科研的力量 | 德胜学子专访剑桥大学天文学教授Christopher Tout：天文学告诉人类，我们还不够有趣|剑桥大学|天文|天文学|宇宙学|物理学|银河系

导语

创新能力的培养离不开科学知识的积累和创新性思维的建构。正所谓“名师出高徒”，在思维方式和学习习惯养成的关键时期，青少年能够有机会与世界顶尖学术大师交流对话，对于激发他们的学习兴趣、拓宽全球视野、培养创新精神、开发科研潜能、提高综合素质都大有裨益。

广东顺德德胜学校（国际）重磅打造“科研的力量”栏目，汇聚稀缺的世界顶尖教育资源，为广大学子提供与全球顶尖学术大师交流对话的平台，让广大学子有机会领略世界级专家学者的科研风采与学术精神，了解各学科领域的前沿研究并获得专业指导。学校特别邀请10位来自哈佛大学、剑桥大学、牛津大学、康奈尔大学、卡耐基梅隆大学的知名教授，他们学术水平突出、教育经验丰富，且研究领域覆盖广泛，包括计算机科学，自然科学，商科，社科和文学等专业，德胜（国际）9-12年级的学子们将以采访的形式，与10位世界级顶尖名师展开10场主题交流，让思想的碰撞点燃科研热情，让科研的力量助力创新人才培养。

提到天文学，许多人的第一反应或许是深邃、神秘。从古人编撰出关于日月星辰的传说，到哥白尼推翻日心说，再到今天世界各国对于宇宙空间的持续探索，天文学一直走在发展的道路上。宇宙中还有许多未被解答与发现的奥秘，天文学的发展前路仍然广阔。

因此，天文学是当代最活跃的前沿学科之一。天文学科主要分为天体物理、天体测量与天体力学、天文技术三个研究方向，分别侧重于利用物理、数学（力学）知识来研究宇宙中的天体和发展天文观测技术。

天文学的就业方向也十分广泛，毕业生可以从事理论研究、学科科研，也能从事群众科普、专业教学或其他技术工作。同时，学习天文学所需的良好的数学与物理能力，也能够成为毕业生的竞争优势。这样的天文学受到了众多大学的青睐，目前全美有100多所大学开设天文专业，并颁发本科、研究生和博士学位；英国的剑桥大学、圣安德鲁斯大学、牛津大学、杜伦大学、萨塞克斯大学、伯明翰大学等多所名校也开设了这一专业。

在本期“科研的力量”栏目中，几名对天文专业感兴趣的德胜学子与剑桥大学天文学教授Christopher Tout进行对话，一同探讨天文专业的基本知识与概念，并在新技术、天文与哲学等话题上进行了延伸。Tout教授还与学生们交流了专业选择与学习经验等话题，引起了学生们极大的兴趣。

以下内容为本次访谈原文，英文版本附在文末。

嘉宾介绍

Christopher Tout

剑桥大学天文学教授

Christopher Tout教授是剑桥大学天文学终身正教授，他还担任匈牙利科学院孔科利天文台英国皇家学会交流研究员，莫纳什大学数学科学学院资深访问研究员，以及太空望远镜科学研究所博士后研究员等职务，多年来致力于恒星与恒星演化方面的研究。

访谈亮点

科研的力量旨在通过与学科领域内最负盛名的科学家深入对话，使科研的种子能够在未来生根发芽，转变为推动世界进步的力量，天文学有悠久的历史，且随着人类对宇宙边界的不断探索，天文学也在不断发展。

德胜学子与Tout教授的访谈围绕天文学领域内的热点问题，如宇宙能量、戴森球、超新星、外星生命等展开；也延伸到了天文与哲学、天文与科技等思考方向；最后，教授从自己的专业选择经历出发为德胜学子们提供了借鉴。

天文专业知识

德胜学子首先向教授请教了自己在天文学方面的疑惑。同学们提出的问题从最宏观的宇宙能量来源到具体的行星、超新星、恒星收缩。在了解了基本知识后，同学们开始思考如何解决天文学内目前存在的问题，并与教授探讨了宇宙学危机、模拟天文系统、宇宙界限等问题的解决方案。

天文与哲学

从天文学专业知识出发，德胜学子们进行了进一步深入思考，并向教授请教天文学中会遇到哪些哲学问题。教授指出了天文学涉及的最主要的两个哲学问题：一是这一切是如何开始的，另一个是其他星球的生命。而后，教授进一步阐释了外星生命这一问题目前已知的前提：太空之旅的可能、太阳系诞生前的恒星历史，接着给出了他的猜想：“为什么我们看不到别处的生活？我认为最好的答案是我们还不够有趣。银河系中也许有一些高级智慧生命，但他们觉得我们无趣，因此不值得一看。 ”

人类星球迁移的可能性

在得到教授关外星生命的阐述与猜想后，德胜学子进一步发散思维，与教授探讨了一个热门而又先锋的话题，即如何看待人类迁移到其他星球的可能性？教授从太阳系生存条件的改变这一前提讲起，再到建造设备、寻找宜居星球并进行开发等必需步骤所面临的困难，最后联系人工智能发展，给出了全面的、具有批判性的回答。

