1 EDISON STRIVES TO LIGHT THE WORLD Until the 1800s people had relied on oil lamps candles and later gas lights to light their homes Then electric power started being used This prompted inventors to develop indoor lighting using electricity But inventors struggled to make a lightbulb that was safe and efficient enough for widespread use In a lightbulb electricity heats materials to make it glow and give off light But this was difficult to do without overheating the bulb One early attempt was produced in 1860 But the wire inside the bulb called a filament burned too fast to make it useful Thomas Edison worked on improving the lightbulb in his New Jersey research lab He tested thousands of materials for the 4 Thomas Edison held 1,093 patents a world record
A lightbulb gives off light when the filament inside is heated filament He used a lower current of electricity for a power source In 1879 Edison tried a platinum filament The bulb burned only a few hours Finally he tried a cotton filament made from sewing thread It burned for approximately 15 hours Edison continued working to improve the lightbulb for which he is famous Soon electric lighting was was used in houses and businesses across the country MORE THAN BULBS M Edison did more than improve the lightbulb He developed a system to provide electricity to homes In the 1880s he designed the first commercial electric power station in New York and oversaw its construction Nearby homes and businesses received power from the station to light their homes 5 6,000 Edison tested at least this many different natural resources when experimenting with filaments Introduced 1879 Inventor Thomas Edison Key features Smaller and more efficient than earlier versions
2 CHEMIST INVENTS MATERIAL FOR BULLETPROOF VESTS In 1964 scientists were working in a research lab at DuPont They were looking for chemical combinations that would make stronger fibers for fabrics One day chemist Stephanie Kwolek heated a new mixture She was trying to turn it into a liquid to be tested but it wouldn’t melt She added another chemical to dissolve it Most mixtures she had tried made thick clear liquids But this one was very thin and cloudy Kwolek could tell it was unlike any other mixture the lab had ever made In 2012 the Swiss Barefoot Company introduced socks made out of Kevlar They can be worn without shoes 6
Another scientist put the liquid into a machine that spun it The spinning separated it into fibers Other scientists tested the fibers They found that the fibers were very lightweight but stronger and stiffer than heavier fibers The lab decided to call Kwolek’s substance Kevlar Kevlar is perfect for making bulletproof vests It is five times stronger than steel but much lighter than fiberglass A vest made with seven layers of Kevlar fibers can stop a 38 bullet fired from 10 feet 3 m away It can also stop a knife Kevlar has saved thousands of lives over the years It is also used to make brake pads suspension bridge cables airplane tires safety helmets and many other products Bulletproof vests have 20 to 40 layers of Kevlar More layers mean stronger protection 17 Number of patents received by Stephanie Kwolek five of which were related to the invention of Kevlar Introduced 1964 Inventor Stephanie Kwolek Key features Lightweight strong stiff material used in bulletproof vests and other products 7
