As of this post the Linux kernal represents 5,552 years of human effort according to https://www.openhub.net/p/linux estimates. Even considering a wide range of error in that estimate it is still incredible. But then again there are a lot of humans on the planet and combining all their work can quickly provide centuries worth of human labor. Raises lots of questions. A a £303 million dollar project in ‘free’ use by the very underpinnings of the internet. Pretty wild.