English 中文 February 11, 2026 Hold Hands and Share Feelings: a Trivial Reflection of 19 Nontrivial Years 牵手与共情:十九个不平凡岁月的平凡回望 Reflections as I enter the last year of the second decade of my life. 进入人生第二个十年的最后一年的随想 #personal #reflection #math A function is continuous if you can draw its graph without lifting your pen?If you use this as your definition, you might as well hold hands and share feelings.— Gautam Iyer, my 21-269 professorIntroductionTime flies. Or does it? Long Qian, my 21-242 TA last semester, once said that “time doesn’t fly.” I think I concur with both.In the blink of an eye, I am already almost 113 semesters into college. Time really flies.But on the other hand, so many things have happened over the past 4 months. I met and made so many friends from around the world. I learned so much, not just academically, but also in life. Life skills, lessons, and tricks. It’s hard to describe in words, because it’s really unbelievable that all of this happened over only a few months. Time really doesn’t fly.As I celebrate my 19th birthday, I would like to take some time to reflect on the current, past, and future.Let’s begin.Assume for the Sake of ContradictionBesides having to survive on my own, the greatest change I observed in college is that all of my courses are proof-based. Say goodbye to calculations (in fact, I bought a new TI NSPIRE CAS II and could never use it outside of writing math contests for high schoolers).You might think this is only for math courses. Nope. Computer science courses are also proof-based. Even Linguistics and Philosophy courses are proof-based. Some examples:•15-122 Principles of Imperative Computation‣I entered the class thinking I was going to code so much. First week of classes, we learned how to prove correctness and safety of code. In the end, we learned how to prove structural invariance.•15-150 Principles of Functional Programming‣Ok, surely now this class is just coding, right?‣Prove your 𝑂(𝑛log𝑛) function is extensionally equivalent to the brute force 𝑂(𝑛2) algorithm.‣Prove this random algorithm has 𝑂(log3𝑛) span.•21-242 Matrix Theory‣Matrix? Determinant? Merely social constructions based on abstract Vector Spaces.•15-151, 15-251, 21-269, 21-373, 80-180, …Here’s one of my 21-269 homework problems from this semester:Prove that any real number lies between two consecutive integers.One year ago, I would complain about how things like this are trivial and we should just assume they are true. I mean, everyone has been taking things like this for granted since elementary school, so it surely is just a fact, right?But after 4 months of proof showers, and given recent current events, I now have a different opinion on this topic.Hold Hands and Share FeelingsI admit that the title of this blog is click-bait, and you might have been expecting something else (don’t worry, me too). But I want to give a semi-serious discussion about my philosophy on math and the world.In this information era of Mass Media and Artificial Intelligence (AI), it is very easy to consume false information. Once in a while, I find myself almost believing an AI-generated misinformation or disinformation post on Instagram, before verifying its validity and realizing