Earth Vs. the Egg: Measuring Earth's layers in the classroom
Science
Lecture video of Earth Vs. the Egg: Measuring Earth's layers in the classroom
The earth versus the egg. The idea here is to provide people with some kind of a conceptual model about the relative dimensions of the lithosphere, the lithospheric plates about a hundred kilometers in thickness. Compared to the total size of the earth, earth radius about 6370. What percent of earth's radius is the lithosphere. Well, if you do the math on this, then you've got a hundred kilometer thickness divided by a radius of 63 70, that works out to about 1.6%. And just to keep it simple numbers, rounded up to 2%. So the thickness of the lithosphere compared to the radius of the entire earth, you know, it's about 2%.
Take a hard-boiled egg, and measure the diameter of the egg. There's some variation, of course. In the diameter of eggs, look at the short dimension of the egg. And you'll get all about an inch and a half or so in diameter. Maybe a little bit more than that. So radius is round about three-quarters of an inch, .75 inches. Now, crack the egg, get a segment of the shell, and then use some calipers capable of measuring to the thousandth of an inch, and measure the thickness of the egg's shell. And of course, there's some variation, but it turns out that on average, you'll get about 15 one thousandths of an inch for the thickness of an eggshell.
And so again, do the math here, eggshell thickness, .015 inches. Compared with the .75 inches for the diameter of the egg. And there you go. What percent of the eggs radius is the shell about 2%. So the lesson here is that the shell is to the egg, what the lithosphere is to the earth. The relative dimensions are about the same. And you can get kids to sort of imagine the next time they peel a hard boiled egg to imagine that there's some humongous giant and they can come up to the earth and they can actually peel the lithosphere off of the earth. So it's important for people to actually get this concept that the lithosphere really is a thin shell, a thin, cold, brittle shell on the outer part of the earth.