Toothbrushes
Although early forms of the toothbrush have existed since 3000 B.C., toothbrushes like we ...
Scientists say that most people in the United States get far less sleep each night than they need. Recent studies show that our cognitive abilities decline when we do not get enough sleep. This means that sleep deprivation affects our motor control, our memory, our reaction time, and our ability to solve problems. Scientists say that the physical impact of being sleep-deprived for many days is much like being drunk. Most doctors recommend that adults sleep between seven and nine hours each night. The average American adult sleeps about five or six hours. Studies show that we need different amounts of sleep at different ages. When we are children, we might need as much as twelve hours of sleep in every twenty-four-hour cycle. The elderly often sleep as little as four or five hours each night. Studies have also shown that sleep habits differ in a variety of cultures.
Although early forms of the toothbrush have existed since 3000 B.C., toothbrushes like we ...
Also known as Hansen's disease, leprosy has plagued the earth since ancient times. Lep...
As the sun sank lower, Jeremy thought about going back to the harbor. However, the full mo...