Aluminum sulfate (“alum”) reacts with bicarbonate alkalinities in raw water to form a gelatinous precipitate (floc) that attracts fine suspended particles, causing them to settle and clarifying the water. Alum (aluminum sulfate) acts as a coagulant in water treatment. It neutralizes charges on fine suspended particles, causing them to clump together and settle out of the water, thus clarifying it by removing turbidity.

Hot-dip galvanizing immerses iron or steel in molten zinc, producing a multi-layered zinc-iron alloy coating that provides long-lasting, maintenance-free corrosion protection; the process has been in use since 1742.

Recommended at the 1992 UN Conference on Environment and Development in Rio, the United Nations first designated 22 March 1993 as World Water Day. The date remains fixed to raise awareness of freshwater issues and the importance of sustainable water management.

The stratospheric ozone layer absorbs the Sun’s harmful ultraviolet (UV-B) radiation, preventing it from reaching the Earth’s surface. Without this natural shield, increased UV exposure would lead to higher rates of skin cancer, cataracts, and ecological damage.

Civil rights leader Dr. Martin Luther King Jr. was 39 years old when he was assassinated on 4 April 1968 in Memphis, Tennessee. His death galvanized the American civil rights movement and led to the passage of legislation aimed at ending segregation and protecting voting rights.

A UN resolution in 1981 established the International Day of Peace to coincide with the General Assembly’s opening. The first observance took place on the third Tuesday of September 21, 1982; from 2002 onward, September 21 became the permanent date. Since then, the day has been marked annually to promote ceasefires, non-violence, and global solidarity in pursuit of lasting peace.

Operation Gibraltar was Pakistan’s covert attempt in August 1965 to infiltrate forces into Indian-administered Kashmir. Its failure triggered the larger Indo-Pakistani War of 1965. Pakistan’s Operation Gibraltar, an infiltration campaign in Kashmir and the Rann of Kutch in August 1965, led directly to the full-scale Indo-Pakistani War of 1965 when hostilities escalated that September.

The Suez Canal—first opened for navigation on 17 November 1869—was nationalized by President Gamal Abdel Nasser on 26 July 1956. This act asserted Egyptian control over the vital waterway and precipitated the Suez Crisis. On 26 July 1956, President Gamal Abdel Nasser announced the nationalization of the Suez Canal, previously controlled by British and French interests. This bold move asserted Egyptian sovereignty over a vital maritime route and triggered the Suez Crisis, during which Britain, France, and Israel launched a military operation that ultimately ended under heavy international pressure.

Operation Enduring Freedom began on 7 October 2001, four weeks after the 11 September attacks. Initial combat operations combined air strikes by B-1, B-2, and B-52 bombers, carrier-based fighters, and Tomahawk missiles, targeting Taliban and al-Qaeda forces in Afghanistan.

Operation Desert Shield began on 2 August 1990, immediately after Iraq’s invasion of Kuwait. Its purpose was to deter further Iraqi aggression by positioning a multinational coalition—led by the United States—along Saudi Arabia’s northern border. This defensive buildup laid the groundwork for the subsequent offensive, Operation Desert Storm, which liberated Kuwait in early 1991. Operation Desert Shield was the U.S. operational name for the buildup of forces and Saudi Arabia’s defense from 2 August 1990 until 16 January 1991. When it became clear that Iraq would not withdraw from Kuwait, Desert Shield transitioned into Operation Desert Storm.