Answer:
In our age of fuel cells and electric cars, steam locomotives (and even gasoline-powered cars) might seem like horribly old technology. But take a broader view of history and you'll see that even the oldest steam engine is a very modern invention indeed. Humans have been using tools to multiply their muscle power for something like 2.5 million years, but only in the last 300 years or so have we perfected the art of making "muscles"— engine-powered machines—that work all by themselves. Put it another way: humans have been without engines for over 99.9 percent of our existence on Earth!
Now we have engines, of course, we couldn't possibly do without them. Who could imagine life without cars, trucks, ships, or planes—all of them propelled by powerful engines. And engines don't just move us around the world, they help us radically reshape it. From bridges and tunnels to skyscrapers and dams, virtually every major building and structure people have made in the last couple of centuries has been built with the help of engines—cranes, diggers, dumper trucks, and bulldozers among them. Engines have also fueled the modern agricultural revolution: a vast proportion of all our food is now harvested or transported using engine power. Engines don't make the world go round, but they're involved in virtually everything else that happens on our planet.
