- [Narrator] Behold, mercury thermometers.
But where did they come from?
Meet Daniel Gabriel Fahrenheit,
born in Poland in 1686.
Daniel was always fascinated
by natural science.
At 16 he began training as a merchant,
but he still conducted
independent research
especially with temperature.
He traveled extensively and
became a glass blower by 1717.
Eventually Daniel started
manufacturing thermometers.
Like any other scientist,
Daniel knew his work
depended on precision
and measuring temperature
requires two things.
First, a reliable way of
indicating a change in temperature.
Second, a scale against which
to measure these changes.
But here's the problem,
neither of these things
existed in the 18th century.
Sure, people had been making
thermometers for centuries,
but they weren't precise.
Daniel knew this and he created several
new types of thermometers.
His first devices used alcohol,
but the most famous of his
thermometers used mercury
in a glass tube.
When the temperature rises,
the heat forces the mercury
up through a narrow bore.
This bore is usually filled with nitrogen
or left as a vacuum.
Yet this wasn't his
biggest stuff of genius.
In 1724, Daniel proposed a
scale for measuring temperature
setting 32 degrees as
the temperature of ice
melting in water and the
temperature of the human body
at 96 degrees.
This system wasn't perfect,
but after a few readjustments
it became the world's standard method
for measuring temperature.
