Back in high school--cause I can talk about high school now, like it's in the past--I had this teacher. He is crazy, terrifying and wonderful in many ways, and I love him and am terrified of him at the same time. He is a good teacher in many ways, to spite how frightening he can be. However, I'm going to tell you a story that has nothing to do with either of those opposing qualities.
One of the classes I had this guy for was Geographie Planetaire (Global Geography), in the last semester of grade twelve. One afternoon--or morning, I don't remember--we were learning about the layers of the earth. I had adopted a pesky habit the previous school year of constantly questioning supposedly absolute knowledge, which often involved playing devil's advocate, not to mention annoying a lot of people.
So, suddenly as I sat there listening to him teach, I thought 'Wait a minute!'. My hand shot into the air, and when he eventually turned away from the board where he had been illustrating as he spoke, he answered my hand. I asked him how we could know what was on the inside of the earth. After a few moments of silence, during which he looked at me with a familiar expression of irritation, he uttered dismissively "Well, it's a scientific fact." Then he went back to drawing.
It's a scientific fact.
As mentioned, this blog is an extra credit assignment for a university Astronomy course. This past week we were on the unit pertaining to earth and the moon, and I found out the answer to my question.
The answer is seismology. "Seismology is is the study of earthquakes and seismic waves that move through and around the earth." according the Michigan Technology University. Basically seismologists measure the seismic waves from earthquakes and things (So, the energy that they give off) when they occur on one part of the planet and then measure them at various other places on the globe. They observe how the waves have been changed or distorted and that can tell them about the density and amount of matter they've had to travel through. It makes sense, doesn't it?
SOURCES
Professor Edward's Lecture on The Earth and the Moon for Solar System Astronomy at Mount Allison University
http://www.geo.mtu.edu/UPSeis/waves.html
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