Pat Kelley, age 13, of Spokane, Wash., for her question:
How old is the thermometer?
The earliest scientists naturally observed the changing temperature of the weather. They knew, of course, that fire makes objects hotter and that warm objects become cooler in the chilly air. It may have occurred to several thinkers that heat might be measured but not one it seems tried to do this tricky job until some 370 years ago.
The scholars of ancient Greece worked out a brilliant system of math and observed the laws of nature with great accuracy. There also were talented scholars in old Babylon and Egypt. These early thinkers mapped and charted and measured the starry heavens and the face of the earth. But they failed to find ways to measure such everyday forces as heat and air pressure. Their minds did not turn to the invention of machines or delicate instruments. The thermometer and the barometer both were unknown to these wise scholars of the ancient world.
Modern science dawned late in the 16th century, perhaps when Copernicus suggested the true picture of our solar system. His theory was proved correct in the late 16th and early 17th century by Galileo, and the mind of mankind was challenged to explore wider fields and to approach the sciences with new methods. Galileo of Italy was one of history's most brilliant astronomers, and more besides. He was a great one for developing instruments to check and measure his observations.
In 1609 he made an instrument with lenses and became the first man to behold the heavens through a telescope. Some 16 years before this wondrous event he had made a delicate glass instrument for measuring temperature. It was the thermoscope, and as far as we know it was the earliest ancestor of our modern temperature measuring thermometers. The year was 1593, which makes the thermometer 372 years old. Galileo, the inventor, was then 29 years old.
The thermoscope was a small air filled globe of glass with a long thin neck. The instrument was warmed with the hands, and the neck was then inserted upside down in a vase of tinted water. As the warmed glass cooled, the level of the water rose higher in the glass tube. This air thermoscope was hampered by atmospheric pressures and far from perfect. But, it was 50 years before anyone made a better thermometer.
In 1654 Grand Duke Ferdinand II of Tuscany made a thermometer with alcohol sealed inside a glass tube. On it the degrees of a temperature scale were marked with small enamel beads. This sealed Florentine thermometer was popular with doctors for years.
Improvements were made, and in 1741 the first mercury filled thermometer was made by Gabriel Fahrenheit. Grand Duke Ferdinand founded a medical center in Florence, and doctors there began to realize the relationship between sickness and body temperature. They had a temperature scale to fix the normal temperature of the human body. In 1701 Isaac Newton suggested a scale based upon the freezing point of water with normal body temperature 12 degrees above it. The modern centigrade scale has 100 equal degrees between the freezing and the boiling points of water.