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Precision Lasers Used To Redefine Temperature, Measure Speed of Atoms

First Posted: Oct 15, 2015 11:58 AM EDT
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Australian scientists have created a precision laser device which has established an international standard for temperature, according to a news release.

Researchers from the University of Adelaide, Queensland and Western Australia have identified a new method to determine Boltzmann's constant, a number which relates the motion of individual atoms to their temperature.

This new study will contribute to a worldwide scientific effort to redefine the international unit of temperature: the Kelvin. (Zero Kelvin or "absolute zero" is the absence of all thermal energy and equivalent to -273.15 degrees Celsius), according to the researchers.

"Although temperature is a familiar concept to all of us, remarkably it can only be measured accurately at a handful of locations around the globe," Professor Andre Luiten, the study's project leader and Director of the University of Adelaide's Institute for Photonics and Advanced Sensing (IPAS), where the experiments were conducted.

In the study, the scientists used lasers to make exceptionally accurate measurements of the speed of individual atoms in a gas.

"An atom sitting at rest will absorb light of a particular frequency or color, if it is moving towards you or away from you then the absorbed light is very slightly changed because of something called the Doppler effect," Luiten said.

Luiten explained that this is the same effect that makes a police siren sound very different when it is moving towards you than whne it's moving away from you.

"We use a pure laser to measure these changes in light absorption, from which we can infer the speeds of the atoms and the temperature of the gas," Luiten said.

The researchers conducted their experiments using world-record precision, and the outcomes were surprising. They found that the light has an effect on the atoms and the measurement itself changes the result, this was one of the breakthroughs of the study, the researchers claimed.

With this breakthrough study, it is possible for any lab to measure temperature once they have the right equipment and skills.

"Our work will bring a universally agreed temperature scale to the globe. As with any upgrade, this one will be deemed successful if people hardly notice the transition on a day-to-day basis," said Associate Professor Tom Stace, from the ARC Centre for Engineered Quantum Systems at the University of Queensland. "But for those at the cutting edge, whether developing new metal alloys at very high temperatures, or measuring the temperatures of the coldest substances, the need for absolute temperature is critical." 

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