Mechanical engineers have changed the world.

You could even say: the course of history. Not just once but countless times.

Because they’ve identified problems that were holding humanity back, and they solved them. Things were too big and heavy to move. Travel was too difficult.

Distances too far. Our bodies were too weak. If you can think of an invention that revolutionized the way people live, odds are it was created by mechanical engineers.

And I don’t think I’m being biased. Theirs is the field of engineering that focuses on the design, construction, operation, and maintenance of machines and mechanical systems – pretty much anything that moves. And since the beginning, mechanical engineering has faced a great many challenges, and solved a lot of problems.

The examples are too many to count, but consider things like the steam engine, airplanes, robots, and biomechanical suits. The engineers behind all of these devices were able to find solutions to big problems. And of course, they faced difficulties along the way.

But great efforts almost always do. [Theme Music] Back in the day, if you wanted to get somewhere, you would have had two options: your own two feet or a horse. And if you wanted to take a heavy load with you, you needed a carriage. Wheels.

The invention of the wheel is one of the oldest roots of mechanical engineering, along with all of the simple tools that went into building the carriage itself. If we include the simple levers that were used to open gates and bring down bridges, we’d have a great, but primitive, base of early mechanical engineering. But horse-drawn carriages aren’t very fast.

A horse needs rest and food, so it would be generous to say you could cover 80 kilometers a day. This gave the engineers of the past a problem. As the world opened up, it became more important to cover distances in less time, and horses just weren't cutting it.

They needed something faster. They needed an engine. Making its first appearance in the early 18th century, the steam engine marked a major turning point in the development of modern mechanical engineering.

It was proposed that a steam engine could do the work of ten, fifteen, or even twenty horses! And you wouldn’t need to bother with any hay...or manure. This brings us to Thomas Newcomen, the British inventor who developed the first successful steam engine with a piston in 1712.

In his design, atmospheric pressure pushed the piston down, after the condensation of steam had created a vacuum in the cylinder. Its original use was to draw water out of the Cornish tin mines, after Newcomen found how expensive it was to use horses to pump the water. Then along came the Scottish inventor James Watt.

In 1763, while repairing one of Newcomen’s engines, Watt realized that about three quarters of the energy from the steam was going to waste, used only to heat the chamber of the engine. His solution was to have a separate condenser. The steam would then be condensed in a chamber separate from the piston chamber, so that the condensed steam didn't go to waste.

Keeping the two processes separate allowed for continued rotary motion, which was really important, because it allowed for a more consistent source of power. Watt’s invention came to be widely used to run machines in the factories that drove the Industrial Revolution. Watt went on to be the first engineer to be commemorated in Westminster Abbey, with a large, white marble statue erected in his memory.

He also had his last name recognized as a unit of power, which is perhaps one of the highest honors that an engineer can get. But steam engines really came into their own, especially in the realm of transportation, in the locomotives of the 19th century. George and Robert Stephenson, an English father-son duo, are famous for their early steam locomotive, which they called, aptly enough, “Locomotion.” In 1825, it became the first public passenger train, carrying 450 people at 24 kilometers per hour.

Quite a bit faster than a horse! But while wheeled vehicles allowed people to travel more quickly on land, transportation was still limited by bodies of water and rough, mountainous terrain. If engineers could figure out a way to get people to fly, all of that could be avoided!

This problem-solving led to the invention of aircraft. The first powered aircraft to take flight was the Wright Flyer in 1903, which was designed by Wilbur and Orville Wright and used a 12-horsepower gas engine. Orville flew the Wright Flyer on its maiden voyage, traveling 36 meters in 12 seconds.

But the best flight of the day belonged to Wilbur, who traveled over 255 meters in 59 seconds, or a speed of about 15 kilometers an hour, earning him some serious bragging rights. Soon after the Wright brothers’ accomplishment, World War I sparked a burst of aircraft innovation. Engineers began using metal in the structures of the airplanes, and better engines, allowing them to reach higher speeds and altitudes.

