The Archimedean screw
While in Egypt, Archimedes invented the device that is mostly closely associated with him by
name, the Archimedean screw. This is a helix in a tube that, when turned in the proper direction,
raises a fluid in which the bottom of the tube is immersed to the top of the tube. Unlike a vacuum pump, the Archimedean screw is not dependent on air pressure and can raise water higher than the 10-m (30-ft) limit of vacuum pumps. The screw is still used for irrigation and other purposes today.
Another invention attributed to Archimedes is the orrery, a kind of planetarium in which model planets are moved by clockwork to simulate the movements of actual planets (in his time, in Ptolemaic epicycles, not in Keplerian ellipses). Such devices were made in Hellenic times, and it is probable that Archimedes made one, although less probable that he had the original idea for the mechanism.
Syracuse in the time of Archimedes
During Archimedes’ time Syracuse was ruled by a cousin, King Hiero II, who kept in close touch with the great engineer. Although Archimedes was reputed to be interested only in his intellectual pursuits, Hiero got him involved in public demonstrations of his inventions, a famous case of fraud
detection, and the defense of the city against the Romans.
Give me a place to stand on and with a lever I will move the whole world
Archimedes is often said to have discovered the lever, but humans had been using levers for thousands if not millions of years. He did work out the mathematics of simple machines and, in the process, may have discovered the compound pulley. According to the story, after he remarked, “Give me a place to stand on and with a lever I will move the whole world,” Hiero challenged Archimedes to a demonstration. Archimedes obliged by using compound pulleys to launch single-
handedly one of the largest ships made up to that time, complete with crew aboard.
The hydrostatic principle
The story of Archimedes’ discovery of the hydrostatic principle while in his bath and his subsequent run naked though the city crying “Eureka” is by far the most famous association with Archimedes in the public mind. The detection of a fraudulent amount of gold in a crown Hiero had ordered was accomplished by measuring the crown’s density using the water displaced when the crown was submerged to find the volume. Despite the detailed story related by Vitruvius of this event, it seems
that the concept of density was generally known previously. Instead, Archimedes apparently discovered that a body immersed partly in a fluid displaces a mass of the fluid equal to the mass of the body. This principle extends beyond the concept needed to detect the fraud in the manufacture of the crown.
Archimedes defense of Syracuse
The details of Archimedes’ defense of Syracuse are less generally known. Apparently, he devised a number of improved catapults and crossbows that pushed back ordinary waves of attackers. When the Roman general Marcellus brought out his own “secret weapon,” a kind of seagoing siege vehicle,
Archimedes used levers to drop huge boulders on the attackers, sinking the ships. Another story is that he focused the Sun’s rays with mirrors on the ships to set them afire, but this is unlikely. Archimedes had investigated the parabola and therefore might have once demonstrated how to set fire to a nonmoving object from a distance with solar radiation focused by a parabolic mirror. But technology of that time or this, for that matter was not up to creating a mirror with the light-gathering power and focal length as any use as a weapon of war. Marcellus’s army finally managed to find a weak spot in the defense of the city and overran it. Although Marcellus had instructed his soldiers to spare Archimedes, one of them encountered him contemplating a geometric figure drawn in the sand (the common way to do geometry at the time). When the soldier damaged the figure and Archimedes protested, the soldier killed him.
Archimedean screw and the use of it today
One of the inventions of Archimedes, this device has been used for lifting fluids to a higher level for over 2000 years. The lower end is place in the fluid and as the mechanism is rotated, the fluid flows up through the hollow screw. It is used today for irrigation in parts of Asia and as a part of some modern tools in the United States.