Scientists have long proposed Earth is like a boiled egg or an onion with many layers: a thin brittle crust, a semifluid silicate mantle, a liquid iron outer core, and an inner core of solid iron and nickel. But all this is speculation.
The latest speculation proposes a “superionic” core. Per this hypothesis, the inner core contains liquid hydrogen that flows within a solid lattice of iron and silicon in a state that shares properties of both solids and liquids. This hypothesis grew from computer simulations done by two independent teams. One, published in the journal Nature, was led by geophysicist Yu He (Chinese Academy of Sciences).