how silly I was to almost fall for them.Nobody is immune to information weapons. If you are connected to the internet, you are already cooked. No matter how knowledgeable or resilient you think you are (I thought I was until AI-Generated Content (AGC) started becoming too realistic), someone or something will eventually get you.However, as the world around us changes rapidly, and as every piece of information you perceive can be manipulated and shaped to influence your behaviors, there are still things that never change: the laws of logic, math, and physics (my father yaps to remind me about this once every few weeks).How do you know your high school math teachers didn’t lie to you? How do you know every real number is bounded by two consecutive integers? Or even better, what is a real number?Why is it that det(𝑎𝑐𝑏𝑑)=𝑎𝑑−𝑏𝑐? Why is a square matrix 𝐴 invertible if and only if det𝐴≠0? Or even better, what is a determinant? Why do we even study this?As I step away from taking in “facts” (do they even exist?) and applying them to compute numerical answers, I find it fascinating to ask myself why. Even more exciting is convincing myself that each of these “facts” is true by proving that they are true, only from the most basic definitions and axioms (of course, then you ask yourself why the axioms are chosen, and then you find even more interesting things behind the world of logic and math).Being rigorous is not just being performative. Being rigorous is a way of recording truth, logical deductions, and evidence. While some people hand-wave proofs and rely on intuition, I firmly believe that information should be formally verifiable. Human intuitions are wrong all the time. Did you know that you could break a solid ball into two identical solid balls? Intuitions and assumptions are feeble. Rigorous proofs are strong.And yes, I agree with Professor Iyer. If you take facts for granted and hand-wave justifications with intuitive definitions, then you might as well “hold hands and share feelings.”Final Year in the Second Decade of My LifeI always tell people that, to me, the “modern” era is anchored at the year 2017. Maybe it was because I didn’t care about things around the world until 2017, or maybe it was because I watched AlphaGo beat Lee Sedol on Live TV around that time, or maybe it was because Attention Is All You Need, or maybe it was because of the invention of 高速に差分計算可能なニューラルネットワーク (Efficiently Updated Neural Networks, NNUE), 2017 felt like the turning point of the world to me.Now, if I can subtract correctly (after spending 99% of my time on abstract proofs recently), we are already 2026−2017=9 years from that anchor. What I imagined as “modern” is soon to become a decade-old past that we would soon view as ancient, given how quickly the world is moving today.Coincidentally, this year also marks the end of the second decade of my life. Hence I thought it would be interesting to reflect on the past nine years before I step into the final year of a decade alongside the 2017 “modern” world.Looking Back: Adversity Creates Opportunity2020 was certainly one of the years of all time. While many people (rightfully) look at the negative sides of the pandemic, I try to observe