The Equator is the 0° latitude line encircling Earth at its widest point, dividing the planet into Northern and Southern Hemispheres and serving as the reference for all other latitude measurements.

Rolling friction is markedly lower than sliding friction. Common methods to reduce friction include polishing, lubrication, ball or roller bearings, and streamlining, all of which aim to convert sliding motion into rolling.

The Pacific Ocean’s area—estimated between 165.2 and 181.3 million km²—constitutes about 46 percent of Earth’s water surface and 32 percent of its total surface area, making it the largest hydrospheric component.

The Greenhouse Effect occurs when atmospheric gases absorb infrared radiation from the Sun, heating the Earth; excess greenhouse gases like CO₂ can disrupt climate systems.

Relative humidity is influenced by air temperature (warmer air holds more moisture), current weather patterns (rain, wind), and geographical location (proximity to water bodies and elevation), making all factors relevant. Relative humidity (RH) is the percentage saturation of air at a given temperature and pressure. RH = 100 × E(Td)/E(T), where E is saturation vapour pressure; RH influences cloud development and precipitation.

Just war theorists recognize that even “justified” wars involve moral wrongdoing; the tragedy of justified war refers to conflicts deemed morally permissible yet inherently destructive and tragic in a broad sense.

Ecology is the branch of biology that examines the relationships between living organisms and their physical surroundings, encompassing ecosystems, biodiversity, and environmental interactions. Ecology examines the distribution, abundance, and interactions of organisms within their physical surroundings, encompassing populations, communities, and ecosystems across all forms of biodiversity.

Hegemonic Stability Theory posits that international order requires a predominant state (the hegemon) to articulate and enforce rules, providing public goods—such as security and open markets—that underpin global stability.

Although Hans Lipperhey patented the earliest telescope in 1608, Galileo significantly improved its design in 1609 and was the first to systematically apply it to astronomy, discovering Jupiter’s moons and Venus’s phases.

Completed around 1010 CE by the poet Hakim Abul-Qasim Mansur (Ferdausi Tusi), the “Shahnameh” chronicles Persian legends and history from mythical times to the Arab conquest, preserving pre-Islamic Iranian culture.