1) The Arctic Ocean is the smallest and shallowest ocean, located at the North Pole. It is covered by sea ice for much of the year.

2) The Hollywood Walk of Fame features more than 2,690 stars embedded in the sidewalk, honoring notable figures in the entertainment industry.

3) The concept of 3D printing, also known as additive manufacturing, was first introduced in the 1980s and has since revolutionized prototyping and small-scale production.

4) The highest-grossing concert tour of all time is U2's "360° Tour," which earned over $735 million in ticket sales.