Author: uniquekey

  • Photo Gallery – Launching Ceremony Highlights (14 May 2019)

    Photo Gallery – Launching Ceremony Highlights (14 May 2019)

  • 2021年11月和12月的天文现象

    2021年11月和12月的天文现象

    在刚过去的11月19日,傍晚时分香港的上空出现了一次月偏食。这次的月偏食其实在香港时间下午约2时已经开始「半影食始」….

    (more…)

  • 2021年11月和12月的天文現象

    2021年11月和12月的天文現象

    在剛過去的11月19日,傍晚時分香港的上空出現了一次月偏食。這次的月偏食其實在香港時間下午約2時已經開始「半影食始」….

    (more…)

  • Astronomical Phenomena in November and December 2021

    Astronomical Phenomena in November and December 2021

    On 19 November 2021, a partial lunar eclipse occurred over the sky of Hong Kong in the evening. In fact, this partial lunar eclipse started at about 2pm HKT when the “Moon enters penumbra”….

    (more…)

  • newsletter (Nov 2021 – Issue 12)

    newsletter (Nov 2021 – Issue 12)


    关于香港桂冠论坛



    欢迎大家来到香港桂冠论坛2021年11月份通讯。

    10月及11月是香港桂冠论坛收获丰富而令人振奋的两个月。我们除了成功举办了首届论坛前奏活动(前奏活动)的首两个主题活动外,还参与了假香港科学园举行的创新科技嘉年华2021(10月23至31日)。

    台风「圆规」于10月中旬袭港,恶劣的天气令我们不得不取消第二轮「科学解密」两场分别关于天文学及数学科学的研讨会。然而,随着台风逐渐远离香港,我们于10月15至16日在西九文化区戏曲中心马上恢复举办公开展览,展示了来自香港城市大学、香港浸会大学、香港中文大学、香港理工大学及香港大学科研团队的研究成果。

    要持续保持香港市民(特别是年轻一代)对科学和科技各个领域的了解和兴趣,香港桂冠论坛很高兴能与法国驻港澳总领事馆携手合作,在创新科技署举办的创新科技嘉年华 2021,首次展出由法国著名艺术家Jeanne SUSPLUGAS制作,名为《I Will Sleep When I’m Dead》的独特虚拟实境体验。这有趣而富启发性的体验,让参加者进入人体大脑神经元和突触的世界,沉浸在科学技术的探索中,更成为创新科技嘉年华的其中一个主要参观项目,吸引了数以千计的市民参与,一探究竟。

    担任创新科技嘉年华2021开幕礼主礼嘉宾的财政司司长陈茂波先生,GBM,GBS,MH,JP及创新及科技局局长薛永恒先生,JP、法国驻港澳总领事官明远(Alexandre GIORGINI)先生与香港桂冠论坛委员会主席唐伟章教授,BBS,JP亦亲临香港桂冠论坛的展位,感受艺术与科学领域碰撞所擦出的创意火花。除了虚拟实境体验外,香港桂冠论坛还设有不同的小游戏和丰富奖品予一众参观人士。

    而前奏活动第二主题—「智者‧智讲」,刚于11月16至18日举行。为期三天的活动,以「线上+线下」的混合形式举行,活动设有世界知名和获奖科学家作演讲嘉宾的研讨会和对谈会。我们邀得10多位世界顶尖科学家,包括邵逸夫奖得奖者、科学突破奖得奖者、法国国家科学研究中心金奖得奖者、菲尔兹奖得奖者和皇家奖章得奖者,共聚于香港青年协会总部,围绕分别就生命科学与医学、天文学及数学科学这三大学科,与一众参加者进行交流。

    鉴于疫情关系,很遗憾身处香港境外的科学家难以亲临现场,然而我们为了提供一个较真实模拟直接学术交流的环境,我们利用最先进的技术取代现行被广泛应用的二维平台,将来自世界各地的讲者以全息投影技术带到现场。我们相信它能为我们的观众带来了引人入胜和激动人心的体验,为活动增添真实感。

