No one has "discovered" the center of the Earth in the sense of physically reaching it. The Earth's core is too hot and under too much pressure for humans to survive.

However, we have learned a lot about the Earth's interior through various methods, including:

* Seismic waves: By studying how earthquake waves travel through the Earth, scientists can infer the different layers of the planet and their composition.

* Gravity measurements: Variations in Earth's gravity field provide clues about the density and composition of different layers.

* Magnetic field: The Earth's magnetic field is generated by the movement of molten iron in the outer core.

* Meteorites: Studying meteorites that have landed on Earth gives us insights into the composition of the early Earth.

So, while we haven't physically reached the center, scientists have pieced together a detailed understanding of its structure and composition through these indirect methods.