Science Focus (Issue 27)

Issue 027, 2024 SCIENCE FOCUS The Great Oxidation Event: How Earth’s Atmosphere Became Oxygen-Rich 大氧化事件:地球大氣層的氧從何而來 Enrico Fermi: Father of the Nuclear Age 恩里科.費米:核子時代之父 Getting Rid of Glasses: A Beginner's Guide to Contact Lenses 擺脫眼鏡:隱形眼鏡新手指南 How Do Hibernating Squirrels Stay Muscular During Winter? 冬眠松鼠如何保持強壯? The Modern Bronze Age: Fake Tan 摩登青銅時代:美黑霜

Dear Readers, Welcome to the summer edition of Science Focus! As always, we bring you amazing and sometimes unexpected discoveries through the ages. Would you choose a natural tan from performing outdoor activities or a fake tan? In this issue, you can read about the science behind fake tan while sunbathing on the beach next time. You can also learn more about a surprising connection between bacteria in the gut and muscle mass, the discovery of a widely used anti-cancer drug, and the contribution of bacteria to an oxygenated atmosphere. For those of you who are budding physicists, we have articles on Enrico Fermi and the James Webb telescope. Finally, I would like to thank those of you who have participated in this year’s “Science in Lyrics” Writing Competition. The number of entries doubled! Many congratulations to our prize winners, and I am sure they will appreciate your comments and encouragements on Instagram. Yours faithfully, Prof. Ho Yi Mak Editor-in-Chief 親愛的讀者: 歡迎閱讀夏季的新一期《科言》!我們將一如至往地橫跨不同年 代,呈上新奇而有時出乎意料的科學發現。 如果想擁有一身古銅色肌膚,你會選擇從事戶外活動還是使用美 黑霜?下次到海灘不妨一邊曬著日光浴,一邊閱讀今期關於美黑霜的 科學吧!此外,你也可以在今期認識到腸道細菌與肌肉質量之間意想 不到的關聯,還有一種常用抗癌藥物的發現,以及細菌如何使大氣層 充滿氧。我們亦為可能成為未來物理學家的你準備了關於恩里科.費 米和詹姆斯.韋伯太空望遠鏡兩篇精彩文章。 最後,我要感謝參加了今年「歌詞與科學」寫作比賽的同學。承蒙 大家支持,參賽人數是去年的一倍!在此恭喜各位得獎同學,亦相信 他們會樂於閱讀大家在 Instagram 的留言和祝賀。 主編 麥晧怡教授 敬上 Message from the Editor-in-Chief 主編的話 Copyright © 2024 HKUST E-mail: Homepage: Scientific Advisors 科學顧問 Prof. Man Fung Cheung 張文峰教授 Prof. Yukinori Hirano平野恭敬教授 Prof. Pak Wo Leung 梁伯和教授 Prof. Kenward Vong 黃敬皓教授 Editor-in-Chief 主編輯 Prof. Ho Yi Mak麥晧怡教授 Managing Editor 總編輯 Daniel Lau 劉劭行 Student Editorial Board學生編委 Editors 編輯 Roshni Printer Aastha Shreeharsh Minnie Soo 蘇慧音 Helen Wong 王思齊 Jane Yang 楊靜悠 Daria Zaitseva Social Media Editors 社交媒體編輯 Zoey Tsang 曾鈺榆 Navis Wong 黃諾軒 Graphic Designers 設計師 Coby Ngai 魏敏儀 Winkie Wong 王穎琪 Contents Science Focus Issue 027, 2024 What’s Happening in Hong Kong? 香港科技活動 “Science in Lyrics” Writing Competition 2024 – 1 Result Announcement 「歌詞與科學」寫作比賽 2024 — 結果公佈 Antarctica 3D 極南之地3D Science in History 昔日科學 The Great Oxidation Event: How Earth’s Atmosphere 2 Became Oxygen-Rich 大氧化事件:地球大氣層的氧從何而來 A Lucky Strike: Rediscovery of an Anti-Cancer Drug 5 by Barnett Rosenberg 把握機遇:Barnett Rosenberg的抗癌藥物大發現 Enrico Fermi: Father of the Nuclear Age 8 恩里科.費米:核子時代之父 Science Today 今日科學 James Webb Space Telescope 12 詹姆斯.韋伯太空望遠鏡 Amusing World of Science 趣味科學 Getting Rid of Glasses: A Beginner's Guide to 16 Contact Lenses 擺脫眼鏡:隱形眼鏡新手指南 How Do Hibernating Squirrels Stay Muscular 20 During Winter? 冬眠松鼠如何保持強壯? The Modern Bronze Age: Fake Tan 22 摩登青銅時代:美黑霜

What’s Happening in Hong Kong? 香港科技活動 Antarctica 3D The Hong Kong Space Museum is currently featuring the breathtaking 3D Dome Show Antarctica 3D, which takes viewers on an aweinspiring journey through the coldest, driest, and windiest place on Earth. The documentary includes never-before-seen footage that showcases a vibrant underwater world beneath the ice, vast penguin colonies, and the largest congregation of whales ever filmed. However, the movie is not just a visual spectacle as it serves as a wake-up call to the urgent need to protect Antarctica's fragile ecosystem which is susceptible to global warming. Narrated by Benedict Cumberbatch, this fully immersive 3D Dome Show is not to be missed! Period: Now – January 13, 2025 Time: 2:00 PM and 6:30 PM (Mon, Wed to Fri) 12:30 PM and 5:00 PM (Sat, Sun and public holiday) Venue: Space Theatre, Hong Kong Space Museum Admission fee: Standard admission: $32 (stalls), $24 (front stalls) Concession admission: $16 (stalls), 12 (front stalls) Remark: Please refer to the museum’s website for more details. 展期: 現在至2025年1月13日 時間: 下午二時及六時半(一、三至五) 下午十二時半及五時(六、日及公眾假期) 地點: 香港太空館天象廳 入場費:標準票:32 元(後座);24 元(前座) 優惠票:16 元(後座);12 元(前座) 備註:更多詳情請參閱太空館網頁。 香港太空館現正上映令人嘆為觀止的立體 球幕電影《極南之地3D》。觀眾將踏上旅程, 前往地球最冷、最乾、最大風的地方,感受大自 然的奧妙。這套紀錄片將展示前所未見的片段, 將冰下多采多姿的水底世界、龐大的企鵝群及 史上拍攝到最大的鯨魚群盡顯眼前。然而這套 電影並不單是一場視覺奇觀,更是提醒我們要 保護南極脆弱生態,避免其受全球暖化進一步 影響的當頭棒喝。不要錯過這個由Benedict Cumberbatch 娓娓道來的沉浸式 3D 電影體 驗! “Science in Lyrics” Writing Competition 2024 – Result Announcement 「歌詞與科學」寫作比賽 2024 – 結果公佈 Visit our Instagram page for the winning entries. To check out what other songs the contestants have written on, scan the QR code for the Spotify playlist! 歡迎到《科言》Instagram 專頁查看得獎作品。想看看參賽者還以甚麼歌曲參賽嗎? 掃瞄 QR 碼收聽今次比賽的 Spotify 播放清單! 冠軍 Champion: 許家和 Xu Jiahe 凡星 – 陳蕾 亞軍 First Runner-Up: 黃可兒 Wong Ho Yee 52赫茲 – KOLOR 季軍 Second Runner-Up: 張子軒Cheung Tsz Hin august – Taylor Swift 優異獎 Honorable Mentions: 隥楚熙 Tang Chor Xi The Moss – Cosmo Sheldrake 趙天朗 Chiu Tin Long 夜曲 – 周杰倫 呂羅斯 Lv Luosi Moses Tongue Tied Twisted – Suit Up, Soldier Fun in Summer Science Activities 夏日科學好節目 Any plans for this summer? Check out the following event! 計劃好這個夏天的好去處了嗎?不妨考慮以下活動! 1 極南之地3D

