The Birthday of Enrico Fermi (1901) – Fermi Problems

Enrico Fermi was a physicist famous for order‑of‑magnitude estimates – ‘Fermi problems’. Example: ‘How many piano tuners are in Chicago?’ Estimate: population 3 million, 1 piano per 20 people = 150,000 pianos, each tuner tunes 4 pianos per day, works 200 days/year → 800 pianos/year per tuner, so 150,000/800 ≈ 190 tuners. The actual number is about 200. Fermi problems teach dimensional analysis, approximation, and the power of back‑of‑envelope calculation. They are used in physics contests and job interviews.