That Would Never Happen 

Wired has a great profile of Margaret Hamilton, an early computer software engineer who helped create the software that helped America reach the moon.

Lauren had crashed the simulator by somehow launching a prelaunch program called P01 while the simulator was in midflight. There was no reason an astronaut would ever do this, but nonetheless, Hamilton wanted to add code to prevent the crash. That idea was overruled by NASA. “We had been told many times that astronauts would not make any mistakes,” she says. “They were trained to be perfect.”…Hamilton wanted to add error-checking code to the Apollo system that would prevent this from messing up the systems. But that seemed excessive to her higher-ups. “Everyone said, ‘That would never happen,’” Hamilton remembers.

But it did.

And thus did Hamilton show why a better understanding of human-computer interaction is so important.