“The fact, experimentally demonstrated, that a pure metal can be brought into a state where its electrical resistance becomes zero is of the utmost importance.” That passage has been recorded following experiments by the Dutch physicist Heike Kamerlingh Onnes in 1911. The Groningen-born physicist discovered what was then ‘the coldest place on earth’. In the cold laboratory in Leiden, he investigated the properties of matter at low temperatures, up to a few degrees above absolute zero of -273.15 degrees Celsius.
Kamerlingh Onnes arrived at these low temperatures with the aid of an experimental set-up of pipes, pumps, taps and pressure and cooling vessels. After many years of struggling, he succeeded in liquefying helium. That feat enabled him to immerse different metals in the cold stuff and measure what happened to the resistance at extremely low temperatures. On the conscious April 8 in 1911 he observed that the resistance of mercury at 4.2 Kelvin or -269 degrees Celsius had been reduced to zero and thus the discovery of the phenomenon of ‘supraconductivity’ or superconductivity was a fact.
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