A thermoscope is a device that shows changes in

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

. A typical design is a tube in which a liquid rises and falls as the temperature changes. The modern

thermometer A thermometer is a device that measures temperature (the hotness or coldness of an object) or temperature gradient (the rates of change of temperature in space). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb ...

gradually evolved from it with the addition of a scale in the early 17th century and standardisation throughout the 17th and 18th centuries.

Function

Devices employing both heat and pressure were common during Galileo's time, used for fountains, nursing, or bleeding in medicine. The device was built from a small vase filled with water, attached to a thin vertically rising pipe, with a large empty glass ball at the top. Changes in temperature of the upper ball would exert positive or negative pressure on the water below, causing it to rise or lower in the thin column. The device established fixed points but does not measure specific quantity, although it can tell when something is warmer than another thing. Essentially, thermoscopes served as a justification of sorts regarding what is observed or experienced by the senses – that the device's basic agreement with the indications of the senses generates initial confidence in its reliability. Large thermoscopes placed outdoors appeared to cause

perpetual motion Perpetual motion is the motion of bodies that continues forever in an unperturbed system. A perpetual motion machine is a hypothetical machine that can do work indefinitely without an external energy source. This kind of machine is impossible ...

of contained water, and these were therefore sometimes called perpetuum mobile. Galileo's own work with the thermoscope led him to develop an essentially atomistic conception of heat, published in his book '' Il Saggiatore'' in 1623.

History

Philo of Byzantium Philo of Byzantium (, ''Phílōn ho Byzántios'', ), also known as Philo Mechanicus (Latin for "Philo the Engineer"), was a Greek engineer, physicist and writer on mechanics, who lived during the latter half of the 3rd century BC. Although he wa ...

is credited with the construction of the first thermoscope (or Philo thermometer), an early version of the thermometer. It is also thought, but not certain, that

Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

discovered the specific principle on which the device is based and built the first thermoscope in 1593. In the 17th century Galileo mentioned to his friend Cesare Marsili that he invented a thermoscope as far back as 1606. The inventor could be his physician friend Santorio Santorio or another person of the learned circle in Venice of which they were members. What is certain is that the thermoscope had started circulating in market squares during Galileo's time. The development of the actual device is attributed to four inventors; namely: Galileo, Santorio Santorio,

Robert Fludd Robert Fludd, also known as Robertus de Fluctibus (17 January 1574 – 8 September 1637), was a prominent English Paracelsian physician with both scientific and occult interests. He is remembered as an astrologer, mathematician, cosmol ...

, and

Cornelius Drebbel Cornelis Jacobszoon Drebbel (; 1572 – 7 November 1633) was a Dutch engineer and inventor. He was the builder of the first operational submarine in 1620 and an innovator who contributed to the development of measurement and control systems, opti ...

. However, the general pneumatic principle of the thermoscope was used in the Hellenic period, and it was written about even earlier, by

Empedocles Empedocles (; ; , 444–443 BC) was a Ancient Greece, Greek pre-Socratic philosopher and a native citizen of Akragas, a Greek city in Sicily. Empedocles' philosophy is known best for originating the Cosmogony, cosmogonic theory of the four cla ...

of Agrigentum in his 460 B.C. book ''On Nature''. Santorio Santorio wrote a ''Commentary on the Medical Art of Galen'' in 1612 that described the device in print. Shortly afterward, in 1617 Giuseppe Biancani published the first clear diagram. The device at this time could not be used for quantitative or standardized measurement and used the temperature of air to expand or contract gas, thereby moving a column of water. It was Drebbel who announced in the early 17th century one of the earliest or possibly the first prototype, which was filled with air and blocked by water containing a little '' aqua fortis'' to prevent it from freezing and being discolored. The device was improved by early German scientist

Otto von Guericke Otto von Guericke ( , , ; spelled Gericke until 1666; – ) was a German scientist, inventor, mathematician and physicist. His pioneering scientific work, the development of experimental methods and repeatable demonstrations on the physics of ...

in the 17th century.

Ferdinando II de' Medici, Grand Duke of Tuscany Ferdinando II de' Medici (14 July 1610 – 23 May 1670) was Grand Duchy of Tuscany, grand duke of Tuscany from 1621 to 1670. He was the eldest son of Cosimo II de' Medici, Grand Duke of Tuscany, Cosimo II de' Medici and Archduchess Maria Mad ...

personally made a further improvement by introducing the use of a colored alcohol, so that the material responding to heat was now liquid instead of gas. It is possible that Francesco Sagredo or Santorio may have added some kind of scales to thermoscopes, and Robert Fludd may have accomplished something similar in 1638.J. E. Drinkwater (1832)''Life of Galileo Galilei'' page 41The Galileo Project: Santorio Santorio
/ref> In 1701 Ole Christensen Rømer effectively invented the thermometer by adding a

temperature scale Scale of temperature is a methodology of calibrating the physical quantity temperature in metrology. Empirical scales measure temperature in relation to convenient and stable parameters or reference points, such as the freezing and boiling point ...

(see Rømer scale) to the thermoscope.

References

The Galileo Project
"The Thermometer" * Benedict, Robert P., 1984. Chapter 1, "Early attempts to measure degrees of heat", in ''Fundamentals of Temperature, Pressure and Flow Measurement'', 3rd ed, Wiley . {{Galileo Galilei Thermometers Meteorological instrumentation and equipment Inventions by Galileo Galilei nl:Thermometer#Thermoscoop pl:Termometr Galileusza#Historia

Function

History

See also

References