Petawatt to Kilogram-force meters/hour

It's a time trick. A petawatt laser concentrates a modest amount of energy (maybe 100–500 joules) into a pulse lasting 10–100 femtoseconds. Dividing a few hundred joules by 10⁻¹⁴ seconds gives you 10¹⁵–10¹⁶ watts — surpassing the Sun's 3.8 × 10²⁶ W is still far off, but these lasers do exceed total human power consumption by 100,000×. The catch: the total energy delivered is only enough to heat a cup of coffee.

Primarily for nuclear fusion research (compressing fuel pellets), particle acceleration (laser wakefield acceleration can produce electron beams rivalling billion-dollar synchrotrons), medical isotope production, and probing extreme states of matter found in stellar cores. The ELI (Extreme Light Infrastructure) project in Europe uses petawatt lasers to recreate conditions found in supernovae, helping astrophysicists study cosmic explosions in a lab.

Solar flares can briefly release 10–100 PW of electromagnetic radiation. The Chicxulub asteroid impact (the one that killed the dinosaurs) delivered roughly 4 × 10²³ watts during the few seconds of impact — about 100 million petawatts. Gamma-ray bursts top everything at 10²⁵–10²⁶ PW, briefly outshining the entire observable universe. Even supernovae "only" sustain about 10³⁶ PW for a few seconds at peak.

Building one costs $50–500 million. Operating costs are surprisingly modest per shot — each pulse uses only a few hundred joules (less than lifting an apple one meter), but the capacitor banks and cooling systems draw megawatts of continuous power. The NIF facility costs about $350 million per year to operate. Individual shots are "cheap" in energy terms but the infrastructure to achieve them is staggering.

In theory yes, but in practice current petawatt lasers are terrible weapons. They fire one pulse every few minutes to hours, require warehouse-sized buildings of equipment, and deliver total energy equivalent to a firecracker. Military-grade laser weapons focus on sustained power (100–300 kW continuous beams), not ultrashort pulses. A petawatt laser is a precision scientific scalpel, not a blunt instrument — brilliant for physics, useless for destruction.

Clock mechanisms (0.01–1 kgf·m/h), self-winding watches using wrist motion (~0.1 kgf·m/h), slow agricultural irrigation pumps powered by animal treadmills (10,000–50,000 kgf·m/h), and historical mining hoists operated by water wheels. Any process where heavy loads move very slowly — like the hour hand of a tower clock lifting its counterweight — naturally operates in kgf·m/h territory.

One metric horsepower = 270,000 kgf·m/h (4,500 kgf·m/min × 60). This means a 1 hp motor working for one hour lifts 270 tonnes by one meter, or 1 tonne by 270 meters. The hourly framing makes large-scale work tangible: a 10 hp engine working all day (8 hours) at full power performs 21,600,000 kgf·m of work — enough to lift 2,160 tonnes by one meter. It's why hourly rates appear in construction and mining productivity calculations.

An ox working steadily produces about 180,000–270,000 kgf·m/h (0.5–0.75 metric hp) and can sustain this for 6–8 hours. A horse produces 270,000–360,000 kgf·m/h (0.75–1 hp) for 4–6 hours. A donkey manages about 90,000–135,000 kgf·m/h (0.25–0.37 hp) but can work longer hours. These rates determined pre-industrial agriculture's productivity ceiling: a farmer with one ox could plow about 0.4 hectares per day.

Surprisingly, yes — in slow-motion structural testing. When engineers fatigue-test a bridge component by slowly cycling loads over hours, reporting the energy input rate in kgf·m/h matches the test timescale. Also in geotechnical engineering: the rate of ground consolidation under building loads, or the power of slow landslide movement, is sometimes expressed in kgf·m/h. These are niche applications, but the unit survives where the process is genuinely hourly-scale.

Resting metabolic rate is about 80 W ≈ 29,400 kgf·m/h of total heat output. But in terms of useful mechanical work output, a resting human produces essentially 0 kgf·m/h — all the energy goes to heat. Even standing costs about 7,000–10,000 kgf·m/h in metabolic power but produces no external work. This highlights the distinction between thermal power (always present) and mechanical power (only when doing physical work).