By Helen Wong 王思齊 The history of life on Earth saw many pivotal moments, but perhaps none, other than the origin of life itself, is more significant than the Great Oxidation Event (GOE). Marking the period when the early Earth’s atmosphere started to fill with free oxygen, the GOE set the foundation for the rise of aerobic life and ultimately, present-day humans [1, 2]. Imagine traveling back to 4.5 billion years ago, when Earth had just formed. The atmosphere was vastly different from what we have today – it consisted of water vapor, carbon dioxide, and methane, but not oxygen. Consequently, the earliest life forms that emerged approximately 3.8 billion years ago were anaerobic. But the entire game changed when a group of bacteria diverged from their anaerobic ancestors around 3.4 billion years ago [3, 4]. These unique microbes developed one of the most crucial innovations in the history of life on Earth – oxygenic photosynthesis – and evolved into what we now know as cyanobacteria (commonly called blue-green algae, although they are not technically algae) (Figure 1). The Great Oxidation Event: How Earth’s Atmosphere Became Oxygen-Rich 大氧化事件: 地球大氣層的氧從何而來 Through oxygenic photosynthesis, oxygen was generated as a by-product of water splitting. Initially, the oxygen levels in the atmosphere remained low, as the first oxygen released into seawater by cyanobacteria was quickly sequestered by chemical reactions with other elements, such as iron [2] (Figure 2). Over a period of 200–300 million years [1], seawater oxygen levels gradually increased, possibly due to a rapid expansion of cyanobacterial populations [3, 4], until the accumulated oxygen began to escape into the atmosphere. The escaped oxygen displaced the abundant methane, kicking off the GOE that took place between 2.4 and 2.1 billion years ago [1]. The implications of an oxygenated atmosphere Figure 1 A stromatolite fossil of cyanobacteria. The layered structure was formed from mats of cyanobacteria. 圖一 屬於疊層石的藍綠菌化石,當中的 層狀結構由多層藍綠菌堆疊而成。 Photo credit 圖片來源: James St. John [5] Figure 2 Banded iron formation as evidence of the GOE. Iron (II) ions in the ocean are thought to be oxidized and precipitated as red iron (III) oxides in the GOE [6]. 圖二 條狀鐵層是大氧化事件的證據之一。科學家認為在大氧 化事件中,海洋中的鐵(II)離子被氧化並沉澱為紅色的氧化鐵 (III)[6]。 Photo credit 圖片來源: Graeme Churchard [7]

3 The implications of an oxygenated atmosphere were immense for both Earth's climate and its inhabitants. Methane, a greenhouse gas, traps heat from sunlight and keeps the Earth warm enough for organisms to survive. Therefore, when methane was displaced by oxygen, global temperatures dropped, causing Earth to enter a series of ice ages known as the Huronian glaciation [8]. Meanwhile, ultraviolet radiation (UV) from the Sun split oxygen molecules (O2) into individual atoms, which then reacted with other oxygen molecules to create ozone (O3), forming the ozone layer that now protects life on Earth from harmful UV radiation. The omnipresence of oxygen on Earth also fundamentally changed the planet’s biological landscape. To the anaerobic bacteria and archaea of the time, oxygen was toxic. This led to a mass extinction in which most anaerobes were wiped out. However, some survivors found ways to adapt and even thrive in the newly oxygen-rich environment. They developed ingenious solutions in terms of oxygen binding, aerobic respiration, and oxygen detoxification. To protect themselves from oxygen, these anaerobic organisms made use of certain proteins to bind oxygen and incorporate it into other molecules they need such as melanin [9]. Scientists believe that some of these ancient proteins eventually evolved into oxygen-transporting respiratory pigments found in animal blood today [9, 10]. For example, hemocyanin was likely derived from the oxygen-binding protein tyrosinase. These organisms also harnessed the power of oxygen as the terminal electron acceptor in respiration, which releases much more energy than anaerobic respiration. On the other hand, they evolved more effective versions of detoxifying enzymes, including superoxide dismutase and catalase (footnote 1), to deal with the harmful reactive oxygen species resulting from aerobic respiration [1]. For those unable to adapt, alternative strategies were employed. Some chose to remain in anaerobic environments, while others “acquired” the ability to perform aerobic respiration by engulfing smaller aerobically respiring cells, as suggested by the famous endosymbiotic theory [11, 12]. The latter gave rise to the ancestors of eukaryotic cells, with the engulfed aerobically respiring cells eventually becoming today's mitochondria. And the story of cyanobacteria did not end with the GOE – the endosymbiotic theory also suggests that they were engulfed by early non-photosynthetic eukaryotes [11] and became chloroplasts in modern plants and algae. 地球生命史有著許多關鍵時刻,但也許除了生命 起源本身,沒有一件大事較大氧化事件(The Great Oxidation Event / GOE)的影響更為深遠。大氧化事件 標誌著早期地球大氣層開始充滿遊離氧的時期,為需氧生 物的出現以及最終現代人類興起奠定了基礎 [1, 2]。 試想像回到 45億年前地球剛形成的時候,當時的 大氣層與我們今天擁有的截然不同 — 它由水蒸氣、二 氧化碳和甲烷組成,但不含氧氣。因此,最早約於38億 年前出現的生物均是厭氧生物。 但在大約34 億年前,一群細菌從這些厭氧祖先分化出 一個分支,改變了整個局面 [3, 4]。這 些獨特的微生物發展出地球生命史 上其中一種最創新的能力 — 以 光合作用製造氧氣,而這些微 生物最終演化成我們現 在熟知的藍綠菌(通常 被稱作藍綠藻,但它們 在分類上並不屬於藻 類)(圖一)。 1. Editor’s note: Superoxide dismutase converts harmful superoxide radicals (O2 _. ) to molecular oxygen (O2) and hydrogen peroxide (H2O2). Catalase further converts H2O2 to O2 and water.

