SLAC National Accelerator Laboratory and University of Nevada, Reno scientists have debunked a 40-year-old theory by heating solid gold to 14 times its normal melting point without melting it!
The scientists achieved this feat and rewrote the rules of high-temperature physics using a combination of ultrafast lasers and X-rays.
Understanding Entropy Catastrophe
For nearly 40 years, physicists have believed there is a hard limit to how hot a solid can get without spontaneously breaking apart.
Known as the “entropy catastrophe,” this theory holds that once a material reaches around three times its melting point, the increased entropy overwhelms its structure, causing it to liquefy.
Hotter Than the Sun
SLAC’s recent experiment, however, challenges this long-standing belief.
The scientists hit a wafer-thin gold film with a 45-femtosecond laser pulse. They followed it up with a flash from SLAC’s 2-mile-long Linac Coherent Light Source X-ray laser that functioned as an atomic thermometer.
While gold’s normal melting point is 1,337 kelvins (1,947°F), the scientists, by observing how the X-rays scattered off the vibrating gold atoms, calculated a mind-boggling 19,000 kelvins (33,740°F) — hotter than even the Sun’s surface (9,900°F)!
And the best part? By heating the material so fast, the atoms didn’t have time to reorganize into a liquid structure. SLAC’s process basically outran the material’s natural melting behavior.
The Future of Thermodynamics
Ask any particle scientist, and they’ll tell you how tough it is to measure and understand extreme states of matter, such as those found in the cores of gas giants like Jupiter or inside fusion reactors on Earth. Even if they do, it would be plagued by large error bars.
By shattering the temperature barrier, the SLAC-Nevada team has now shown it is possible to probe the inner temperatures within ultra-hot systems accurately.
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