    香港桂冠论坛衷心感谢所有演讲嘉宾、研究团队、合作伙伴、与会者和各界朋友的支持,使上述活动完满举行,协助推动我们的使命 – 为来自世界各地、各个领域的科学家,提供一个平台,促进科学发展,并启发科学界的年轻一代。


    百年物理 – 贺杨振宁教授一百岁生辰



    摘要

    现代物理学始于约一百年前出现的量子力学。在过去几十年内,人们从电磁作用出发,掌握了弱作用和强作用的规律——它们都遵从杨振宁和米尔斯提出的规范场论。而弱作用更区分左手和右手,展示杨振宁和李政道提出的宇称不守恒。本文谨在杨振宁教授百岁生辰之际,综述过去百年物理学的一条主线,亦介绍杨教授事略,并展望物理学在二十一世纪的前景。

    1. 引言

    杨振宁教授是当代最重要的理论物理学家之一,也是最早获得诺贝尔奖的华人之一,与中大有超过半世纪的情谊,现晋百龄高寿,实在难得而可喜。中国物理学会、清华大学、香港中文大学,合办庆祝,于9月22、23日在北京召开「展望未来100年的物理学——杨振宁先生学术思想研讨会」,而香港友好则在中大连线与会。 「研讨会」的对象为物理工作者,今天这个讲座则以科普为目的,旨在向香港年青学生介绍杨先生的事略和学术工作,并展望未来。必须指出,「展望未来」看似陈腔滥调,任何讨论会都可以套上,但这里却全无夸张,因为未来百年的物理进展,其中很大部分(主要是关于基本粒子,但亦延伸往其他领域)必然建基于杨先生所首创的非交换规范场之上,正如所有的古典物理都建基于牛顿定律之上。这一点,很多人尚未充分了解,所以有阐述之需要。

     

    作者︰
    香港中文大学物理系荣休教授杨纲凯教授
    2021年11月


    肥皂膜、极小曲面的趣谈



    极小曲面是微分几何学里最重要的研究对象之一。极小曲面除了本身富有数学美之外,在诸多物理现象中亦会自然出现,例如相变(phase transition)以及蝴蝶翅 膀鳞片的生物光子纳米结构。极小曲面在材料科学、工程学,甚至艺术、建筑领域均占有席位。 Frei Otto 亦在几项建筑作品的设计中运用了极小曲面,包括1972年德国慕尼黑奥林匹克运动场。

    肥皂膜及普拉托的实验

    事实上,要窥探何谓极小曲面,并不需要有科学家或建筑师的知识水平,因为这类曲面其实我们自小就见过,就是肥皂膜以及其类似的形态 – 肥皂泡。如果将一条金属圈浸入皂液再取出,就会看到线的边缘拉出一层薄肥皂膜。例如,用圆形线圈可以拉 出一只平碟。如果用两个平行同轴圆形线圈,就会拉出一个旋转对称肥皂膜,这种型状叫作悬链曲面(catenoid)。在十九世纪 ,比利时物理学家兼数学家约瑟夫.普拉托(Joseph Plateau)是首位利用不同形状金属线做实验、大规模研究肥皂膜的学者。他从实验的观察结果总结出一套名为「普拉托定律」的法则,用以描述一切有可能形成的肥皂膜之形状及特性。

     

    作者︰
    香港中文大学数学系副教授李文俊教授
    2021年11月


    2021年11月和12月的天文现象

    月偏食

    在刚过去的11月19日,傍晚时分香港的上空出现了一次月偏食。这次的月偏食其实在香港时间下午约2时已经开始「半影食始」,即月球开始进入地球的半影,中间经过了「初亏」,即月球正式进入地球的本影、「食甚」,即食分最大的时间、「复圆」,即月球离开了地球的本影及在晚上8时06分的「半影食终」﹐即月球完全离开了地球的半影而结束。整个过程历时多于6小时,是自15世纪以来最长的一次月偏食。不过,这次月偏食当日在香港的月出时间是下午5时38分,而「食甚」的时间是下午5时03分,所以「半影食始」、「初亏」和「食甚」这3个过程在香港是看不到的,这个情况和在5月发生的月全食一样,称之为「带食而出」,即当月亮刚刚升过地平线的时候,月食其实已经发生中。

    为什么这次的月偏食历时这么久呢?