References 參考資料: [1] Aiyer, K. (2022, February 18). The Great Oxidation Event: How Cyanobacteria Changed Life. American Society for Microbiology. Articles/2022/February/The-Great-Oxidation-Event- How-Cyanobacteria-Change [2] Blaustein, R. (2016). The Great Oxidation Event: Evolving understandings of how oxygenic life on Earth began. BioScience, 66(3), 189–195. https://doi. org/10.1093/biosci/biv193 [3] Chu, J. (2021, September 28). Zeroing in on the origins of Earth’s “Single most important evolutionary innovation”. MIT News. https://news. [4] Fournier, G. P., Moore, K. R., Rangel, L. T., Payette, J. G., Momper, L., & Bosak, T. (2021). The Archean origin of oxygenic photosynthesis and extant cyanobacterial lineages. Proceedings of the Royal Society B: Biological Sciences, 288(1959). https://doi. org/10.1098/rspb.2021.0675 [5] St. John, J. (n.d.). STROMATOLITE [Photograph]. [6] The Stephen Hui Geological Museum. (n.d.). O2 - Free Atmosphere - Banded Iron formation. https:// evo_03_arc04_3.php [7] Churchard, G. (2014, January 24). Dales Gorge [Photograph]. Flickr. graeme/12116315164/ [8] Bekker, A. (2015). Huronian Glaciation. In Gargaud, M., et al. (Eds.), Encyclopedia of Astrobiology (2nd ed.). Springer Berlin. [9] Lutz, D. (2010, February). The Many Colors of Blood. ChemMatters. chemmatters/february-2010/the-many-colors-ofblood [10] van Holde, K. E., Miller, K. I., & Decker, H. (2001). Hemocyanins and Invertebrate Evolution. Journal of Biological Chemistry, 276(19), 15563–15566. https:// [11] Archibald, J. M. (2015). Endosymbiosis and Eukaryotic Cell Evolution. Current Biology, 25(19), R911-R921. [12] Sessions, A. L., Doughty, D. M., Welander, P. V., Summons, R. E., & Newman, D. K. (2009). The Continuing Puzzle of the Great Oxidation Event. Current Biology, 19(14). j.cub.2009.05.054 氧氣是產氧光合作用中,水的光解所產生的副產 物。起初,由於藍綠菌釋放到海水中的氧很快就因與鐵 等元素產生化學反應而被耗用(圖二),所以大氣中的 氧氣含量一直維持於低水平 [2]。但在隨後兩三億年間 [1],大概因為藍綠菌種群快速擴張,導致海水的氧含 量逐漸增加 [3, 4],最終令累積的氧氣逃逸到大氣中。 這些逸出的氧氣取代了大氣中的甲烷,為發生於21 至 24億年前的大氧化事件揭開序幕 [1]。 有了氧氣的大氣層為地球氣候及棲息生物帶來深遠 的影響。甲烷是一種溫室氣體,能困住從太陽而來的熱, 使地球保持在能孕育生命的適當溫度。因此,當甲烷被 氧氣取代時,全球氣溫下降,導致地球進入一系列冰河 時期,史稱休倫冰川時期(Huronian glaciation)[8]。 與此同時,來自太陽的紫外線將部分氧分子(O2)分解 成氧原子,這些氧原子進而與其他氧分子發生反應產生 臭氧(O3),最終形成今天保護地球生物免受紫外線侵 害的臭氧層。 無處不在的氧亦徹底改變地球的生物景觀。對於當 時的厭氧細菌和古細菌來説,氧無疑是一種劇毒,因此 帶氧的大氣層引發了一場大滅絕,當中厭氧生物幾乎被 殲滅。 然而,倖存者在富氧的新環境裡找到生存之 道。它們在與氧結合、有氧呼吸和氧解毒(oxygen detoxification)等方面均發展出巧妙的對應方案。為 了保護自身免受氧的侵害,這些厭氧生物使用特定蛋白 質抓住氧,並將其併入黑色素等它們本身就需要的生物 分子裡 [9]。科學家認為今天動物血液中負責輸送氧的 呼吸色素正是演化自這些遠古的蛋白質 [9, 10],例如 血藍蛋白很可能演化自能與氧結合的酪胺酸酶。另一方 面,這些生物亦透過利用氧作為需氧呼吸中的最終電 子受體,獲得比缺氧呼吸多很多的能量。它們還演化出 更有效的解毒酶,例如過氧化物歧化酶和過氧化氫酶 (註一),以處理需氧呼吸產生的有害活性含氧物 [1]。 至於無法適應新環境的生物則另闢蹊徑。它們有些 選擇留在無氧環境中,有些則如著名內共生學說所提 出的,透過吞噬較小但又能進行需氧呼吸的細胞,藉此 獲得進行需氧呼吸的能力 [11, 12]。後者最終演化成 真核細胞的始祖,而被吞噬的需氧呼吸細胞則成為了今 天的線粒體。 等等,藍綠菌的故事並沒有隨著大氧化事件落幕而 結束 — 內共生學説亦提出藍綠菌由於被不能進行光合 作用的早期真核生物吞噬 [11],最終演化為現代植物和 藻類中的葉綠體。 Related Article 延伸閱讀 Check out the following articles to learn more about mitochondria! 閱讀以下《科言》文章以了解更多關於線粒體的 有趣知識! Mitochondria: So Much More Than the Powerhouses of the Cell (Issue 020) 線粒體:遠不只是細胞的發電站(第二十期) 1 編按:過氧化物歧化酶將有害的過氧自由基(O2 _. )轉化為氧分子(O2) 和過氧化氫(H2O2)。過氧化氫酶則進一步將 H2O2 轉化為O2 和水。

5 By Daria Zaitseva Some scientific discoveries would not happen if it was not for luck. An apple falling next to Newton led to the notion of gravitation [1]; Roentgen’s investigation into the mysteriously glowing little screen in his laboratory resulted in the discovery of X-ray [2]. Serendipitous discoveries are never lacking in the history of science. This article reveals yet another unintentional but lifesaving discovery, or more precisely – the rediscovery of cisplatin by Barnett Rosenberg. Rosenberg graduated from Brooklyn College with a bachelor’s degree in physics in 1948, and obtained his master’s and doctorate degrees in physics from New York University in 1950 and 1955 respectively [3]. Being trained as a physicist allowed him to come up with insights that may not be obvious to biologists: He noticed how the mitotic spindle in a dividing cell look like the electric field lines between two opposite charges (or the magnetic field lines between two opposite poles) (Figure 1). Is it just a coincidence? Or does electromagnetism have to do with cell division? Figure 1 A dividing cell with chromosomes attached to the mitotic spindle (left) and the electric field lines between two opposite charges (right). In 1965, Rosenberg tested his unusual idea on the bacteria Escherichia coli [4, 5], although it did not rely on the formation of mitotic spindle for cell division. Using platinum electrodes which were supposed to be both biologically and chemically inert, he sent a current through the bacterial solution containing ammonium chloride as a pH buffer [6]. Whatever his predictions had been, the results were simply mind-blowing. The microorganisms did not divide faster; instead, they stretched as if they wanted to divide but failed to do so. Their length increased up to 300 times