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Archimedes' Principle of Buoyancy
Why Do Ships Float?
The Greek Mathematician and inventor Archimedes lived during the 3rd
century BC. According to history he was in the bath one day when he
discovered the principle of buoyancy which is the reason why huge Greek
ships weighing thousands of pounds could float on water. He noticed that
as he lowered himself into the bath, the water displaced by his body
overflowed the sides and he realised that there was a relationship
between his weight and the volume of water displaced. It is said that he
ran naked into the street yelling "heurEka" which is
where we get our word "eureka!" (I found it), Greek heurEka
I have found, from heuriskein to find.
Archimedes was not thinking about ships at the time,
he was on a mission to solve a question that was asked of him by King
Hieron II of Syracuse, the home of Archimedes which was a Greek city at
the time. The question that the king had asked was about his crown. Was
it pure gold or partly silver? Archimedes reasoned that if the crown had
any silver in it, it would take up more space than a pure gold crown of
the same weight because silver is not as dense as gold. He compared the
crown's volume (measured by the amount of water displaced) with the
volume of equal weights of gold and then silver, he found the answer. He
had to inform his king that the crown was not pure gold.
The Buoyancy Principle
Archimedes continued to do more experiments and came up
with a buoyancy principle, that a ship will float when the weight of the
water it displaces equals the weight of the ship and anything will float
if it is shaped to displace its own weight of water before it reaches
the point where it will submerge.
This is kind of a technical way of looking at it. A
ship that is launched sinks into the sea until the weight of the water
it displaces is equal to its own weight. As the ship is loaded, it sinks
deeper, displacing more water, and so the magnitude of the buoyant force
continuously matches the weight of the ship and its cargo.
The Metacenter
Archimedes figured out that the metacenter had to be
determined which is a point where an imaginary vertical line (through
the center of buoyancy) intersects another imaginary vertical line
(through a new centre of buoyancy) created after the ship is displaced,
or tilted, in the water.
The center of buoyancy in a floating ship is the point
in which all the body parts exactly balance each other and make each
other float. In other words, the metacenter remains directly above the
center of buoyancy regardless of the tilt of the floating ship. When a
ship tilts, one side displaces more water than the other side, and the
center of buoyancy moves and is no longer directly under the center of
gravity; but regardless of the amount of the tilt, the center of
buoyancy remains directly below the metacenter. If the metacenter is
above the center of gravity, buoyancy restores stability when the ship
tilts. If the metacenter is below the center of gravity, the boat is
unstable and capsizes.
Why is this important in
the study of Biblical history?
Good question! As the study of physics and various sciences were being
developed in ancient Greece it, among other things, opened a door for
the Lord to bring new learning and new technology into the world that
would eventually help to prepare the world at just the right time for
the coming of the Savior and His gospel. We have to keep in mind that
men were living in darkness and the darkness was increasing in its
intensity and the only hope for mankind was the message that Jesus
Christ and His followers would bring. God is very aware of the times and
seasons and the rising and falling of the nations of the world and the
Bible says that "at the fullness of time God sent forth His
Son," and His coming was an epochal event that changed the culture
of western civilization forever and hurled it into a new direction.
Written by Rusty Russell (Bible History
Online)
Webmaster: rusty@bible-history.com
http://www.bible-history.com |
