冬至,又稱「冬節」、「賀冬」,二十四節氣之一,每年12月22日前后,太阳到达黃经270°时开始。
《月令七十二侯集解》:“十一月中,终藏之气,至此而极也。”
《通纬•孝经援神契》:“大雪后十五日,斗指子,为冬至,十一月中(夏历)。阴极而阳始至,日南至,渐长至也。”
此日太阳几乎直射南回归线,北半球白昼最短,北極圈呈永夜狀態,南極圈呈白夜狀態,其后阳光直射位置向北移动,白昼渐长。由于太阳辐射到地面的能量仍比地面向空中发散的少,所以在短时间内气温继续降低。天文学上规定冬至为北半球冬季的开始。
習俗
傳統上冬至半月是喜慶氣氛濃重的節期。冬至日這一天,北半球黑夜最長,故又稱「長至 」(夜長至,或稱日短至)。冬至日的前夜稱為「冬至夜」。冬至日是數九寒天的第一天,俗諺「冬至交九」,從冬至日開始即進入「數九天」。古時冬至節氣是計算二十四節氣的起點。因冬至節以往是僅次於新年的重要節日,所以又俗稱「亞歲」。在民間廣泛流傳着「冬至大如年」的說法,意指冬至的禮俗如同過新年春節一樣隆重。冬至還有「新正」、「如正」、「喜冬」、「交冬」、「消寒節」、「一陽節」、「履長節」、「小年」等稱謂。冬至亦代表舊的一年快過。
在傳統的陰陽五行理論中,冬至是陰消陽長轉化的關鍵節氣。在十二辟卦為地雷復卦,稱爲冬至一陽生。易復卦象曰:「雷在地中,復。先王以至日閉關,商旅不行,后不省方。」那天象徵太阳死亡,种植全面停止。
《後漢書》「禮儀志」中記載:「冬至前後,加子安身靜體,百官絕事,不聽政,擇吉辰而後省事。」由此可知從漢代起冬至是國定假日。
目前澳門是華人社會唯一以冬至作公眾假期的地區。
江苏的相当一部分地区,如苏中苏南一带,会把冬至称为小年。
汤圆在冬至節,中國北方有冬至日吃饺子的习俗,南方某些地方有冬至日吃湯圓、粉糍粑的習俗,傳說在漢朝的醫聖張仲景體念家鄉鄉民在寒冬中工作的辛苦,在冬至那天利用羊肉等祛寒的藥材包在麵皮中,作成耳朵的樣子,給鄉民們治病補身,這個藥方的名字叫作「祛寒嬌耳湯」,嬌耳就是餃兒。
中國南方則有吃湯圓等甜食的習俗,江浙一帶在冬至吃汤圆外,还要吃桂花酒酿,并祭祖,苏州还有桂花冬酿酒,只在此时节上市。大湯圓有餡的「粉團」是用于晚上祭祖,而無餡較小的粉圓用于早上拜神。福建的福州一带则在冬至吃𥻵。祭祖之后还有将汤圆粘在门窗上,称为「冬節圓」,等干燥以后再给孩子们吃,有保佑健康成长之用。冬至扫墓叫“过冬纸”。
《台灣府志》(一六九六)卷七記載:「冬至,人家作米丸祀眾神及祖先,舉家團圞而食之,謂之『添歲』;即古所謂『亞歲』也。門扉器物各粘一丸其上,謂之『餉耗』。是日,長幼祀祖、賀節,略如元旦」。在台灣冬至的湯圓有紅白兩色,另有較大的湯圓,內包有芝蔴、花生、或鮮肉等內餡。
在中国,人们从冬至开始数九,以九天为一九,九九八十一天,寒冬就会过去,稱為九九數盡。
source : Wikipedia
Ongzi thinks that life is a journey of seeking|sharing knowledge. Thus, one needs to be eager|passionate, open-mind|generous-heart , and humble|dedicated for the betterment of man. For without it, man shall not prosper. However, only the one with pure heart shall find the ultimate truth.
Thursday, December 23, 2010
Friday, October 29, 2010
Saturday, October 16, 2010
Colour of Water
Relatively small quantities of waters observed by humans to be colourless. The fact is, pure water has a light blue colour which become deeper blue as the thickness of the observed samples increases. Impurities dissolved or suspended in water may give water different coloured appearance.
Liquid water’s intrinsic natural colour may be demonstrated by looking at a white light source through a long pipe, filled with purified water, that is closed at both ends with a transparent window.
The light turquoise blue is caused by weak absorption in the red part of the visible spectrum. Absorptions in the visible spectrum are attributed to excitations of the electronic energy states in matter.
The water molecule has 3 fundamental modes of vibration. There are two O-H stretching vibrations which occure at ca. 3500 cm-1 and an H-O-H bending vibration at ca. 1640 cm-1. Absorption due to these vibrations occurs in the infrared region of the spectrum.
The observed absorption in the visible spectrum is due mainly to 4th harmonic frequency ( 3rd overtone ) of O-H bond-stretching vibrations. 4 x 3500 = 14000 cm cm-1 is equivalent to a wavelength of ca. 715 nm. The actual absorption maximum occurs at 698 nm.
Because absorption intensity decreased significantly with each successive overtone, absorption due to the 4th overtone is very weak, so to see the blue colour the pipe needs to be a meter or more in length and the water be removed any particles that would otherwise cause color to be generated by Rayleigh scattering.
