Winters | Intresting facts about winters

For about 10% of the population, includingthe entirety of Australia, it is now Summer. But for the other 90% living in the Northern Hemisphere, including most of Asia, all of Europe, and all of Central and North America,it's time for winter. Temperatures drop, snow falls from the sky, and a guy in a redsuit breaks into homes all over the globe and we're all weirdly okay with this? But even though most of us associate winter with cold, the Earth is actually at its closestto the Sun during late December and early January. 

So how's that possible? Well, incase you didn't know, the Earth's orbit is not perfectly spherical, it has a slight ovalshape. Which means that there are points in the Earth's orbit at which it is closer orfarther away from the Sun. The most distant point is known as aphelion and occurs aroundthe 4th of July. The closest point is known as perihelion and occurs around the 3rd ofJanuary. So while that makes a lot of sense for the Southern Hemisphere it doesn't makemuch sense to the other half of the globe. 

That is, until you account for the 23.4°tilt of the Earth which is what gives us seasons to begin with. Also known as axial tilt orobliquity. And if we look at the Sun-Earth system from afar we find that the Earth'saxis maintains the same orientation regardless of its position in its orbit around the Sun.And that's the key to the paradox. When the Earth is closing in on the Sun during Decemberthe Northern Hemisphere is turned away from the Sun giving us a cooler climate even thoughthe Earth is now at its closest to the sun.

 Meanwhile the Southern Hemisphere is directedtowards the Sun and thus gets a warmer climate. When the Earth is moving away from the Sunagain the opposite occurs. In summary, the tilt of our planet has a much greater significancecompared to the variations in distance to the Sun. Rough estimates show that around 28,000 km³ of snow falls down on the Earth ever single year. It's more or less impossible to imaginewhat the number really means but this is what only 1 km³ looks like compared to the cityof New York. 28,000 km³ of snow also contains roughly one septillion snowflakes. That'sa 1 with twenty four 0's. And as the saying goes: "No two snowflakes are alike." But isthat really true? This adage begins with a man known as Wilson Bentley. In 1885, Bentleybecame one of the first photographers to capture an image of a single isolated snow flake and for the rest of his life he was obsessed with snowflakes. Even gaining the nickname TheSnowflake Man and taking over 5000 photos before his death in 1931. 

He caught the snowflakeson a piece of black velvet which allowed him to capture an image before the snowflakes melted or sublimated. And even with his limited technology at the time, he was so good atthis that hardly anybody bothered to take photographs of snowflakes forthe next century or so. In 1925 he wrote: "Every crystal was a masterpiece of design,and no one design was ever repeated. 

When a snowflake melted,that design was forever lost." The thing is, two snowflakescan definitely look alike if they happen to be exposed to the exact sameconditions. These conditions includes humidity, temperature, wind speeds and so on. This claimcan also be demonstrated in a controlled environment like a lab for example. Shown here in a videofrom snowcrystals.com in which a pair of snowflakes grows to look very much alike. Of course,nature is not a controlled environment and thus two of the same is a very unlikely occurrence.

However in 1988 scientist Nancy Knight did actually find two tiny ice crystals in a snowstormthat looked quite similar. So maybe a more accurate saying would be something like: "No two snowflakes are identical." According to Guinness World Records, the largestsnowflake ever recorded measured in at a staggering 38 cm. Though the truthfulness of this recordis questionable at best as this supposedly happened back in 1887 which means there'sno corroborating evidence to support this claim. And it is a quite fantastical claimto make given that most reports with more substantial evidence usually range between5-12 cm. I mean can you imagine seeing half a meter wide snowflakes just sailing downfrom the sky. It would be a really bizarre sight. And speaking of bizarre, the largest hail stone ever found measured in at roughly 20 cm, weighing almost 1 kg. 

