your heart

and speaking of......your heart. The average heart beats 100,000 times per day -- in an average life span, this amounts to as many as 3 billion heart beats. The heart pumps blood through a series of vessels ranging in size from the aorta, which is as thick as a garden hose, to capillaries, which are so small a dozen of them could fit inside a human hair. Every 24 hours, the body's blood travels about 12,000 miles, a trip that comes close to equaling the Earth's circumference at the equator, around 24,800 miles. Credits: The World Almanac 2010