All That Matters

Heike Kamerlingh Onnes (photo from Museum Boerhaave)

Today marks the 100th anniversary of superconductivity by Heike Kamerlingh Onnes. In a superconductor, the electrons flow without any electrical resistance.

Apart from their fundamental scientific interest, superconductors are used to make powerful electromagnets, for example for MRI and NMR machines in medical diagnostics. Other promising applications include power transmission cables with low losses, highly sensitive devices to measure magnetic fields and so on.

Working in his lab at Leiden University, on 8 April 1911 he experimented with the electrical resistance of mercury at low temperatures. In his notebook he noted that at 3 K (-270°C), ‘Kwik nagenoeg nul’, mercury’s resistance drops to ‘practically zero’.

This discovery at such low temperatures was only made possible by Kamerlingh Onnes previous achievement of liquifying helium at 4.22 K. this provided the means to cool samples down to even lower temperatures. For this breakthrough in cryogenics, Kamerlingh Onnes received the 1913 Nobel prize in physics.

When superconductivity was discovered, it certainly was a puzzling observation at the time. Some scientists believed that at low temperatures electrical resistance would shoot up towards infinity, whereas others thought that it would gradually go down, which is what indeed happens for many materials. However, superconductivity is not simply a new form of electrical resistance – it is a thermodynamic state in its own right, and its unique properties can’t be explained by classical physics alone. Indeed, it was not until 1957, when Bardeen, Cooper and Schrieffer provided the quantum-theory that explains superconductivity of materials such as mercury.

However, that’s not where research into superconductivity stops. In 1987, the so-called high-temperature superconductors were discovered. Their superconducting temperatures are so high that cooling with helium isn’t even necessary. Interestingly, mercury (Hg) plays a key role there as well: the superconductor with the highest known temperature at normal pressures (135 K) is HgBa₂Ca₂Cu₃O_x!

The origin of superconductivity in these new superconductors is different to the classical superconductors, and remains not fully understood. This makes Kamerlingh Onnes discovery all the more relevant to this day.

Further reading:

it seems this nice article is free access:

van Delft, D., & Kes, P. (2010). The discovery of superconductivity Physics Today, 63 (9) DOI: 10.1063/1.3490499

This post was chosen as an Editor’s Selection for ResearchBlogging.org

The crisis at the Fukushima Daiichi nuclear plants is a real tragedy. Tens of thousands of people have been evacuated around the plants, many of which continue to live in shelters with little comfort and privacy. And even worse, there are more than 27,000 people that are either dead or declared missing as a consequence of the earthquake and the tsunami.

The stream of media reporting on the status of the Fukushima plants is continuing, although ironically we are now in a situation where although the continuing release of radiation into the plant’s immediate environment is accumulating to radiation levels that are worryingly high, the broader interest on the issue outside of Japan appears to have ebbed away. And that despite the fact that these problems will be with us for months, if not years.

What is still going strong in the media, however, is the debate on the future of nuclear energy. Some see the accident as a sign that we should stop all nuclear power plants – immediately – whereas others such as George Monbiot see the fact that the implications of this accident so far seem geographically limited as a sign to support nuclear power. Unfortunately, this pro/contra nuclear is where the debate stops, and there appears little movement on either side.

It’s about our energy future

What I am missing in this entire debate is the vision for our energy future. That’s because a sustainable energy supply is a complex issue, where broad brush strokes such as pro or contra nuclear unfortunately don’t help. Take the German government’s decision to shut down seven of its oldest nuclear reactors: unlike the shutdown of nuclear reactors in Japan this hasn’t led to power cuts in Germany. So where does the missing energy come from? This power is bought on the international market. So who can offer spare capacities of around seven gigawatts power or more? My guess is that most likely it’s nuclear energy from elsewhere….

But short-term politics and Fukushima-related knee-jerk reactions aside, how do we envision our energy future? […]