天文与科技

在理论与哲学层面充分探讨后，德胜学子们将目光落在了天文实践层面。首先从智能设备入手，与教授探讨了当前天文学所用的设备及能得到的数据。教授从最基本的天文望远镜与计算机出发，援引实例与数据讲解了其用途。谈及计算机，同学们又进一步和教授探讨了天文学中的编程语言，教授指出，在天文学中，“你可以使用任何你喜欢的语言”。

专业方向选择

最后，同学们基于即将面对的升学问题，与教授探讨了天文学的专业选择。而教授也基于自己的经验，与同学们分享了自己选择天文学是因为对物理与数学都感兴趣，对同学们产生了新的启发。

在本次访谈中，来自德胜的几位同学收获颇丰，通过与教授的交流，同学们对感兴趣的天文学问题、天文学的具体实践等话题有了进一步的透彻了解，也对天文学中的哲学问题进行了思考。

同时，那些纠结于自己本科学习方向的德胜同学们也在本次访谈中有了新的认识，意识到学习天文学，数学与物理的学科基础很重要。

下面，让我们透过文字，一同穿越回访谈时刻，在德胜学子的带领下，走进天文学的世界，在学子们与教授的对话中见证思想碰撞的火花，感受科研与创新的魅力。

访谈全文

天文专业知识和理论

宇宙中的能量从何而来？这在大爆炸发生之前是否存在？

在量子力学中，我提到过海森堡测不准原理，也就是不能同时知道一个粒子的位置和它的速度。但你可以从中得出能量和时间之间类似的不确定性原理，这意味着可以在一定时间内借用能量。这基本上就是在大爆炸时发生的事情，借用了宇宙的全部能量，然后膨胀得非常快，以至于能量不会再次消失，这类似于霍金辐射的概念。

说起黑洞，黑洞的概念就是一个光无法逃脱的物体。没有任何东西可以从黑洞中逃脱。但如果是一个非常厚的小黑洞，它的表面就会非常弯曲。那里的量子力学可以自发地产生能量，因此可以自发地产生成对的粒子。现在，如果其中一个粒子落入黑洞，另一个粒子就可以逃脱。所以，你的黑洞实际上是有辐射的。实际上黑洞已经创造了一些能量，从无到有，宇宙的开始是一个稍微不同的拓扑，但它是相同的概念。创造能量一段时间，其中一些消失了，其中一些扩展到我们所知的宇宙中。

请问您认为2016年观察到的EPIC 204278916极度变暗是由戴森球引起的吗？

澳大利亚天文学家发现了这一点，这是一个有趣的可能性。大家知道什么是戴森球吗？为了增加可以生存的陆地质量，在恒星周围建造了一个固体球壳，与地球轨道在同一位置，这样就可以在整个地球上获得来自太阳的相同辐射。

它比地球表面大得多，以获得更大的区域。假设在未来，甚至我们自己的文明，可能能够建造这样的东西。当然，它需要大量的材料，这确实是主要问题之一。它也很可能影响太阳演化的方式，因为需要开始将它的一些辐射发送并反射回它。但这些都是未来工程师可能要克服的问题。

所以我的想法是，一颗在很长一段时间内逐渐变暗的恒星，是某些文明在恒星周围建造了一个戴森球，切断了它的光，让我们看不到它的结果。但是，我认为这种猜想的主要问题是，虽然调暗需要很长时间，但与构建戴森球所需的时间相比，实际上只需要很短的时间。建造一个塔楼需要几年，但要在这个地方建造一些东西，却要数千年。

更好的解释是这颗恒星散发出了一些尘埃，而这些尘埃在恒星周围循环，将它抹去。也许这只是一些大太阳黑子。所以，如果太阳黑子在太阳表面，那里有很强的磁场，或者稍微冷一点，如果其中一个变得，那么就会减少很多星星的光，所以会发现这种调光。所以，我认为主要的反对意见是戴森球太快了，除非这种文明先进到足以让他们极快地建造好。

这是我们所见过的唯一一颗极其暗淡的恒星吗？

不，我们看到很多变星。在某些情况下，我们实际上可以解决表面上的斑点，因为恒星在旋转。因此，我们可以看到，当恒星旋转时，光点有时在恒星前面，有时在恒星后面，并且会周期性地变暗。这不是周期性的，所以它似乎不仅仅是与这些东西的旋转有关的东西。它正在改变。如果它是一个太阳黑子或一团尘埃，它必须随着时间的推移而改变它的形状。

双星系统中的两颗恒星有可能一起成为超新星吗？

大家对超新星了解多少呢？有各种类型的超新星。以太阳为例，太阳此刻正在其核心将氢融合成氦，这就是它获取能量的地方，这是氢愈合的核聚变。在某个时候氢燃料会用完，它必须开始在核心中燃烧氦气，然后氦气会用完，它会开始燃烧碳，最终会用完，它会通过镁、磺胺、硅最终建立起一个铁芯，而铁芯不能再产生任何能量，所以铁芯开始坍塌。起初，铁芯可以通过量子力学效应来支撑。

