1) The universe is estimated to be around 13.8 billion years old.

2) The ancient city of Athens, Greece, is often considered the birthplace of democracy, where citizens had a say in the decision-making process.

3) J.K. Rowling's "Harry Potter" series of books has sold over 500 million copies worldwide and has been translated into 80 languages.

4) The smallest unit of time is known as a zeptosecond, which is equal to one trillionth of one billionth of a second.