the more positive things made possible uniquely because of it.Social Media. Short-form Content. Online Meetings. Virtual Classrooms. Before 2020, these technologies were never allowed their full potential to grow. As I read Algospeak by Adam Aleksic (@etymologynerd), I realize just how much the growth of these technologies has transformed both the world and myself.As for me. Sitting in front of a computer 24/7, I practiced American English slang with friends on Discord. I joined programming communities and learned to code. Who knows who I would be today without being able to stare at VSCode and Discord for 10 hours a day? Would I even pass the high school entrance English exam? Would I even code? Would I even ever learn and use a programming language other than Python? It’s hard to say, but I sure am proud of who I am today as brought up by this journey.As for the technologies. Within a year, Google turned Hangouts, a functionally unusable app in my experience, into Meet, an arguably almost flawless app now used by many public school districts. As a result, Google expanded its effort on online education and turned Google Classroom from essentially an organized storage to the core of everyday student-teacher interaction. At the same time, Zoom zoomed ahead (really no pun intended) and solidified itself as the industry standard for online meetings. Discord grew. People began scrolling on Tiktok. Perhaps without the pandemic, we would still be relying on paper for assignments and grades and be forced to shut down all educational activities during a snowstorm. The world changed fundamentally because of the pandemic.Adversity creates opportunity, I guess. That’s my main takeaway from the pandemic.But even 2020 was six years ago. It certainly does not feel like we have completely parted ways with the pandemic.Time moves on……and so do challenges and danger.Looking Ahead: a Homogenized but Divided WorldRapid advancements in technology continue to enlarge the socioeconomic divide between wealthy elites and average citizens. Capital accumulation and elite-favoring policies are intensifying global economic inequalities. Corporation-controlled mass media are amplifying elite voices and suppressing average citizens’ opinions. Monopolies and standardization of practices are homogenizing the world’s diverse cultures.— My (Rejected) Stanford ApplicationLook at all those kids in joy because the answer to a contest math problem was exactly 67. Or when an NBA team reaches a score of 67. Or when the professor asks for a random number between 1 and 100 to demonstrate binary search, and everyone shouts 67.Everyone around the world is heavily affected by social media, whether positively or negatively. And social media is extremely powerful. Or perhaps too powerful.Look at recent nationalist movements across every continent. Or the extinction of languages. Or the alienation of cultures.The rapidity of these global developments amazes me. But as we become homogenized, we remain divided. There’s no need to say more about this — just look outside in 2026.Society is beautiful. Languages are beautiful. Cultures are beautiful.People are beautiful. Communities are beautiful. Nature is beautiful.We are beautiful.Looking forward, in the next decade, I hope to make the world more beautiful.But the world is changing so quickly, and we must adapt to this speed. I hope to ride the waves of frontier technologies and work for a better future that does not yet exist.Let’s do it together. Rigorously. Truthfully. Beautifully. A function is continuous if you can draw its graph without lifting your pen?If you use this as your definition, you might as well hold hands and share feelings.