    其实这与月球同地球的距离有关。我们都知道月球围绕地球移动的轨道并不是圆形而是椭圆形的,所以月球在不同的时间点和地球的距离都不一样。当月球距离地球最近的位置,称为「近地点」(Perigee),这个时候的满月会是全年最大的,而月球距离地球最远的位置,称为「远地点」(Apogee)。今次的月偏食「食甚」发生在月球较为接近「远地点」,月球与地球的距离比较远,亦即是月球需要更多的时间才会离开地球的影子,所以这次月偏食的时间便会比较长。

    下一次要在香港看到月食现象,需要等到2022年11月8日,这次将会是一次月全食,大家可以留意更多有关月食的不同时间和历时等有趣资讯。

    双子座流星雨

    除了11月的月食,一场双子座流星雨将会在本年12月13至14日发生,在香港也有机会看到。我们在之前的通讯提过,流星是宇宙中被称为流星体的碎片以极高速度进入地球大气层的现象。而流星雨就是当地球遇上一大群流星体时,看起来夜空中有许多流星出现的天文现象。今次流星雨的天顶每小时数目高达150,不过当晚月亮是上弦月,观赏时有可能较容易受到月光的影响。有兴趣观赏这个天文现象的人士可选择视野广阔和较黑暗的郊区,如果天气良好,便有机会看到流星雨。


  • newsletter (Nov 2021 – Issue 12)

    newsletter (Nov 2021 – Issue 12)


    關於香港桂冠論壇



    歡迎大家來到香港桂冠論壇2021年11月份通訊。

    10月及11月是香港桂冠論壇收獲豐富而令人振奮的兩個月。我們除了成功舉辦了首屆論壇前奏活動(前奏活動)的首兩個主題活動外,還參與了假香港科學園舉行的創新科技嘉年華2021(10月23至31日)。

    颱風「圓規」於10月中旬襲港,惡劣的天氣令我們不得不取消第二輪「科學解密」兩場分別關於天文學及數學科學的研討會。然而,隨著颱風逐漸遠離香港,我們於10月15至16日在西九文化區戲曲中心馬上恢復舉辦公開展覽,展示了來自香港城市大學、香港浸會大學、香港中文大學、香港理工大學及香港大學科研團隊的研究成果。

    要持續保持香港市民(特別是年輕一代)對科學和科技各個領域的了解和興趣,香港桂冠論壇很高興能與法國駐港澳總領事館攜手合作,在創新科技署舉辦的創新科技嘉年華 2021,首次展出由法國著名藝術家Jeanne SUSPLUGAS製作,名為《I Will Sleep When I’m Dead》的獨特虛擬實境體驗。這有趣而富啟發性的體驗,讓參加者進入人體大腦神經元和突觸的世界,沉浸在科學技術的探索中,更成為創新科技嘉年華的其中一個主要參觀項目,吸引了數以千計的市民參與,一探究竟。

    擔任創新科技嘉年華2021開幕禮主禮嘉賓的財政司司長陳茂波先生,GBM,GBS,MH,JP及創新及科技局局長薛永恒先生,JP、法國駐港澳總領事官明遠(Alexandre GIORGINI)先生與香港桂冠論壇委員會主席唐偉章教授,BBS,JP亦親臨香港桂冠論壇的展位,感受藝術與科學領域碰撞所擦出的創意火花。除了虛擬實境體驗外,香港桂冠論壇還設有不同的小遊戲和豐富獎品予一眾參觀人士。

    而前奏活動第二主題—「智者‧智講」,剛於11月16至18日舉行。為期三天的活動,以「線上+線下」的混合形式舉行,活動設有世界知名和獲獎科學家作演講嘉賓的研討會和對談會。我們邀得10多位世界頂尖科學家,包括邵逸夫獎得獎者、科學突破獎得獎者、法國國家科學研究中心金獎得獎者、菲爾茲獎得獎者和皇家獎章得獎者,共聚於香港青年協會總部,圍繞分別就生命科學與醫學、天文學及數學科學這三大學科,與一衆參加者進行交流。

