The reading notes record thoughts from things I read. 這網誌是我的一些閱讀後的思考和摘要記錄。My website 我的網頁: http://raympoon.playgroundhk.com

Renewable energy

Renewable energy has been a buzz word for several decades.  In the 1970s, there was a prediction that by 2000, 33% of America’s energy would be provided by small, decentralized renewable sources.  In 2008, Al Gore claimed that the country’s entire electricity supply would be re-powered within a decade.  In 2009, science journal published a plan on how to achieve sustainable energy by 2030.  All these turned out to be hot air spoken by politicians.  Scientific American in the first issue of 2014 posted an article explaining the realistic situation, and why renewable energy is still unable to take off.

The world underwent several changes of global energy source since human knew how to use fire.  The first fuel used was wood and plant.  It was until the middle of the 19th century that coal was mined in a large scale and used in industries.  Despite the great efficiency of coal over wood, it took about 60 years for coal to get to the point of providing 50% of the world’s energy needs.  The next breakthrough was crude oil.  It was brought into use at the beginning of the 20th century.  It also took 60 years for the consumption to reach 40% of world energy supply.  Coal is still being used in many large facilities.  Then came natural gas in the middle of the 20th century.  It has an advantage of being cleaner and more abundant than oil.  In 60 years, it supplied 25% of the world’s energy.  In 2012, modern renewable energy sources only account for 3.4% of the world’s energy.  From history, even with good intention and good effort, it is unlikely that renewable energy would provide a significant portion of the world’s energy in the next few decades.

From a realistic point of view, there are several reasons that modern renewable energy would still need quite some time to become mainstream energy supply.  Of the various types of modern renewable energy, only wind and solar energy have the potential of future growth.  However, the nature of the energy sources, sunlight and wind, make them unreliable to be used as a continuous supply.  Efforts have been made on the storage of surplus energy to be used between gaps.  But most of them are not scalable to be used at the industrial scale.  Unless there are major breakthroughs in technology, the pace of growth will remain to be slow.

Another barrier for growth is the infrastructure changes required to accommodate the distribution of renewable energy.  Both wind and solar energy generation require large area of land in remote area.  For the energy generated to be integrated with the power supply grid, new infrastructure is required to be built.  They usually are met with local resistance on which much time and effort are required to resolve.  The amount of investment needed to achieve effective distribution is very large, and could be larger than the energy generation installation.  At present, the pace of building such infrastructure has been very slow.

In replacing the present energy sources, it has to be borne in mind that the existing facilities are well established, working efficiently, producing good profits and that very heavy investment has been made on them.  Unless renewable energy could provide much greater benefits, and could be introduced with seamless transition, investors would not easily abandon their valuable assets and take unnecessary risks.

All these factors aside, the author pointed out one major reasons is the very rapid expansion of world energy consumption.  The demand increase is so fast that any new technology would not be able to fill up the void quickly.  Existing technology has to be deployed intensively to meet demand.  Progresses in developing countries show that fire-powered plants and nuclear plants are being built much faster than renewable energy facilities.

To speed up the use of renewable energy, the authors proposed that certain policies could be introduced.  These include providing funding for research into many technologies to facilitate competition, devising pricing mechanism to reflect the environmental and health costs imposed by energy sources, and improving energy efficiency worldwide to curb demand growth.

末世列車 Snowpiercer

snowpier

末世列車 Snowpiercer 是今年新片,韓國導演韓國監製,有美國、英國、韓國演員。廣告標榜它是一套科幻電影;我覺得畫面並不太科幻,但卻盡量借用環保議題和政治議題。主打感官刺激,除了激烈的動作,還以另類的劇情去刺激觀眾的思維。

首先在環保議題抽水。地球暖化情況惡化,科學家自作聰明,將化學物CW7放入大氣層高層,以降低地球溫度。結果失控,全球溫度降至冰點以下,地面冰封,所有生物凍死,人類滅絕。

倖存少量的人,藏身於一高科技列車,有無盡能量,在封閉的空間內可以自給自足,在特定的鐵路環球運行。這個列車影射方舟,又代表地球在太空中的孤獨。列車一卡接著一卡;第一卡是全能的引擎,順著次序是豪華的頭等卡、直至車尾窮人的座位。

