Blood rain — red rainfall — has been recorded across Europe, caused by airborne algae or dust from the Sahara.

Sandstorms can travel across continents.

Titan has lakes and rivers, but they're filled with liquid methane instead of water.

Greenland is the world's largest island — Australia is considered a continent.

The Irish Potato Famine caused Ireland's population to drop by 25% in just a decade through death and emigration.

Greenland is 80% covered by ice — if it all melted, global sea levels would rise about 20 feet.

The Aztec capital Tenochtitlan had a population of around 200,000 in the early 16th century, larger than most European cities.

Canada has more lakes than the rest of the world combined.

The entire population of Earth in 1 AD was around 300 million — roughly equal to the current population of the United States.