Satellites

A satellite is an object moving sideways so fast that as gravity pulls it down, the Earth's surface curves away beneath it — perpetual falling that never lands. Sputnik 1, launched by the Soviet Union on 4 October 1957, was an 84-kilogram polished sphere whose 20 and 40 MHz transmitters beeped every three-tenths of a second; the frequencies were chosen so that any amateur with a shortwave receiver could hear it pass overhead. Getting there is a chemistry problem as much as a physics one: multistage rockets burning propellants made, handled, and pumped at industrial scale.

A platform above the atmosphere sees a third of the planet at once and is visible from all of it — the ultimate hilltop. Within two decades of Sputnik, satellites were relaying telephone calls and television across oceans, photographing hurricanes before they made landfall, verifying arms-control treaties from orbit, and mapping the planet continuously. They made the Earth observable and addressable as a single system for the first time.

Sputnik rode a modified R-7 intercontinental ballistic missile: clustered kerosene–liquid-oxygen engines whose stages dropped away as they emptied, the only way chemical propellants can reach orbital speed. The satellite itself was minimal by design — a pressurized aluminum sphere, silver-zinc batteries, two radio transmitters, and four whip antennas — built in months when the sophisticated science payload fell behind schedule. Its batteries lasted three weeks; its point was made in one orbit.

Satellites gave civilization global communications and live intercontinental broadcasting, weather forecasting that saves thousands of lives per storm, and Earth observation for agriculture, climate, and cartography. GPS and its successors turned precise position and time into a free public utility that logistics, aviation, power grids, and financial networks now quietly depend on — with daily relativity corrections as the price of that precision. Sputnik also ignited the space race that produced crewed spaceflight and planetary exploration.