The World's Most Sensitive Thermometer Can Measure to 30 Billionths of a Degree

The world's best thermometer isn't made of mercury; it's made of light. Physicists have created the most sensitive thermometer yet that's three times more precise than the best thermometers in existence today.

So how does this new thermometer work? It injects two colors of light, red and green, into a highly polished crystalline disk. The two colors travel at slightly different speeds in the crystal, depending on the temperature of the crystal. For example, when the researchers heat up the crystal, the red light slows down by a tiny amount with respect to the green light.

"By forcing the light to circulate thousands of times around the edge of this disk in the same way that sound concentrates and reinforces itself in a curve in a phenomena known as a 'whispering gallery'-as seen in St. Paul's Cathedral in London or the Whispering Wall at Barossa Reservoir-then we can measure this miniscule difference in speed with great precision," said Andre Luiten, one of the researchers, in a news release.

The new thermometer could have lots of applicable uses. In fact, the thermometer could be redesigned for ultra-sensitive measurements of other things such as pressure, humidity, force or searching for a particular chemical.

"We believe this is the best measurement ever made of temperature-at room temperature," said Luiten in a news release. "We've been able to measure temperature differences to 30 billionths 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. 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."

Being able to measure temperature and other aspects of our environment so precisely could revolutionize technologies. Researchers could detect trace amounts, which could have a great use for a variety of industrial and medical applications.

The findings are published in the journal Physical Review Letters.