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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Although the Roman numeral for the number 4 has always been taught to have been "IV," according to historians, the ancient Romans probably used "IIII" most of the time. This is partially backed up by the fact that early grandfather clocks displayed IIII for the number 4 instead of IV. Early clockmakers apparently thought that the IIII balanced out the VIII (used for the number 8) on the clock face and that it just looked better.
Increased intake of vitamin D has been shown to reduce fractures up to 25% in older people.
This year, an estimated 1.4 million Americans will have a new or recurrent heart attack.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.