你们可能听说过海森堡测不准原理，或者听说过无法同时知道粒子的位置和速度的想法。这意味着如果恒星的核心变得非常小，确实知道原子或核的确切位置，但因此你无法知道它们的移动速度。越挤压它移动得越快。该过程意味着必须在核心上进行工作。当挤压核心使其更小时，必须对其进行处理。这意味着有一种力量支撑它，所以它可以支撑恒星的其余部分。

因为当挤压它时，必须做功，可能做不到足够的工作。但最终，当你挤压它时，核心中的电子开始以光速移动，一旦它们以光速移动，狭义相对论就会告诉你它们不能再快了。到那时，不能再产生进一步的挤压。相反，整个球体都会崩溃。它从地球大小的物体坍缩到大约10公里宽的物体，然后变成中子星。所以，所有的电子都被迫进入质子，它们变成中子，有一个固体中子物体，但它很小。因为它塌缩到那个微小的物体上，所以它释放出大量的引力势能。

正是这种能量将恒星炸开并使其成为超新星。所以能量将恒星的表面推开，使其看起来很亮，但这是一个非常快速的过程。超新星的这个过程在巅峰期是几天，然后持续几个月。但是恒星的寿命很长。太阳大约有50亿年的历史，它还需要50亿年才能发生任何有趣的事情。因为恒星的寿命比超新星的时间长得多，所以除非双星系统中是两颗完全相同的恒星，否则超新星不会同时产生。因此，即使一颗恒星的质量比太阳稍微大一点，它也会演化得更快，并且它的超新星将首先出现。

所以，我认为这并非不可能，但是考虑到宇宙中的统计数据，同时产生超新星的可能性极小。如果确实同时产生了两颗超新星，那么同时形成了两颗这样的中子星会抛出很多物质，这也可能会破坏二进制文件，因为失去了太多的质量。请记住，将它们结合在一起的是两颗恒星之间的引力，扔掉了很多质量，然后它们开始分崩离析，这可能就是它会发生的事情。

我们如何确定恒星何时停止收缩？

借助量子力学，我们可以很好地理解那些快速移动的电子的物理特性，可以几乎精确地计算出发生这种情况的质量，它大约是太阳质量的1.44倍。

除了中子星的引力波，我们还有什么方法可以解决宇宙学危机（λ-CDM和哈勃常数不相容）？

它们不相容的数据很小，大约是千分之一。与天文学中的其他观测相比，我不会说这是一场危机。我认为，宇宙学家希望这是一场危机，以便他们能够研究出一些新的宇宙学。所以，我认为目前λ-CDM模型是我们拥有的最好的模型。

但主要问题是爱因斯坦方程的常数，爱因斯坦说把它放进去是他最大的错误，然而我们现在似乎有一个宇宙，我们需要这种额外的暗能量。但是我们不知道它是从哪里来的，我们也不知道我们的暗物质是从哪里来的，这同样有问题。但至少对于暗物质，我们有一些想法，可以从中找到适合暗物质的正确粒子。对于λ，暗能量，目前解释它的最佳粒子物理模型，有十到一千倍左右的误差。

但我认为整个主题是由观察引导的，而不是由模型引导的。人们肯定相信观察结果。当观察可能使模型不成功时，我们会提出一个新模型。在我的一生中，我见证了宇宙学的彻底变化，至少三倍于不同的观测结果出现。最后一个是宇宙在加速和膨胀的事实，这就是需要暗能量的原因。但那是不久前的事了，距今大约25年前。所以，也许是时候再次彻底改变模型了，但到目前为止，还没有人提出新的模型，我们也没有明显观察到它。

如果熵值趋于消失和混乱，将如何模拟天文系统？我们可以建立一个算法或模型来模拟熵吗？

我认为我们确实应该理解，至宇宙走向完全混乱，还有很长的路要走。正如我已经说过的，太阳将继续存在50亿年。一颗只有太阳质量十分之一的恒星将持续一千倍的时间。当然，这一切都取决于宇宙是否会永远膨胀下去。因为如果宇宙没有永远膨胀并再次开始坍缩，那么我们就开始限制事物，我们可以倒退，我们可以开始制造新的恒星。但目前，观测表明宇宙正在膨胀，与之相反的是黑洞。

黑洞实际上可以吸收熵。所以，虽然能量熵在增加，但如果创造了黑洞，会对宇宙的其他部分产生相反的效果。这些是重要的哲学问题，取决于你是否相信宇宙是开放的，以及你是否相信它会永远膨胀。目前的观察表明，我们不知道它是否完全开放，因为我们看不到远处。我们只能看到光的旅行时间，如果回头看相同的距离，我们就看不到宇宙的边缘。所以，我们不知道它是否是无限的，只知道它正在扩张，而且它始于一个特定的大爆炸点，但它本可以从任何地方开始并继续扩张。

