Sleep

Contrary to popular belief, there is no ideal number when it comes to how much sleep a person needs each night. While eight hours is widely considered the benchmark for sleep, that number is more arbitrary than absolute. Researchers are discovering that how much sleep a person needs depends largely on the individual and his or her situation. Researchers are finding is that two factors have the biggest influence on how much sleep a person needs each night. One is a person's basal sleep need. Basal sleep need refers to how much sleep a person's body needs on a regular basis for optimal performance. This varies greatly depending on the individual. The second factor is a person's sleep debt. Sleep debt is the accumulation of sleep lost, whether it's sleep lost to sickness, environmental changes, or just overall poor sleeping habits. Some research has suggested that sleep debt can impact how a person feels for a long time, evenif that person has met their basal sleep need several nights in a row.

20/20 vision

The term "20/20 vision" does not translate to perfect vision. Rather, the term was coined by eye doctors and refers to what a normal person should be able to see from 20 feet away. People with 20/40 vision, then, can see at 20 feet what a normal person can see from 40 feet away. It is also possible to have vision that is better than the norm. People with 20/10 vision, for example, can see from 20 feet away what a normal person can see from 10 feet away. On the opposite end of the spectrum, the cutoff for legal blindness in the United States is 20/200 vision, meaning you can see at 20 feet away what a normal person can see from 200 feet away.