Michael De Podesta, Principal research scientist at the National Physical Laboratory, explaining how he made the worlds most precise thermometer, on the Engineering Stage at New Scientist Live 2019
Michael de Podesta has been on Earth for 59 complete orbits of the sun, during which time he studied physics at Sussex University, and then taught physics at the University of London. Since the year 2000 he has been working at the National Physical Laboratory where he has learned an awful lot about measuring the temperature of just about anything. Together with colleagues, Michael De Podesta has made the most accurate thermometer ever. This super thermometer is able to measure how wrong all the other thermometers on Earth are. It works by measuring the way changes in the speed of motion of molecules affect the speed of sound in a gas. In this talk Michael will use this principle to make a fundamental measurement of temperature live on stage, hoping that nothing will go wrong. He'll explain how and why this principle has been used to redefine the fundamental unit of temperature, the kelvin, and the benefits his super thermometer will bring. Dr Michael de Podesta's wide-ranging research interests concern all aspects of temperature measurement: from building the most accurate thermometer ever made; to developing industrial sensors capable of surviving harsh conditions; to measuring the temperature underneath the wheel of a train travelling at over one hundred miles per hour; to representing NPL on the steering committee of the International Surface Temperature Initiative. Acoustic thermometry exploits the fact that the speed of sound in a gas is directly related to the average speed of molecular motion. So, by accurately measuring the speed of sound in a gas of known molecular mass it is possible to work out the average speed of molecular motion and hence the temperature of the gas. NPL has built an apparatus for ultra-precision measurements of speed of sound in a gas. Up until 2013, the apparatus was used at the temperature of the triple point of water ( K, °C) to make very low uncertainty measurements of the Boltzmann constant.
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Location: ExCel London, One Western Gateway, Royal Victoria Dock,
Photo credit: © John Gaffen / Alamy / Afripics
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