有一些关于界限方面的，这些界限如何计算，人们最初是如何获得这些界限的？

目前，太阳正在失去少量的质量。所以它很慢，但我们看到了，它与磁场相互作用。如果太阳爆发很大，那么我们会看到更好的极光。或者我们甚至可以中断通信。但是当太阳耗尽了它的氢和核心时，我们形成了第一个氦核心。在氦核心点燃之前。它的收缩方式与我在超新星爆发之前提到的铁芯相同。随着它的缩小，这颗恒星会膨胀并变成一颗红巨星，它会变得几乎和地球轨道一样大。但是当它这样做时，表面上的材料就不会受到引力的束缚，因此它可以更容易地进行。

天文与哲学问题

当学习数学、物理或天文学时，您会遇到哪些其他哲学问题？

这里会涉及两个主要问题。一是这一切是如何开始的，另一个是其他星球的生命。我认为这是人们想要回答的两大哲学问题。到目前为止，我们还没有其他地方存在生命的证据。而且我们知道这些可能涉及到我们太阳系中的其他行星。我们知道可以在太阳系之外旅行，并且可以到达其他恒星。我们知道细菌可以在陨石内部生存并穿越太空，不知道持续时间有多久，但我们知道肯定存在。我们可以期待一次持续的太空之旅，但我们不能绝对确定这一点，我们确信他们可以去到火星。而且我们知道，岩石碎片已经从地球上被撞到了火星，如果我们最终没有在火星上发现生命迹象，我会感到非常惊讶，即使这种生命起源于地球。

太阳只存在了我们银河系生命的一半时间。所以在太阳之前有很多恒星，我们现在知道在我们的银河系中有大约600万颗行星围绕着恒星，比如地球，所以生命很可能起源于其他地方，它可能被其中一颗行星击落，漂浮在银河系中，并在地球形成后与地球相撞。这是一个非常有趣的哲学问题：为什么我们看不到别处的生活？对此有很多答案，我认为最好的答案是我们还不够有趣。银河系中也许有一些高级智能，但他们觉得我们无趣、因此不值得一看。

居高不下的热点话题

您如何看待或思考人类迁移到另一个星球？

太阳实际上正在以大约每年2厘米的速度增长，增长速度非常缓慢。但最终在一亿年左右之后，它会变得更热。而全球变暖会因太阳的变化而加剧。因此，在某个时刻，地球可能会变得不适合居住。而且即使我们不需要人口增长，但无论如何，我们可能想去其他地方，我们甚至没有能力将人类送上月球，更不用说去另一个星球了。长途太空旅行会遇到各种各样的困难，因为我们低估了离开地球磁场后将要经历的辐射量。

因此，必须拥有一艘非常重的LED飞船，以阻止A宇宙射线进入宇航员体内。事实上这不是我们想要做的，因为我们不想加速一个非常重的物体。所以这可能是最大的问题之一。

这也会影响计算机，导致某些组件损坏。由于某些组件会损坏，因此必须拥有一台能够对损坏进行编码的计算机。于是就有了经济问题。如果我们还不开始计划逃离这个星球，很快我们可能就没有能力了，因为我们可能已经用尽了地球上的所有资源，这些资源对于下一步行动是必要的。如果我们可以进行下一步，如果我们可以去月球或小行星并开始开采它们，在那之后，经济问题就不再是问题了。但我认为，真正离开地球，前往我们太阳系中的其他星体并实际开采它的第一步，是我们可能无法通过的第一步。

然而，另一方面，我认为这是不可避免的。一位计算机科学家告诉我，虽然有点过于乐观，但我们将不可避免地创造人工智能，人工智能将能够进行长途太空旅行，并且不会受到辐射的太大影响。人工智能没有那么重，也不需要氧气，所以我认为我们最终可能会用我们创造的人工智能更加深入了解银河系，它会在某种程度上记住我们。但是我们是否真的有人类生命能走出地球是非常值得怀疑的。我批判性地认为，国际空间站也受到地球磁场的保护，免受宇宙射线的影响。我认为这可能是我们目前最大的问题。

智能设备和编程

我们使用什么样的设备和研究天文学，我们通常能得到什么样的数据？

这在很大程度上取决于从事的领域。但显然最基本的设备是望远镜，望远镜是我们用来观察大多数事物的工具。光学望远镜是从18世纪开始开发的。现在我们有非常大的望远镜，可以满足对于不同物体的观察需要。我们有太空望远镜，基本上可以观察到想要的数据，它们可以分辨微小的物体。你可以看到像月亮上的蜡烛一样微弱的东西。也可以看到一个可能类似的星团，我不知道你是否有机会看到一个球状星团。如果有一个黑暗而晴朗的天空，你应该能够用肉眼看到Hercules中的m13。但如果你用肉眼看到它，它看起来就像一团模糊的云。如果你用一百年前的望远镜看它，你会看到中间有一个模糊的部分，边缘是地方可以看到个别的星星。

你意识到在其中某个地方有一百万颗星星，但你看不到中间的那些。但是有了哈勃太空望远镜，我们就可以看到，因为它在太空中并且没有任何来自大气的扭曲，它可以看到那个星团中间的单个恒星。我们通过使用望远镜获得了所有这些信息。还有一些其他类型的望远镜，比如射电望远镜。在第二次世界大战期间从事雷达工作的人开发出能够让他们看到来自太空的无线电波的技术。现在有非常大的射电望远镜，可以映射无线电中的各种事物。我们有X射线望远镜，有新的、下一代的太空望远镜，詹姆斯韦伯望远镜，它能观察到红外辐射。

