Thermometers
are
used
to
measure
temperature.
The
first
one
was
invented
in
1593
by
Galileo
Galilei.
In
this
device,
tiny
glass
globes
floated
inside
a
cylinder
filled
with
liquid.
On
warmer
days,
the
liquid
became
less
dense
and
the
globes
dropped
down.
On
cooler
days,
the
liquid
became
denser
and
the
globes
floated
upward.
A
Galileo
thermometer