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