曾经在中国，在青藏高原有一个实例，它就是这样做的。因为还需要将它们置于大气层之上。所以在观察方面，这就是数据的来源。事实上，天文学在很大程度上是以数据为主导的。目前的数据比我们所能理解的要多得多。但那是因为我们想了解特定的问题，而这些特定的问题需要更强大的望远镜。但是一旦望远镜被用于解决这个问题，它也可以用于各种其他事情。因此，我们在理论方面获得了许多其他有趣的数据。如果你看看我的领域，特别是我在看恒星革命的地方，我们为员工建模所做的就是需要了解物理学。所以我们有一组包含物理学的方程，我们必须解决这些方程。

因此，如果我们回到1960年代，人们用手动机械计算器进行这些计算，房间里挤满了人，但这是一个非常高成本的过程。然后，直到大约1980年代，我们仍然使用最强大的计算机来解决像太阳这样的单个恒星的方程。如今，我们可以在笔记本电脑上在几分钟内完成同样的计算，因为计算机已经进步了很多，开始建模更多细节。我过去所做的一件非常有趣的事情是，我们只是对恒星的结构以及它如何演化感兴趣。它看起来为什么像太阳？为什么会这样？例如，当它的氢耗尽时，它会在未来做什么。但现在我们可以对其他元素的结构产生感兴趣了。所有元素都超出了氢。本质上，氦是在恒星中产生的，但它们不是，它们不是恒星结构或其演化的基础。

所以有很多随之而来的副作用，但是有成千上万的这些反应同时发生，这样就产生了一个巨大的反应网络。为了演化所有这些反应网络的方程，现在，再次需要更多的超级计算机。在天文学的其他部分，如果你在模拟星系的形成，或者模拟宇宙如何演化，让我们看看我已经提到的球状星团的问题，那里有一百万颗恒星，每颗恒星都有引力。所以如果你要计算每颗恒星的运动方式，你需要计算所有其他恒星的引力，然后随着时间的推移对其进行积分。

如果我们回到20年前，计算机能够为一千颗恒星做到这一点。回到10年前，他们能够做到500000颗星。但是现在我们已经到了他们可以为百万美元做这件事的地步，现在我们已经到了与运算上百万颗星的地步。如果你去整个银河系，那么我们就有十亿颗恒星。因此，尽管一切都在变化，我们总是尽可能利用目前拥有的计算机不断推进。

编程技巧是天文学研究的一个非常重要的部分，那么我们通常会使用什么样的语言呢？

可以使用不同的语言，你可以使用任何你喜欢的语言。我个人仍然使用fortune，因为fortune是我们最初编写恒星革命代码的语言。它起源于 1960 年代。它在四分之一个世纪后的2000年前后有所发展。但作为一种科学编程语言，将方程式转换为计算机命令非常容易。类似地，需要一种可以编译它的语言，以便优化程序的运行。

很多人会在日常任务中使用Python，但是当涉及到进行硬核计算时，就需要一些可以尽可能优化的手段。但你使用什么语言并不重要，我认为最终这取决于将其转换为计算机实际运行的机器代码的编译器的质量。所以我们依靠计算机科学家来编写好的编译器。

不知道您有没有类似调设备的经验，比如用特殊设备拍星星。您可以描述一下细节吗？

我实际上并不经常用望远镜进行专业观察，但我参观过其中一些，并且有几次，我确实进行了专业观察。我认为我最好的一次观察是在澳大利亚天文台实现的，我在那里使用了他们的一台旧望远镜，有一个很大但看起来很旧的钠线和星星。我们试图测量恒星中钠的丰度，那是为了检验恒星中钠形成的理论。而最激动人心的体验，就是刚刚从里面出来，就有一只比我还大的大袋鼠站在外面。正如你所说，这些望远镜在偏僻的地方。我还在剑桥用望远镜设备做了一些工作，因为在剑桥，每天晚上都是阴天，所以没有很多观测机会。但我们这里有一台测量恒星无线电速度的机器。

在剑桥，有一位天文学家开发了一种测量这个的机器，它本质上是一个机械机器，和照相底片一起工作。现在，我们会再次使用CCD相机，我们使用的相机类似于手机中的相机，但价格更高。

但在那些日子里，这一切都是通过摄影完成的。他所做的就是给一颗恒星的光谱拍一张照片，再把这张照片拍成负片，然后用另一根工作人员发出的光穿过那个负片。你可以移动负片，当它与恒星的光谱完全对齐时，它会挡住所有的光。这是一种非常精确地测量恒星速度的方法，他可以测量状态，两个恒星的速度不到10公里/秒。罗杰格里芬这样做了大约40-50 年，因此它拥有最长的双星观测基线之一。我更倾向于理论而不是观察。