compared to their normal size [7]! So, Rosenberg thought the current did affect cell division. Nevertheless, this is not true. Over the next two years, Rosenberg found that it was not the electricity that stopped the cell division, but the chemical compound cisplatin (Figure 2) produced in the reaction [4, 5]. Cisplatin had already been discovered by the Italian chemist Michele Peyrone in 1854, but was not studied much until Rosenberg’s rediscovery [4]. Together with many new substances which had the ability to inhibit cell proliferation, cisplatin was considered as a drug candidate for chemotherapy [4]. Figure 2 Chemical structure of cisplatin. A Lucky Strike: Rediscovery of an Anti-Cancer Drug by Barnett Rosenberg 把握機遇: Barnett Rosenberg的 抗癌藥物大發現

In 1969, Rosenberg’s lab published the promising results on the antitumor property of cisplatin in mice [3, 8]. Then clinical trials followed. At first, it caused a public shock as heavy metal compounds were believed to be extremely toxic [4, 5]. Despite so, cisplatin turned out to be effective for many types of cancer when used in combination with other medications [4], especially for testicular cancer which had no known effective drug at that time [9]. In 1978, cisplatin was approved by the Food and Drug Administration (FDA) in the US, followed by other countries [4]. It remains as one of the key medicines for cancer treatment today [10]. Modern research shed light on how cisplatin works. Cisplatin inhibits DNA replication mainly by “tying” (or, forming crosslinks between) two purine bases (adenine and guanine) on the same strand together [11, 12], which eventually leads to failure in cell division and apoptotic cell death [11]. From the non-specific mode of action of cisplatin, it can also harm actively dividing cells in normal tissues, such as the intestine, thus causing severe side effects [13]. This partly explains why researchers were looking for new generations of platinum-based drugs. Notably, carboplatin entered the market in 1989 with a much lower systemic toxicity [5, 13, 14], and oxaliplatin was approved in 1994 with a high efficacy against colon cancer [5, 14]. Thanks to the Rosenberg’s serendipitous rediscovery, an array of platinum-based drugs was made available and saved the lives of many cancer patients. The rediscovery of cisplatin was an extremely lucky combination of events. Yet, it was also the open mindset and curiosity of Rosenberg that brought this fundamental discovery to all of us. The story of cisplatin also serves as a reminder of how multiple scientific fields can powerfully intertwine, as there is no actual boundary between chemistry, physics and biology. Chance favors only the prepared mind. Was it luck or a good grip? You decide for yourselves. 如果不是運氣,有些科學發現就不會發生:蘋果落在牛 頓身旁使他想到萬有引力 [1],Roentgen對他實驗室裡神 秘發光小屏幕的調查最終使他發現了X射線 [2]。科學史 上從不乏偶然遇上的驚喜。本文將介紹另一個無意中的發 現,它拯救了無數生命 — 這是Barnett Rosenberg對順鉑 (cisplatin)的二次發現。 Rosenberg 於1948 年從布魯克林學院取得物理學學 士學位,並分別於1950 和1955 年從紐約大學獲得物理學 碩士和博士學位 [3]。由於他一直接受物理學訓練,使他能提 出生物學家未必能想到的獨特見解:他注意到細胞分裂中的 有絲紡綞體看起來就像兩個相反電荷之間的電場線(或兩個 相反極性之間的磁場線)(圖一)。這只是巧合嗎?還是電磁 學與細胞分裂有關? 儘管大腸桿菌(Escherichia coli)並不使用有絲紡綞 體來進行細胞分裂,Rosenberg 還是於1965 年在大腸桿 菌上試驗了他這個不尋常的想法 [4, 5]。他使用了在生物和 化學上也被認為是具惰性的鉑電極,向以氯化銨作為pH 緩衝劑的細菌溶液傳送電流 [6]。不管他原來的預測結果 是甚麼,他也不會猜到接下來的事情:微生物並沒有分裂 得更快;反而,它們全部呈現被拉長,彷彿想分裂但不能成 功的樣子。與正常大小相比,它們的長度增加了足足300 倍 [7]!因此,Rosenberg認為是電流影響了細胞分裂。 然而,這不是正確的結論。在接下來的兩年, Rosenberg 發現阻礙細胞分裂的不是電流,而是在反應中 產生的順鉑(圖二)[4, 5]。這種化合物早於1854年已被意 大利化學家Michele Peyrone發現,但在Rosenberg二 次發現前並沒有人對其作出過深入研究 [4]。與當時許多具 有抑制細胞分裂能力的新物質一樣,順鉑被視為化療的候選 藥物之一 [4]。 圖一 分裂中的細胞,當中有絲紡綞體與染色體連接(左)和兩個相 反電荷之間的電場線(右) Fun fact: Is there transplatin? Yes, it is a stereoisomer of cisplatin with no anti-tumor activity [4]. transplatin

7 1969 年,Rosenberg 的實驗室發表了有關順鉑在小鼠 中具抗腫瘤特性的結果 [3, 8],臨床試驗也隨即展開。起初, 它震驚了社會大眾,因為重金屬化合物被認為是具劇毒的物 質 [4, 5]。儘管如此,當與其他藥物結合使用時,順鉑對不同 類型癌症皆宣告有效,特別是當時沒有有效藥物治療的睾丸 癌 [9]。1978年,順鉑被美國食品及藥物管理局(FDA)批准 使用,在其他國家也相繼獲得許可 [4]。它至今仍是治療癌症 的關鍵藥物之一 [10]。 近年研究揭示了順鉑的運作原理,它主要透過「綁住」(更 準確地說是使其形成交聯)同一條 DNA 鏈上的兩個嘌呤鹼 基(腺嘌呤和鳥嘌呤)來抑制DNA複製 [11, 12],最終導致 細胞分裂失敗及細胞凋亡 [11]。從順鉑無差別的運作方式 來看,它同時亦會影響正常組織中經常需要分裂的細胞,例 如腸道內的細胞,引起嚴重副作用 [13]。這在某程度上解釋 了為甚麼研究人員在尋找新一代的鉑藥物。對身體毒性較低 的卡鉑(carboplatin)在1989年進入市場 [5, 13, 14],對 結腸癌尤其有效的奧沙利鉑(oxaliplatin)則在 1994 年被 批准使用 [5, 14]。Rosenberg的偶然發現最終使一系列鉑 藥物得以問世,拯救了無數癌症患者的生命。 雖然順鉑的二次發現的確是由許多巧合交織而成,但正 是 Rosenberg 勇於接受新觀點的心態和強烈的好奇心使他 能將這重要發現帶給所有人。順鉑的故事亦提醒我們化學、 物理和生物之間並沒有實質界限,不同科學領域的緊密合作 可以帶來意想不到的重要成果。 機會只留給有準備的人。這是單純的運氣嗎?你自己決 定吧。 