至此為止,影片將故事環境定下來,劇情展開就是描述政治階級鬥爭的現實。車尾的人認為自己被壓迫,生活水平低。為了改善生活,爭取自由,要由車尾一卡一卡的攻向前卡。車頭的人要極力控制現狀,對反抗的人說教。列車環境有上限,大家要各安其位才可能生存。而且大家的存亡在於至高無上的全能引擎,它是一定要被尊敬被祟拜。車尾的人鍥而不捨,努力向前攻。我以為影片寓意人民反抗專制努力不懈。到了最後原來有一個大陰謀,反映了列車孤獨封閉環境的殘酷現實。故事明顯是影射封閉的地球,有限的資源,人類的紛爭,權力的製造,宗教的產生。到了最後,面臨一個抉擇,究竟是要保持列車繼續運行,還是要放棄這個唯一的維生環境。影片提出一個痛快但不合理的結局,但這卻是地球大有可能走向的結局。影片的娛樂性並不太強,但發人深省。

回收的失敗

香港鼓吹回收已有一段日子。民間宣傳算是足夠,呼籲大家將垃圾分類。但回收業總是搞不起來。政府亦有姿態略盡綿力,還聘用合約商代為收集分了類的垃圾,以循環再用。但我們近期在新聞看到,有垃圾回收合約商收集了垃圾後,竟然再將之棄置或送到堆填區。大家將垃圾分類的努力完全白費。

但同時,我卻發現屋苑管理處要對垃圾分類箱嚴加保護。下面這個垃圾箱,本來只是三個桶,後來加了保護箱又有門。之後又在每一道門上加了鎖。今天發現整個垃圾箱加了金屬條再加一把堅固的鎖。問一問管理員,原來垃圾有價,有拾荒的人晚上到來將有用的廢紙膠樽取走。結果是垃圾箱都要上鎖使他們無法得益。

recycle

這在邏輯上有點問題。將垃圾分類的目的就是想回收循環再用。但拾荒的人回收卻不受歡迎。反之收取費用的合約商卻只收垃圾不處理。另外,合約商棄置垃圾應該是商業考慮;只收回收費用已有利潤,而回收垃圾成本更高。但拾荒的人卻可以靠回收垃圾維生,證明市場是有需求吸納有用的垃圾。問題出在那裡呢?

政府近期諮詢回收業發展,有商人解釋因國際環保條例收緊,垃圾不能隨便運送別處。香港將廢紙和塑膠廢物出口有阻力。將垃圾處理至可以接受的安全程度所需人力成本很高,要大量處理更不可能。反之,拾荒個體戶可以人手分出少量有用的物料,回收商願意收購,就形成小型互利生存狀態。

回收業有此困局,是基於不周詳或欠缺了的全盤計劃。二十年前環保意識興起,大家都一窩蜂的要攪環保,垃圾分類以供回收再用是每一個家庭都可做。大家由小學生開始已被洗腦,垃圾分類像賣旗一樣是善事。但之後的工作如何進行呢?政府的想法很天真:既然垃圾有價,市場就會想辦法使用它。其後果是整個回收生態平衡不是由需求驅動 need-driven 而是由道德推動 moral-driven。環保以宗教手法宣傳,一定正確,一定要去做。其結果是很成功,但供應卻大大超出需求,因為回收業現時的模式不能有效處理,大家的努力徒勞無功。

香港是七百多萬人的大城市,入口消費物資數量龐大,而產生的垃圾數量同樣龐大。真正要回收所有可再用的垃圾所需的各種資源更驚人。現在我們主要的處理方法是將有用的垃圾分類後運去另一國家,由他人去處理垃圾。本土使用回收物料再造規模甚小。當其他方收緊入口垃圾控制,這個模式即時變得不可行。

