Feeds

Boffins chill out with new temperature measurement

Forget water temperature, all the hip scientists are measuring the Boltzmann constant

Beginner's guide to SSL certificates

Why would you get excited about a new measurement of the Boltzmann constant that took six years to achieve?

In the case of the UK scientists who made the measurement at the UK's National Physical Laboratory (NPL), it's because the long-held standard for temperature measurement is problematic at extremes.

The kelvin and the degree Celsius are currently both defined using what's known as the triple point of water – “the point at which liquid water, solid ice and water vapour can all exist in equilibrium”, the NPL says in a statement.

The triple point is a definition rather than a measurement: the three states of water can be calculated to exist at 0.01°C and a partial vapour pressure of 611.73 pascals – in kelvin, 273.16K. All other measurements of temperature are made relative to this value.

However, as Dr Michael de Podesta of the NPL explains, “The further away one measures from the temperature of the triple point of water, the harder it gets to precisely determine the ratio of exactly how much hotter or colder the temperature is than the standard temperature. This adds uncertainty to temperature measurements on top of the normal practical difficulties.”

The paper he and his collaborators (from Cranfield University and the Scottish Universities Environmental Research Centre, SUERC) have prepared for the journal Metrologia focuses on the Boltzmann constant: the relationship between a particle's temperature and its energy. The paper sets the constant as 1.38065156 (98) x 10-23 J K-1 with (98) expressing the uncertainty of the last two digits in the value.

It's those last two digits that matter: the uncertainty, which amounts to 0.7 parts per million, is around half of that in previous measurements.

The measurement was made using acoustic thermometry: an acoustic resonator was chilled to the triple point of water, and filled with a high purity argon gas. High-accuracy measurements of the speed of sound in the gas provides a measurement of the average speed of the argon molecules, from which their kinetic energy – and therefore the Boltzmann constant – could be calculated.

The resonating chamber also needed to be measured to high accuracy, using microwaves that provided an overall uncertainty of just 600 atoms' worth, or 11.7 nanometres.

Since the same constant is useful in calculating the thermal voltage of semiconductors, The Register supposes the measurement might prove useful beyond the world of basic science. ®

Intelligent flash storage arrays

More from The Register

next story
Bond villains lament as Wicked Lasers withdraw death ray
Want to arm that shark? Better get in there quick
Renewable energy 'simply WON'T WORK': Top Google engineers
Windmills, solar, tidal - all a 'false hope', say Stanford PhDs
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
Reuse the Force, Luke: SpaceX's Elon Musk reveals X-WING designs
And a floating carrier for recyclable rockets
The next big thing in medical science: POO TRANSPLANTS
Your brother's gonna die, kid, unless we can give him your, well ...
NASA launches new climate model at SC14
75 days of supercomputing later ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
Simon's says quantum computing will work
Boffins blast algorithm with half a dozen qubits
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
A strategic approach to identity relationship management
ForgeRock commissioned Forrester to evaluate companies’ IAM practices and requirements when it comes to customer-facing scenarios versus employee-facing ones.
How to determine if cloud backup is right for your servers
Two key factors, technical feasibility and TCO economics, that backup and IT operations managers should consider when assessing cloud backup.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
The Heartbleed Bug: how to protect your business with Symantec
What happens when the next Heartbleed (or worse) comes along, and what can you do to weather another chapter in an all-too-familiar string of debilitating attacks?