed. She had been molting when she died, and as such she was missing a few feathers, including some of her longer tail feathers. William Palmer skinned Martha while Nelson R. Wood mounted her skin. Her internal parts were dissected by Robert Wilson Shufeldt and are also preserved and kept by the National Museum of Natural History

From the 1920s through the early 1950s she was displayed in the National Museum of Natural History’s Bird Hall, placed on a small branch fastened to a block of Styrofoam and paired with a male passenger pigeon that had been shot in Minnesota in 1873. She was then displayed as part of the Birds of the World exhibit that ran from 1956 to 1999. During this time she left the Smithsonian twice—in 1966 to be displayed at the Zoological Society of San Diego‘s Golden Jubilee Conservation Conference, and in June 1974 to the Cincinnati Zoo for the dedication of the Passenger Pigeon Memorial. When the Smithsonian shut down its Birds of the World exhibit, Martha was removed from display and kept in a special exhibit at the Cincinnati Zoo.Martha was back on display in the Smithsonian from June 2014 to September 2015 for the exhibit Once There Were Billions.

Adolf Hitler sign the order that begins the systematic euthanasia of mentally ill and disabled people.

The last passenger pigeon dies in captivity in the Cincinnati Zoo.