1) The Beatles hold the record for the most number-one hits on the Billboard Hot 100 chart, with 20 songs reaching the top spot.

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

3) Mountains are important water sources, as they capture and store precipitation, feeding rivers and supporting ecosystems downstream.

4) The concept of virtual reality (VR) involves creating a simulated environment that can be explored and interacted with using specialized headsets and input devices.