政府有責任在很早之前就要評估整個回收生態。她的短視顯現初期輕視市民對垃圾回收的反應,以為問題不大,市場已有機制使用少量回收的垃圾。其實大量垃圾必須處理,大眾自行分類與否都要想辦法去焚化或堆填。但垃圾有價,這其實是商機。垃圾不能出口,本土亦不能使用全部回收的物料。可行的辦法是讓工業界將垃圾半加工成為原材料,就可以出售到其他國家。這需要科研界和工程界的協助,建立高科技設施。政府可在資源、融資、政策上配合和推動。可做的例子甚多,我舉出幾個。

廢紙最客易再做。但困難是在分類處理。將不同質地的紙張分開又去除雜物,要使用大量人力。拾荒的人通常可做一點。廢紙分類如在工廠處理,可以使用科技器械 協助減低人力和提高效率。廢紙可再處理成為再造紙的原材料,就可以有出口市場。初期投入的成本會很大,政府可以用公帑作前期投資。

塑膠是甚受歡迎的回收物料。但未經處理的塑膠廢物被視為垃圾,別的國家可拒入口。塑膠廢物可集中在大型設施處理,以機械協助分類清洗切碎成為原材料,就可直接出售至塑膠製品工廠。

近期一個新議題是回收玻璃樽。消化的方法是將玻璃打碎混合其他物料造地磚。這一種低溫低成本的地磚質地粗糙,只可供室外場地使用。而且工廠規模很小,每日使用的玻璃不多,在全港每日玻璃樽垃圾數量中比例很少。除非收集玻璃樽垃圾成效不大,否則大部份回收的玻璃樽其下場仍是堆填區。但玻璃是可再造物料,壓碎的玻璃已可作原材料出口。如要增值,可將玻璃再提煉除去雜質變為高品質物料。成本會非常高但價值和需求亦會增加。這需要一個有遠見的政府去推動。

Privacy in the world of big data

Personal data privacy is everyone’s concern.  But our understanding of such may be limited.  Scientific American has an article on this in the November 2013 issue.  It was written by a privacy advocate on privacy in the world of big data.  We may read it bearing in mind his bias, but there is some insight in his observation.

We think privacy of personal data mainly concerns our identity card number and data which may easily identify us.  For the privacy advocates, privacy is about naked information available to some but unavailable to others.  Privacy is the arbiter of who gets to be in more control.  At present, most of the debate on privacy is the type of personal data which can be collected, used, disclosed.  The most talked about point is the trade-off.  In the modern environment where we need the society network for goods and services, there is a need to provide our personal data to other providers.  The question is framed to be how much privacy are people willing to give up for certain benefits.  The underlying notion of this question is that if people would only share more, they would enjoy more convenience or create more value in online networks.  The disadvantages of giving too much personal data away have been limited to unwanted advertisements.

In fact, this form of privacy is only an illusion covering the real situation.  Information about a person include anything that a person did, whether online or got into the network from other means.  Anything we interact with another entity, say the government, banks, purchases, services are all recorded.  Anything we did in any kind of social media are all recorded.  This is done with our tacit consent.  The debate on privacy is lopsided as no one has complete information on what kind of personal data is stored and processed by others.  What we can see are the unwanted advertisements, unwanted friends in social network, and some secrets disclosed by Snowden.  But that is only the tip of the iceberg.

You may encounter the scenario where a Google search gives you the desired results; or Amazon recommends the books your like.  They are able to do that because they maintain a profile on you.  The information in your profile is built up from your previous connections with them.  In fact, anything you did with them are recorded, analyzed, and used to refine your profile so that they can provide the goods and services most likely suit your needs.  This kind of refined and targeted service is a two-edged sword.  On the one hand, people may get information on what they like, and at the same time, information limited to what they like.  It is an information filter which may keep one-half of the real world away from you.  The big data also work for the commercial world.  With personal information on the population obtainable, medical insurance companies may be able to devise sales strategy excluding high-risk customers, thus depriving those who need insurance most.

