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He
realised that the density of a liquid changes with the temperature.
That’s why, in the thermometer named after him, as the temperature
rises and the density of the liquid in this tube decreases,
differently weighted glass globes sink to the bottom of the
tube.
Each
globe corresponds to a different temperature, but what temperature
scale should we use? If only Galileo knew what what a can
of worms he had opened!
Gabriel Fahrenheit was a German. He devised his temperature
scale about 300 years ago. On the Fahrenheit scale water boils
at 212 degrees and freezes at 32 degrees. And therein lies
the problem - these are not easy numbers to deal with.
Step
forward Anders Celsius, a Swede, who was a contemporary of
Fahrenheit. His scale used 0 and 100 degrees as his reference
point and this scale was the one that became established.
In fact it has been universally recognised for over fifty
years.
So
why is this scale not universally accepted? A lot of older
people - like David Garmston for example - are used to Fahrenheit.
The media love Fahrenheit in hot weather. ‘Scorchio! - temperatures
hit the nineties’ is a great headline - far better than ‘Temperatures
in the twenties’ with Celsius.
But
almost everyone under 40 was taught Celsius at school and
- by definition - it is easier to use. When the weather turns
colder Celsius winds hands. Zero is much easier to understand
than 32 when the thermometer plunges to freezing.
So when you hear me talking about degrees Celsius - it’s not
some directive from Brussels that I’m following. It is the
recognised scale. And if you’re still struggling with Celsius
after all this time then just remember….
Five,
ten and twenty one, winter, spring and summer sun.
We
may use hi-tec remote sensors for measuring temperatures these
days and the Galileo thermometer is now nothing but an attractive
curiosity but there is a quite a history behind the development
of temperature and temperature measurement. And it all began
with Fahrenheit, Celsius and Galileo.
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