专业方向选择

为什么会选择在这个研究领域学习天文学？是什么让您对这个领域如此热衷？

我对物理和数学都非常感兴趣。恒星演化这个天文学的特定领域需要物理学的每一知识点，比如恒星的中心发生核反应，它们有辐射过程，表面有一些化学反应。你必须了解物理学各个方面，甚至是结晶，因为当一颗恒星死亡并变成白矮星时，它会结晶。所以，物理的每一点都会涉及到，这就是我喜欢的地方。

我在大学里教数学，也教过一些天文学的课，但是比较少，我们主要做教学和研究。我也很喜欢教书，最初我对它感兴趣的原因是，我出生在1964年，在很早的时候我几乎就能够理解登月和其中的内容。那时我对太阳系真的很感兴趣，我在学校数学和物理成绩都很好，所以我就继续学了下去。

结语

天文学在探索宇宙中的自然规律、促进其他自然学科的发展、推动技术进步和提高全民素质教育中有着不可替代的作用。多年来，国际上相继投入、使用一系列大型的先进设备，大大加快了全球天文资料共享以及天文资料处理和理论研究工作的进程，同时各国正在积极加强国际合作，共同开展天文学研究，这也极大地激发了公众的科学热情。本次教授采访进一步调动了德胜的同学们参与天文领域学习的积极性，也让同学们对该专业的研究方向有了更清晰的认识。

Interview Content

Where does the energy in the universe come from? Does this exist before the big bang happens?

In quantum mechanics, I've mentioned already, the Heisenberg uncertainty principle, which tells you that you cannot know the position of a particle and its velocity at the same time. You can, from that derive a similar uncertainty principle between energy and time. What that means is that you can borrow energy for a certain amount of time. That's essentially what happens in a big bang. You borrow the entire energy of the universe, and then it expands so fast that energy doesn't disappear again. It's similar to the idea of Hawking radiation. So if you have a black hole, the concept of a black hole is an object from which light cannot escape.

So nothing can escape from a black hole. But if you have a very thick of a small black hole, it has a very curved surface. The quantum mechanics there, can spontaneously generate energy, and therefore can spontaneously generate pairs of particles. Now, if one of those particles falls into the black hole, the other one can escape. And so your black hole is actually radiated. So you have actually created some energy out of your black hole, out of nothing. The beginning of the universe is a slightly different topology, but it's the same concept. You create your energy for some time. Some disappear, and some expand into the universe as we know it.

Do you think the extreme dimming of EPIC 204278916 observed in 2016 was caused by a Dyson Sphere?

Australian astronomers discovered this. It's an intriguing possibility. Does everybody know what a Dyson Sphere is? A Dyson Sphere, in order to increase the land mass on which you can live, you build a solid sphere shell around the star, at the same place as the earth orbit, so that you get the same radiation coming from the sun over the whole of that sphere.

It is vastly bigger than the surface of the Earth. So, you can cultivate and you can live in a much bigger area. It is sort of postulated that future, civilizations, or even our own, that might be able to build such a thing. Of course, it requires a huge amount of material, that's really one of the major problems. It may well also affect the way the sun evolves, because you're going to start sending and reflecting some of its radiation back to it. But these are problems that future engineers might be able to overcome.

So, my idea is that a star which was seen to dim gradually over a long period of time, was the result of some civilization building a Dyson Sphere around the star, cutting out its light, so that we wouldn't see it. However, I think the main problem with this is that although it took a long time to dim, it took actually a very short time compared to the time it would take to build a Dyson Sphere. If you imagine how long it takes to build a single tower block, you're talking about several years. To build something of this place, you are going to be talking about thousands of years. So, it's too fast in many ways.

The better explanations are that the star emitted some dust, and the dust was circulating around the star, and that obliterated it. Perhaps it's just some big sunspots. So, if the sunspots are on the surface of the sun, where there's a strong magnetic field, or a bit cooler, if you make one of those very big, then you can cut out quite a lot of the stars’ light, and so you would get this kind of diming. So, I think the main objection is that it's too fast to be a Dyson Sphere, unless the civilization is so advanced that they can build extremely quickly.

Is this the only star that we have seen that with such extreme dimming?

No, we see many variable stars. And in some cases, we can actually resolve the spots on the surface because the stars rotating. So, you can see that as the star is going round, the spots sometimes are in front of the star, sometimes behind it, and you get a periodic dimming. This one is not periodic, so it doesn't appear to be just something associated with the spinning of the stuff. It's changing. If it were a sunspot or a cloud of dust, it would have to be changing its shape over time.

Is it possible for two stars in a binary system to go supernova together?

What does everybody know about supernovas? There are various types of supernovas. If you take the sun, the sun is fusing hydrogen into helium in its core at the moment. That's where it's getting its energy from. It's a nuclear fusion of hydrogen healing. At some point that the hydrogen fuel will run out, and it'll have to start burning helium in the core, and then the helium will run out and it'll start burning carbon, and eventually that will run out, it will go through magnesium, sulfa, silicon. It eventually will build up an iron core, and the iron core cannot produce any more energy, so the iron core starts to collapse. At first, that iron core can be held up by a quantum mechanical effect.

