- published: 04 Apr 2015
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In physics, buoyancy ( /ˈbɔɪ.ənsi/) is an upward force exerted by a liquid, gas or other fluid, that opposes the weight of an immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the column than at the top. This difference in pressure results in a net force that tends to accelerate an object upwards. The magnitude of that force is proportional to the difference in the pressure between the top and the bottom of the column, and (as explained by Archimedes' principle) is also equivalent to the weight of the fluid that would otherwise occupy the column, i.e. the displaced fluid. For this reason, an object whose density is greater than that of the fluid in which it is submerged tends to sink. If the object is either less dense than the liquid or is shaped appropriately (as in a boat), the force can keep the object afloat. This can occur only in a reference frame which either has a gravitational field or is accelerating due to a force other than gravity defining a "downward" direction (that is, a non-inertial reference frame). In a situation of fluid statics, the net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body.
William Sanford "Bill" Nye (born November 27, 1955), popularly known as Bill Nye the Science Guy, is an American science educator, comedian, television host, actor, mechanical engineer, and scientist. He is best known as the host of the Disney/PBS children's science show Bill Nye the Science Guy (1993–1998) and for his many subsequent appearances in popular media as a science educator.
William Sanford Nye was born in Washington, D.C., the son of Jacqueline (née Jenkins; c. 1920–2000), a codebreaker during World War II, and Edwin Darby "Ned" Nye (died 1997), also a World War II veteran whose experience in a Japanese prisoner of war camp led him to become a sundial enthusiast. Nye is a fourth-generation Washington, D.C. resident on his father's side of the family. After attending Lafayette Elementary and Alice Deal Junior High in the city, he was accepted to the private Sidwell Friends School on a partial scholarship, graduating in 1973. He studied mechanical engineering at Cornell University, where one of his professors was Carl Sagan, and graduated with a Bachelor of Science in 1977. He was awarded an honorary doctorate by The Johns Hopkins University in May 2008. In May 2011, Nye was awarded an Honorary Doctor of Science degree from Willamette University where he was the keynote speaker for that year's commencement exercises.
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