The first people who coined the word 'Earth', which came from the word 'erda', were from the 5th century BC. During those times, they didn't know that much of the world is made up of water. In fact, they thought that the Earth was flat. They didn't have the ability to see Earth from above, and therefore, can only see what's underneath their feet (or what's on the horizon). If you look at the earliest world maps, you'll see how limited their knowledge about the Earth was. We've come a long way to understanding our planet, but there is still so much to learn.

We know today that our planet is mostly covered in water. The best way to tell, as you say, is by looking at satellite images. But what about when our planet was named by humans who lived hundreds of years ago? People back then didn’t' have satellites and all they knew about our planet was what they saw -- and they saw the earth that they stood on. It wasn't until the explorers set out to discover new continents that we started to make modern maps and see how big the planet really is, and how much of it is water.

People named this planet Earth before satellites were invented. They named it based on their experience of the world, which, since we're land-dwelling creatures, was mostly earth.

Most of the Earth's surface is covered by water, but that water is a roughly 10-kilometer deep layer around the world. Underneath that is rock.