 In this video, we want to explore categorization and classification, particularly in the context of science. The definitions for categorization and classification, depending on what dictionary you use, you might have slightly different wordings, but they basically overlap. It's a process or an act of distributing or placing individual things into categories or groups of the same type of thing. Categories are a collection of things sharing some common attribute. So that's what we're going to focus in here a little bit. Now I'm using this as one of my college classes. So let's look at our first example as college students. We could classify or categorize college students in a lot of different ways. And these four are just a few of the examples, not all of the possible ones. So let's look at residency status. That's actually a pretty easy one to implement. Students are either in-state, out-of-state, or international students. And again, this is the way we classify them in the United States. And it's useful for tuition categories. And that's partly based on a rationalization, based on taxes paid. So determining the residency status depends on home address. It's useful for tuition categories, but really isn't used for anything outside of that tuition classification. Major and class are a lot more useful when you're talking about college students. Because all the students in a particular major are going to have a common set of course requirements. They'll have to study the same sorts of things. And there's some classes that all of them will have to take. But students from other majors don't take. Class standing, and by that I mean the freshman, sophomore, junior, is an indication of how far you've progressed in that major. So how much have you probably studied already related to that major? Now there are some complications with this. For example, you could have a student who's a double major. So which category do you put them into? They're going to have a common set of courses with each of those different majors. And what about a student who changes their major? If you change your major, you might be classified as a senior based on the total number of courses you've taken. But you might just be starting out in the particular courses needed for your new major. So separating students by major and class standing is definitely useful for determining their course requirements and getting an estimate for how far they've progressed. But it also has some complications and doesn't fully tell you what all they've studied and learned. Age is another thing that we often use for students, and we could classify them based on year, 18, 19, 20, etc. Difficulty with that is that the category keeps changing. You're 18 one year, but you're 19 the next year. And it doesn't change for everybody at the same time. It changes on their birthday. The other thing is that there's not a lot of difference between a student who's 18 about to turn 19 and a student who's just turned 19. They'd be in different categories, but really not that much difference between them. If you use bigger bins, you might be able to get a little bit of those difficulties to put aside. You could say the students who are in their 20s, the students who are in their 30s, etc. And you would expect that students in their 20s are going to be different from students in their 50s. Each group is going to kind of have some things that are really sort of common to that group, but different from the other groups. But again, not all 20 year olds act like their peers and not all 50 year olds act like their peers. So there's going to be exceptions. And again, there's not a lot of difference between a 29 year old and a 30 year old. So exactly where you put the break is a little bit arbitrary. So let's talk about some other examples. So common things you're going to see in terms of classifications and categorizations. If you type into a search engine something about classifications and biology, it's going to all be about the different classifications of living organisms into all the different kingdoms and phylums and their very formalized structure for classifying and categorizing living things. We've already seen it in my course here on Earth Science where we separated things out into the four spheres, biosphere, hydrosphere, atmosphere, and geosphere. And again, we had some difficulties with that with our clouds part of the atmosphere or they part of the hydrosphere because it's got water in the clouds, but yet it's up in the sky. Astronomy is our focus right now for this week and looking at how do we classify the planets or how do we classify other small bodies in our solar system. So you can imagine that again, as with any sort of categorization, there's going to be some benefits and there's going to be some difficulties. The benefits always relate back to being able to use the common characteristics as a simplified way of examining all the objects in that category. So you don't have to learn the density of each planet. You don't have to learn the size of each planet. If you know what general category they're in, you have a little bit of an idea of which ones are bigger or smaller. But there's always going to be difficulties as well. Sometimes it's arbitrary in terms of where you put a boundary between two different ones and then you might discover some new object that doesn't quite fit either of the existing categories and you have to decide you expand the category or do you create a new category, which is what they did with Pluto when they started discovering other dwarf planets. So while this video is about categorization and classification in general, I do want you to think about how that applies to our topic for this week with the solar system. But this video should also be useful for students thinking about classification and categorization in any aspect of life.