    鑒於疫情關係,很遺憾身處香港境外的科學家難以親臨現場,然而我們為了提供一個較真實模擬直接學術交流的環境,我們利用最先進的技術取代現行被廣泛應用的二維平台,將來自世界各地的講者以全息投影技術帶到現場。我們相信它能為我們的觀眾帶來了引人入勝和激動人心的體驗,為活動增添真實感。

    香港桂冠論壇衷心感謝所有演講嘉賓、研究團隊、合作伙伴、與會者和各界朋友的支持,使上述活動完滿舉行,協助推動我們的使命 – 為來自世界各地、各個領域的科學家,提供一個平台,促進科學發展,並啟發科學界的年輕一代。


    百年物理 – 賀楊振寧教授一百歲生辰



    摘要

    現代物理學始於約一百年前出現的量子力學。在過去幾十年內,人們從電磁作用出發,掌握了弱作用和強作用的規律——它們都遵從楊振寧和米爾斯提出的規範場論。而弱作用更區分左手和右手,展示楊振寧和李政道提出的宇稱不守恆。本文謹在楊振寧教授百歲生辰之際,綜述過去百年物理學的一條主線,亦介紹楊教授事略,並展望物理學在二十一世紀的前景。

    1. 引言

    楊振寧教授是當代最重要的理論物理學家之一,也是最早獲得諾貝爾獎的華人之一,與中大有超過半世紀的情誼,現晉百齡高壽,實在難得而可喜。中國物理學會、清華大學、香港中文大學,合辦慶祝,於9月22、23日在北京召開「展望未來100年的物理學——楊振寧先生學術思想研討會」,而香港友好則在中大連線與會。「研討會」的對象為物理工作者,今天這個講座則以科普為目的,旨在向香港年青學生介紹楊先生的事略和學術工作,並展望未來。必須指出,「展望未來」看似陳腔濫調,任何討論會都可以套上,但這裡卻全無誇張,因為未來百年的物理進展,其中很大部分(主要是關於基本粒子,但亦延伸往其他領域)必然建基於楊先生所首創的非交換規範場之上,正如所有的古典物理都建基於牛頓定律之上。這一點,很多人尚未充分瞭解,所以有闡述之需要。

     

    作者︰
    香港中文大學物理系榮休教授楊綱凱教授
    2021年11月


    肥皂膜、極小曲面的趣談



    極小曲面是微分幾何學裏最重要的研究對象之一。極小曲面除了本身富有數學美之外,在諸多物理現象中亦會自然出現,例如相變(phase transition)以及蝴蝶翅 膀鱗片的生物光子納米結構。極小曲面在材料科學、工程學,甚至藝術、建築領域均佔有席位。Frei Otto 亦在幾項建築作品的設計中運用了極小曲面,包括1972年德國慕尼黑奧林匹克運動場。

    肥皂膜及普拉托的實驗

    事實上,要窺探何謂極小曲面,並不需要有科學家或建築師的知識水平,因為這類曲面其實我們自小就見過,就是肥皂膜以及其類似的形態 – 肥皂泡。如果將一條金屬圈浸入皂液再取出,就會看到線的邊緣拉出一層薄肥皂膜。例如,用圓形線圈可以拉 出一隻平碟。如果用兩個平行同軸圓形線圈,就會拉出一個旋轉對稱肥皂膜,這種型狀叫作懸鏈曲面(catenoid)。在十九世紀 ,比利時物理學家兼數學家約瑟夫.普拉托(Joseph Plateau)是首位利用不同形狀金屬線做實驗、大規模研究肥皂膜的學者。他從實驗的觀察結果總結出一套名為「普拉托定律」的法則,用以描述一切有可能形成的肥皂膜之形狀及特性。

     