A more frightening scenario, which was predicted by novelists long time ago, and which has gradually becoming a reality, is the behaviour changing tactics based on big data.  A profile on anybody can be set up using any personal data which can be collected from the network.  The profile can be refined as more information is gathered and analyzed, to the extent which could reflect the preference and intention of such person.  A harmless proposal is to locate the position of the person at all time.  If this person likes to have a cup of coffee whenever he leaves the MTR station, a text message could be sent to his phone indicating the best coffee shop nearby.  This can be used as a business opportunity in selling advertisement slots to coffee shops.  This could also be used in electioneering where a person may be steered to vote for a particular candidate.

With personal information so widespread, there is no way we could keep it all from others.  The author suggests that people should be given control on the level of privacy they could keep.  One of the ways is to attach a monetary value to personal information.  All information identified with a person are given a code so that a small amount is credited to the person whenever it is used.  In this way, businesses and the government may be more careful in using others’ personal information, in stead of freely mining the big data.  But this charging system may be very complicated, and I think it may itself become a source of personal information.

Incidentally, I just saw this video on YouTube on a social media experiment.  This guy used his smartphone to check social media on other users near his location.  Then he checked their status, profile, posts and photo which were open to public, and then approached them by name.  People were surprised that a complete stranger could know so much of their personal details just by checking on a smartphone.

東華義莊

東華義莊位於大口環,全盛時期佔據整個山谷。今日時移勢易,該區已發展,它被其他建築物圍繞,經過大口環道都不容易看見它。但它的功能仍然存在, 提供遺體存放服務。她通常不會開放給公眾自由遊覽。今次得工會安排,由專人帶領講解參觀,是非常難得的機遇。

義莊這個名詞給人不安的感覺。一般人覺得它是用來處理不明來歷、無人認領的遺體。其實這些是政府的工作,由政府殮房直接處理。東華義莊最早的功能是提供義務殯葬服務給在東華醫院病逝的窮人,遺體運來處理後葬在義山。香港曾發生幾次重大災害,死者眾多,東華出手幫助,由義莊處理遺體。最近一次沙士之役,因殯儀館不敢接收病者遺體,義莊亦承擔了工作。因為其處理遺體的經驗,在二十世紀初海外華僑團體都要求東華轉運遺體到內地安葬,義莊成為重要中轉站。現時尚有少量遺體骨殖因各種原因滯留在此。

tungwah0

十九世紀末期至二十世紀初段,美國急速發展基建,又發現金鑛,需要大量勞工。廣東福建沿海一帶的居民被招募到美國工作。有些人希望尋找機會、有些人被騙亦有人被強擄。到了美國,很多人被勞役。美國曾出現數次排華事件,國家亦曾立法歧視華人。美國近代史有不少研究,華人在美國的遭遇有詳細記錄,為美國歷史重大原素之一。最近美國更通過議案,為歧視法向華人道歉。在中國,廣東福建鄉間有很多農村,因移民問題以致人口凋零。但在中國這些歷史資料很零碎,近年才說要重整華僑史。

這段歷史中間有一個重要環節,就是美國移民還鄉的情況。鄉間有不少例子是移民致富後歸來,在故鄉大興土木。但有更多的移民客死異鄉,希望返回故鄉安葬。當時可行的安排是由當地的華僑會館和中國對口鄉間組織聯絡,然後將遺體以郵輪運來香港,委託東華義莊轉運到中國。在全盛時期,東華義莊要收容六百副棺木和八千多副骨殖。要重整這段歷史很困難,因為很多文件都已失落。窮苦的勞工在美國的遭遇並不光彩,很多文件都不會珍重保存。中國在二十世紀動亂不絕,記錄更是殘缺不全。

