The World's Most Sensitive Thermometer

Researchers have developed the most sensitive thermometer ever made, and in a very unorthodox way, according to a recent study.

The study, published in the journal Physical Review Letters, details how an experimental thermometer known as the "nano-Kelvin thermometer" uses a pair of light beams and a crystal to measure temperature.

Most traditional thermometers use colored alcohol or mercury to tell temperature. The liquids, confined to a small clear-tube, rise or fall as they expand or contract with temperature. Unlike water, both mercury and alcohol tend to expand when heated and contract when cold, meaning that a vertical liquid thermometer will indicate a high temperature when the tube appears nearly filled with its respective liquid. Other digital thermometers measure temperature by measuring the expansion rate of these same liquids and the tension of the solid that confines them.

However, such thermometers are not terribly accurate, as the expansion and contraction rate of the liquids vary.

Now, researchers from the University of Adelaide claim that their light-based thermometer can measure temperature within a 30 billionth of a degree in one second.

"To emphasize how precise this is, when we examine the temperature of an object we find that it is always fluctuating," study leader Andre Luiten said in a statement. "We all knew that if you looked closely enough you find that all the atoms in any material are always jiggling about, but we actually see this unceasing fluctuation with our thermometer, showing that the microscopic world is always in motion."

According to the study, the thermometer uses a pair of red and green beams fired through a crystal.

"When we heat up the crystal we find that the red light slows down by a tiny amount with respect to the green light," Luiten explained.

The lights are then made to circulate thousands of times around a disk in a phenomenon of forced light curvature. This process exaggerates the difference between the light speeds, allowing the researchers to measure the minuscule changes "with great precision."

Researchers are confident that this new technology could revolutionize engineering and medical fields, in which temperature change readings are paramount in making accurate observations and adjustments.

The study was initially published in Physical Review Letters April 21.