1) The Eiffel Tower can be 15 cm taller during the summer due to thermal expansion.

2) The term "bull market" refers to a period of rising stock prices, while a "bear market" refers to a period of falling stock prices.

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 fastest recorded serve in tennis was achieved by Sam Groth at 163.7 miles per hour (263.4 kilometers per hour) during a tournament in 2012.