A Galileo thermometer (or Galilean thermometer) is a thermometer made of a sealed glass cylinder containing a clear liquid and several glass vessels of varying density. The individual floats rise or fall in proportion to their respective density and the density of the surrounding liquid as the temperature changes. It is named after Galileo Galilei because he discovered the principle on which this thermometer is based—that the density of a liquid changes in proportion to its temperature.
Although named after the 16th–17th-century physicist Galileo, the thermometer was not invented by him. (Galileo did invent a thermometer called Galileo's air thermometer, more accurately called a thermoscope, in or before 1603.) [1]
The instrument now known as a Galileo thermometer was invented by a group of academics and technicians known as the Accademia del Cimento of Florence, [2] who included Galileo's pupil, Torricelli and Torricelli's pupil Viviani. [3] [4] Details of the thermometer were published in the Saggi di naturali esperienze fatte nell'Academia del Cimento sotto la protezione del Serenissimo Principe Leopoldo di Toscana e descritte dal segretario di essa Accademia (1666), the academy's main publication. The English translation of this work (1684) describes the device ('The Fifth Thermometer') as 'slow and lazy', a description that is reflected in an alternative Italian name for the invention, the termometro lento (slow thermometer). [5] The outer vessel was filled with 'rectified spirits of wine' (a concentrated solution of ethanol in water); the weights of the glass bubbles were adjusted by grinding a small amount of glass from the sealed end; and a small air space was left at the top of the main vessel to allow 'for the Liquor to rarefie' (i.e. expand).
The device now called the Galileo thermometer was revived in the modern era by the Natural History Museum, London, which started selling a version in the 1990s. [6]
In the Galileo thermometer, the small glass bulbs are partly filled with different-colored liquids. The composition of these liquids is mainly water; some contain a tiny percent of alcohol, but that is not important for the functioning of the thermometer; they merely function as fixed weights, with their colors denoting given temperatures. Once the hand-blown bulbs have been sealed, their effective densities are adjusted using the metal tags hanging from beneath them. Any expansion due to the temperature change of the colored liquid and air gap inside the bulbs does not affect the operation of the thermometer, as these materials are sealed inside a glass bulb of approximately fixed size. The clear liquid in which the bulbs are submerged is not water, but some organic compounds (such as ethanol or kerosene) the density of which varies with temperature more than water does. Temperature changes affect the density of the outer clear liquid and this causes the bulbs to rise or sink accordingly. [2]
As the temperature rises the bulbs will sink one by one according to their individual density as the clear holding fluid's density gradually changes around them. Eventually all the bulbs may be at the base of the tube depending on the temperature of the surroundings and therefore that of the clear holding fluid. As the temperature falls the reverse happens with the bulbs, until they can all be at the top.
The metal tags on each bulb are stamped with a temperature. If a bulb is in the centre of the column, that gives a close approximation of the environment temperature outside the tube. If there are some at the top and some at the base but none in between the average of the lowest bulb at the top and the highest at the base provides that figure.
A thermometer is a device that measures temperature or temperature gradient. A thermometer has two important elements: (1) a temperature sensor in which some change occurs with a change in temperature; and (2) some means of converting this change into a numerical value. Thermometers are widely used in technology and industry to monitor processes, in meteorology, in medicine, and in scientific research.
A barometer is a scientific instrument that is used to measure air pressure in a certain environment. Pressure tendency can forecast short term changes in the weather. Many measurements of air pressure are used within surface weather analysis to help find surface troughs, pressure systems and frontal boundaries.
This is a timeline of temperature and pressure measurement technology or the history of temperature measurement and pressure measurement technology.
The mercury-in-glass or mercury thermometer is a thermometer that uses the thermal expansion and contraction of liquid mercury to indicate the temperature.
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Evangelista Torricelli was an Italian physicist and mathematician, and a student of Galileo. He is best known for his invention of the barometer, but is also known for his advances in optics and work on the method of indivisibles. The torr is named after him.
Vincenzo Viviani was an Italian mathematician and scientist. He was a pupil of Torricelli and Galileo.
Ferdinando II de' Medici was grand duke of Tuscany from 1621 to 1670. He was the eldest son of Cosimo II de' Medici and Maria Maddalena of Austria. Remembered by his contemporaries as a man of culture and science, he actively participated in the Accademia del Cimento, the first official scientific society in Italy, formed by his younger brother, Leopoldo de' Medici. His 49-year rule was punctuated by the beginning of Tuscany's long economic decline, which was further exacerbated by his successor, Cosimo III de' Medici. He married Vittoria della Rovere, a first cousin, with whom he had two children who reached adulthood: the aforementioned Cosimo III, and Francesco Maria de' Medici, Duke of Rovere and Montefeltro, a cardinal.
The Accademia del Cimento, an early scientific society, was founded in Florence in 1657 by students of Galileo, Giovanni Alfonso Borelli and Vincenzo Viviani and ceased to exist about a decade later. The foundation of Academy was funded by Prince Leopoldo and Grand Duke Ferdinando II de' Medici. The tenets of the society included:
Drinking birds, also known as dunking birds, drinky birds, water birds, or dipping birds are toy heat engines that mimic the motions of a bird drinking from a water source. They are sometimes incorrectly considered examples of a perpetual motion device.
Temperature measurement describes the process of measuring a current temperature for immediate or later evaluation. Datasets consisting of repeated standardized measurements can be used to assess temperature trends.
A medical thermometer or clinical thermometer is a device used for measuring the body temperature of a human or other animal. The tip of the thermometer is inserted into the mouth under the tongue, under the armpit, into the rectum via the anus, into the ear, or on the forehead.
A thermoscope is a device that shows changes in temperature. A typical design is a tube in which a liquid rises and falls as the temperature changes. The modern thermometer gradually evolved from it with the addition of a scale in the early 17th century and standardisation throughout the 17th and 18th centuries.
The alcohol thermometer or spirit thermometer has a similar construction and theory of operation as a mercury-in-glass thermometer. However, the thermometric fluid of an alcohol thermometer is less toxic and evaporates quickly making it a safer alternative to mercury thermometers. The ethanol version is the most widely used due to the low cost and relatively low hazard posed by the liquid in case of breakage.
A lava lamp is a decorative lamp, invented in 1963 by British entrepreneur Edward Craven Walker, the founder of the lighting company Mathmos.
A hand boiler or love meter is a glass sculpture used as an experimental tool to demonstrate vapour-liquid equilibrium, or as a collector's item to whimsically "measure love." It consists of a lower bulb containing a volatile liquid and a mixture of gases that is connected usually by a twisting glass tube that connects to an upper or "receiving" glass bulb.
The Tribune of Galileo is a Neoclassic architectural addition, built to commemorate the famous Florentine scientist, Galileo Galilei and to house some of his scientific instruments.
The tall-stem thermometers are a kind of thermometer, resting on branched feet.
The frog thermometer or - as the Cimento academicians defined it, the botticino [small-toad] thermometer - contained small glass spheres of different density, which were immersed in alcohol. The device was used as a clinical thermometer, tied to the wrist or the arm of the patient with the head of the frog facing upward. The variations in body temperature were registered by the movement of the spheres. The rise in temperature causes an increase in the volume of the alcohol, reflected in the movement of the small spheres. Because of the spheres' sluggish motion, this thermometer was also called infingardo [slothful, slow]. The invention of this model is attributed to Ferdinand II de' Medici.
A Galilean is a person from Galilee, a region of northern Israel and southern Lebanon
