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Electricity and magnetism: 5th century BC

Two natural phenomena, central to the study of physics, are observed and speculated upon by Greek natural scientists - probably in the 5th century BC, though Aristotle gives credit for the first observation of each to the shadowy figure of Thales.

One such phenomenon is the strange property of amber. If rubbed with fur it will attract feathers or bits of straw. Modern science, in its terms for the forces involved, acknowledges this Greek experiment with amber (electron in Greek). The behaviour of the amber is caused by what we call electricity, resulting from the transfer of what are now known as electrons.
 









The other natural phenomenon, observed in lodestone rather than amber, also derives its scientific name from Greek experiments. Lodestone is a naturally occurring mineral (formed of iron oxide), and it will surprisingly attract small pieces of iron. .

The Greeks find this mineral in a region of Thessaly called Magnesia. They call it lithos magnetis, the 'stone of Magnesia'. Thus the magnet is identified and named, though like rubbed amber it will only be a source of interest and amusement for the next 1000 years and more - until a practical purpose is found for it in the form of the compass.
 






Distillation: 4th century BC

The principle of distillation is probably in use long before it is applied to the production of alcohol. Greek sailors of the 4th century BC know how to derive fresh water from the sea, by boiling salt water and suspending a sponge in the steam (pure water condenses in the sponge).

The distillation of alcohol is possible because it boils at a lower temperature than water. In the simplest form of still, the alcohol vapour condenses on a cold surface held in the steam. Subsequent improvements, achieved at various places and different times, involve channelling the steam into a separate condenser and cooling it in such a way as to separate any intrusive water vapour from the alcohol.
 








Pulley: 4th century BC

An important adaptation of the wheel in technology is the pulley - a wheel round which a rope is run to exert force on an object at the other end. Such a machine is first mentioned in a Greek text of the 4th century BC, but it is likely to have been known much earlier.

In the simplest pulley a single wheel is used (as in hauling a flag up a flagpole), but major mechanical advantages can be achieved with two or more wheels - making it possible to lift a heavier object, albeit more slowly. The effect of two pulleys is that a force capable of pulling the rope two yards at one end will exert twice that force over a distance of only one yard at the other. The effect increases dramatically with more pulleys.
 








Mechanical organ: 3rd century BC

Pipes of varying sorts are among the earliest of musical instruments, and pipers must often have imagined a pipe too large for human lungs. A scientist in Alexandria, by the name of Ctesibius, is credited with being the first to invent an organ - with a hand-operated pump sending air through a set of large Pipes. Each pipe is played by pressing a note on a board. This is the beginning of keyboard instruments.

By the time of the Roman empire, a few centuries later, the organ is a familiar and popular instrument - playing a prominent part in public games and circuses as well as private banquets. The emperor Nero, an enthusiastic performer, is proud of his talents on the organ.
 








Archimedes: water and specific gravity, c.250 BC

Archimedes, working in Syracuse in the 3rd century BC, features in popular tradition as one of the most practical of Greek mathematicians. His study of spirals is reflected in the simple irrigation machine known as the Screw of Archimedes.

The legend is that the king of Syracuse, Hiero II, is troubled by the problem of how to get water out of the hold of a large ship. He turns to the local genius, who devises a spiral watertight tube, inclined at an angle with its lower end in the water. When it is turned, the effect of the spiral is to raise the water. As if by magic, it pours out at the top end.
 










Another problem confronting the king proves equally stimulating to the scientist's inventive faculties. Hiero suspects that he may have been cheated by his goldsmiths. He has ordered a crown of pure gold. How can he be certain, when it is delivered, that it has not been adulterated with some cheaper silver?

He asks Archimedes, who - the story goes - is nonplussed until he steps into his bath.
 








The overflow of water from the bath gives Archimedes the solution to the problem. His body displaces a certain amount of water. Another object, of the same weight but more dense, will displace less water. Archimedes only has to immerse an ingot of pure gold of the same weight as the crown. If it and the crown displace the same amount, then the crown too is pure gold.

The popular legend accurately reflects an important discovery about specific gravity - and naturally dresses it up in lively detail. The scientist is so excited that he leaps from his bath and runs naked down the street crying eureka (Greek for 'I have found it').
 






Cement: c.200 BC

Builders in Greek cities on the coast of Turkey (and in particular Pergamum) evolve cement in about 200 BC as a structural material, in place of weaker mortars such as gypsum plaster (used in Egypt) or bitumen (in Mesopotamia). The secret of the new material is the lime which binds sand, water and clay.

The Romans subsequently use finely ground volcanic lava in place of clay, deriving it mainly from the region of Pozzuoli. Their cement, known for this reason as pozzolanic, is the strongest mortar in history until the development of Portland cement. When small fragments of volcanic rubble are included, the result is concrete - making possible the great arches and aqueducts of Roman architecture, and playing its part in Roman roads.
 