References 參考資料: [1] Gefter, A. (2010, January 18). Newton's apple: The real story. New Scientist. https://www.newscientist. com/article/2170052-newtons-apple-the-real-story/ [2] This Month in Physics History – November 8, 1895: Roentgen's Discovery of X-Rays. (2001, November). APS News, 10(10), 2. [3] Hoeschele, J. D. (2014). Biography of Professor Barnett Rosenberg: A Tribute to His Life and His Achievements. Anticancer Research, 34(1), 417–421. [4] Barnett Rosenberg i ego schastlivyj sluchaj [Barnett Rosenberg and his lucky case]. (2021). Kvantik, 6. biblioteka/436262/Barnett_Rozenberg_i_ego_ schastlivyy_sluchay [5] National Cancer Institute. (2014, May 30). The "Accidental" Cure—Platinum-based Treatment for Cancer: The Discovery of Cisplatin. https://www. [6] Department of Chemistry, College of Natural Science, Michigan State University. (n.d.). Barney Rosenberg. [7] Rosenberg, B., Van Camp, L., & Krigas, T. (1965). Inhibition of Cell Division in Escherichia coli by Electrolysis Products from a Platinum Electrode. Nature, 205(4972), 698–699. https://doi. org/10.1038/205698a0 [8] Rosenberg, B., Van Camp, L., Trosko, J. E., & Mansour, V. H. (1969). Platinum Compounds: a New Class of Potent Antitumour Agents. Nature, 222(5191), 385–386. [9] In remembrance of Barnett Rosenberg. (2009). Dalton Transactions, (48), 10648–10650. https://doi. org/10.1039/B918993A [10] Gandin, V., Hoeschele, J. D., & Margiotta, N. (2023). Special Issue "Cisplatin in Cancer Therapy: Molecular Mechanisms of Action 3.0". International Journal of Molecular Sciences, 24(9), 7917. https:// [11] Tchounwou, P. B., Dasari, S., Noubissi, F. K., Ray, P., & Kumar, S. (2021). Advances in Our Understanding of the Molecular Mechanisms of Action of Cisplatin in Cancer Therapy. Journal of Experimental Pharmacology, 13, 303–328. JEP.S267383 [12] Imai, R., Komeda, S., Shimura, M., Tamura, S., Matsuyama, S., Nishimura, K., Rogge, R., Matsunaga, A., Hiratani, I., Takata, H., Uemura, M., Iida, Y., Yoshikawa, Y., Hansen, J. C., Yamauchi, K., Kanemaki, M. T., & Maeshima, K. (2016). Chromatin folding and DNA replication inhibition mediated by a highly antitumor-active tetrazolato-bridged dinuclear platinum(II) complex. Scientific Reports, 6. [13] Zhang, C., Xu, C., Gao, X., & Yao, Q. (2022). Platinum-based drugs for cancer therapy and antitumor strategies. Theranostics, 12(5), 2115–2132. [14] Monneret, C. (2011). Platinum anticancer drugs. From serendipity to rational design. Annales Pharmaceutiques Françaises, 69(6), 286–295. https:// 圖二 順鉑的化學結構 知多一點點:有順鉑, 有沒有反鉑 (transplatin)? 有,它是順鉑的立體異構體, 但沒有抗腫瘤活性 [4]。 反鉑

By Minnie Soo 蘇慧音 Father of the Nuclear Age 恩里科.費米:核子時代之父 Enrico Fermi: The 20th century was a golden era for physics, with brilliant minds pushing the boundaries of scientific innovation. Prominent physicists include Albert Einstein, Werner Heisenberg, Niels Bohr, Richard Feynman, and one must not forget the legendary Enrico Fermi, a giant in the history of nuclear physics. When we think of the word “Fermi”, a whole array of related notions comes to mind. Fermilab, a renowned scientific institution dedicated to the study of particle physics; fermions, particles with an odd half-integer spin such as electrons; Fermi’s Paradox, a perplexing conundrum which challenges the possibilities of existence of extraterrestrial life. The use of such nomenclature highlights Fermi’s contributions and status in the scientific community. Enrico Fermi and the Atomic Bomb Enrico Fermi is a consequential contributor to the atomic bomb launched on Hiroshima and Nagasaki. He was burdened with no less responsibility than J. Robert Oppenheimer, the leading scientist in the Manhattan Project [1]. The story started with racial discrimination in Fascist Italy. In 1938, the establishment of antisemitic policies by Mussolini [2] posed a significant threat to Fermi particularly because his wife is of Jewish heritage [3, 4]. When Fermi was awarded the 1938 Nobel Prize in Physics at the age of 37, he took this opportunity to go directly from Stockholm, the place where he received the award, to the United States and never returned to Italy [5, 6]. In the summer of 1939, Fermi met Heisenberg in a lecture tour in the States, during which he tried to convince Heisenberg to join him at the physics faculty of Columbia University [7]. However, to his bafflement, Heisenberg decided to head back and serve the Nazi’s project to build an atomic bomb [7]. Disappointment in this unsuccessful recruitment has evolved into a fear that, with the great mind of Heisenberg, the Nazis would succeed in developing the atomic bomb and win the war. While the scientists in the US were making continuous efforts to alert the government to the destructive power that uranium fission chain reactions could bring [8], they teamed up to push forward the progress of uranium research [9]. In 1942, Fermi successfully initiated the first controlled chain reaction of nuclear fission [6]. As World War II progressed, Fermi joined the Manhattan Project as an associate director in Los Alamo [1, 4]. In three years, the first atomic

