[Music] Problems. Problems, problems, problems. We've been learning a lot about engineering lately and engineering always starts with a problem that needs to be solved. But I'm tired of talking about problems, so let's talk about solutions instead. We've already learned about how engineers design problems. Now it's time to discover how they define success. I don't mean how they define success in general, like "success is graduating from a good school" or "success is getting a good bonus check at work" or "success is winning a lifetime supply of macaroni and cheese." Although, I'm not gonna lie, that sounds like success to me. When engineers define success, they do it in relation to the problem they're trying to solve. So, for example, what does a successful solution to my problem look like? The big question we're asking today is "what makes a solution successful?" [MUSIC] OK. Let's back up a bit. A solution is what again? A solution is something an engineer designs or builds to solve a problem he or she has. Some solutions that engineers have come up with include the telephone, a solution to the problem of how people in different places can communicate with each other. Or the refrigerator, a solution to not being able to keep foods fresh for long periods of time. Or light bulbs, a solution to not being able to see at night, using something that's safer, brighter, and more reliable than an open flame. Every day engineers design and build solutions, but how do they decide which of the many potential solutions that they brainstorm will be the most successful? I think an example would be helpful here, and we've already invented a fake problem, so why not invent a fake solution too? Back to the canyon. You know, that insanely deep one with no bridge and a raging river at the bottom of it? Yeah. That one. [Music] The problem we defined at that spot was "How do we fly across this canyon?" I'll be your stand-in engineer again. Being a good engineer, I know it's time to identify the criteria for my solution. Basically, I need to figure out which things my solution needs to do in order to be considered successful. Think of it like making a checklist. Number one, it should get me to the other side, and let me be more specific, it should get me to the other side alive. Number two, it - the thing that gets me to the other side - should be something I currently have or can easily access. Number three, it would be nice if I could reuse whatever "it" is once I'm on the other side. Now, if Superman's Fortress of Solitude was nearby, I'd snag him and make him fly me over this canyon no prob. But sadly, I don't have access to Superman's secret lair. So, like any other engineer, I have to make do with what I have. So what do I have? I've got the tent that I camp with, and that's about it. You guys! I could make a hang glider out of my tent! It's a resource I already have and if I build it properly, it will get me to the other side alive, which is ultimately where I want to be. Plus, bonus, I can dismantle the glider on the other side and use the pieces for their original purpose, keeping me sheltered from lions and tigers and bears. Oh my! [Music] So, Superman's a solution in that if he were real and if I could somehow contact him to get him to carry me over this canyon, he could get me to the other side alive. But, he's not the most successful solution because he doesn't meet all of my criteria. He's not currently with me and I can't easily find him. I mean, the whole point of a secret lair is that it's secret. So a hang glider meets all of my criteria, which means that's our solution. We'll fly across this very big canyon with a hang glider. And of all the solutions that an engineer can brainstorm to whatever problem he or she has, the most successful one - the one that meets all or most of the criteria - is the one that engineers actually attempt to design. Now, actually making a hang glider out of a tent is a different step in the engineering process, so it's one that we kind of fortunately don't have to mess with today, because I have zero idea about how to build or fly a hang glider. And anyway, remember that this is a totally fake, made-up solution. Don't go jumping into a canyon or anything with a tent, OK? We're here to solve problems, not create new ones. [Music]