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posted by chromas on Tuesday May 14 2019, @01:01AM   Printer-friendly

https://arstechnica.com/science/2019/05/study-finds-ultimate-fate-of-leidenfrost-droplets-depends-on-their-size/

In 1756, a German scientist named Johann Gottlob Leidenfrost reported his observation of an unusual phenomenon. Normally, water splashed onto a very hot pan sizzles and evaporates very quickly. But if the pan's temperature is well above water's boiling point, "gleaming drops resembling quicksilver" will form and will skitter across the surface. It's known as the "Leidenfrost effect" in his honor.

In the ensuing 250 years, physicists came up with a viable explanation for why this occurs. If the surface is at least 400 degrees Fahrenheit (well above the boiling point of water), cushions of water vapor, or steam, form underneath them, keeping them levitated. The Leidenfrost effect also works with other liquids, including oils and alcohol, but the temperature at which it manifests will be different. In a 2009 Mythbusters episode, for instance, the hosts demonstrated how someone could wet their hand and dip it ever so briefly into molten lead without injury, thanks to this effect.

But nobody had been able to identify the source of the accompanying cracking sound Leidenfrost reported. Now, an international team of scientists has filled in that last remaining gap in our knowledge with a recent paper by Mathai et al. in Science Advances.

The answer: it depends on the size of the droplet.


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  • (Score: 2) by bob_super on Tuesday May 14 2019, @01:31AM (2 children)

    by bob_super (1357) on Tuesday May 14 2019, @01:31AM (#843227)

    The Ars comment thread already includes a long tech-site-should-do-SI argument.
    We don't need it here. We know our furlongs-per-hogsheads-fortnight are homogenous to swimming-pool-per-library-of-congress-over-...-over... hem, help me out, here.

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  • (Score: 2) by fido_dogstoyevsky on Tuesday May 14 2019, @02:43AM

    by fido_dogstoyevsky (131) <axehandleNO@SPAMgmail.com> on Tuesday May 14 2019, @02:43AM (#843236)

    Trouble is things like football fields aren't standardised (eg rugby, gridiron, soccer etc. Maybe we should look at more universal measures, such as using number of public statements per week from $politician_just_voted_against for temperature rise? That could be used for pressure as well.

    --
    It's NOT a conspiracy... it's a plot.
  • (Score: 3, Informative) by PartTimeZombie on Tuesday May 14 2019, @03:38AM

    by PartTimeZombie (4827) on Tuesday May 14 2019, @03:38AM (#843259)

    This should be all the measurements you need. [theregister.co.uk]
    Note however the football pitch measurement of area is a British football pitch, not an American one, so adjust your expectations accordingly.