9 bomb was built and dropped on Hiroshima, causing numerous deaths and catastrophic damage. The Chicago Pile Experiment As for the invention of the atomic bomb, one must mention the breakthrough in the Chicago Pile experiment. On a chilly winter day in 1942, Fermi and his colleagues placed a 6.1-meter wide by 7.6-meter high pile of graphite bricks with 6 tons of uranium metal and 40 tons of uranium-235 in the squash court under the University of Chicago football field, together with cadmium rods [1, 6, 10, 11]. The theory behind the experiment is as follows. As a neutron hits a uranium-235 atom, the latter splits into two smaller atoms and releases energy [6, 12]. This fission reaction also releases neutrons as by-products to split other uranium-235 atoms, resulting in a chain reaction to unleash gargantuan amounts of energy [6, 12]. For each mole of uranium-235 that goes under fission, the resulting products weigh approximately 0.2 grams less than the reactants [13]. By the famous equation E = mc2, this loss in mass corresponds to the conversion of order of 1013 joules of energy. In fact, the fission reaction of one kilogram of uranium-235 produces energy that is 2.5 million times greater than the energy generated by burning one kilogram of coal [13]. Therefore, for the reaction to be controllable, cadmium rods were inserted to absorb some neutrons during the reaction, thereby controlling the reaction rate and the amount of energy produced [6]. If Fermi’s calculations had been wrong and the cadmium rods had been insufficient to control the reaction, catastrophic amount of energies could have been unleashed, potentially destroying half of Chicago [6]. Fortunately, the experiment turned out to be a success, creating the first controlled, self-sustaining nuclear chain reaction. The pile was later refined by a substantial reduction in size, which made the controlled nuclear chain reaction possible to be incorporated into an atomic bomb that is small enough to be carried in an airplane. A Mistake in Fermi’s Nobel Prize The Nobel Prize is widely regarded as one of the most prestigious awards in the scientific community. Consequently, Fermi was rightfully honored with this esteemed recognition. However, there was a critical mistake concerning the scientific discovery for which Fermi received the award [14]. This is actually a story about Fermi discovering nuclear fission without realizing it. In 1938, Fermi was granted the Nobel Prize "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons [15]." At that time, the known heaviest element was uranium with an atomic number of 92. It was believed that Fermi had successfully produced transuranic (beyond uranium) elements with atomic numbers 93 and 94 by bombarding uranium with slow moving neutrons. They called the new elements Ausenium and Heperium, respectively. However, German chemists Otto Hahn and Fritz Strassmann subsequently made a pivotal discovery that the elements produced through uranium bombardment were not novel entities, but lighter elements like barium with an atomic number of 56 [14]. In fact, uranium split into two lighter elements upon neutron bombardment, through a reaction later known as nuclear fission. Based on the discovery of nuclear fission, Hahn was awarded the Nobel Prize in Chemistry in 1944 [16]. As for the actual elements 93 and 94, they were eventually created in 1940, and named neptunium and plutonium [17]. Fermi’s Paradox One question that bugged scientists, including an intelligent physicist like Fermi, is the possible existence of extraterrestrial creatures, a.k.a. aliens. From geocentrism to realizing that we are not the center of the universe, from thinking that the Milky Way was all that there was to discovering that there are billions of galaxies [18], we should be wise enough to know that we are not special in the vast universe. Fermi proposed that if we are not unique and the Earth is young compared to the copious stars and planets out there, extraterrestrial civilizations should have evolved and colonized nearby galaxies by now [19]. Yet, where did everyone go? Before making further discoveries on this subject, Fermi died in 1954, and the question fell to other scientists. Despite ongoing research and numerous papers being published on this topic, the question remains unresolved and highly debatable. Fermi Problem During the Trinity Test, the first detonation of the atomic bomb in history, Fermi tore paper into scraps and threw them from a height of 1.83 meters [20]. While standing 16 kilometers away from the explosion site [21], he utilized their displacement shift of 2.5 meters to estimate the energy produced by the detonation through a series of deductions and calculations. Fermi’s estimate (10 kilotons of T.N.T.) was within the same order of magnitude of the true value (21 kilotons of T.N.T.) despite employing what initially seemed like an unrelated method. This led to the emergence of a new class of problems known as the Fermi problems, to be solved using this estimation method to approximate the order of magnitude of values when our knowledge is limited. It involves making educated guesses by breaking down complex problems to simpler components, with reasonable assumptions.