You may have heard of the Heisenberg uncertainty principle, or the idea that you cannot know the position of a particle and its speed at the same time. What this means is that if the core of your star becomes very small, that means that you do know precisely where the atoms are, or the nuclear is, but therefore you can't know how fast they're moving. As you squeeze it, they move faster and faster. That process means that you have to do work on the core. As you squeeze the core to make it smaller, you have to do work on it. That means there's a force which holds it up, so it can hold up the rest of the star.

Because as you squeeze it, you'd have to do work. You can't do that work. You can't do enough work. But eventually, as you squeeze it, your electrons in the core start to move at the speed of light, and once they move at the speed of light, special relativity tells you that they can't move any faster. At that point, you can't squeeze it anymore and squeeze them into higher philosophy steps. Instead, the whole thing collapses. It collapses from something about the size of the Earth to something that's about 10 km across and becomes a neutron star. So, all of the electrons are forced into the protons, they become neutrons, and you have a solid neutron object, but it's tiny. Because it collapsed into that tiny object, it releases a lot of gravitational potential energy.

It is that energy that blows the star apart and powers it as a supernova. So that energy pushes the surface of the star off, and then it appears very bright, but that's a very quick process. This process of the supernova takes the rise time is a few days, and then it lasts for a few months. But the lifetime of the star is very long. The sun is about 5000 million years old, and it'll have another 5000 million years before it does anything interesting. So, because the lifetime of the star is so much longer than the time of the supernova, unless you get two stars in the binary system that are absolutely identical, you are not going to get the supernova at the same time. So, even if one star is even slightly more massive than the sun, it will evolve faster, and its supernova will come first.

So, I think it's not impossible, and given the number of stats in the universe, it's probably incredibly unlikely to get the supernova at the same time. If you did get a supernova at the same time, you had formed two of these neutron stars at the same time, and you'll throw off a lot of material. You'll probably disrupt the binary because you've lost so much mass. Remember, it's the gravitational force between the two stars that are holding them together. You throw away a lot of the mass, then they start to fall apart. That is probably what would happen.

How do we determine when the stars will stop shrinking?

With quantum mechanics, we can understand the physics of those fast-moving electrons very well. You can calculate almost precisely the mass at which this will happen. It's about 1.44 times the mass of the sun.

How would you model astronomical systems if entropy forces to go to death and disorder? So do you think that maybe we could set up an algorithm or a model to seem to model entropy?

I think we do understand and should be fairly well. The universe will eventually end up in complete disorder. This is a long way off. As I said already, the sun's going to last another 5000 million years. He takes a star that's only the 10th of the mass of the sun, that's going to last thousand times as long. Of course, this all depends on whether or not the universe is going to go on expanding forever. Because if the universe doesn't expand forever and starts to collapse again, then we start to constrain things, and we can go backward, we can start making new stars, even at the end. But at the moment, the observation suggests that the universe is expanding, and we'll expand forever. The opposite effect is a black hole.

A black hole can actually absorb entropy. So, although you are in an increasing energy entropy, if you create black holes, you can have the opposite effect on the rest of the universe. These are important philosophical questions that depend on whether or not you believe the universe is open or not, and whether you believe it's going to expand forever or not. Current observations suggest that we don't know if it's completely open, because we can't see beyond. We can only see as far as the light travel time, and if we look back that far, we don't see the edge of the universe. So, we don't know whether it is infinite in size. They just know that it's expanding, and that it started at a particular big bang point, but it could have started everywhere and gone on expanding.

There is something about the limit. I'm curious about how these limits are calculated. How do people get these limits at first?

So at the moment, the sun is losing a tiny amount of mass. So it's very slow, but we see it. It interacts with the magnetic field. And if there's a big outburst from the sun, then we see a better aurora. Or we can even disrupt communications. But when the sun has exhausted its hydrogen and core, we form the first helium core. And before that helium core can ignite. It shrinks in the same way as I mentioned for the iron core before the supernova. As it shrinks, the star expands and becomes a red giant, and it'll get almost as big as the earth's orbit. But as it does that, it's the material at the surface is then not so gravitationally bound, and so it can much more easily.

So I want to say that what other philosophical questions that you encounter when you have your study math or physics or astronomy?

There are always two main questions.One is that how it all begins. And the other one is their life elsewhere. I think those are the two big philosophical questions that people want to answer.We have so far no evidence of life elsewhere. And we know that these can travel to other planets in our solar system. We know that they can also travel outside our solar system, and they can reach other stars. We also know that bacteria can survive inside the meteorite and travel through space. We don't know for how long they can do that, but we know they can do it for certainly. We can expect them to last a space journey, but we can't be absolutely certain of that. But we know for sure that they could get Mars. And we know that pieces of rock have been knocked off the Earth and gone to Mars, though I would be very surprised if we don't eventually find signs of life on Mars, even if that life originated on the Earth.

The sun only exists for half the lifetime of our galaxy. So there were a lot of stars around before the sun, and we now know that there are about 6 million planets in our galaxy, like the Earth, around stars, and so it's very likely that life possibly originated and elsewhere, and it could have been knocked off one of those planets, been floating around in the galaxy, and collided with the Earth after it formed. So this is a very interesting philosophical question. You always have to also ask, why do we not see life elsewhere? There are a number of answers for that. My best answer is that we're just not interesting enough yet.So I think perhaps there is some superior intelligence in our galaxy, but they find us uninteresting and therefore not worth looking at.