— Gautam Iyer, my 21-269 professorIntroductionTime flies. Or does it? Long Qian, my 21-242 TA last semester, once said that “time doesn’t fly.” I think I concur with both.In the blink of an eye, I am already almost 113 semesters into college. Time really flies.But on the other hand, so many things have happened over the past 4 months. I met and made so many friends from around the world. I learned so much, not just academically, but also in life. Life skills, lessons, and tricks. It’s hard to describe in words, because it’s really unbelievable that all of this happened over only a few months. Time really doesn’t fly.As I celebrate my 19th birthday, I would like to take some time to reflect on the current, past, and future.Let’s begin.Assume for the Sake of ContradictionBesides having to survive on my own, the greatest change I observed in college is that all of my courses are proof-based. Say goodbye to calculations (in fact, I bought a new TI NSPIRE CAS II and could never use it outside of writing math contests for high schoolers).You might think this is only for math courses. Nope. Computer science courses are also proof-based. Even Linguistics and Philosophy courses are proof-based. Some examples:•15-122 Principles of Imperative Computation‣I entered the class thinking I was going to code so much. First week of classes, we learned how to prove correctness and safety of code. In the end, we learned how to prove structural invariance.•15-150 Principles of Functional Programming‣Ok, surely now this class is just coding, right?‣Prove your 𝑂(𝑛log𝑛) function is extensionally equivalent to the brute force 𝑂(𝑛2) algorithm.‣Prove this random algorithm has 𝑂(log3𝑛) span.•21-242 Matrix Theory‣Matrix? Determinant? Merely social constructions based on abstract Vector Spaces.•15-151, 15-251, 21-269, 21-373, 80-180, …Here’s one of my 21-269 homework problems from this semester:Prove that any real number lies between two consecutive integers.One year ago, I would complain about how things like this are trivial and we should just assume they are true. I mean, everyone has been taking things like this for granted since elementary school, so it surely is just a fact, right?But after 4 months of proof showers, and given recent current events, I now have a different opinion on this topic.Hold Hands and Share FeelingsI admit that the title of this blog is click-bait, and you might have been expecting something else (don’t worry, me too). But I want to give a semi-serious discussion about my philosophy on math and the world.In this information era of Mass Media and Artificial Intelligence (AI), it is very easy to consume false information. Once in a while, I find myself almost believing an AI-generated misinformation