The development of the stirrup: 2nd c. BC - 7th c. AD

It is probable that early nomadic horsemen, such as the Scythians, use some form of looped fabric to support their feet. But the first direct evidence of a stirrup is a loop for the big toe used by Indian cavalry from the 2nd century BC. Suitable only for use by barefoot warriors in warm climates, this device spreads gradually through southeast Asia.

At some time before the 5th century AD the Chinese, who need to keep their boots on, transform the toe loop into a metal stirrup for the whole foot. From China this crucial device moves westwards, through Iran to the Muslim world in the 7th century, and then through the Byzantine empire to western Europe.
 








Pergamum and parchment: 2nd century BC

During the 2nd century BC people in the region of the Mediterranean begin using a much more expensive alternative to papyrus. Tradition credits its invention to Eumenes II, who rules in Pergamum on the west coast of Turkey from 197 to 159 BC. The substance is parchment (the word derives from a variation of Pergamum). It is a form of leather.

Ordinary leather has occasionally been used for these purposes since about 2500 BC, but only one side can be written on. With parchment both sides are treated and rubbed until smooth, to form a flexible double surface.
 








Astrolabe: c.140 BC

The astrolabe (meaning 'star taker') is arguably the world's oldest scientific instrument. It is often credited as an invention to Hipparchus, a leading Greek astronomer of the 2nd century BC.

The astrolabe measures the angle of the sun or of a star above the horizon and provides a chart (in later examples often beautifully engraved in metal) showing the heavens at differing latitudes and times. The altitude of the Pole Star will reveal the observer's latitude, in relation to which the position of sun and stars will give the time of day or night. The instrument is therefore of great use to sailors, until eventually replaced in the 18th century by the sextant.
 








Glassblowing: c.50 BC

The craftsmen of Phoenicia maintain their pre-eminence in glass technology when they discover, in the 1st century BC, how to produce glass vessels in large quantities. Instead of the laborious processes of building up molten glass around a core, or casting it in prepared moulds, the new method is one of startling originality. And it offers potential for very skilled work.

The Phoenicians discover that if a blob of molten glass is fixed to the end of a tube, air blown through the tube will form the blob into a hollow vessel. By turning the tube and controlling the pressure of his breath, the glassblower can vary the shape of the developing vase.
 









The new technology comes within a few years of Pompey bringing this region of the Middle East under Roman control, as the province of Syria. As a result, glass spreads rapidly through the Roman empire.

As a standard household commodity, produced in fairly large quantities, this glass is often of relatively poor quality. But at the top end of the market the skills of the glass-blowers rapidly reach extraordinary standards - making, for example, glass in which one colour is blown within another and the outer skin is partially engraved away to provide a cameo scene. The famous Portland Vase, dating from about 25 BC, is an outstanding example of this technique.
 






Greek atmospheric devices: 1st century AD

Hero, a mathematician in Alexandria in about AD 75, enjoys inventing mechanical gadgets, which he describes in his work Pneumatica. Whether he has the technology to make them we do not know, but his scientific principles are correct.

One such gadget is a primitive version of a steam turbine. Hero says steam should be directed into a hollow globe with outlets through nozzles on opposite sides of the circumference. The nozzles are directed round the rim of the globe. As the steam rushes out, like sparks from a catherine wheel, the globe spins.
 









Hero makes another significant use of atmospheric pressure in a magic altar, putting to work the expansion and contraction of air. A fire heats the air in a container, causing it to expand and force water up a tube into a bucket. The increased weight of the bucket opens the doors of an altar. When the fire is extinguished, the air contracts, the water in the bucket is sucked out and the doors close.

Any temple managing to work this trick is certain to attract more pilgrims, and more money, than its rivals.
 






The discovery of paper: AD 105

Chinese tradition attributes one of the most wide-reaching of inventions to a eunuch at the imperial court, by the name of Cai Lun, in the year AD 105.

Cai Lun may merely have presented the emperor with a report on the new substance, but certainly paper is produced in China in the second century AD. Fragments of it survive, made from rags and the fibres of mulberry, laurel and Chinese grass.
 








Knitting: from the 3rd century AD

Knitting, as a concept, is very simple but extremely hard to imagine. It is likely, therefore, to be one of the few technological developments in ancient history to have an actual inventor. As a challenge to the inventive mind, the problem ('Transform a continuous thread into a piece of fabric without at any point cutting the thread') still seems difficult.

The likelihood of a single moment of invention is also made more probable by the late arrival of knitting. Even though it makes no technological demands (neolithic communities could provide a skein of wool and two long needles), civlization is 3000 years old before the first row is knitted.
 









Knitting first appears in the Roman empire, in the 3rd century AD. The earliest examples to survive are socks (found in tombs in Egypt), and it is in footwear that the advantages of the new technology are most obvious.

Until this time feet have usually been kept warm and protected within the shoe by wrapping them in strips of cloth or leather. In the 2nd century AD the Romans evolve a tailored sock, made of pieces of cloth sewn together. But these lack the elasticity of a knitted fabric. Eventually the demand for knitted stockings is so great that the first knitting machine, devised in 1589, is an early landmark of the Industrial Revolution.
 






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