Iron has the highest specific gravity, (yes i DO mean gravity, NOT density, because density implies volume)., of the 10 most common elements in milky Way Galaxy. That is why Iron and nickel form the cores of ALL planets that have enough mass to chemically differentiated.. We know from iron nickel meteorites that iron and nickel go together. Radioactive isotopes of nickel decay to become iron. About 5 % or earth's core is sulfur, which lowers the melting point points and pressure of an iron nickel mixture. Seismic data confirms The basic structure of the Earth is solid iron nickel core surrounded by liquid outer core surrounded bey Viscous mantle solid Crust the thinner in the oceans than in the continents and islands.
Scinetist s measure how much heat earth is radiating into space at the surface and in space. This is heat from Earth's core, Not reflected by earth from the sun at the surface.. Yes, includes heat from radioactive decay as well, but only about 14% of Earth's heat comes radioactive decay. Earth's core is STILL cooling off from the time that Earth was formed. NA d from after Theia, the size of Mars slammed into Earth and the seismic waves ripped off the crust and part of the mantle that were flung out into space that colesced in about 10,000 years to form the Moon. which STILL has 30 kilometer thisl LIQUID outer core...
In other words. NO ONE has to BE at Earth's core to measure the temperature or chemical com[position because we use remote sensing methods to observe and gather data..
I am also another scientist who takes a lot of offense at the word speculate" because you are implying that ALL scientists ESPECIALLY GEOLOGISTS are all LIARS and make things up out of thin air. THAT IS WHAT YOU DO. Yes, we COULD try to each about how minerals and rocks BECOME mineral and s and rocks from magma and lava., but since you have NO desire to learn anything new and would reject anything new because it makes you afraid because it exposes your ignorance and pushes you out of your comfort zone, Trying to TEACH you anything would be a total waste of time. ALL you want to do ARGUE so your precious ego gets fed.Your mind rusted tight closed decades ago from not being used.. Supposedly ignorance is bliss. Funny how ignorance obviously is really mental hell because of your FEAR of the unknown and scientists who really DO understand what they are talking about..