20世紀是物理學的黃金時代,誕生了許多將科學 推向嶄新領域的傑出科學家,其中包括阿爾伯特.愛 因斯坦(Albert Einstein)、維爾納.海森堡(Werner Heisenberg)、尼爾斯.玻爾(Niels Bohr)和理查德.費曼 (Richard Feynman)等物理學巨匠,但在這眾多科學巨 擘中,我們不能忽視另一位同等傑出的核子物理學傳奇 — 恩里科.費米 (Enrico Fermi)。 提起「費米」,人們會聯想到許多與之相關的重要概念和 成就,例如費米實驗室 — 專門研究粒子物理學的著名科學 機構;費米子 — 包括電子在內具奇數半整數自旋的粒子;以 及費米悖論 — 試圖推斷外星生命存在可能性的千古難題。 從各種以費米命名的例子就能充分體現他在科學界無可替 代的貢獻和卓越地位。 恩里科.費米與原子彈 恩里科.費米可算是有份研發出在廣島和長崎引爆的原 子彈,要說的話其責任不次於曼哈頓計劃的首席科學家 J. 羅伯特.奧本海默(J. Robert Oppenheimer)[1]。 故事始於法西斯意大利的種族歧視政策。墨索里尼於 1938年頒布的反猶太政策 [2] 為妻子擁有猶太血統的費米 帶來了切身威脅 [3, 4]。因此在同一年,費米以37歲之齡獲 得諾貝爾物理學獎的同時,就由領獎地斯德哥爾摩直接前往 美國,再也沒有回到意大利 [5, 6]。 1939 年夏天,費米在海森堡於美國進行巡迴演講時遇 見他,並試圖說服他加入哥倫比亞大學物理學系一起共事 [7],但最令費米費解的是海森堡竟然決定返回德國,為納粹 德國的原子彈計劃效力 [7]。這次招攬失敗所帶來的失望最 終演化成眾人的驚恐,擔心納粹最終能憑藉海森堡的機智頭 腦搶先研發出原子彈,從而贏得戰爭。美國科學家在不斷提 醒政府鈾裂變鏈鎖反應可能帶來的毀滅性威力同時 [8],眾 人亦決定團結起來全力加速推進鈾研究 [9]。1942年,費米 成功進行了史上第一次受控的核裂變鏈式反應 [6]。隨著第 二次世界大戰的發展,費米加入了曼哈頓計劃,成為洛斯阿 拉莫斯國家實驗室的副總監 [1, 4]。三年後,第一枚原子彈 研發完成,被投放到廣島,造成大規模死亡和災難性的破壞。 芝加哥堆實驗 談到原子彈的發明,我們必須提及芝加哥堆實驗所帶來 的突破。在 1942 年的一個寒冷冬日,費米和同事在芝加哥 大學欖球場下的壁球場中放置了一座 6.1 米寬、7.6 米高的 石墨磚堆,當中含有六噸鈾金屬和 40噸鈾-235,還有一些 鎘棒 [1, 6, 10, 11]。 實驗原理是這樣的:當中子撞擊鈾-235原子時,後者 會裂變成兩顆較小的原子並釋放能量 [6, 12]。這個裂變反 應亦會釋出更多中子作為副產物,分裂其他鈾-235原子, 從而引發連鎖反應,釋放巨大能量 [6, 12]。每摩爾鈾-235 進行裂變後,產物的總重量會比反應前輕約0.2克 [13]。 根據著名方程式E = mc²,上述物質質量的減少能轉化成 約 10¹³ 焦耳的能量。事實上,一公斤鈾-235經裂變反應所 產生的能量,比燃燒一公斤煤所產生的能量高出 250 萬倍 [13]。因此,為了使反應能受到控制,他們在實驗堆裡放入 鎘棒,吸收反應中的一些中子,以控制反應速率和產生的 能量 [6]。如果費米的計算出現錯誤或鎘棒不足以減慢反 應,釋放的巨大能量甚至可以摧毀半個芝加哥 [6]。幸好實 驗取得了空前成功,實現了史上首個受控、自我持續的核鏈 鎖反應。科學家及後再對反應堆設計作大幅改良,大大減少 了其體積,使受控的核鏈鎖反應能應用於體積小至可以用 飛機承載的原子彈內。 費米諾貝爾獎的一個錯誤 諾貝爾獎是科學界最崇高的獎項之一,費米亦無容置疑 地值得擁有這個卓越殊榮。但實際上,費米因著一個後來證 明是錯誤的科學發現而獲獎 [14]。 這其實是一個關於費米發現了核裂變卻不自知的故事。 1938 年,費米因「發現以中子撞擊所產生的新放射性元素, 以及慢中子引發的核反應」獲得諾貝爾獎 [15]。那時已知的 最重元素是原子序數為92 的鈾,而科學界普遍相信費米成 功透過以緩慢移動的中子撞擊鈾,製造出原子序數為93 和 94 的超鈾(鈾外)元素,費米和同事當時分別把新元素命名 為 Ausenium 和 Heperium。可是,德國化學家奧托.哈恩 (Otto Hahn)和弗里茨.斯特拉斯曼(Fritz Strassmann) 其後作出了一個關鍵性的發現,證明在費米的實驗中,鈾經 過撞擊後所產生的元素並不是新元素,而是原子序數為56 的鋇等較輕的元素 [14]。事實上,鈾在中子撞擊下分裂成兩 個較輕的元素 — 這個反應後來被稱為核裂變。基於核裂變 的發現,哈恩在1944年獲得諾貝爾化學獎 [16];至於其後 在1940 年成功被製造的真實元素 93和 94,它們被正式 命名為錼(neptunium)和鈈(plutonium)[17]。 費米悖論 有一個問題一直困擾科學家,即使像費米如此聰明的物 理學家也深受困擾,那就是外星生物存在的可能性 — 對, 我們指的是外星人!從地心說到意識到我們並非身處宇宙 中心;從認為銀河系就是宇宙的全部,到發現宇宙其實擁有 數十億個星系 [18],我們至今應該知道,在這廣闊無垠的宇 宙中,我們並非特殊的一群。費米曾提出,如果我們的地位 並非超然,而地球與無數恆星和行星相比下亦算年輕,那麼 外星文明應該早已演化並在附近星系殖民 [19]。然而,外星 人呢?遺憾的是在這個問題有進一步發現之前,費米就已於 1954 年逝世,疑問只好留給後世科學家解答了。儘管科學 家仍就這個範疇進行研究,亦有發表大量論文,但這個問題 至今仍未得到解決,並存在廣泛爭議。 費米問題 在人類首次引爆原子彈的「三位一體」(Trinity Test) 核試中,費米把紙張撕成碎屑,然後從1.83米的高度扔出 紙屑 [20]。在距離爆炸點16公里的地方 [21],他觀察到紙 屑移動了約2.5米,利用這項資訊結合一系列推斷和計算, 他嘗試估算爆炸釋放的能量。雖然他採取了看似風馬牛不

相及的行為,但費米的估計值(10,000噸 T.N.T. 炸藥)與真 實值(21,000噸 T.N.T. 炸藥)非常接近,甚至屬於同一數量 級。這使人們把此類問題定義為「費米問題」,在資訊有限的 情況下,估計其答案的數量級。過程涉及將複雜問題分解為 多個簡單部分,在一些合理假設下,進行有根據的猜測。 References 參考資料: [1] Badash, L. (2024, April 12). American career of Enrico Fermi. Encyclopædia Britannica. https://www.britannica. com/biography/Enrico-Fermi/American-career [2] Burgwyn, H. J. (2018). Persecution of the Jews. In Mussolini and the Salò Republic, 1943–1945 (pp. 141-164). Palgrave Macmillan Cham. [3] Goodchild, P. (1986, August 10). Time Bomb!FERMI, HEISENBERG, AND THE RACE FOR THE ATOMIC BOMB by Malcolm C. MacPherson (Dutton: $18.95; 293 pp., illustrated). Los Angeles Times. archives/la-xpm-1986-08-10-bk-2027-story.html [4] Whitacre, M., & Belotti, A. (2022, January 28). How science earned Enrico Fermi a Nobel Prize (and saved his Jewish wife and children). Los Alamos National Laboratory. [5] U.S. Department of Energy. (n.d.). The Life of Enrico Fermi. [6] PBS. (n.d.). A science odyssey: People and discoveries: Fermi creates controlled nuclear reaction. https://www. [7] MacPherson, M. (1987). Time Bomb: Fermi, Heisenberg, and the race for the Atomic Bomb. Berkley Books. [8] U.S. Department of Energy. (n.d.). EINSTEIN'S LETTER. The Manhattan Project–an interactive history. https:// Events/1939-1942/einstein_letter.htm [9] U.S. Department of Energy. (n.d.). EARLY URANIUM RESEARCH. The Manhattan Project–an interactive history. [10] Allardice, C., & Trapnell, E. R. (1946). The First Pile. https:// bulletin/bull4-0/04005004147su.pdf [11] Dean, K. M. (2022, December 1). Chicago Pile 1: A bold nuclear physics experiment with enduring impact. Argonne National Laboratory. https://www.anl. gov/article/chicago-pile-1-a-bold-nuclear-physicsexperiment-with-enduring-impact#:~:text=An%20 unassuming%20pile%20of%20black,to%20deliver%20 on%20its%20promise [12] Hellman, M. E. (2012). The Physics of Nuclear Weapons [Class handout]. sts152_03/handout02.pdf [13] Flowers, P., Theopold, K., & Langley, R. (n.d.). 