Look down at the ground you're standing on. What do you think is below it? A magical world made of candy and cake? Different colored layers of fire? Vast nothingness with a tiny little bouncy ball in the middle? These are pretty close to what scientists used to think Earth's core was made of.

In reality, it's pretty gnarly down below Earth's crust, let alone nearly impossible to get to—unless we've got something powerful enough to dig through thirty miles of solid rock. (We don't.) This means actually seeing what's going on below Earth's surface isn't going to happen. Bummer.

Fortunately, technology came along, as it often does, and gave scientists the tools they needed to "see" Earth's innards. They were able to study how seismic waves from earthquakes bounced around and use magnetic field data to put together a pretty sweet explanation of what's at the heart of our planet. And no, it doesn't involve cake. Instead think ridiculously hot iron and melted rock.

This is a perfect example of how scientists use technology to create a model of something they can't observe directly. We can use this model to predict how plates will move, explain how island chains form, and show what Earth's nether regions are really like. This is also a great example of how scientists can take what they need from the evidence potluck and use it as building blocks for their own awesome theory.

Lastly, it's an excellent example of how theories change over time. Someday getting to the center of the Earth might be easier than battling rush hour traffic, and who knows? We might find out that that whole iron core idea was all wrong. Our money is on chocolate lava cake.