Before the invention of the wheel in 3500 B.C., humankind was severely limited in how much stuff it could transport over land, and how far. Wheeled carts facilitated agriculture and commerce by enabling the transportation of goods to and from markets, as well as easing the burdens of people traveling great distances. Now, wheels are vital to our way of life, found in everything from clocks to vehicles to turbines.
The printing press
The German Johannes Gutenberg invented the printing press around 1440. Key to its development was the hand mold, a molding technique that enabled the rapid creation of large quantities of metal movable type. Printing presses exponentially increased the speed with which book copies could be made, and thus they led to the rapid and widespread dissemination of knowledge for the first time in history. Twenty million volumes had been printed in Western Europe by 1500.
The light bulb
When all you have is natural light, productivity is limited to daylight hours. Light bulbs changed the world by allowing us to be active at night. As well as initiating the introduction of electricity in homes, this invention also had the consequence of changing people’s sleep patterns. Instead of going to bed at nightfall (having nothing else to do) and sleeping in segments throughout the night separated by periods of wakefulness, we now stay up except for the 7 to 8 hours allotted for sleep.
Not only have birth control pills, condoms and other forms of contraception sparked a sexual revolution in the developed world by allowing men and women to have sex for leisure rather than procreation, they have also drastically reduced the average number of offspring per woman in countries where they are used. On the global scale, contraceptives are helping the human population gradually level off; our number will probably stabilize by the end of the century.
The global system of interconnected computer networks known as the Internet is used by billions of people worldwide. In the 1960s, a team of computer scientists working for the U.S. Defense Department built a communications network to connect the computers in the agency,called ARPANET. It was the predecessor of Internet.
Today, an estimated 3 billion people worldwide have access to this network.