21.6: Nuclear Fission. LibreTexts Chemistry. Bookshelves/General_Chemistry/Map%3A_Chemistry_-_ The_Central_Science_(Brown_et_al.)/21%3A_Nuclear_ Chemistry/21.06%3A_Nuclear_Fission [14] Galison, P. (2005). Author of Error. Social Research: An International Quarterly, 72(1), 63-76. https://doi. org/10.1353/sor.2005.0032 [15] The Nobel Prize in Physics 1938. (n.d.). The Nobel Prize. summary/ [16] Spence, R. (2024, March 11). Otto Hahn. Encyclopædia Britannica. [17] American Chemical Society. (n.d.). Discovery of Transuranium Elements at Berkeley Lab. https://www. transuranium-elements-at-berkeley-lab.html [18] Gunn, A. (2024, March 18). How many galaxies are there in the universe? BBC Sky at Night Magazine. https://www. [19] Howell, E. (2023, August 24). Fermi paradox: Where are the aliens? [20] Tanner, B. (2022, January 10). Fermi Problems Part 1: Envelopes at the Ready! Tom Rocks Maths. https:// [21] Fermi, E. (n.d.). My Observations During the Explosion at Trinity on July 16, 1945. https://www. html 11 Example solution: 題解一例: Physics Books in HKUST Library 科大圖書館裡的物理書 To get a sense of this estimation method, let’s try to solve this problem: What is the order of magnitude of the number of physics books (including e-books) in the HKUST Library? 讓我們嘗試用「費米估算」的方法解答以下問題:哪 個是香港科技大學圖書館物理學書藏(包括電子書) 數量的數量級? A) 10 B) 100 C) 1,000 D) 10,000 This is an open-ended question. You are free to tackle the problem in your own way, and make any useful assumptions, e.g. science books can be generally divided into four subjects. A basic fact: The six-story HKUST Library has a collection of 2,442,592 books (including e-books). 這是一道開放式問題,你可以用自己的方法解題,隨 意作任何有用的假設,譬如假設科學書大致可以分成 四個科目等。以下一項基本資訊:科大圖書館是個有 合共六層的圖書館,共收藏2,442,592本書(包括電子 書)。

By Roshni Printer Photo credit: NASA GSFC/CIL/Adriana Manrique Gutierrez 詹姆斯.韋伯 太空望遠鏡 James Webb Space Telescope In the vast realm of space, a revolutionary tool has been geared up to propel our exploration of the cosmos – the James Webb Space Telescope. Set up as a successor to the Hubble Space Telescope, Webb was launched in December 2021 with the aim of uncovering the formation of galaxies, stars, and planets [1]. As an extremely long duration is needed for the light from a very distant object to reach us, the observation we make today is actually reflecting their appearance in the past, providing us a peek into the early universe. Observing the conditions during the formation of the first galaxies enables scientists to trace the origins of our own galaxy, along with the planets and stars it encompasses. Named after a prior administrator of NASA [2], Webb represents key advancements in the usage of space telescopes, and is the largest and most intricately designed observatories ever sent into space. The main component of the telescope, known as the primary mirror, functions to capture red and infrared light to facilitate the observation of far-off objects that are highly redshifted (footnote 1) [3, 4]. The mirror then reflects the light onto a smaller secondary mirror, where it is redirected to scientific instruments for interpretation. A large primary mirror can reveal more details of a far-off object by collecting more light signals from it. Webb has a light collecting area 6.25 times greater than that of the Hubble Space Telescope [4], but one of the biggest challenges was the technical restriction of launching such a large mirror into space. To overcome this hurdle, the telescope was innovatively designed to be a folding telescope – much like origami – where the mirror would unfold once they had detached from the launch vehicle. Webb is also an incredible feat of engineering that has the capability of adjusting its focus with very fine precision. The primary mirror is made up of 18 hexagonal segments of beryllium [3], whose position can be adjusted independently by the tiny mechanical motors called actuators behind each segment. Controlled by the team on the ground, adjustments as fine as about 1/10,000th of the width of a human hair can be made to produce focused, sharp images [5].