The Indus Valley Civilization (2600–1900 BCE) was centered in present-day Pakistan, with sites like Mohenjo-Daro and Harappa.

The Mayan Long Count calendar ended a cycle in December 2012, which led to widespread doomsday speculations.

Nitrogen fixation—by bacteria or lightning—converts atmospheric N₂ into biologically usable ammonia or nitrates.

Gabriel García Márquez wrote "One Hundred Years of Solitude", a landmark of magical realism and Latin American literature.

Sulfur dioxide emitted from fossil fuel combustion oxidizes to sulfuric acid in the atmosphere, contributing to acid rain.

Pax Romana (27 BCE – 180 CE) was a period of relative peace and stability across the Roman Empire, fostering prosperity and growth.

The Big Bang theory describes the origin of the universe 13.8 billion years ago as a rapid expansion from a singularity.

The Pauli Exclusion Principle states no two fermions (like electrons) can occupy the same quantum state, critical for atomic structure.

Silver has the highest electrical conductivity of all elements, making it ideal for electronics, though copper is more widely used.

James Chadwick discovered the neutron in 1932, completing the model of atomic structure and earning the Nobel Prize in Physics.