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Galileo
is said to have built the first thermometer about 400 years ago.
He realised that the density of a liquid changes with the temperature.
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| Each
globe corresponds to a different 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 he'd started!
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 wins
hands down. Zero is much easier to understand than 32 when the thermometer
plunges to freezing.
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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.
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| Richard
Angwin |
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.
by
Richard Angwin
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