Question: Who and what are the Quiet Birdmen?
- a branch of sailplane enthusiasts
- a colloquial name for a local chapter of deaf pilots
- The Ancient and Secret Order of Quiet Birdmen, a fraternal organization founded in 1919
- a postumous title for deceased EAA members
Answer: Number 3. Charles Lindbergh was a QB, however he was not a founder of the organization, as is often stated. The Quiet Birdmen was founded by seven World War I pilots who, beginning in 1919, regularly met at Marta’s Restaurant in Manhattan to share war stories.
In the spring of 1920 the group, which had grown considerably, rented the roof garden restaurant on top of a Manhattan hotel populated principally by elderly residents. They kept the roof for the entire weekend during which they partied quite heartily. They created quite a ruckus on the roof and while going up and down the stairwells and the elevator. Due to the noise, the elderly residents dubbed the group “The Quiet Birdmen”. The name stuck and “Ye Anciente and Secret order of Quiet Birdmen” was officially founded in January of 1921.
Subject: Ice Nine?
Question: Does ice always melt at zero degrees C, and does water always freeze at zero degrees C?
- At normal atmospheric pressures (and up to and including 1000 atmospheres or so), yes.
- The same as number 1, however water doesn’t always freeze at zero C. At up to 70 Centigrade degrees below ‘freezing’ however, and about 1000 atmospheres, water will stay liquid and in fact separate into two separate densities, one about 15% less dense than the other.
- Although some weird stuff (like the above) happens at very high pressures, even here on normal old earth, water can supercool if there are no condensation nucleii. Supercooled cloud droplets at -50 degrees C have in fact been observed, albeit rarely.
- It depends on wind. If there is any advection (a fancy word for wind) greater than about 10 knots, supercooled water cannot exist.
Answer: Number 3, of course. Ice, at normal atmospheric pressure always melts when warmed to temperatures above zero degrees C. But water doesn’t always freeze when cooled to zero C. Water in very small drops may take some tens of minutes to freeze when the temperature drops well below -50 degrees C or so. Water droplets, even rain-sized drops, can exist in liquid form well below ‘freezing’ if they do not have a freezing nucleus. The ice crystals ‘can’t get started’. After the water temperature goes below zero Celsius, the temperature decline is slow but significant. At some temperature below the ‘freezing point,’ the water finally does freeze and the temperature rises rapidly to zero Celsius. This means that heat is released from the freezing of water. There are around 80 calories of heat released for every gram of water which freezes. Just as heat is released in the condensation of water, freezing also causes heating (though less than one sixth as much, per gram). What this means though, is that to some extent, the presence of snowflakes implies that an additional boost of heat is transferred to the air in the form of updrafts (and downdrafts when it melts).
Question: They say no two snowflakes ever look alike. Aside from the obvious question of whether or not it’s true (which it is), are there other types of snowflakes besides the familiar flat, frilly, dendritic six-sided ‘doily’ shape?
- There is only one basic shape for snowflakes. Their variety however, is infinite.
- Snowflakes can come in three forms. They are the familiar hexagonal ‘flake’, hairy ‘spheres’ when condensation nucleii are over 50 microns and air temperatures are below 30 degrees C, and at about -4C, needles.
- The number of shapes, as well as the variety within each, are both infinite.
- Depending on temperature there are actually at least five types, although all are basically hexagonal in form. Between zero and -50F, snowflakes can be hexagonal tile shapes, needles, hollow prismatic tubes, tubes with hexagonal plates at either end, or the familiar frilly one with six (sometimes 12) arms.
Answer: Number 4. And the reason most people DON’T know about the other snowflakes (aside from the fact that the other types aren’t nearly as photogenic) is that those ‘grow best’ at a range of temperatures (-12 to -16 C) where the difference in vapor pressure over ice and liquid water is at its maximum. At 12C, *the* most energy is released when liquid water evaporates and condenses on ice crystals.