tungwah1 tungwah2

東華義莊保存的記錄成為這一個歷史環節的重要考究證據。東華文物館保存了大量二十世紀初期海外會館和義莊的通訊,包括委托轉運遺體的指示、死者籍貫資料。可聯絡的美洲城市很多,由北美一直到南美都有。中國沿海鄉鎮更多,之間連接的路線多不勝數。因為義莊珍貴文件提供的資料,現時已考究了在三藩市的廣福堂,它是最主要的美洲華人會館,定期運回華僑遺體。根據付運文件,文物館人員追尋到其中一個目的地開平的百合墟,找到一位曾經目睹運載遺體漁船抵岸的老伯,還找出當年泊岸碼頭的位置。紙上描述的歷史就此考證成為事實,其中一條華人渡過遠洋到美洲打工又再落葉歸根回到中國的循環路線被確立。其中香港的貢獻,在中美關係史和香港現代史中應佔一重要位置。多年來讀到的香港歷史,其實只是英國殖民地歷史,最早開埠事件就只是英軍登陸水坑口。義莊的工作除了是香港本土民間自發的重要事件,更是中國近代史以至世界人口遷徙歷史中的一篇。香港現時要力尋本土歷史內涵,義莊歷史地位和它對世界華人的貢獻就是一個很好的起點。

人口政策諮詢文件

剛剛發表的2013人口政策諮詢文件,即時引來不少批評。但我覺得這份文件比去年的人口政策報告書已寫得較好。因為這是一份諮詢文件,除了現狀之外,只可提出問題,諮詢市民意見;所以沒有即時清楚說明長遠的解決方案。若以此來批評有點不公平。

雖然如此,文件內容仍有不足,很多提出的議題只是想當然,很難說政府在未來人口上有一個願景和期望。首先要說港童在深圳的問題。早前謠傳文件會諮詢雙非兒童父母來港的政策,現證實並無其事。反之,文件極度低調處理港童在深圳的問題。首先,它將問題縮小至局限於雙非兒童;接著重複教育局剛做的應對,即是將他們派入現有的新界區幼稚園和小學,包括北區至大埔區;最後,說因現時雙非零配額,雙非兒童問題幾年後會自然解決。這是很膚淺的想法。港童在深圳不只是雙非兒童問題。深港融合已漸漸發生,不少香港家庭居於深圳,可以舉家每天都回港。深圳當局推算幾年後有五萬港童在深圳, 而超過一半約三萬人要跨境上學。今年北區小學學位已不足夠,現在的規劃更不能支持幾年後的增長。距離香港不太遠的深圳市區使可以跨境上學的範圍其實不是無限,學童數目有一個上限。但該區會漸有更多香港家庭居住,跨境學童問題應不可能消失。現時政府的態度和方法實在不能持續。

不過這只是人口的一小部份。最基本的人口變化當然是出生率。這一個概念有一個基本的矛盾。世界人口爆炸,科學家預言在不久的將來世界人口將會由現在的七十億增加至一百億。而一百億的人口將是地球資源所能承受的極限。其中已發展的國家出生率減低而發展中國家增大。全球的科學家都勸告所有國家要管理好家庭計劃,以免人口膨脹得太快。但香港卻十分短視,認為要鼓勵市民生育。已發展國家的人民選擇只生一個小孩,是由於知識水平提高和女性權益受尊重。這一個趨勢是不可逆轉的。再者,政府提出的方法,是以金錢和福利來增加生育的意欲。但生育所帶來的責任和負擔,是遠比政府所能提供的福利高。星加坡已有例子證明這些措施沒有效用。

輸入人才是一個可行的辦法。但全世界的國家都想輸入人才,香港如何和別的國家競爭。現今世界人口流動相對自由,人才亦會擇沃土而居。輸入人才不同輸入外勞以暫時解決某些人手不足的工作。輸入人才是想改造未來的人口結構。以短期的高薪吸引外來的人才不是好辦法,反而會引起本地人才不滿。報告指出困難在於高樓價、空氣質素和國際學校學額不足。學額問題是由我們自己做成,因為國際學校收了大量本地學生。首兩點不是人口問題,而是對全港市民的責任。輸入人才關鍵在香港的整體吸引力。在現階段,現實是香港仍對中國人才有吸引力,輸入人才可傾向中港融合。

我覺得老人問題不盡是人口問題,而是老人福利問題。至於退休年齡,實際上社會已視65歲為界線,已由強積金安排落實;例外的只是公務員條例。公務員事務局再諮詢也否,可以預見未來新入職公務員將會以65歲為退休法定年齡。不過其影響要三四十年後才發生。其間,政府只需放寬退休再聘任的安排。