It is a common misconception that in large bodies, such as the oceans, the water’s colour is blue due to the reflection from the sky on its surface. It is true only when the water surface is extremely still, i.e. mirror-like, and the angle of incidence is high, as water’s reflectivity rapidly approaches near total reflection under these circumstances, as governed by the Fresnel equations.
Optical scattering of unabsorbed light from water molecules as well as from impurities in the water of oceans or lakes back into the atmosphere provides the opportunity to visibly observe the blue color of water from land or airplanes.
If the oceans owed their colour to the sky, they would be a lighter shade of blue and would be colourless on cloudy days.
Particles and solutes can absorb light. Green algae in rivers often lend a blue-green colour. The red sea has occasional bloom of red Trichodesmium erythraeum algae. Tannins caused rivers to be dark brown. High concentration of dissolved lime give the water a turquoise colour.
Slight discoloration is measured in Hazen Units ( HU ).
The colour of a water sample can be reported as :
1. Apparent colour, colour of the whole water sample, and consists of colour from both dissolved and suspended components
2. True colour, is measured after filtering the water sample to remove all suspended material.
Tuesday, September 21, 2010
Drake Equation : Are We Alone ?
Drake Equation is an equation used to estimate the potential number of extraterrestrial civilizations in the Milky Way galaxy. It is used in the fields of exobiology and the search for extraterrestrial intelligence (SETI). The equation was devised by Frank Drake in 1962.
Where :
N = the number of civilizations in our galaxy with which communication might be possible ;
and
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fℓ = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time such civilizations release detectable signals into space
Considerable disagreement on the values of these parameters exist, there are several disagreement on the value of the parameters, thus resulting in different answers :
Drake | Current | Pessimist | Optimist | |
N | 10 | 2.31 | 0.000065 | 20000 |
R* | 10 | 7 | 10 | 20 |
fp | 0.5 | 0.5 | 0.5 | 0.5 |
ne | 2 | 2 | 0.01 | 2 |
fℓ | 1 | 0.33 | 0.13 | 1 |
fi | 0.01 | 0.01 | 0.001 | 0.1 |
fc | 0.01 | 0.01 | 0.01 | 0.1 |
L | 10000 | 10000 | 1000 | 100000 |
Current estimate is based on NASA and the European Space Agency (2008) R* = 7 ; and fℓ = 0.33 ,
\ Current N = 2.31 ( 2 communicative civilization exist in our galaxy at any given time, on average, plus 200 more that are not trying to communicate )
A pessimist believes that suitable planets are rare, life seldom becomes intelligent, and intelligent civilizations do not last very long, thus a Pessimist N = 0.000065. ( we are almost surely alone in our galaxy )
Alternatively, making some more optimistic assumptions, assuming that planets are common, life always arises when planets are favorable, 10% of civilization become willing and able to communicate, and then spread through their local star systems for 100,000 years : an Optimistic N = 20,000 ( there’s quite a few civilizations, although the closest one would still be about 1,500 light years away. )
Criticism
1. The equation is largely based on conjecture, thus cannot be used to draw firm conclusions of any kind.
2. Drake Equation assumes that civilizations arise and then die out within their original solar systems. If interstellar colonization is possible, then this assumption in invalid, and the equations of population dynamics would apply instead.
3. Drake originally formulated the equation merely as an agenda for discussion at the Green Bank Conference. Even though the Drake Equation involves speculation about unmeasured parameters, it was not meant to be science, but intended as a way to stimulate dialog on these topics.
4. Drake Equation is a Fermi problem which involves the multiplication of several estimated factors. The basic question of why, if there is a significant numbers of such civilizations, ours has never encountered any others is called the Fermi paradox.
Friday, August 13, 2010
拼音符号 vs 注音符号
ㄓㄨˋ | ㄧㄣ | ㄈㄨˊ | ㄏㄠˋ | pin | yin | fu | hao | ||||||||||||||
注 | 音 | 符 | 号 | 拼 | 音 | 符 | 号 | ||||||||||||||
发音 | |||||||||||||||||||||
韻 | 介 | 聲 | |||||||||||||||||||
ㄦ | er | ㄢ | an | ㄞ | ai | ㄚ | a | ㄧ | i | ㄗ | z | ㄓ | zh | ㄐ | j | ㄍ | g | ㄉ | d | ㄅ | b |
儿 | 安 | 哀 | 啊 | 衣 | 资 | 知 | 基 | 哥 | 得 | 玻 | |||||||||||
ㄣ | en | ㄟ | ei | ㄛ | o | ㄨ | u | ㄘ | c | ㄔ | ch | ㄑ | q | ㄎ | k | ㄊ | t | ㄆ | p | ||
恩 | 诶 | 喔 | 乌 | 雌 | 蚩 | 欺 | 科 | 特 | 坡 | ||||||||||||
ㄤ | ang | ㄠ | ao | ㄜ | e | ㄩ | ü | ㄙ | s | ㄕ | sh | ㄒ | x | ㄏ | h | ㄋ | n | ㄇ | m | ||
昂 | 熬 | 鹅 | 迂 | 思 | 诗 | 希 | 喝 | 讷 | 摸 | ||||||||||||
ㄥ | eng | ㄡ | ou | ㄝ | ê | ㄖ | r | ㄌ | l | ㄈ | f | ||||||||||
欧 | 日 | 勒 | 佛 |
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