Physics I / Maxwell's Equations
Practice question · Estimate

Light crosses the 150 million km from the Sun to Earth. Estimate how many minutes that takes.

Estimate on a scale from 0 min (0) to 30 min (30).

Hints
  1. c≈3×108c \approx 3\times10^{8} m/s =3×105= 3\times10^{5} km/s.
  2. 1.5×108 km÷3×1051.5\times10^{8} \text{ km} \div 3\times10^{5} km/s =500= 500 s. Convert to minutes.
Show the answer

8.3 (answers within ±1.5 count)

Why

About 500 s ≈ 8.3 minutes: you always see the Sun as it was eight minutes ago. Maxwell’s equations predicted this finite speed from two lab-bench constants, ε0\varepsilon_0 and μ0\mu_0, the moment physics realized light is electromagnetism.

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