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) Angelina Jolie is an American actress, filmmaker, and humanitarian. She has received critical acclaim for her performances in films such as "Girl, Interrupted," "Mr. & Mrs. Smith," and "Maleficent," and has been actively involved in humanitarian work around the world.

3) The Appalachian Mountains, running along the eastern coast of the United States, are one of the oldest mountain ranges in the world.

4) The sitcom "Friends" is known for its iconic Central Perk coffee shop, where the main characters often gather.