(SciShow kids intro plays)

Sabrina: Everyone gets a case of the "What Ifs" sometimes. You know, how you ask yourself questions like "what if I run out of popcorn and the movie's not over yet," or "what if it's raining when I walk home from school and I forgot my umbrella?" The threat is real people! But you know who asks themselves "what if" questions everyday? Engineers.

These kinds of questions are really important when you're trying to come up with possible solutions to a problem. Like what if we tried to cross a gorge by building a hang glider from a tent? Remember that? To come up with solutions to problems, like crossing a gorge, you already know that engineers use a series of steps known as the trusty engineering process.

A quick recap: we started by defining a solvable problem, in our case how can we get across the gorge? We looked at more than one solution and chose a solution that met our criteria: it used the materials we had available and it would successfully get us across the gorge on one piece, plus we could reuse the pieces afterwards. Then, in the real world, an engineer would build a prototype of the solution and test a bunch of prototypes before actually using it, and if the solution didn't work they'd go back to the drawing board. Engineers are not quitters!

And there's something else engineers do during the process that we haven't talked about yet, and that's defining variables. Excellent, so now we just need to figure out what variables are.

(text: Big Question)

A variable is just a condition or a value that can be changed, and sometimes a variable is something we can control, where we as the engineers do the changing, but other times variable are totally out of our control. So say we want to see how high a ball bounces after it hits the ground, let's identify some of the variables involved in that.

We can change the height from which we drop the ball, or we can change the kind of ball we drop. Those are conditions we can change, but one thing we can't change is the gravity that pulls the ball toward the center of the Earth after we drop it, that's not a variable we can control. Now, what about our attempt to cross that giant gorge? What are the variables there?

(text: investigation)

First, let's think about the variable that we can control. One variable we can change is the weight of our hang glider. We can reduce the weight that it has to carry by, say, leaving our umbrella behind, or we can add more weight by asking cat-bot to hitch a ride. We can also change part of the hang glider's design. If you've ever built a paper airplane, you know that you can change things like the size or the angle of the wings. These things affect how far or high the airplane flies. The same goes for our hang glider. What about variables we can't control?

Let's talk wind. The wind over our gorge can be nice and breezy, it can also be forceful during a storm, but we can't control that, sorry. Also, just like bouncing a ball, we can't control gravity. Now, whether we can control the variables or not, once we've identified what could possibly change when we're trying to solve a problem, we can start asking what if questions.

Like "what if the wind speed is higher than normal," or "What if we decide to leave our umbrella behind?" We can use the answers to those what-if questions to help us decide if our solution is going to work, which would be nice to know before we go flying off into the gorge, right?

(text: Conclusion)

So engineers identify variables - which are conditions or values that can be changed - when they're looking at and testing solutions to a problem. And by asking yourself what-if questions, you can practice your engineering skills. What if questions can help you identify variables when looking at a problem. Just don't ever ask yourself, "what if I forget something I've learned in Sabrina's awesome engineering videos?" Cuz that's definitely not gonna happen. Right cat-bot? Right.

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