Many subspecies of the tiger are either endangered or already extinct. Humans are the primary cause of this through hunting and the destruction of habitats.

Used for water distribution, the Delaware Aqueduct in New York, USA is the longest tunnel in the world (as of 2010). Drilled through solid rock, it reaches a staggering 137 kilometres (85 miles) in length. More tunnel facts.

More energy from the sun hits Earth every hour than the planet uses in a year.

AMAZING FACTS