    作者︰
    香港中文大學數學系副教授李文俊教授
    2021年11月


    2021年11月和12月的天文現象

    月偏食

    在剛過去的11月19日,傍晚時分香港的上空出現了一次月偏食。這次的月偏食其實在香港時間下午約2時已經開始「半影食始」,即月球開始進入地球的半影,中間經過了「初虧」,即月球正式進入地球的本影、「食甚」,即食分最大的時間、「復圓」,即月球離開了地球的本影及在晚上8時06分的「半影食終」﹐即月球完全離開了地球的半影而結束。整個過程歷時多於6小時,是自15世紀以來最長的一次月偏食。不過,這次月偏食當日在香港的月出時間是下午5時38分,而「食甚」的時間是下午5時03分,所以「半影食始」、「初虧」和「食甚」這3個過程在香港是看不到的,這個情況和在5月發生的月全食一樣,稱之為「帶食而出」,即當月亮剛剛升過地平線的時候,月食其實已經發生中。

    為什麼這次的月偏食歷時這麼久呢?

    其實這與月球同地球的距離有關。我們都知道月球圍繞地球移動的軌道並不是圓形而是橢圓形的,所以月球在不同的時間點和地球的距離都不一樣。當月球距離地球最近的位置,稱為「近地點」(Perigee),這個時候的滿月會是全年最大的,而月球距離地球最遠的位置,稱為「遠地點」(Apogee)。今次的月偏食「食甚」發生在月球較為接近「遠地點」,月球與地球的距離比較遠,亦即是月球需要更多的時間才會離開地球的影子,所以這次月偏食的時間便會比較長。

    下一次要在香港看到月食現象,需要等到2022年11月8日,這次將會是一次月全食,大家可以留意更多有關月食的不同時間和歷時等有趣資訊。

    雙子座流星雨

    除了11月的月食,一場雙子座流星雨將會在本年12月13至14日發生,在香港也有機會看到。我們在之前的通訊提過,流星是宇宙中被稱為流星體的碎片以極高速度進入地球大氣層的現象。而流星雨就是當地球遇上一大群流星體時,看起來夜空中有許多流星出現的天文現象。今次流星雨的天頂每小時數目高達150,不過當晚月亮是上弦月,觀賞時有可能較容易受到月光的影響。有興趣觀賞這個天文現象的人士可選擇視野廣闊和較黑暗的郊區,如果天氣良好,便有機會看到流星雨。


  • newsletter (Nov 2021 – Issue 12)

    newsletter (Nov 2021 – Issue 12)


    About the Hong Kong Laureate Forum



    Welcome to the November 2021 issue of the newsletter of the Hong Kong Laureate Forum!

    The past two months were exciting for us as we had successfully concluded the first two chapters of the “Prelude to the Inaugural Forum” series (Prelude Events) and took part in the InnoCarnival 2021 (23-31 October) at the Hong Kong Science Park.

    With the fresh memories of having Typhoon Kompasu roared past Hong Kong in mid-October, it was with much regret that the seminars in the second round of “Science Exposition” covering Astronomy and Mathematical Sciences were called off due to inclement weather. Yet, when the typhoon was gradually moving away from Hong Kong, we had resumed the exhibition at Xiqu Centre, West Kowloon Cultural District on 15-16 October to showcase the outstanding research achievements from teams of City University of Hong Kong, Hong Kong Baptist University, The Chinese University of Hong Kong, The Hong Kong Polytechnic University and The University of Hong Kong.

    To keep up the good vibes of promoting understanding and interests of the public, particularly the young generation, in Hong Kong in various disciplines in science and technology, the HKLF partnered with the Consulate General of France in Hong Kong and Macau (CGF) to present the Hong Kong debut of the virtual reality (VR) artwork, “I Will Sleep When I’m Dead”, created by renowned French artist, Ms Jeanne SUSPLUGAS at the InnoCarnival 2021, organised by the Innovation and Technology Commission. This unique fun-filled yet thought-provoking VR experience, which invited participants to venture into a world of brain neurons and synapses and enable them to immerse themselves in the exploration of science and technology, had become a major attraction at the InnoCarnival and enjoyed by thousands of visitors.

