1 The Birth of Science - MSRI

4.9 Heron’s Role 115
from one wheel to another, he never uses gears, only friction devices. This
is easily explained if we assume that in his time it had become difficult to
procure not just precision metal screws but even gears.
In the few cases where direct documentation is available, the technology
of earlier centuries appears more sophisticated than Heron’s; for example, page 157
from his work we would never suspect the existence of differential gears
of the type used in the Antikythera machine, which predates Heron by
about 150 years. 136
We see that Heron’s writings provide precious, but late and incomplete,
documentation about the level of Hellenistic technology, and cannot be
used unless with great caution to evaluate the motivations that led to that
technology’s appearance and development in a completely different cultural
and political climate, centuries earlier. Some relevant observations
toward such an evaluation:
Mechanics and pneumatics arose in close connection with technology
and, as we have seen, allowed the creation of many economically useful
devices as early as the third century B.C.
Heron himself describes many devices that are not at all just amusements:
artillery weapons, various types of press, machines to lift weights,
the dioptra, the screw maker.
A growing number of aspects of Heronian technology are now known
to have had serious uses in Hellenistic times. For example:
– We knew that some of Heron’s models were moved by water power.
Now we know that those models reflected real-life installations based
on efficient vertical water wheels, which had been in use long before.
– We knew about the use of fluid pressure in Heron’s “toys”. From twentieth-century
archeological excavations we have learned that the same
principles were used to build pumps in widespread use and pressure
pipes that supplied cities with water.
– We knew about the use of hydrostatic principles in Heron’s works. The
same principles, as we have seen, were very likely used in the third
century B.C. in naval technology.
Sometimes Heron obtains the spectacular effects he seeks by altering
simple experimental devices. Take for instance the thermoscope described
by Philo in chapter vii of his Pneumatics, a simple setup to demonstrate
136 See Section 4.8 above. Also Archimedes’ planetarium must have reproduced the correct ratio
of angular velocities not only of sun and moon, but also of the planets. Since we know that various
gears were already in use in Archimedes’ time and that science was already on the wane at the time
of the Antikythera machine, we may imagine that Archimedes’ planetarium was technologically
even more sophisticated.
Revision: 1.14 Date: 2002/10/24 04:25:47