Audioguida Hall: Thermology and Meteorology

Thermology, the science that studies phenomena related to heat, makes enormous progress in the nineteenth century.

Thanks to the research of Benjamin Thompson and others, the theory that postulated the existence of "caloric", a sort of fluid responsible for the temperature of bodies, is slowly abandoned and the idea that heat is linked to the internal movement of the bodies catches on.

In-depth studies on materials dilation brought significant improvements in the construction of thermometers; in the collection of the Physics dozens of thermometers both for purely didactic use and for precision, measurements are preserved.

The phenomena related to gas physics started being studied and thanks to various calorimeters the specific heats, the latent heats and the heats of combustion were measured with precision.

The first experiments for the liquefaction of gases started being carried out thanks to machines capable of simultaneously compressing and cooling them, and machines that made it possible to freeze water and obtain ice artificially were also invented.

In 1824, studying steam engines, Sadi Carnot, one of the fathers of thermodynamics, demonstrated that work can be obtained through the heat exchange between two sources at different temperatures.

Carnot, while still thinking in terms of caloric, quantified this work and introduced the concepts of thermodynamic cycle and performance.

The thermodynamic cycle includes processes, among which a diabatic compression, that had already been empirically put to use, for example, in the pneumatic tinder-boxes.

In the 1840s, after extensive research, which played an essential role in the development of the law on energy conservation, James Joule accurately determined the mechanical equivalent of the calorie.

In the middle of the century James C. Maxwell and Ludwing Boltzmann laid the foundations of the kinetic theory of gases, according to which their physical properties are explained in terms of the microscopic dynamics of molecules.

The theoretical-mathematical apparatus of thermodynamics became increasingly sophisticated and, starting from the last decades of the century, it found very important practical applications, for example in the design of thermal machines such as steam engines, internal combustion engines, etc.

Finally, thanks to Macedonio Melloni, a systematic study of infrared rays was carried out: at the time, they were called "radiant heat" and were studied through experiments such as those with parabolic reflectors.

Meteorology is the science that studies atmospheric phenomena.

Their influence on human life, and on its activities such as agriculture, has meant that the first climate observations and the first meteorological theories date back to antiquity.

From the end of the eighteenth century, the meteorological observations started being made systematically and in the nineteenth century they were extended thanks to the establishment of an increasingly widespread network of observers and also thanks to the introduction of recording instruments.

The Cabinet owns a small collection of instruments related to meteorology that, in the nineteenth century, was considered a branch of physics.

The collection includes a series of barometers of various types, that allowed measurements not only inside the laboratories but also outside.

It is also possible to find some hygrometers that measure humidity, mercury or alcohol thermometers, anemometers that measure wind speed and some instruments that measure solar radiation.

The introduction of systematic meteorological observations required the presence of an observer who periodically transcribed the indications of the various instruments, thanks to tedious and repetitive procedures.

To overcome this drawback, recording devices were introduced in the nineteenth century: the recording was made possible thanks to a sheet of paper that was moved by a clockwork movement.