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WB
297549.  Mon Mar 17, 2008 2:15 pm Reply with quote

Wilson ‘Snowflake’ Bentley b.1865, a self-educated farmer from Vermont coined the phrase “no two are alike” when describing snowflakes. Starting in 1885, he photographed over 5000 during his lifetime. Although there is nothing to stop two (dendritic) snowflakes being exactly alike, the probability of such is microscopically small. Some snowflakes develop as hexagonal prisms or needles though and these are certainly self similar.

 
WB
297550.  Mon Mar 17, 2008 2:15 pm Reply with quote

Hexagonal prism snowflakes are responsible for the parhelion and effects known as Sun Dogs. These are false suns created by total internal reflections within the ice crystals (an effect somewhat akin to a rainbow being created by water droplets). Moon Dogs have also been observed.

 
WB
297551.  Mon Mar 17, 2008 2:16 pm Reply with quote

In the first half of the C19th ice became a valuable commodity, largely due to the extraordinary effort of Frederick Tudor, the Ice King from Boston. Tudor harvested ice from frozen lakes in the Boston area and shipped it all over the world. When he died he had icehouses in Cuba, Jamaica, New Orleans, Calcutta, Madras, Bombay, Galle and Singapore. 146,000 tons of ice were exported in 1856. Amazingly this was viable even though up to 75% of cargo might melt on the voyage! Tropical natives had never seen ice, so the effect was dramatic (ice cream, cool drinks etc.). Wenham Lake Ice was the ‘Evian Water’ of Victorian Britain. A lens made from this ice could “ignite gunpowder”. The trade led to the first refrigerators that ran on half a hundredweight of ice per week.

 
WB
297553.  Mon Mar 17, 2008 2:16 pm Reply with quote

Vostok, a base in Antarctica, is the place where the coldest temperature was recorded (-89oC in 1983). 4km under the ice at Vostok is a liquid lake the size of Lake Ontario. It may have been sealed off 1 million years ago and could contain its own ecosystem. Scientists have drilled to within a few hundred metres of its surface, but haven’t broken through because they can’t figure out how without polluting it! Vostok is near to the southern pole of inaccessibility, which boasts a bust of Lenin as its marker.

 
WB
297554.  Mon Mar 17, 2008 2:17 pm Reply with quote

The school laboratory experiment of passing a piano wire through a block of ice is usually explained by saying that the freezing point of water drops under high pressure. This latter is true but the effect is small (0.5oC or so), not enough to account for the wire trick. The real reason is that a very thin film of water forms naturally at the surface of ice (12-70 nanometers thick). The wire is constantly in contact with the ice, so constantly forming a new water layer. Eventually, nanometer by nanometer it falls through the block. Faraday first proposed this idea in 1850 at the Royal institution as the reason that ice is slippery, but couldn’t prove it. Lord Kelvin proposed the pressure melting theory, but he has now been proved wrong. Interestingly the surface layer does not form below –33oC and this is possibly a reason why Scott had such difficulty in the Antarctic. Scott reported “skiing easily” at –30oC, but Ed Wilson noted that at low temperatures (-46oC) the snow surface became sandlike and skiing was much harder. Scott experienced unusually low temperatures.

 
WB
297555.  Mon Mar 17, 2008 2:17 pm Reply with quote

Sir Ranulph Fiennes reported sawing his own frostbitten fingers off to ease the pain. In 2000 two doctors in Kilmarnock reported on a case of frostbite in a PE teacher who had put a bag of frozen chips on her foot to ease muscular pain. It was successfully treated but did require surgery.

 
WB
297556.  Mon Mar 17, 2008 2:17 pm Reply with quote

In 1985 some Austrian wine producers added diethylene glycol (DEG) a type of antifreeze to their wine to make it sweeter. This led to the temporary collapse of Austrian wine exports. It is estimated that someone would have needed to drink 28 bottles of the wine each day for two weeks to be affected by the small amount added. The Austrian wine industry is now much more closely regulated and producing better wine as a result. More recently Chinese counterfeiters have added DEG to toothpaste that has turned up in Costa Rica, US, Spain & now UK.

