1) The ozone layer, located in the Earth's stratosphere, protects us from harmful ultraviolet (UV) radiation.

2) The Rocky Mountains, also known as the Rockies, extend from Canada through the United States, offering stunning landscapes and outdoor recreational opportunities.

3) The strongest natural material known to man is spider silk. It is stronger than steel and more flexible than nylon.

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