Cosmic Velocity - First to Knot

The first cosmic velocity (escape velocity from Earth's surface to orbit) is approximately 7,900 m/s (7.9 km/s), the minimum speed needed to achieve Earth orbit.

v₁ = √(GM/r) where G is gravitational constant, M is Earth's mass, r is Earth's radius. Approximately 7.9 km/s.

To km/h: × 3,600. To mph: × 17,672. 7.9 km/s = 28,440 km/h = 17,672 mph.

Minimum speed for satellites, space station orbit, and low Earth orbit (LEO) calculations.

ISS orbits at ~7.66 km/s. Below this speed, you fall back to Earth. Above it, you stay in orbit (if horizontal).

Confusing with escape velocity (second cosmic velocity, 11.2 km/s) — orbital velocity is lower.

Remember: ~8 km/s for orbit, ~11 km/s to escape. v₁ is minimum for orbit, not escape.

A knot is one nautical mile per hour, where a nautical mile equals exactly 1,852 meters. It's the standard speed unit in maritime and aviation contexts.

1 knot = 1 nautical mile/hour = 1,852 m/h = 1.852 km/h = 0.514 m/s. One nautical mile = 1,852 meters exactly.

To km/h: × 1.852. To mph: × 1.151. To m/s: × 0.514. To ft/s: × 1.688.

Ship cruising speeds (cruise ships: 20–25 knots), aircraft speeds (Boeing 747: 490 knots cruise), wind speed in aviation weather reports (METAR), and sailing.

Fastest ship: 60+ knots (naval vessels). Blue whale swim: 5–20 knots. Jet stream winds: 80–140 knots. Hurricane-force winds: 64+ knots.

Saying 'knots per hour' — incorrect! A knot already includes 'per hour.' Just say 'knots.' Also, confusing nautical and statute miles.

1 knot ≈ 1.85 km/h. Roughly: 10 knots ≈ 20 km/h. Remember: knots are for sea and sky, km/h and mph are for land.