A thermoscope is a device that shows changes in

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

. 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 or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a mercury-in-glass thermometer ...

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 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

It is thought, but not certain that

Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He wa ...

discovered the specific principle on which the device is based and built the first thermoscope in 1593. Or the 17 Centary 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, 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, ...

. However, the general pneumatic principle of the thermoscope was used in the

Hellenic period In Classical antiquity, the Hellenistic period covers the time in Mediterranean history after Classical Greece, between the death of Alexander the Great in 323 BC and the emergence of the Roman Empire, as signified by the Battle of Actium in 3 ...

, and it was written about even earlier, by

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

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 Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

'' to prevent it from freezing and being discolored. The device was improved by early German scientist Otto von Guericke in the 17th century.

Ferdinando II de' Medici, Grand Duke of Tuscany Ferdinando II de' Medici (14 July 1610 – 23 May 1670) was grand duke of Tuscany from 1621 to 1670. He was the eldest son of Cosimo II de' Medici and Maria Maddalena of Austria. He was remembered by his contemporaries as a man of culture ...

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, such as the freezing and boiling point of water. Absolute ...

(see

Rømer scale The Rømer scale (; notated as °Rø), also known as Romer or Roemer, is a temperature scale named after the Danish astronomer Ole Christensen Rømer, who proposed it in 1701. It is based on the freezing point of pure water being 7.5 degrees a ...

) 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