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Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.
There are 60,000 miles of blood vessels in every adult human.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
An identified risk factor for osteoporosis is the intake of excessive amounts of vitamin A. Dietary intake of approximately double the recommended daily amount of vitamin A, by women, has been shown to reduce bone mineral density and increase the chances for hip fractures compared with women who consumed the recommended daily amount (or less) of vitamin A.