Thermometer [ 2026 Update ]

Traditional bulb thermometers rely on the expansion and contraction of liquids (like alcohol or historically mercury) as temperatures fluctuate. As the temperature increases, the liquid expands and moves up the narrow, calibrated glass tube.

All thermometers operate based on specific physical changes that occur when heat increases or decreases: thermometer

These measure the infrared heat inside the ear canal. Traditional bulb thermometers rely on the expansion and

Digital thermometers use an electronic device known as a thermistor. A thermistor’s electrical resistance changes based on temperature, and this change is measured to compute a precise numerical value. Digital thermometers use an electronic device known as

These scan the temple to detect the temperature of the temporal artery. They are non-invasive and excellent for screening, though they may require more precise reading with a traditional thermometer if a high fever is suspected.

The invention of the thermometer is widely credited to Italian mathematician and physicist Galileo Galilei around 1592, who created a crude water thermometer that measured temperature changes through the expansion or contraction of air. This early instrument was also sensitive to air pressure, making it part-barometer.