August 21

On August 21, 1888, inventor William Seward Burroughs received a patent for his improved adding machine design, which automated arithmetic calculations. His invention used a system of keys and gears to accurately add large columns of numbers, significantly reducing errors and manual labor in businesses. Burroughs established the American Arithmometer Company to manufacture his machines, later renamed the Burroughs Adding Machine Company. The company's success paved the way for future advancements in office equipment and computing technology. By the early 20th century, Burroughs machines were widely adopted in banks, railroads, and government offices. The legacy of this innovation endures in modern calculators and computers.

Physicist Harry Daghlian was conducting a plutonium criticality experiment on the Demon core at Los Alamos National Laboratory. On August 21, 1945, a lapse in protocol caused a reflector brick to slip, triggering an uncontrolled neutron chain reaction. Daghlian received a massive dose of radiation while attempting to halt the reaction and collapsed soon after. He endured severe radiation burns and died 25 days later, becoming the first casualty of a criticality accident. The incident led to the implementation of stricter safety procedures and remote-handling techniques. Daghlian's sacrifice highlighted the grave risks inherent in early nuclear research and shaped laboratory protocols worldwide.

On August 21, 1957, Soviet engineers launched the R-7 Semyorka from the Baikonur Cosmodrome. It became the first missile capable of delivering a warhead across intercontinental distances. The successful test demonstrated advanced rocketry and guidance systems developed by Sergei Korolev's design bureau. This breakthrough intensified the Cold War arms race and prompted the United States to accelerate its missile programs. The R-7 design would later serve as the launch vehicle for Sputnik and the Vostok space missions. Its legacy underscores the close relationship between military and space exploration technologies.

Launched in 1992, the Mars Observer was the United States' first mission to study Mars from orbit. On August 21, 1993, mission controllers suddenly lost all contact with the spacecraft. The loss occurred just three days before the scheduled insertion into Martian orbit. Extensive efforts to reestablish communication over subsequent months proved unsuccessful. The failure led to significant analysis of mission operations and reinforced the challenges of deep-space exploration. Lessons from the Mars Observer guided the design of future Mars missions such as the Mars Global Surveyor.

On August 21, 2017, a total solar eclipse made its way across the continental US for the first time in 99 years. Starting at 10:16 AM PDT on the Oregon coast, the Moon's shadow - or umbra - moved southeastward, passing through 14 states before exiting in South Carolina at 2:48 PM EDT. Observers within the narrow path of totality experienced darkness at midday, revealing the Sun's corona and prompting widespread awe. Millions gathered at viewing events, parks, and private gardens, using proper eye protection to safely observe the phenomenon. Scientists took advantage of the event to study solar flare activity and atmospheric changes in real time. The eclipse also spurred tourism, boosted local economies along the path, and increased interest in astronomy across the country. Media coverage beamed the spectacle worldwide, uniting viewers in a shared moment under the shadow of the Moon. The 2017 eclipse remains one of the most observed and celebrated astronomical events in American history.