 
WB
297557.  Mon Mar 17, 2008 2:18 pm Reply with quote

Pykrete (named after its inventor Geoffrey Pyke – an eccentric C20th genius) is a concrete like material formed as a mixture of a porous, fibrous material (sawdust or paper) and ice. It is immensely strong and melts only slowly. Pyke proposed it as a material suitable for making aircraft carriers during the war. Lord Mountbatten championed this (there are funny stories involving Churchill in his bath and Mountbatten nearly wounding a fellow officer with a ricochet bullet whilst demonstrating its strength). [Having seen J Clarkson behaving v. badly with a shotgun on sport relief, maybe we could let him have a go at Pykrete…….] A prototype was made in Canada (60’ x 30’ weighing 1000 tons and kept frozen with a tiny 1hp motor). Sadly never reached production.

 
WB
297558.  Mon Mar 17, 2008 2:18 pm Reply with quote

Megacryometeors are large blocks of ice that fall from a seemingly clear sky. The largest known was 400lbs and fell on a Mercedes factory in Brazil. Airplane loos can sometimes be responsible, but can often be discounted after analysis of the ice. No one knows the reason for them.

 
WB
297560.  Mon Mar 17, 2008 2:19 pm Reply with quote

Absolute zero is a temperature that can never be reached. Helium is the only substance known not to freeze at normal pressures. It will freeze at low temperatures above 25 atmospheres. Solid Helium is practically invisible.

 
WB
297561.  Mon Mar 17, 2008 2:19 pm Reply with quote

The coldest temperature ever reached in a lab is generally accepted as 450 picoKelvin at MIT in 2003. Physicists at Helsinki University of Technology are doing some very weird work where they claim to have created a ‘negative temperature’ inside some Rhodium. In true Alice-in-Wonderland style negative temperatures turn out to be hotter than positive temperatures. The transition from positive to negative is induced by a sudden magnetic flip. The temperature gradually returns to the positive by passing through ‘an infinite temperature’ - as passing through absolute zero would contradict 3rd law of thermodynamics. The effect is I think a mathematical conceit to describe a system at a quantum level (where nothing is as it seems). The science is beyond me but I can understand the invention of a concept like imaginary numbers to complete a system. This is a link if anyone can make sense of it: http://ltl.tkk.fi/triennial/positive.html

 
WB
297562.  Mon Mar 17, 2008 2:20 pm Reply with quote

Freeze-drying or Lyophilisation is a preservation technique where items are cooled to below 0oC and then slowly thawed at low pressure. The ice turns directly to vapour by sublimation and so the item is dried out. Space food, Cut flowers and restoration of flood damaged paper artifacts all use this technique. A lady in Sweden says she wants to “freeze-dry” bodies instead of cremating them. (A new one for Monty Python’s Burn her, bury her or dump her…). I don’t think that the process is freeze-drying as such. It involves dipping the body in liquid nitrogen, shaking it so that it shatters (you can do this with flowers….), removing metallic lumps (plates & fillings) and burying the powder in an eco-friendly casket made from potato starch. New EU laws have left traditional crematoria in need of expensive overhauling to meet emission targets so it is an attractive option economically, but is still awaiting licensing by the Swedes. Many UK councils are considering this technology. I’ve posted a thread on Funerals.

 
Flash
297616.  Mon Mar 17, 2008 5:41 pm Reply with quote

What's the temperature if the ambient temperature is 10 but there's a wnd-chill factor of -15?

10. The wind-chill is a subjective measure of how a fully-dressed, slightly overweight person facing the wind is likely to perceive the temperature. If the temperature is above freezing, no amount of high wind will result in a frost.

Apparently.

 
Frederick The Monk
297715.  Tue Mar 18, 2008 3:03 am Reply with quote

How do they measure wind chill then - is there a metric standard fat bloke who gets wheeled out?

 
Flash
297740.  Tue Mar 18, 2008 4:52 am Reply with quote

Yes, I think so. They stand him next to the Imperial standard guy, who's getting on a bit now and always insists that he doesn't feel cold at all. There's often a fight.

 

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