Thermodynamics: The 2016 advent calendar
Day 18

The Dewar flask

The device that allowed James Dewar to create the coldest temperature ever seen, and that now keeps our coffee warm.

James Dewar created the first ever vacuum flask. In 1892, as he worked to liquefy gases at extremely low temperatures, he created a flask that insulated its contents from heat exchange with a thin vacuum layer.

That invention allowed him to liquefy hydrogen at -252.5 degrees Celsius, just 20 degrees above absolute zero. His invention was the forerunner to the Thermos flask we rely on today to keep our coffee warm, but at the time helped him create matter colder than had ever before been seen on Earth.

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