Then, in 1930, Sir Frank Whittle obtained his first patent for a turbo-jet engine. But it wasn’t until the outbreak of World War II that the British government had a compelling reason to support his work. By 1941, Whittle’s engine featured a multistage compressor, a combustion chamber, a single turbine, and a nozzle – which was a big improvement, since previous engine designs only had an internal-combustion engine and a propeller.

Jet engines outperformed the older designs, flying farther, faster, and cheaper too. These advances ultimately made commercial air travel possible, and soon people were traveling where once only the birds had ruled. But mechanical engineering doesn’t stop in the air!

Beyond planes, we’ve sent satellites into orbit, astronauts to the moon, and spacecraft carrying rovers all the way to Mars. The aerospace side of engineering actually arose from the mechanical field. And much of what has allowed us to build these machines that move us is another big part of the mechanical engineering field: robotics.

For most of industrial history, humans have been at the center of our workforce. But humans have their limits. Some things are too big and too awkward to move, while other processes needed a finer precision than the human hand allows.

Industrial environments are also often uncomfortable and sometimes even dangerous. And that’s where robots and automation come in. The first industrial robot, called Unimate, appeared around 1960.

It was designed by American inventor George Devol, Jr., who worked with engineer and entrepreneur Joseph Engelberger to get it into factories. Unimate robots had up to six fully programmable axes of motion and could handle parts weighing up to around 225 kilograms at high speeds. They soon joined the assembly line at a General Motors plant, where they took die castings from machines and welded them onto auto bodies.

Since then, robots have gone beyond manufacturing, showing up in our homes to clean the floors, and even hospitals to perform surgeries. But as their applications get more advanced, engineers have more and more factors to consider. They need to worry about how well robots sense their surroundings, how they move and manipulate their environments, and much more.

It’s possible one day that we’ll have robots in many of the places you could imagine a human working. I mean, we’re seeing that now. And speaking of humans, you can think of the human body as just a super complex mechanical system of its own, made of links and connecting joints.

And this is where biomechanics comes in. Engineers need to take into account the stress, load, and impact that our bodies can withstand, and apply it to machines that are modeled on us. Advanced biomechanics is one of the newest divisions of mechanical engineering.

From it, we’re already seeing the beginnings of exoskeleton-suits, limbs that move like their biological counterparts, and other robotic implants. One of the more impressive projects is the Berkeley Lower Extremity Exoskeleton. Funded by the Defense Advanced Research Project Agency in 2000, this device is designed to provide mechanical support to allow nearly anyone to carry larger, heavier loads than they could ever lift on their own.

The ability to carry heavy loads is often a problem for soldiers and disaster relief workers, so finding a solution to this is pretty important. But the problems are many. For one thing, power sources for exo-suits are often too heavy or cumbersome.

But the BLEEX, as it’s called, overcomes this by using a small hybrid power source that delivers hydraulic power for the suit’s locomotion and electrical power for its computer. The first prototype was recently introduced, consisting of two powered, anthropomorphic legs, a power unit, and a backpack-like frame. Using the frame, a person can carry a heavy load, but only have it feel like a few pounds.

In similar fashion, Berkeley is also behind the Austin project, which aims to develop exoskeleton systems for people with mobility disorders. So it’s almost as if we’ve gone full circle, from the inventors who developed the first steam engine to replace the horse, to the biomechanical engineers who are using robotics to simulate the most basic means of transportation: walking. Those are some of the very big problems that mechanical engineers have managed to solve.

And when it comes to the problems that we still face today – from driving in traffic to getting food and water to remote areas – you can bet that mechanical engineers will be there to tackle them. So today we learned all about many different areas of mechanical engineering, beginning with the steam engine. We then moved on to aircraft and the work behind them.

And we finished by going into the more modern areas of robotics and biomechanics. In the next episode we’ll explore electrical engineering, its history, and the work that electrical engineers do. Thanks for watching and I’ll see you then.

Crash Course Engineering is produced in association with PBS Digital Studios. You can head over to their channel to check out a playlist of their latest amazing shows, like PBS Space Time, Above the Noise, and Physics Girl. Crash Course is a Complexly production and this episode of was filmed in the Doctor Cheryl C. Kinney Studio with the help of these wonderful people. And our amazing graphics team is Thought Cafe.