發展跨境服務

幾十年前的深圳,門禁深嚴,出入要仔細檢查,旅客只是在這裡過境,不會逗留。八十年代起,過境手續放寬,香港人自由出入,有人到深圳買點農產品。遊人漸多,為遊客提供的各種服務湧現,佔據了整個深圳墟。遊客業務不斷膨脹,深圳居民獲利不少,市區向外幾何式發展。結果是深圳成為香港後花園,為大部份香港人假日消閒首選之地。深圳吸納香港的消費開支達天文數字。深圳於是再度升格,變身為特區,以香港為範本,發展商業、財務服務、機場、貨櫃碼頭。發展方向非常清晰,務求可取代香港。這是利用機遇的最佳例 子。

不久之前的香港,為中國人禁地,平民不得進入香港,邊境地區被封鎖。只有少數特權人士可來港探訪。近十年來,香港經濟下滑,中國略為放寬人民出境到香港的限制,增加在香港的消費,以助經濟復甦。遊客區如尖沙嘴銅鑼灣即時有反應,興旺起來。但香港不同深圳,我們不能把握商機,反而不能勤勞應對發展,而視增加了的訪客為滋擾。現時社會上普遍的氣氛是敵視中國遊客,北區和元朗區因遊客較多而情況更覺嚴重。深圳和香港面對轉變的態度分別真大。

回到港童問題,感覺更切身。什麼是港童?他們有永久香港居民身份。但因為他們住在邊界的另一面,距離香港可能只有一公里,就被視為異類,被認為是來港搶奪資源。故不論政府在此有何過失,但是一定有責任去糾正。港童住在深圳,是有其原因。跨境服務這個現實短期內都會存在。因為要跨境,粉嶺以南的地區很難有效協作。要有效率的提供服務,只有大力發展北區,包括東北和元朗。況且如果只提供跨境學童服務是虧本生意,倒不如發展新市鎮,加入工商業和住屋元素。北區和元朗原居民因地權問題可能反對。但該區可發展的土地很多,包括河套區和邊境禁區。現時缺乏的是願景和決心。

 

香港兒童在深圳

我去年六月評論過香港的人口政策, 覺得除了生育率和移民之外,香港還有深圳因素,影響了真正人口推算和民生服務需求的水平。國民移居海外的情況各國都會發生。但香港人在中國的情況並不一 樣。因香港是特別行政區,香港人有特殊地位,進出中國沒有限制。而且深圳只在隔鄰,在深圳的香港人可以天天回港工作和接受各種服務。

因此,人口政策必須準確收集這些香港人的資料和預測適當的服務水平。但過去政府看待這一個因素是想取便宜。香港人往中國就業、求學、定居就可減低香港的負擔。這個想法證實是錯誤的。香港人在中國沒有戶藉。雖然行動自由,但不能享受中國國民福利。到有困難的時候,香港政府不能坐視,社會福利署的廣東計劃和福建計劃就是好例子。

香港兒童在深圳更是一個重大問題。上一任政府鼓吹來港產子服務,亦是想取便宜。先讓醫療界賺一筆,然後讓這些富裕中國家庭的小孩由其父母照顧和教育。直至長大成材就以港人身份來港服務作出貢獻。這個算盤打不響。原來這些有香港人身份的小孩沒有中國戶藉,不能接受中國國民福利,包括醫療和教育。在中國,他們要如外國人般找醫生或國際學校。另一個做法就是回港接受服務。

人口政策要應對這個趨勢,但我們似乎手忙腳亂;母嬰健康院爆滿、醫院有大量大陸港童病人、旺角私家醫生都大排長龍,北區幼稚園和小學學位供不應求。市民抱怨政府後知後覺,未能早作準備。教育局長將之歸咎於忽然湧現的跨境學童潮,說不符其精算師的推算。但港童在中國的數字是否這樣神秘?在港出生的兒童有詳細的出生記錄,而出入境亦有記錄。政府是低估了這些兒童需要回港的比例,以為大部份可能因為路途遙遠而不能每天回港。但其實深圳當局就已有準確的數字,政府只需作簡單的聯絡就可取得。剛公佈的數字是現時有3.2萬名在港出生的學童居於深圳,當中1.7萬要跨境到港上學,比率為53%,包括單非、雙非和父母都是港人的港童。深圳當局推算到2018年,深圳港童將增至5萬人。

