1) The phenomenon known as "black holes" occurs when matter is crushed into an infinitely small space, creating a gravitational pull so strong that nothing can escape.

2) Online banking and mobile banking have become increasingly popular, providing convenient access to banking services through digital platforms.

3) The name "Bluetooth" comes from the 10th-century Danish king, Harald Bluetooth, who united Denmark and Norway.

4) The Pacific Ocean is the largest ocean on Earth, covering more than 30% of the planet's surface.