This might sound trivial, but have you ever wondered why modern jet engines are so big? For sure, when you have to fly hundreds of people thousands of miles you need some serious power. But the reality is that jet engines have become bigger, while the planes themselves have shrunk in size. The Boeing 747 is significantly bigger than the Airbus A350, but has a smaller jet engine. Well, it all has to do with thrust and efficiency. The bigger the engine, the better its efficiency because it uses less energy to push the same amount of air. MinutePhysics has the breakdown in this amazing video.