How can we proove the fact that the earth has a core?

Question

I was just wondering, how scientists come up with the idea that the earth has an outer and inner core. It's an honest yet stupid question.

Hey "ideamanbmg", Yes I know it's a fact, and it has been prooven, I was asking about that proof because I do not know what it is... if you don't have the answer, dont feel like a genius commenting on my question. I'm looking for an answer not a comment okei? and by the way, that's an honest and stupid answer I've got so far.

Answer 1

The earth is round, therefore it has a center - therefore it has a core. If you mean the structure of the core, the simple way to tell this is to observe the movement of seismic waves through the earth. E.g., if an earthquake happens at position X on the planet, and gets picked up at stations at other points around the planet (via seismograph), based on the time of first arrival of the signal and the recorded intensity, you can deduce some things about how the wave must have traveled - specifically, its density, whether it's moving through solid or liquid, etc. This quickly becomes abstruse and technical, and depends on complicated stuff about sound and waves that I don't understand. But, this is the rough outline of how this stuff is understood - studying the properties of waves moving through this matter.

Answer 2

Good answers from astazangasta and brooks b.
In addition to knowing that the Earth has a solid inner core and a liquid outer core, we also know the Earth's core is mostly made of Iron.
Based on what we know about Earth's orbital dynamics and gravity field strength, we know what the average density of the whole Earth must be, and this density is higher than the average density of the crust (the part where we live). So, to bring the overall density up to what we know it must be, the core has to be made of a much heavier material. And if you do the quantitative calculations, you come up with the density of iron (plus some nickel and some lighter elements, like sulfur and fluorine).
And what do you know? Iron meteorites that we find, and that we think might represent pieces of the cores of other planets that never stayed formed, have exactly the density and composition (iron + nickel) that we expect Earth’s core to have based on our density calculations! Pretty cool.

Answer 3

The first answer was very good. I just want to add that it is known that the earth has a liquid outer core bacause s-waves (shear waves) cannot travel through liquids. When an earthquake sends s-waves and p-waves through the inner earth, the p-waves go right through the core, but the s-waves are blocked by the outer core creating a "shadow zone". It is known that the inner core is solid because of the behavior of p-waves passing through the core. P-waves pass through liquids differently than solids, so it is known that there is a liquid outer core but a solid inner core.

Answer 4

It's a fact. Facts don't need to be proven, they already are.
Yes, it's an honestly stupid question.