    Officiating guests of the InnoCarnival 2021’s opening ceremony, Mr Paul CHAN, GBM, GBS, MH, JP, Financial Secretary, and Mr Alfred SIT, JP, Secretary for Innovation and Technology, together with Mr Alexandre GIORGINI, Consul General of France in Hong Kong and Professor Timothy W TONG, BBS, JP, Chairman of the HKLF, marveled at how the crossover between science and art unleased new creativity during their tour of the HKLF booth. Besides the VR experience, the public also found fun games with awesome prizes at the HKLF booth.

    The second chapter of the Prelude Events was the inspirational three-day “Masterminds, Masterclasses”. This chapter was presented in a hybrid format of online and offline engagement, comprising seminars and dialogue sessions hosted by renowned and award-winning scientists around the globe. Over 10 prominent scientists including Shaw Laureates, recipients of Breakthrough Prize, CNRS Gold Medal, Fields Medal and Royal Medal were gathered at the headquarters of The Hong Kong Federation of Youth Groups on 16-18 November as guest speakers for three disciplines of science, namely Life Science and Medicine, Astronomy and Mathematical Sciences.

    Given the difficulty to have in-person participation of non-local speakers, we were excited to find an alternative to the usual online platforms – by beaming some of the speakers in innovative three-dimension holographic images from different parts of world to participate in the seminars. We believe it spiced up our event with an engaging and thrilling experience for our audience.

    The HKLF would like to express our heartful appreciation for all our speakers, research teams, partners, attendees and friends for making the abovementioned events such a great success and helped us continue to pursue our missions to provide a platform for renowned scientists of different disciplines from the world over to come together to promote science; and to enlighten the younger generation in the scientific community.


    A Century of Physics – A Public Lecture in Honour of Professor Yang Chen-Ning at One Hundred



    Summary

    Modern physics had its beginnings about a century ago with the birth of quantum mechanics. Over the past few decades, scientists have built on knowledge of electromagnetism to master the laws of the weak and strong interactions. They interactions all follow the gauge theory first proposed by Yang Chen-Ning and Mills. The weak interaction distinguishes left from right, exhibiting the non-conservation of parity first proposed by Yang together with Lee Tsung-Dao. This article is an excerpt from a public lecture, “100 Years of Physics: Celebration for CN Yang at One Hundred”. It sketches the main developments in physics over the past century, provides a brief history of Professor Yang’s life and his ground breaking works, and offers a look ahead to physics in the 21st century.

    1. Introduction

    Professor Yang Chen-Ning is one of the most important theoretical physicists of the contemporary era, and one of the first Chinese to receive the Nobel Prize. He has also been a friend of The Chinese University of Hong Kong (CUHK) for more than half a century. As he enters the hundredth year of a remarkable life, the Chinese Physical Society, Tsinghua University and CUHK have jointly organised the “Celebratory Conference for CN Yang at One Hundred”, held in Beijing on 22 and 23 September and attended online by friends and fellow physicists in Hong Kong. Unlike the conference targeting physicists, the seminar today aims to provide young Hong Kong students with some insight into the life and work of Professor Yang, and to look ahead to the future of physics in the next hundred years. Of course, ‘looking ahead to the future’ is a trite phrase often bandied about in many discussions, but the phrase is especially apt for today’s event, given that much of the progress in physics in the next one hundred years (mainly concerning elementary particles, but also extending to other fields) will inevitably be built upon on the non-commutative gauge theory pioneered by Professor Yang, just as all classical physics is built upon Newton’s laws. The pivotal position of gauge theories is not well appreciated by the general public, and it will be one purpose of the present talk to explain the unique contributions of Professor Yang.