It would be likebowling balls falling from the sky. If you look at a close-up picture of a snowflakeit will appear translucent, just like any other piece of ice. Then why is snow white?Shouldn't it just be a massive pile of translucent ice? Well when light enters a material somecolors are absorbed and others are reflected away. The reflected color or colors determinewhat color we perceive that material to have. In a translucent material like ice light insteadpasses trough the material which means that no color is reflected nor absorbed. Howeverit's not completely transparent like a sheet of glass so the light doesn't always go troughin a straight line. Instead sometimes the light enters the material from one direction, bouncesaround a bit, and then exits the material in a new random direction. 

Now if you take a bunchof tiny pieces of ice and pack them close together (just like snow) the light just keepsbouncing around between the snowflakes. Eventually, the bouncing light will find a way to escapethe pile of snow and reflect back into the eyes of any potential observers. And becausethis happens to every frequency in the visible spectrum, the combined color of all colorsis white. 

The same thing happens with ice cubes. One ice cube is translucent,but if you put a bunch of them together, they obtaina collective white shade. Have you ever noticed that when it's snowing outside ambient noise seem to dampen and everything becomes a lot more quiet and muted. The reasonfor this is that, like many other porous materials, fresh snow is very good at absorbing sound.The pockets of trapped air in between the snowflakes actually weaken the vibrationsand converts the sound into small amounts of heat. That's one of the reasons it canbe so difficult to find someone lost in an avalanche. 

Just a couple of meters of snowcan be enough to make it incredibly difficult for the sound to reach the surface. While most people use the words blizzard andsnowstorm synonymously there's actually a few distinctions between the two. A blizzardis typically characterized by strong winds of at least 56 km/h, has to last at least3 hours, and visibility must be reduced to only 400 meters. Anything that does not meatthese criteria is classified as a snowstorm. The deadliest blizzard on record is the 1972blizzard in Iran. Some places received as much as 8 meters of snow in the course ofa week and around 4000 people lost their lives. 

The blizzard was so devastating that entirevillages were completely buried in snow. An interesting survival tactic used by someanimals is to change the color of their fur to white during the winter. One example isthe Arctic fox. It's a rather small species of fox, native to the Arctic regions of theNorthern Hemisphere, with thick brown fur during the summer and white fur during thewinter to blend in with the snow-covered landscape. The fur of the Arctic fox provides the bestinsulation of any mammal and it can survive in temperatures as low as -70 °C. 

Anothe rexample is the bird Rock ptarmigan which has brown feathers during the summer and whiteduring the winter. When we look at a flat map of the world, it usuallylooks like this, and it's easy to forget that Russia and the US are actually right nextto each other. In fact, in the middle of the Bering Straight in between Alaska and Siberialies two islands. The one on the right belongs to the United States and is known as LittleDiomede and the one on the left belongs to Russia and is known as Big Diomede. Duringthe winter, an ice-bridge usually spans the distance between these twoislands and thus it's possible, altough illegal, to walkback and forth between the two nations. 

The coldest temperature ever recorded at groundlevel on Earth was at the Soviet Vostok Station in Antarctica in 1983. Temperatures dropped to a staggering -89.2 °C. The Vostok Station is by far the coldest placeon Earth with an average summer temperature of -32 °C. In the winter, the average temperature drops to about -68 °C. The highest temperature ever recorded at thestation was -14 °C. For many animals and insects, the winter isone of the more challenging of the four seasons. Not only does food become significantly morescarce but there's a constant struggle to stay warm in the bitter cold. 

One of the morefascinating strategies for survival, is not by fighting the cold, but rather to surrenderand give in. It's known as "freeze tolerance" and it allows some insects and animals to survivethe winter by essentially freezing. The wood frog can be found in many parts of Canadaand during summer it just frogs around and does whatever a normal frog would do. But during winter,something remarkable happens. 

Ice begins to penetrate the body of the frog creating large flat ice crystals between layers of skin and muscle, encasing all the internal organs.The blood stops circulating and there's no heartbeat, breathing, or any other naturalsigns of life. By all common sense, the frog appears to be dead. But it's more accuratelyin a state of suspended animation because when the climate warms up again the frog returnsto his normal froggy-life.