or disinformation post on Instagram, before verifying its validity and realizing how silly I was to almost fall for them.Nobody is immune to information weapons. If you are connected to the internet, you are already cooked. No matter how knowledgeable or resilient you think you are (I thought I was until AI-Generated Content (AGC) started becoming too realistic), someone or something will eventually get you.However, as the world around us changes rapidly, and as every piece of information you perceive can be manipulated and shaped to influence your behaviors, there are still things that never change: the laws of logic, math, and physics (my father yaps to remind me about this once every few weeks).How do you know your high school math teachers didn’t lie to you? How do you know every real number is bounded by two consecutive integers? Or even better, what is a real number?Why is it that det(𝑎𝑐𝑏𝑑)=𝑎𝑑−𝑏𝑐? Why is a square matrix 𝐴 invertible if and only if det𝐴≠0? Or even better, what is a determinant? Why do we even study this?As I step away from taking in “facts” (do they even exist?) and applying them to compute numerical answers, I find it fascinating to ask myself why. Even more exciting is convincing myself that each of these “facts” is true by proving that they are true, only from the most basic definitions and axioms (of course, then you ask yourself why the axioms are chosen, and then you find even more interesting things behind the world of logic and math).Being rigorous is not just being performative. Being rigorous is a way of recording truth, logical deductions, and evidence. While some people hand-wave proofs and rely on intuition, I firmly believe that information should be formally verifiable. Human intuitions are wrong all the time. Did you know that you could break a solid ball into two identical solid balls? Intuitions and assumptions are feeble. Rigorous proofs are strong.And yes, I agree with Professor Iyer. If you take facts for granted and hand-wave justifications with intuitive definitions, then you might as well “hold hands and share feelings.”Final Year in the Second Decade of My LifeI always tell people that, to me, the “modern” era is anchored at the year 2017. Maybe it was because I didn’t care about things around the world until 2017, or maybe it was because I watched AlphaGo beat Lee Sedol on Live TV around that time, or maybe it was because Attention Is All You Need, or maybe it was because of the invention of 高速に差分計算可能なニューラルネットワーク (Efficiently Updated Neural Networks, NNUE), 2017 felt like the turning point of the world to me.Now, if I can subtract correctly (after spending 99% of my time on abstract proofs recently), we are already 2026−2017=9 years from that anchor. What I imagined as “modern” is soon to become a decade-old past that we would soon view as ancient, given how quickly the world is moving today.Coincidentally, this year also marks the end of the second decade of my life. Hence I thought it would be interesting to reflect on the past nine years before I step into the final year of a decade alongside the 2017 “modern” world.Looking Back: Adversity Creates Opportunity2020 was certainly one of the years of all time. While many