     

    Author:
    Prof Kenneth YOUNG, Emeritus Professor, Department of Physics, The Chinese University of Hong Kong
    November 2021


    Soap Films, Minimal Surfaces and Beyond



    Minimal surfaces are amongst the most important objects studied in differential geometry. Apart from its intrinsic mathematical beauty, they appear naturally in a wide range of physical phenomena, for example, in phase transitions and in the biophotonic nanostructures in butterfly wing scales. Minimal surfaces also make their presence in material science, engineering, and even in art and architecture. Frei OTTO used minimal surfaces in several of his architectural designs including the 1972 Summer Olympic Games Stadium in Munich, Germany.

    Soap films and Plateau’s experiments

    In fact, we do not need to be a scientist or an architect to understand what a minimal surface is. We all have early acquaintance with such surfaces in the form of soap films as well as their related cousin, soap bubbles. If you dip a piece of metal wire into soap solutions and take it out, you will see a thin layer of soap films bounded by the wire. For example, a flat disk will be formed for a round circular wire. If you take two parallel coaxial circles instead, then you will obtain a rotationally symmetric piece of soap film known as the catenoid. In the 19th century, the Belgian physicist and mathematician Joseph PLATEAU was the first to conduct extensive studies of soap films through experiments with different shapes of metal wire. Through his experimental observations, he formulated a set of laws – known as Plateau’s laws – that describe the shape and configuration of all possible soap films.

     

    Author:
    Prof Martin LI, Associate Professor, Department of Mathematics, The Chinese University of Hong Kong
    November 2021


    Astronomical Phenomena in November and December 2021

    Partial Lunar Eclipse

    On 19 November 2021, a partial lunar eclipse occurred over the sky of Hong Kong in the evening. In fact, this partial lunar eclipse started at about 2pm HKT when the “Moon enters penumbra” of Earth, that is, the instant of first external tangency of the Moon with Earth’s penumbra. After that, “Moon enters umbra”, that is the instant of first external tangency of the Moon with Earth’s umbra; then “the greatest eclipse” which is the moment when the centre of the Moon is the closest to the centre of Earth’s shadow. This was followed by “Moon leaves umbra”, that is the instant of the last external tangency of the Moon with Earth’s umbra; and “Moon leaves penumbra” at 8:06pm, that is the instant of the last external tangency of the Moon with Earth’s penumbra. It also marks the end of this lunar eclipse. The whole process lasted over six hours, which was the longest partial lunar eclipse since the 15th century. However, the moonrise on that day was at 5:38pm and “the greatest eclipse” took place at 5:03pm. Therefore, on that day, the process of “Moon enters penumbra”, “Moon enters umbra” and “the greatest eclipse” were not observable in Hong Kong. It was actually similar to the situation of total lunar eclipse in May this year where the eclipse observable was already in progress upon moonrise.

    Why did this partial lunar eclipse last so long?

    This is actually related to the distance between the Moon and Earth. We all know that the Moon’s orbit around Earth is elliptical, so the distance between the two is different at different times. When the Moon is the closest to Earth, the position is called “Perigee” and the full moon will be the largest in the year. When the Moon is furthest from Earth, the position is called “Apogee”. “The greatest eclipse” this time occurred when the moon was quite close to the apogee and the distance between the Moon and Earth was relatively far and therefore, it took more time for the Moon to leave the shadow of Earth. This is why the partial lunar eclipse lasted longer.

    The next time a lunar eclipse can be observed in Hong Kong will be on 8 November 2022 and it will be a total lunar eclipse. You can try to find out interesting information about the different time and duration of the lunar eclipse.

    Geminid Meteor Shower

    Besides lunar eclipse in November, a Geminid meteor shower will occur on 13-14 December this year and we may be able to observe it in Hong Kong. As we had mentioned in previous issue of the newsletter, a meteor is a phenomenon in which cosmic debris called meteoroids entering Earth’s atmosphere at extremely high speed. A meteor shower is a celestial event in which many meteors appear in night sky when Earth encounters a large number of meteoroids. This time the Zenithal Hourly Rate is projected to be about 150. However, the Moon phase on that night will be “First Quarter” and the observation may be more affected by moonlight. If you are interested in observing this phenomenon, you can choose a spot in the suburbs with an unobstructed view and low light pollution. You may be able to observe the meteor shower, if weather permits.


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