The thermometer

Finding the difference in this pair of images at first sight looks as if it would be easy – but it isn’t.

The picture of the thermometer in the sun reminds us that temperature readings should always be taken in the shade, otherwise you are getting the temperature of the thermometer rather than the air temperature.
Credit for the invention of the thermometer is often given to Galileo, the 17th century Italian astronomer and physicist, but as usual with technological developments there was probably no one ’eureka’ moment but rather a series of discoveries over a long period of time and in different cultures. Galileo’s “invention“ showed increases and decreases in temperature, but did not have any scale on it. The first instrument similar to the one we take for granted today was invented in 1654 by the Grand Duke of Tuscany. Its name comes from two Greek words, ’thermos’ meaning hot, and ’metron’ meaning measure.