Chemical Reactions. Four minutes of the best moments of stuff burning, breaking, freezing, exploding, melting, and generally reacting in interesting ways. [more inside]
The first nuclear reactor was in Africa, 2 billion years ago. Two billion years ago, there was enough uranium 235 in a naturally occurring deposit in Africa to fuel a nuclear fission reaction. In 16 separate locations, spontaneously occurring fission reactions went on for some hundreds of thousands of years, cycling multiple times per day. A picture of Fossil Reactor 15. The American Nuclear Society info site.
Pavement Terror! Do you jump out of your skin whenever a car backfires? Just hope this guy didn't catch you on film. Interesting photos of people reacting to his backfiring van.