Have you ever wondered about the difference between an ocean and a sea? Or questioned why Australia is a continent instead of an island? You’re not alone. The Earth is so mind-boggling in its size and scope that it fosters genuine curiosity. From the deepest point in the world to the Earth’s real age, here are 15 geography facts you’ve always wondered about.

How Old Is the Earth And How Do We Know?

Although there is no way to know the Earth’s exact age, scientists have calculated it to be roughly 4.54 billion years old, give or take 50 million years. But how did they arrive at this number? Although scientists have pondered this question for centuries, more recent technological advances have made it easier for researchers to understand the Earth’s age. Above all else, radiometric dating has been the most helpful in figuring out the Earth’s birthday because it allows scientists to pinpoint the age of rocks. The oldest rocks on Earth — 4.03 billion years old — were found in Canada, while Greenland, Australia, and Swaziland are home to rocks that range from 3.4 to 3.8 billion years. To top that, scientists have discovered stardust that’s a staggering 7 billion years old, which means the Earth is relatively young in comparison to the rest of the universe.

What Does the Prime Meridian Denote?