其實這只是深圳居民的情況。有很多在港出生的學童居住於珠江三角洲較遠的地區,亦有一些遠至廣東省之外。他們不能每天跨境來港上學,但有不少竟然被托養於香港的親朋,甚至是職業監護人。政府現時仍是採取不解決問題的態度,只是在想辦法不鼓勵他們回港求學,學位先要留給居港學童。這是一個沒有成效的方法,很多人已經在北區租用物業,只為一個香港住址;而有不少人只借用地址以申請學校。其後果是會引致整個北區的人口統計嚴重錯誤。

政府應該面對現實。如果這些兒童就是香港十多年後的生產力,香港是應該負責他們的成長和教育。跨區接受服務在特別行政區的體制下如果不能避免,就要想辦法使之運作流暢;之間可做的事很多。例如過境安排,可以簡化至無需檢查、加建適量邊境學校和醫療設施。政府如果有遠見,可以藉此機會轉危為機。因為這一些需求,可以轉化為發展北區、發展新市鎮、發展邊境禁區的契機;其中商機無限,亦可為香港日漸衰退的經濟帶來新動力。

The Signal and the Noise – Why so many predictions fail

The Signal and the Noise – Why so many predictions fail
by Nate Silver

Last Friday, the CU Book Club invited Prof Kwong Chung-ping to give a talk on Nate Silver’s best selling book The Signal and the Noise – Why so many predictions fail.  I was interested on how to differentiate signal and noise, but the emphasis of the talk was not that.  Rather, Prof Kwong focused on the failure of predictions.  Although this was only the sub-title of the book, the underlying thought of Nate Silver was heavily connected to it.

prediction

To predict an unknown outcome, we basically depend on probability.  However, probability is not certainty.  Mathematically, we could derive the probability of an outcome.  But the reality may not yield the calculated outcome.  It is only on theory that such outcome would definitely appear if the event is repeated for infinite times.  Thus the truth of probability could be said as just a belief.  Over the years, men had been trying to improve mathematical models with the hope of improving predictions.  The fundamental flaw of such thinking is that effort is spent to find out repeated patterns in past data, whereas such data may not have any causality with future outcome.  Thus the basis of technical analysis or chart analysis of stock market movement does not have solid grounds.

For complex dynamical systems like the stock market, politics or weather, the forces which could affect outcome are so complex that they are unknown to us.  The efficient market could react to changes instantly, but to observers the outcome could appear at random.  Prof Kwong demonstrated a chart generated by random walk movements.  The shape of the chart highly resembles the movement of stock market over a certain period.  He further showed a method by Brownian Motion, said it was random walk at higher frequency.  It is not my understanding of Brownian Motion.  Brownian Motion is a form of random walk where the random outcome would depend on the position of the previous event.  But the formula shown by Prof Kwong did show a time series consisting of the difference between two consecutive events.  This method was further developed into the Fractal Brownian Motion where the Hurst index is included.  Despite all these mathematical development, the conclusion is that the predictions generated by all of them failed.

The Bayes Theorem was said to be the basic explanation of such hope and failure.  The theorem proved that the probability of an event could be changed if the probability of a preceding event is taken into account.  This leads to attempts that the known outcome of previous events could affect, or improve, the probability of a later event.  Thus what happened previously in the market could affect the probability of stock movement.  However, there is no way to know whether it is correct to put in whatever probability of previous events.

My understanding of Bayes Theorem is different from this aspect.  On probability, there are two different types.  One is frequentist probability where the probability is confined to the frequency of events or the probability space.  Tossing a coin has a probability space of 2, where a dice is 6.  However, there is also the Bayesian probability where the probability space is not defined, and the probability is based on the belief of the observers.  We can calculate that the probability of one side of a dice is 1/6 by experiments.  However, take the example of the risk of the raid on Bin Laden, there is no way that experiments could be performed to test the probability.  What can be done is the arbitrary assessment of the command team.  Each member of the team may have a belief of the success probability of the action, and the final probability could be an average of such belief.  In real life, we encounter Bayesian probability more often than frequentist probability because in most cases the probability space is not easy to determine.

