UKC

Frost patterns on a neighbour's car this morning makes me wonder how inanimate forces, devoid of life and DNA, can create something so artistic.

In reply to Rog Wilko:

Aliens innit.  When there are no massive fields of corn to leave patterns on, they'll do it anywhere they can.

In all serious though, that's really pretty

In reply to Rog Wilko:

I did once read (but admittedly didn't understand) about the process that makes a snowflake form in a symmetric shape, even though each 'arm' is separate from it's opposite number.  I wonder if something similar is at play here?

In reply to Rog Wilko:

I suspect it is kinda the other way round - that it is precisely because these sort of patterns are found in nature that we have evolved to experience them as ‘artistic’ and aesthetically pleasing. There is a sort of anthropic principle at play; if we were in a parallel universe where nature formed totally  different patterns, then we would have evolved to find those patterns attractive instead and would be equally amazed by what seem like remarkably improbable correlations between what we see in nature and what we find artistic. 

In reply to Rog Wilko:

Jack Frost has been busy your way! 

Frost patterns on roofs are amazing, they remind me of crystal patterns in a cross section of metal.  Any frost experts care to comment if it's the same sort of process?

In reply to Rog Wilko:

Listening to Hoared Frost makes me wonder how animate forces of life and DNA can create such useless hot air and unnecessarily offensive moves during negotiations

He gives the beauteous phenomenon you pictured a bad name

In reply to wintertree:

Same physics at work.  The rate of advance of the crystal front (whether the crystal is growing into the melt, as in the metal, or into vapour, as happens in the ice crystals) is limited by how fast the latent heat of crystallisation can diffuse away.  The boundary of the crystal is at the melting point, so there's a temperature gradient from there to the lower temperature of the environment, and it's this temperature gradient that drives the diffusion of the latent heat away.  Imagine you start out with a flat interface, but a random fluctuation leads to some waviness.  The bits of the crystal that stick out further then have a steeper temperature gradient next to them, so the latent heat diffuses away faster, so the waviness is amplified and you end up with fingers sticking out.  The length scale selection comes about because very narrow fingers create too much interfacial area, and there's an energy penalty from the interfacial tension.  Because this interfacial tension depends on the orientation relative to the crystal structure, the symmetry of the crystal is reflected in the relative growth rates in different directions, hence the hexagonal symmetry of the frost patterns.  

Probably easier to explain with diagrams!  (It's called a Mullins-Sekerka instability in the trade).

"Patterns in Nature, Why the Natural World Looks the Way it Does", by Philip Ball, is great on all this stuff.  

https://www.philipball.co.uk/patterns-in-nature

In reply to Richard J:

Thanks for that. I won’t pretend I really understand it but it gives me a glimmer of light.

In reply to Rog Wilko:

Reminds me of the insides of bedroom windows before central heating.

In reply to Rog Wilko:

 Apparently it's caused by micro imperfections in the glass(100 plus year old), dust particles, even minute traces of cleaning fluids left on surface. There were more, I just needed to chop them down to meet the file size. For scale that image is roughly 20cm high. 

In reply to ThunderCat:

I think a snowflake is different, as I understand it perfectly symmetrical snowflakes are rare but they are the ones people take pretty photographs of.  Where each 'arm' is the same it is because they all formed at essentially the same temperature, pressure and humidity.

In reply to Richard J:

Excellent, thank you indeed for that.  

That's your second recommended book on here I've now shelled out for!

In reply to Richard J:

Does Philip Ball tell us why you get those ripples in the sand on beaches, every 10cm or so?

In reply to mbh:

I'm sure he does (though I can't check as I seem to have lent my copy to somebody).

I think beach ripples and desert sand-dunes arise from similar processes - if you have a flat surface, and wind or water is carrying sand-grains parallel to the surface, if by chance a lump arises then the disturbance in the flow makes the sand grains fall out to make the lump bigger.

There's a general principle here - many of these natural patterns arise because there's some mechanism that takes some natural fluctuation - whether that's scratches on a glass surface or even just the natural fluctuations of Brownian motion - and amplifies it, but with some physical mechanism that means that the fluctuations on some particular length scale gets to grow fastest.  Sometimes - as in the ice crystal case - there's something that imposes a directionality on the pattern as well.  

This gives a characteristic mixture of order - e.g. the sand ripples all have more or less the same spacing, the snowflake has obvious hexagonal symmetry - and randomness - the ripples aren't quite straight and undulate a bit, the exact pattern of each snowflake is different.  Maybe it's this mixture of randomness and order that makes the patterns aesthetically appealing.

In reply to Rog Wilko:

Pretty awesome. Here's one from my windscreen a couple of years ago.

In reply to Rog Wilko:

I had a frost pattern on top of my car earlier this week, best I've ever seen, I'm now kicking myself I didn't take a photo, but the kids were late for school so I was distracted.

On a related note to the formation of patterns, I watched this the other day, it's not just a same old same old aren't snowflakes amazing video, it has a lot more depth and I learned a lot, like most snowflakes aren't what I expect as "snowflake shaped", why do they have six fold symmetry etc etc. Enjoy ..

youtube.com/watch?v=ao2Jfm35XeE&

In reply to Richard J:

Thanks for that. I suppose the spacing of the ripples is determined by how far the water motion due to wave action can take a typical sand grain. If so, the ripples should be more widely spaced on more exposed beaches and less widely spaced where the sand grains are bigger.

In reply to CantClimbTom:

That's excellent, thanks for the link.

In reply to Rog Wilko:

I'm strongly getting the sense that many on this thread would quite enjoy a fractal viewing session with a backing techno score post consumption of some organic Autumnal consumables. 

In reply to Rog Wilko:

I've noticed that frost patterns seem to appear more on cleaner cars. On dirty cars the frost is usually an unbroken covering of white. It might be because particles of dirt interfere with the development of patterns..?

In reply to AllanMac:

Certainly my neighbour is exceptionally car-proud