It has been known for more than 2000 years that the Earth is round, but we were able to actually see this much later only when we flew into space.
The knowledge why we do not fall off from the Earth is much more recent.
A journey as described by author JULES VERNE in his book JOURNEY TO THE CENTER OF THE EARTH was, after all, impossible.
Only one thing was known:
The Earth is made up of soil, rocks and water.
Today, we know that the Earth is also surrounded by an air cover called atmosphere.