David Muir
Edinburgh, UK
If you observe a glass of fizzy drink, you will see that streams ofÌýbubbles originate from definite points called nucleation sites. These are microscopic aberrations on the glass surface that facilitate the liberation of dissolved carbon dioxide gasÌýfromÌýthe liquid.
Advertisement
The formation of ice crystals is also promoted by nucleation sites. This is demonstrated by water being supercooled to well below its freezing point, but with no ice formation if the vessel holding it is highly smooth, with no nucleation sites.
The iceÌýpatterns in the picture have crystallised at nucleation sites onÌýthe glass door,Ìýwhich, at some point in its existence, has been scratched. These scratches may beÌýdifficult to see in daylight. TheyÌýcan be easier to detect in theÌýdark, using a torch pointing atÌýan angle to the glass.
Celia Berrell
Hervey Bay, Queensland, Australia
In response to this question, IÌýwrote a poetic answer.
Frosty Window Pane
Fractal fingers jab and curl
like jagged knife and leafy swirl.
Jack Frost’s patterned composition
forms through vapour’s deposition.
Water goes from gas to solid.
Missing out the stage of liquid.
Touching freezing window glass
forms crystals from air’s water gas.
Blobs of dust, smudged greaseÌýandÌýgrime
inspires ice crystal’s frost design.
A window pane that’s pristine clean
won’t grow such pretty, frostyÌýscenes
To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
¿ìè¶ÌÊÓƵ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
Ìý