How can we tell what the earth core is made of?

Question

Lydia Allen · Accepted Answer

This a great question, the answer is we basically use methods that are similar to medical imaging. Just like we can diagnose tissue make up and pathology using Computer Tomography (CT) and X-Ray we can make out the earth inner making using seismic waves. Notice the modality, in medical imaging we are using electromagnetic waves in geo-imaging we use seismic waves.
In CT the main physics is the attenuation of beam as it traverse your body in seismic waves you look at chance of the velocity of propagation of the seismic waves (a little like ultrasound, which also measure change in velocity across the tissue for imaging)

Since it is obviously impossible to obtain a sample of the Earth's core, we study, map, and determine the inner composition of our planet's core using techniques very similar to medical imaging. Today, seismological and magnetic field data, along with other theoretical calculations, allow us to get a sense of the actual size and composition of our planet's inner core. Seismologists observe changes in the speed of the waves as they move from one tracking station to another, and they can get a pretty good idea of what the ground that wave is traveling through looks like. In fact, that is how geophysics explores the interior of our Earth when looking for hydrocarbons. Seismic waves bounce around, changing direction and speed based on the material they pass through, just like an X-ray used in CT scanning. The Earth is divided into three layers, each slightly different in structure, which scientists have discovered (or confirmed through theoretical postulates) using seismology. The heat in the core is primarily caused by the slow decay of radioactive elements left over from the planet's formation; the molten iron outer core is located approximately 3000 kilometers below the surface, while the solid iron inner core is located another 2000 kilometers below. A few other elements, such as silicon and oxygen, are thrown in for good measure, but iron dominates the Earth's interior for the most part.

Olivia Aldridge · Answer

undefined Scientists use two main methods to determine the composition of the Earth's core: laboratory experiments conducted under conditions of extreme pressure and temperature, and seismic waves generated by earthquakes that travel through the Earth and are affected by its composition. By analyzing how these waves propagate, scientists can infer properties of the Earth's core.