people (rightfully) look at the negative sides of the pandemic, I try to observe the more positive things made possible uniquely because of it.Social Media. Short-form Content. Online Meetings. Virtual Classrooms. Before 2020, these technologies were never allowed their full potential to grow. As I read Algospeak by Adam Aleksic (@etymologynerd), I realize just how much the growth of these technologies has transformed both the world and myself.As for me. Sitting in front of a computer 24/7, I practiced American English slang with friends on Discord. I joined programming communities and learned to code. Who knows who I would be today without being able to stare at VSCode and Discord for 10 hours a day? Would I even pass the high school entrance English exam? Would I even code? Would I even ever learn and use a programming language other than Python? It’s hard to say, but I sure am proud of who I am today as brought up by this journey.As for the technologies. Within a year, Google turned Hangouts, a functionally unusable app in my experience, into Meet, an arguably almost flawless app now used by many public school districts. As a result, Google expanded its effort on online education and turned Google Classroom from essentially an organized storage to the core of everyday student-teacher interaction. At the same time, Zoom zoomed ahead (really no pun intended) and solidified itself as the industry standard for online meetings. Discord grew. People began scrolling on Tiktok. Perhaps without the pandemic, we would still be relying on paper for assignments and grades and be forced to shut down all educational activities during a snowstorm. The world changed fundamentally because of the pandemic.Adversity creates opportunity, I guess. That’s my main takeaway from the pandemic.But even 2020 was six years ago. It certainly does not feel like we have completely parted ways with the pandemic.Time moves on……and so do challenges and danger.Looking Ahead: a Homogenized but Divided WorldRapid advancements in technology continue to enlarge the socioeconomic divide between wealthy elites and average citizens. Capital accumulation and elite-favoring policies are intensifying global economic inequalities. Corporation-controlled mass media are amplifying elite voices and suppressing average citizens’ opinions. Monopolies and standardization of practices are homogenizing the world’s diverse cultures.— My (Rejected) Stanford ApplicationLook at all those kids in joy because the answer to a contest math problem was exactly 67. Or when an NBA team reaches a score of 67. Or when the professor asks for a random number between 1 and 100 to demonstrate binary search, and everyone shouts 67.Everyone around the world is heavily affected by social media, whether positively or negatively. And social media is extremely powerful. Or perhaps too powerful.Look at recent nationalist movements across every continent. Or the extinction of languages. Or the alienation of cultures.The rapidity of these global developments amazes me. But as we become homogenized, we remain divided. There’s no need to say more about this — just look outside in 2026.Society is beautiful. Languages are beautiful. Cultures are beautiful.People are beautiful. Communities are beautiful. Nature is beautiful.We are beautiful.Looking forward, in the next decade, I hope to make the world more beautiful.But the world is changing so quickly, and we must adapt to this speed. I hope to ride the waves of frontier technologies and work for a better future that does not yet exist.Let’s do it together. Rigorously. Truthfully. Beautifully. 