Absolute zero is to total zero as stopped is to slow - Dr Bill Phillips, physics nobel laureate gives 'whizzbang' lecture at DCU
31 October 2002

In our everyday lives, what do we know and understand about cold? The arctic conjures up an image of the coldest 'state' that we can think of. What could possibly be colder than that? In his 'whizz-bang' lecture at Dublin City University on Wednesday 30 October, Dr Bill Phillips, 1997 physics Nobel laureate, gave a very dynamic, almost explosive demonstration of what happens when temperatures go even lower.

Dr Phillips of the National Institute of Standards and Technology (NIST), USA was co-winner of the Nobel prize with Professor Steven Chu of Stanford University and Professor Claude Cohen-Tannoudji of the Collège de France and Ecole Normale Supérieure for "development of methods to cool and trap atoms with laser light".

A layperson might well ask what this has to do with cold. Well, according to Dr Phillips, if atoms can be cooled down towards absolute zero they react slower and can be trapped, and as a result they can be controlled and used to push the frontiers of precision measurement out even further. One major practical application of this research has resulted in the development of the most precise atomic clocks in the world as well as other tools such as ultra-sensitive gyroscopes used in navigation and atom imaging systems for the fabrication of ultra-small electronic components.

While the arctic is 185º above absolute zero, Dr Phillips brought into the lecture theatre a number of buckets, flasks and other containers which held a substance even colder than that - liquid nitrogen which is 77º above absolute zero. He 'sloshed' the nitrogen onto the floor to demonstrate that in the comparatively warm temperature of the lecture theatre, the nitrogen appeared to boil as it evaporated in clouds around our feet.

By way of demonstrating even further just how things behave under extremely cold temperatures - and in keeping with the spirit of Halloween - Dr Phillips blew up orange and black balloons and immersed them in a flask full of liquid nitrogen. While the audience waited to see the results, Dr Phillips dipped a carnation into a bucket of nitrogen and within seconds pulled it out, like a rabbit out of a magician's hat, and crumpled the flower in his hand.

After similar tricks with a bouncy ball and an elastic band, he pulled the blown-up balloons out of the flask to the amazement of the non-scientists who witnessed the frozen and flattened balloons as they appeared to re-inflate themselves.

While this might appear to us as magic, Dr Phillips was very keen to point out that this was in fact science. And science is a 'magic' subject to him. It has fascinated him from an early age when, as a child, his parents had allowed him to carry out demonstrations in his basement at home which often resulted in electricity blow-outs. By following his almost instinctive fascination with science, and working in a collaborative way with other scientists around the world, he has been able to bring down temperatures in his laboratory at NIST to almost absolute zero.

When asked how he felt when Dr Ketterle of MIT succeeded in bringing atoms to just billionths of degress above absolute zero (-273°) in 1999, he said that scientists enjoy the discoveries of others. And as for the next step? "Well, we will try to go even lower than that", he quipped.

The university is extremely grateful to our own Dr John Costello of the School of Physical Sciences, and to the Institute of Physics of Ireland who organised Dr Phillips's lecture tour to Ireland which included talks at the University of Cork, Queen's University, Belfast and Dublin City University.