The International Space Station (ISS) is a place where astronauts can live for many months at a time. Some have lived a full year there. This means that the ISS must provide for all the needs of the astronauts living there, with only occasional spacecraft arriving with food and supplies sent from Earth. In that sense, we say that the International Space Station represents a system that makes life aboard it possible.
Discussion
ISS – One System or Many?
We can think of the International Space Station (ISS) as a single system that makes it possible for astronauts to live there. But we can also think of it as consisting of many component systems that all work together (the word component means a part of a larger whole). As an example of a component system, the ISS has a sophisticated water recycling system that allows astronauts to survive despite the very limited amount of water available to them. In small groups or as a class, discuss the following questions about systems on the ISS.
- Think of at least 3 other component systems (besides water recycling) that must exist on the ISS.
- Why might it sometimes be useful to think of the ISS in terms of its component systems rather than as a single system?
- Are there circumstances in which it makes more sense to think of the ISS as a single system?
- In what sense might we say that the ISS is a single system made up of “subsystems”? Does it matter whether we call them “subsystems” or “component systems” or “systems”? Defend your opinion.
This discussion is designed to get students to think about the definition of a “system” and to address the semantic issue of whether “subsystems” can simply be called systems (as they often are, including in the case of Earth’s 4 systems discussed in this section). Specific notes:
- For (1): There are many legitimate answers that students might offer, and the goal is simply for students to realize that water recycling is only one of many systems that exist on the ISS. Other examples include systems for air recycling, heating and cooling, energy generation (the solar panels), spacecraft control, science operations, and many more.
- (2): Students may think of a number of different advantages to considering the ISS as a collection of component systems. One of the most important advantages is that, from an engineering and design standpoint, it allows the design and operation of the full ISS to be broken into pieces that individual engineering/design teams can work on.
- (3) It is critical to think in terms of a single system when you are making sure that all the component systems will work together successfully.
- (4) The component systems can be called “subsystems” because they are subsets of the full system. With regard to whether they should be called “systems” or “component systems” or “subsystems”: Allow students to voice and defend their opinions, but most scientists and engineers use the terms interchangeably, because in some sense almost all “systems” are a “subsystem” of some larger system. For example, in the case of Earth (to be discussed shortly): The four systems (geosphere, atmosphere, hydrosphere, biosphere) can be considered subsystems of a single “Earth system.” But we can also think of the Earth system as a subsystem of our solar system, and our solar system as a subsystem of our galactic system, and so on. What matters is being aware of how different systems (or subsystems) interact with one another.
The International Space Station offers a good analogy to our Earth as a whole, which is one reason that it can be useful to think of our planet as “Spaceship Earth.” That is, much like the International Space Station, we can think of our planet either as a single large system that makes our lives possible or as a set of component systems that work together.
Both viewpoints are valuable, but it is generally easier to study our planet by first learning about the component systems, then thinking about how they all work together. This approach, in which we consider both the component systems and Earth as a whole, constitutes what usually called Earth system science .
Section Learning Goals
By the end of this section, you should be able to answer the following questions:
- What are Earth’s four major systems?
- What drives Earth system changes?
- What IS energy and how do we measure it?
Before you continue, take a few minutes to discuss the above Learning Goal questions in small groups or as a class. For example, you might discuss what (if anything) you already know about the answers to these questions; what you think you’ll need to learn in order to be able to answer the questions; and whether there are any aspects of the questions, or other related questions, that you are particularly interested in.
Journal Entry
Your Family System
As a middle schooler, you depend on other people in many ways. For example, you depend on your teachers to provide structure for your education, and you probably depend on family members for food, shelter, comfort, and much more. Write a journal entry of any length to describe how your family functions as a “system” that makes it possible for you to live and go to school. Be sure to include at least a brief discussion of whether or how your family system can be considered as a set of component systems (such as a system for meals and a system for transportation to school), and of the roles that different family members (including you) play in each system or in the overall system.
This journal entry is intended to get students to think a bit more about the nature of a “system,” this time in the context of their own family. Note that it might also give you some insight into your students’ lives and the challenges that they face, which is always useful to know given your daily interactions with them.