你刚说,一个函数是连续的,如果你能不抬起笔就画出它的图像?如果你把这当作定义,那你们还不如找个伴儿牵手共情好了。— 我的 21-269 教授 Gautam Iyer引言时光飞逝。真的吗?我上学期 21-242 课程的助教钱隆曾说过“时光并不飞逝”。我想我两者都同意。转眼之间,我进入大学已将近 113 个学期了。时光真的在飞逝。但另一方面,过去的四个月里发生了太多事情。我结交了来自世界各地的许多朋友。我学到了如此之多,不仅是学术上的,也有生活上的。这一切都发生在仅仅几个月内,实在难以置信,很难用语言描述。这样来说,时间真的没有飞逝。庆祝十九岁生日之际,我想花些时间反思现在、过去和未来。假设除了必须独立生活之外,我在大学里观察到最大的变化是我所有的课程都基于证明。和计算说再见吧(我买了一台新的计算器,却除了给高中生出数学竞赛题外根本没地方用)。如果你以为只有数学课才是这样,那你就错了。计算机科学课程也基于证明。甚至语言学和哲学课程也基于证明。比方说:•15-122 命令式计算原理‣我进这门课时还以为要写很多代码呢。开学第一周,我们学习了如何证明代码的正确性和安全性。最后,我们学习了如何证明结构不变性。•15-150 函数式编程原理‣好吧,这门课总该只是写代码了吧?‣证明你的 𝑂(𝑛log𝑛) 函数在扩展意义上等价于暴力 𝑂(𝑛2) 算法。‣证明这个莫名其妙的算法具有 𝑂(log3𝑛) 的跨度。•21-242 矩阵理论‣矩阵?行列式?不过是基于抽象向量空间的社会建构罢了。•15-151, 15-251, 21-269, 21-373, 80-180, …这是我这学期 21-269 课的一道作业题:证明任何实数都位于两个连续的整数之间。一年前,我会抱怨这种东西是多么繁琐,我们应该直接假设它们成立。既然每个人从小学起就一直把这种东西视为理所当然的事实,那它一定就是个事实,对吧?但经过四个月的证明“洗礼”,以及考虑到近来的时事,现在我对这个问题有了不同的看法。牵手与共情在这个大众媒体和人工智能的信息时代,我们很容易受虚假信息的影响。时不时地,我发现自己会几乎相信 Ins 上一条 AI 生成的错误信息或虚假信息,直到验证它的(非)真实性后才意识到自己差点上当是件多么愚蠢的事。没有人能对信息武器免疫。如果你连接到互联网,你就已经完蛋了。无论你认为自己多么有见识(在 AI 生成内容开始变得过于逼真之前,我也曾这样认为),某人或某事最终会影响到你。然而,尽管我们的世界在迅速地变化,尽管你感知到的每一则信息都可能被操纵和影响你的行为,但有些事情从未改变:逻辑、数学和物理的定律(我父亲基本每隔几周就会提醒我这一点)。你怎么知道你的高中数学老师没有骗你?你怎么知道每个实数都被两个连续整数所界定?或者更甚,实数是什么?为什么 det(𝑎𝑐𝑏𝑑)=𝑎𝑑−𝑏𝑐?为什么一个方阵 𝐴 可逆当且仅当 det𝐴≠0?或者更甚,行列式是什么?我们为什么要研究这个?当我不再只是接受“事实”(它们真的存在吗?)并应用它们来计算数值答案时,我发现向自己提问“为什么”的过程非常有趣。更令人兴奋的是,通过仅从最基本的定义和公理出发证明这些“事实”是正确的(然后你会问自己为什么选择这些公理,接着你会在逻辑和数学的世界背后发现更有趣的东西)。保持严谨不是为了在别人面前凡尔赛。严谨是记录真理、逻辑推论和证据的一种方式。虽然有些人会挥手“证明”并依赖直觉,但我坚信所有信息应该要是可形式化验证的。人类的直觉经常是错误的。你知道吗,我们可以把一个实心球分解成两个一模一样的实心球。直觉和假设是脆弱的。严谨的证明是强大的。我同意 Iyer 教授的观点。如果你把事实视为理所当然,并用直观的定义来挥手示意论证,那么你不如找个伴儿“牵手共情”。我人生第二个十年的最后一年我总是告诉别人,对我来说,“现代”时代锚定在 2017 年。也许是因为在那之前我不太关心世界上的事情,也许是因为我大概在那时在电视直播上观看了AlphaGo 击败李世石,也许是因为Attention Is All You Need,也许是因为高速に差分計算可能なニューラルネットワーク (高效差分更新神经网络)的发明,2017 年对我来说感觉像是世界的转折点。现在,如果我能正确计算(最近 99% 的时间都花在抽象证明上)的话,我们距离那个锚点已经 2026−2017=9 年了。我认为的“现代”很快将变成十年之久的过去,鉴于当今世界变化之快,我们很快就会将其视为远古。巧合的是,今年也标志着我人生第二个十年的结束。因此,我想在我踏入一个十年最后一年的同时,与 2017 年的“现代”世界并肩,反思一下这过去的九年。回顾:逆境创造机遇2020 年无疑是人类历史上无法除去的一年。虽然许多人(理所当然地)看到了疫情带来的负面影响,但我试图观察那些因其而得以实现的、独特的、更积极的事。社交媒体、短视频内容、在线会议、虚拟课堂。在 2020 年之前,这些技术从未被允许充分发挥它们增长的潜力。阅读 Adam Aleksic (@etymologynerd) 的《Algospeak》时,我深刻意识到,这些技术的发展在多大程度上改变了世界,也改变了我自己。先讲讲我自己。我每天从早到晚地坐在电脑前在 Discord 上与朋友们练习美式英语俚语。我加入了一些编程社区,以学习编程。谁知道如果当时没有每天盯着 VSCode 和 Discord,今天的我会是什么样子?我能融入美国的社会吗?我还会写代码吗?我甚至会学习并使用Python 之外的编程语言吗?很难说,但我为这段旅程造就的今天的自己感到自豪。再讲讲技术。一年内,谷歌将 Hangouts(在我看来完全用不了的应用)变成了 Meet(一个现在被许多公立学区使用的、可以说几乎完美的应用)。谷歌扩大了它在在线教育方面的努力,并将 Google Classroom 从一个存储平台变成了日常师生互动的核心。与此同时,Zoom 迅速领先,并巩固了自己作为在线会议的行业标准。Discord 成长了起来。人们开始天天在抖音上刷短视频。也许没有疫情,老师们现在仍然会用纸来布置作业,并被迫在暴风雪期间暂停所有教育活动。世界因疫情而发生了根本性的改变。逆境创造机遇。这是我从疫情中得到的主要收获。但即使是 2020 年也是六年前了。我们似乎并没有完全与疫情分道扬镳。时间在流逝…………但挑战和危险还在迎我们而来。展望:一个同质化却分裂的世界看看那些因为一道竞赛数学题的答案正好是 67 而欣喜若狂的孩子们。 看看那些当一支 NBA 球队得分达到 67 分时的年轻球迷。 看看那些当教授要求在 1 到 100 之间随机选一个数字来演示二分查找,喊 “67” 的学生。世界各地的每个人都深受社交媒体影响,无论是积极的还是消极的。社交媒体是极其强大的。