How Fast Is Nuclear Fireball Edge?

A nuclear fireball expands at about 300 km/s in its earliest milliseconds. Tsar Bomba — the largest weapon ever detonated, at 50 megatons — produced an 8 km fireball that briefly reached temperatures hotter than the Sun's core.

Tsar Bomba's flash was visible from 1,000 km away. The shockwave circled the entire Earth three times before dissipating.

• Briefly hotter than the Sun's core
• Tsar Bomba: 50 megatons