We often fall into the trap of confusing these probabilities and make wrong predictions.  Sometimes when we consider the probability of an event and we think of all the possible scenarios and assess the best chance of an action.  However, for such Bayesian probability with undefined probability space, there is a high chance that many possible scenarios are ignored.  The decision could just be a belief that the action would succeed.  On the other hand, we often ignore probability space and frequentist probability, and overestimate probability.  One example is that we always ignore the frequentist probability of Mark 6 first prize which is astronomically low, but believe in a Bayesian probability that the chance is not low because someone won first prize every week.

The June 2013 issue of Scientific American has an article on the application of Bayesian theory to Quantum Mechanics.  Very simply put, Quantum Mechanics is based on probability of movement of electrons.  The mathematical formula proved that all probabilities of an event would occur simultaneously in parallel until the outcome is observed, then it collapses into one reality.  Thus the Schroedinger’s Cat is both alive and dead until the box is opened.  The new Quantum Bayesianism, still in debate, argues that the Bayesian probability used is only a belief.  The simultaneous existence of probable events only appears in mathematical thought and is not real.  The reality is a dead or alive cat but not a dead and alive cat.  This is an emerging branch of Quantum Mechanics which we may hear more about in the next few years.

引力邊緣 Gravity

引力邊緣 Gravity是一套很奇特的電影。它有2D和3D版本,可想而知攝影應有點特別技巧。故事非常簡單,接近無劇情;美國穿梭機任務遇上意外,太空人逃往ISS太空站,再逃往中國的天宮號,最後靠其逃脫艙返回地球。

電影的賣點是超級攝影,整套電影差不多全都是在太空的環地球軌道拍攝。攝影師當然不可能上太空,攝影效果是模型和電腦合成技術的結果。這使觀眾有看科幻片 的期望。但它拍攝的手法卻完全不科幻;它沒有像星球大戰和星空奇遇等的超時代幻想科技,而是極度寫實,將我們所知在太空沒有引力的狀態會遇上的事真實地表 現出來。現代科學故事多會引用最新物理如相對論和量子力學,搞時空交錯平行宇宙等。但這套電影毫不賣弄,只根據牛頓的力學,在沒有引力的狀態下的作用力和 反作用力的關係,拍攝所有物體移動的情況;當中亦包括在沒有引力時液體和火焰的表現。製作的效果是想做成真實記錄片的感覺。很少人有機會上太空;全套在太 空活動的電影相當吸引。我們現時中學科學的課程仍很古舊,現代物理欠奉,牛頓的力學仍是物理科重要題目。所以如果中學生對物理有興趣,當可明白這套電影的 動作細節。

gravity

這套電影另一個值得看的理由是由太空看地球的景色,和各種寫實的太空載具。我們或都看過很多衛星拍攝的地球相片,但這套電影有不斷出現的地球表面影像,再配合人物動作事件發展,真實感加強了很多。

電影的主題是引力,但實情是引力邊緣,這個中文譯名說得很好。在地球外的太空,物體仍受地心吸力影響而在環地球軌道運行,但其他運動已不感覺到其引力,而 只是動者常動。但不論是地球引力或是物件自己的引力,都已由希格斯場和希格斯玻色子解釋了,引力的來源是粒子穿過希格斯場的效應。而希格斯因此理論在今年 獲得諾貝爾獎。這套引力電影推出真是合時。

雖然其實沒有劇情,但影評還是要尋根究底。有人比較電影中ISS太空站和天宮號設備,說是諷刺中國的航天發展很慢;又有人說太空人靠中國設備逃脫,是電影 向中國獻媚。又有人說太空人跌入海中再爬上陸地,暗示進化論人是自然由海洋生物進化而成。更有人說片中太空設備不準確,不知他是否自己上過太空船。我覺得 幾十元票價,能看到這樣的場景已是非常值得。