或许过于强大了。看看近来各大洲的民族主义运动。 或者语言的灭绝。 或者文化的异化。这些全球发展的迅速性令我惊讶。但当我们变得同质化时,我们却变得愈加分裂。社会是美丽的。语言是美丽的。文化是美丽的。人类是美丽的。社区是美丽的。自然是美丽的。我们是美丽的。展望未来,在下一个十年里,我希望能让世界变得更美丽。但世界变化如此之快,我们必须适应这种速度。我希望能乘前沿技术的浪潮,为更美好的未来而努力。让我们一起努力吧。 你刚说,一个函数是连续的,如果你能不抬起笔就画出它的图像?如果你把这当作定义,那你们还不如找个伴儿牵手共情好了。— 我的 21-269 教授 Gautam Iyer引言时光飞逝。真的吗?我上学期 21-242 课程的助教钱隆曾说过“时光并不飞逝”。我想我两者都同意。转眼之间,我进入大学已将近 113 个学期了。时光真的在飞逝。但另一方面,过去的四个月里发生了太多事情。我结交了来自世界各地的许多朋友。我学到了如此之多,不仅是学术上的,也有生活上的。这一切都发生在仅仅几个月内,实在难以置信,很难用语言描述。这样来说,时间真的没有飞逝。庆祝十九岁生日之际,我想花些时间反思现在、过去和未来。假设除了必须独立生活之外,我在大学里观察到最大的变化是我所有的课程都基于证明。和计算说再见吧(我买了一台新的计算器,却除了给高中生出数学竞赛题外根本没地方用)。如果你以为只有数学课才是这样,那你就错了。计算机科学课程也基于证明。甚至语言学和哲学课程也基于证明。比方说:•15-122 命令式计算原理‣我进这门课时还以为要写很多代码呢。开学第一周,我们学习了如何证明代码的正确性和安全性。最后,我们学习了如何证明结构不变性。•15-150 函数式编程原理‣好吧,这门课总该只是写代码了吧?‣证明你的 𝑂(𝑛log𝑛) 函数在扩展意义上等价于暴力 𝑂(𝑛2) 算法。‣证明这个莫名其妙的算法具有 𝑂(log3𝑛) 的跨度。•21-242 矩阵理论‣矩阵?行列式?不过是基于抽象向量空间的社会建构罢了。•15-151, 15-251, 21-269, 21-373, 80-180, …这是我这学期 21-269 课的一道作业题:证明任何实数都位于两个连续的整数之间。一年前,我会抱怨这种东西是多么繁琐,我们应该直接假设它们成立。既然每个人从小学起就一直把这种东西视为理所当然的事实,那它一定就是个事实,对吧?但经过四个月的证明“洗礼”,以及考虑到近来的时事,现在我对这个问题有了不同的看法。牵手与共情在这个大众媒体和人工智能的信息时代,我们很容易受虚假信息的影响。时不时地,我发现自己会几乎相信 Ins 上一条 AI 生成的错误信息或虚假信息,直到验证它的(非)真实性后才意识到自己差点上当是件多么愚蠢的事。没有人能对信息武器免疫。如果你连接到互联网,你就已经完蛋了。无论你认为自己多么有见识(在 AI 生成内容开始变得过于逼真之前,我也曾这样认为),某人或某事最终会影响到你。然而,尽管我们的世界在迅速地变化,尽管你感知到的每一则信息都可能被操纵和影响你的行为,但有些事情从未改变:逻辑、数学和物理的定律(我父亲基本每隔几周就会提醒我这一点)。你怎么知道你的高中数学老师没有骗你?你怎么知道每个实数都被两个连续整数所界定?或者更甚,实数是什么?为什么 det(𝑎𝑐𝑏𝑑)=𝑎𝑑−𝑏𝑐?为什么一个方阵 𝐴 可逆当且仅当 det𝐴≠0?或者更甚,行列式是什么?我们为什么要研究这个?当我不再只是接受“事实”(它们真的存在吗?)并应用它们来计算数值答案时,我发现向自己提问“为什么”的过程非常有趣。更令人兴奋的是,通过仅从最基本的定义和公理出发证明这些“事实”是正确的(然后你会问自己为什么选择这些公理,接着你会在逻辑和数学的世界背后发现更有趣的东西)。保持严谨不是为了在别人面前凡尔赛。严谨是记录真理、逻辑推论和证据的一种方式。虽然有些人会挥手“证明”并依赖直觉,但我坚信所有信息应该要是可形式化验证的。人类的直觉经常是错误的。你知道吗,我们可以把一个实心球分解成两个一模一样的实心球。直觉和假设是脆弱的。严谨的证明是强大的。我同意 Iyer 教授的观点。如果你把事实视为理所当然,并用直观的定义来挥手示意论证,那么你不如找个伴儿“牵手共情”。我人生第二个十年的最后一年我总是告诉别人,对我来说,“现代”时代锚定在 2017 年。也许是因为在那之前我不太关心世界上的事情,也许是因为我大概在那时在电视直播上观看了AlphaGo 击败李世石,也许是因为Attention Is All You Need,也许是因为高速に差分計算可能なニューラルネットワーク (高效差分更新神经网络)的发明,2017 年对我来说感觉像是世界的转折点。现在,如果我能正确计算(最近 99% 的时间都花在抽象证明上)的话,我们距离那个锚点已经 2026−2017=9 年了。我认为的“现代”很快将变成十年之久的过去,鉴于当今世界变化之快,我们很快就会将其视为远古。巧合的是,今年也标志着我人生第二个十年的结束。因此,我想在我踏入一个十年最后一年的同时,与 2017 年的“现代”世界并肩,反思一下这过去的九年。回顾:逆境创造机遇2020 年无疑是人类历史上无法除去的一年。虽然许多人(理所当然地)看到了疫情带来的负面影响,但我试图观察那些因其而得以实现的、独特的、更积极的事。社交媒体、短视频内容、在线会议、虚拟课堂。在 2020 年之前,这些技术从未被允许充分发挥它们增长的潜力。阅读 Adam Aleksic (@etymologynerd) 的《Algospeak》时,我深刻意识到,这些技术的发展在多大程度上改变了世界,也改变了我自己。先讲讲我自己。我每天从早到晚地坐在电脑前在 Discord 上与朋友们练习美式英语俚语。我加入了一些编程社区,以学习编程。谁知道如果当时没有每天盯着 VSCode 和 Discord,今天的我会是什么样子?我能融入美国的社会吗?我还会写代码吗?我甚至会学习并使用Python 之外的编程语言吗?很难说,但我为这段旅程造就的今天的自己感到自豪。再讲讲技术。一年内,谷歌将 Hangouts(在我看来完全用不了的应用)变成了 Meet(一个现在被许多公立学区使用的、可以说几乎完美的应用)。谷歌扩大了它在在线教育方面的努力,并将 Google Classroom 从一个存储平台变成了日常师生互动的核心。与此同时,Zoom 迅速领先,并巩固了自己作为在线会议的行业标准。Discord 成长了起来。人们开始天天在抖音上刷短视频。也许没有疫情,老师们现在仍然会用纸来布置作业,并被迫在暴风雪期间暂停所有教育活动。世界因疫情而发生了根本性的改变。逆境创造机遇。这是我从疫情中得到的主要收获。但即使是 2020 年也是六年前了。我们似乎并没有完全与疫情分道扬镳。时间在流逝…………但挑战和危险还在迎我们而来。展望:一个同质化却分裂的世界看看那些因为一道竞赛数学题的答案正好是 67 而欣喜若狂的孩子们。 看看那些当一支 NBA 球队得分达到 67 分时的年轻球迷。 看看那些当教授要求在 1 到 100 之间随机选一个数字来演示二分查找,喊 “67” 的学生。世界各地的每个人都深受社交媒体影响,无论是积极的还是消极的。社交媒体是极其强大的。或许过于强大了。看看近来各大洲的民族主义运动。 或者语言的灭绝。 或者文化的异化。这些全球发展的迅速性令我惊讶。但当我们变得同质化时,我们却变得愈加分裂。社会是美丽的。语言是美丽的。文化是美丽的。人类是美丽的。社区是美丽的。自然是美丽的。我们是美丽的。展望未来,在下一个十年里,我希望能让世界变得更美丽。但世界变化如此之快,我们必须适应这种速度。我希望能乘前沿技术的浪潮,为更美好的未来而努力。让我们一起努力吧。