Surprising Facts About Volcanoes, Vacuums, and the Invention of Paper

Where Are the Most Volcanoes?
The area with the most volcanoes in the world is Southeast Asia. Lake Toba, in northern Sumatra, sits in the crater of a massive supervolcano. The lake is about 100 kilometers long and 30 kilometers wide and includes four overlapping giant volcanic craters.

What Is a Vacuum?
A vacuum, or “void,” means a space where there is no matter at all, not even air. It’s a physics idea used to describe completely empty space. Vacuums naturally attract matter, which is why vacuum cleaners work, they create a space with no air which pulls in dust and dirt.

Outer space is an example of a partial vacuum. Scientists use a unit called a “Pascal” to measure the pressure inside these spaces.

When Was Paper Invented?
Paper was invented in China, and unlike many inventions, we actually know who invented it. In the year 105 CE, a Chinese official named Cai Lun came up with a cheaper way to make writing material. At the time, people used papyrus, but it was expensive and hard to get. So Cai Lun used hemp plants and wood chips to make a soft pulp, which he then stretched and dried into sheets. That’s how the first paper was born! The Chinese emperor was so impressed that he rewarded Cai Lun with wealth and a noble title. This invention helped spark one of the biggest changes in history.