World's most sensitive thermometer developed

Australian researchers claim to have produced the world's most sensitive thermometer - three times more precise than the best thermometers in existence.
Researchers from the Institute for Photonics and Advanced Sensing (IPAS) at the University of Adelaide developed the thermometer which uses light to measure temperature.
They have been able to measure temperature with a precision of 30 billionths of a degree.
"We believe this is the best measurement ever made of temperature - at room temperature," said project leader Professor Andre Luiten, Chair of Experimental Physics in IPAS and the School of Chemistry and Physics.
He pointed out that it is possible to make more sensitive measurements of temperature in cryogenic environments (at very low temperatures) near absolute zero.

"We've been able to measure temperature differences to 30 billionths of a degree in one second," said Luiten.

"To emphasise 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," Luiten said.
The thermometer injects two colours of light (red and green) into a highly polished crystalline disk. The two colours travel at slightly different speeds in the crystal, depending on the temperature of the 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 said.
"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 minuscule difference in speed with great precision," Luiten said.
Luiten said the team has developed a new technique which could be redesigned for ultra-sensitive measurements of other things such as pressure, humidity, force or searching for a particular chemical.

"Being able to measure many different aspects of our environment with such a high degree of precision, using instruments small enough to carry around, has the capacity to revolutionise technologies used for a variety of industrial and medical applications where detection of trace amounts has great importance," Luiten said.
The study was published in the journal Physical Review Letters.