雪花 Snowflake

雪花以极快的速度从卧室窗口的右上方向左下方划过，这是早上起来后拉开窗帘不小心说出“好大的雪”后对雪的运动方式的第一印象。前天在参考天气预报决定去超市买花的时间时便知道：这个周日有百分之五十的降雪概率。昨晚入睡前，随着距离“这个周日”的时间拉近，降雪概率已经可以被细分到每小时：这个周日（明天）的凌晨三点至下午的三点都被明确标明了降雪的发生（以一个标准的六角雪花的形状为标识）。回到早上起床后关掉暖气拉开窗帘的时刻，即使我已经早在两天前就知道今天会是一个雪天，但眼前雪花滑落的速度及密度还是让我的感叹发出了声：“好大的雪。”作为一个在南方城市长大和生活的人，在这边第一次经历“下雪“作为动词的过程和缓慢学习在没有摩擦力的地面上直立行走到现在也已经看过了不少的雪，但“下雪”依旧出现在我习以为常的天气类别范围之外。吃过早餐后，我坐回卧室的窗边开始着手写一写雪。此时的雪的颗粒相比于一个小时前已经小了许多，也可能是背景处的天空光线变得稍亮的缘故。雪花仍然在以极快的速度从卧室窗口的右上方向左下方划过，是的，今天更早时得出的结论并没有出错；但是，如果你好好地坐在窗边，或者捧着一杯咖啡站在窗边，更仔细地观察他们各自的运动轨迹时（是的，要观察他们各自的运动轨迹，而不是急于得出一个整体的结论，不要被最靠近自己房间的玻璃的那群雪花给主导了）你会发现“从右上方至左下方”这个简洁的描述只能算作是被要求限制字数地去描述得出的第一印象而已。首先，大部分的雪花的确是以同样的，从左至右地，出现在视野里，但他们其实在以诸多不同斜率的运动角度出现。稍靠近楼体的雪的运动角度更大，远离一些的那些部分运动的角度稍小些。再仔细一点地去观察，你会发现这个整体性的运动中不乏许多脱离队伍的个体。他们有的在顺着规定的轨道滑行的途中突然逃脱了加速度的作用散漫地垂直向下飘落，有的反方向地从左至右“冒雪“行动着，有的甚至垂直向上升起，但万一被定向行驶的部队中的某一个迎面撞上，事故发生的那一带便会像涟漪一样出现一定范围的、秩序被削弱的混乱。一般来说，这些脱离队伍的个体能在我的（你的）视野里停留相对较长的时间，但依然是以比秒钟要更小的单位计算。

雪从右上方来，到左下方去。左下方的降落地点虽然也各异，但都可以总结为“地面”。他们来自的右上方的尽头是哪里呢？如果想象雪的运动轨迹是一个长方体的一条对角线，他存在的空间便是这些由对角线定义和延伸出来的被分割成连续的长方体的空间。但这些长方体不是无尽出现的：在这个时刻地球表面的空间里没有连续不断的雪的对角线。如果一直追溯到下雪的状态的边缘，追溯到在边界处的那一片雪花划过的那一条对角线，再站在那一片雪花按这条对角线的轨道落下、与地面连接的那一个端点朝对角线的另一个端点抬头仰望，或许就能看到雪的右上方的尽头。又有一片雪花落下，轻盈地接近你的眼睛，在你还没有意识到你已经成功地找到了雪的尽头时它便已经落下，准确地降落在你站在的地面上的那个端点的那双靴子的皮面上，形状和天气预报里那个标准的六角雪花的标识一样。它还没有开始融化。

From upper right to lower left, snowflakes fell down from my bedroom window at an extremely fast pace. It was my first impression of the movement of snow when I opened the curtains in the morning and heard myself exclaim, “The snow is heavy.” When I was deciding when to buy flowers in reference to the weather forecast the day before yesterday, I knew that there was a 50 percent chance of snow this Sunday. Last night before sleep, as "this Sunday" drew closer, the chances of snow were broken down by hours: from 3:00 a.m. to 3 p.m., a hexagonal snowflake symbol marked each hour. Let us rewind a bit to the moment when I got up from bed, turned off the heat, and opened the curtains. Even though I knew it was going to snow today two days ago, I was astonished by how fast and dense the snowfall was, and uttered, "the snow is heavy." Having lived in a southern city, I experienced “snow” as a verb for the first time here and have slowly learned to walk upright on a ground without friction.So far, I have seen quite a bit of snow. But "snow" still falls outside of the weather categories I'm used to. After breakfast, I sit by my bedroom window and start to write about the snow. Snow particles seem smaller than an hour ago, or perhaps it is because the sky is brighter now. The snowflakes are still falling across my bedroom window from the upper right to the lower left at an extremely fast speed, and yes, it appears my initial conclusion was correct. Sitting at the window or leaning on it with a steaming cup of coffee, if you examine more closely the trajectory of each piece of snowflake (rather than rushing to an overall conclusion or be dominated by the flock of snowflakes closest to your window), you will realize the brief description of "from the upper right to lower left" is only a first impression when asked to depict the snow in a few words. To begin with, most of the snowflakes appear in my view from left to right, but they appear from many different angles. The snowflakes closer to the building move obliquely, whereas those further away move less sideways. If you look closer, you will find that many individual snowflakes are lagging behind in this overall movement. Some suddenly lose their acceleration while sliding along the prescribed track, drifting downward sloppily. Others move “against the snow” from left to right in the opposite direction, and some even rise. But a snowflake that is hit head-on by another ordinary one falls into a receding range of weakened disorder, much like ripples. In general, these detached individuals remain in my (your) view for a relatively long period, yet the time is still measured in units less than seconds.

The snow comes from the top right and falls to the bottom left. Landing places on the lower left side vary, but all can be summed up as "ground". Where is the end of the upper right side from which the snowflakes come? Assuming a snowflake's trajectory is a long diagonal line, then the space it occupies is the continuous rectangular spaces defined and extended by those lines. In spite of this, these rectangular spaces are not infinite: at this moment in time, there is no continuous diagonal line of snow on Earth's surface. If one goes all the way back to the liminal state when the snow is about to fall, back to the diagonal line where the last and first piece of snowflake at the boundary fall, then when you stand at the ground where this snowflake falls according to its trajectory, and look up from this end to the other end of the diagonal line, you may see the end of the upper right side of snow. Another piece of snowflake falls, lightly, approaching your eyes. Before you know you have managed to find the end of the snow, it has already fallen, landing exactly on the other end of the line on the ground where your leather boots stand. Its shape is the same as the standard hexagonal snowflake symbol you saw on the weather forecast. It has not yet begun to melt.