How do you view or think about the human being, we migrate to another planet?

The sun is definitely going to get a lot hotter. The sun is growing actually, and about, 2cm a year. And so it's very slow, but eventually after a thousand million years or so, it'll be significantly hotter. And the global warming, we already know is the problem, but it'll be exacerbated by the grace of the sun. And so it's at some point the Earth is probably going to become uninhabitable. And even if we don't have to be population growth, but whatever, we may want to go elsewhere, we don't even have the ability to descend men to the moon, let alone to another planet. And there are all sorts of difficulties with a long space travel journey because we underestimate the amount of radiation that is going to be experienced once you get out of the earth's magnetic field.

So you'd have to have a very heavy LED ship, for instance, to stop the A cosmic rays from getting into the astronauts. And that's not what you want to do. So, you don't want to have to accelerate a very heavy object. So that may be one of the biggest problems, and that would also affect computers.

You know that some of your components are going to get damaged, you have to have a computer that's able to code that damage. So there is the economic problem. If we don't start escaping from this planet, soon, we may run out of the ability to do it, because we may have used up all the resources on the earth that would be necessary to make the next step. If we can make the next step if we can go to the moon or asteroids and start mining them, then after that, the economic problem becomes less of a problem. But I think the first step of actually leaving the Earth, going to some other object in our solar system and actually mining it, is one that we may not pass.

However, on another note, I think it is inevitable. A computer scientist will tell me that I'm being optimistic here, but I think it's inevitable that we will create artificial intelligence, and that artificial intelligence will be able to make long space journeys and will not be affected so much by the radiation, and is not so heavy, mustn't require oxygen. And so I think we will probably eventually colonize the galaxy with artificial intelligence that we have created, and so it will remember us at some level. But whether we actually have human life going beyond the Earth is very questionable. And I think critically, the International Space Station is also protected by the earth's magnetic field from the cosmic rays. That I think is probably the biggest problem we have at the moment.

What kind of equipment do we use and research of astronomy, and what kind of data do we usually get?

Well, that very much depends on the field that you're working in. But obviously, the fundamental piece of equipment is the telescope.So the telescope is what we use to see most things. And so optical telescopes have been developed since the time of gathering there, and which was the 18th century. And now we have very large telescopes that can feed to very different objects. And we have space telescopes that can see essentially very clearly, so they can resolve tiny objects. You could see something as faint as a candle on the moon. You can look at a probably like cluster of stars, which I don't know whether you had the opportunity just to look at a globular cluster. But if you see it with a naked eye, it just looks like a fuzzy cloud. If you look at it with a telescope that we would have had a hundred years ago, you can see that there's a fuzzy part in the middle, and then on the edge, you can see individual stars.

And so you realize that it's a million stars in one place, but you can't see the ones that are right in the middle. But then with the Hubble Space Telescope, we are able to look, because it's in space and it doesn't have any distortion from the atmosphere, it could look at the individual stars right in the middle of that cluster. And so that's supposed. We've gained all of that information by using telescopes. Then we've introduced other kinds of telescopes. Radio telescopes were the next ones. So mostly people working on radar during the 2nd World War, develop techniques that allowed them to see radio waves coming from space. And now there are very large radio telescopes that can map all sorts of things on the radio. We have X ray telescopes, we have the new, the next generation space telescope, the James Webb Telescope, that's going to look at it, infrared telescope, infrared radiation.

You used to have one in them in China, on the Tibetan plateau, which does that. Because you need to get those well above the atmosphere as well, so that's on the observational side. That's where the data comes from. And in fact, astronomy is very much data led. There's much more data than we can understand at the moment. But that's because we want to understand particular problems, and those particular problems require more powerful telescopes. But once the telescope has been used for that problem, it can then be used for all sorts of other things as well. And so there's a lot of other interesting data that we get on the theoretical side. And if you look at my field, in particular, where I'm looking at Stellar Revolution, what we do to model a staff is e need to understand the physics. And so we have a set of equations that encompass physics, and we have to solve those equations.

And so if we go back to the 1960s, people were doing these calculations by hand, with hand mechanical calculators, rooms full of people, but then a very expensive process. And then, up until about the 1980s, we were still using the most powerful computers that were built to do this just to solve the equations for a single star like the sun. Nowadays, we can do those same calculations in a few minutes on a laptop, because computers have advanced so much. What we can do instead then is to start modeling more details. One thing that is very interesting, and what I do is to in the past, we were just interested in the structure of the star and how it would evolve. How does the sun look? Now, why is it like that? What's it going to do in the future, when its hydrogen runs out, for instance. But now we can be interested in the production of other elements. All elements are beyond hydrogen. Helium, essentially, is produced in stars, but they're not, they're not fundamental to the structure of the star or its evolution.

So there are very much side reactions. But there are thousands of these reactions going on at the same time. And so that produces a huge network of reactions. And in order to evolve the equations for all of those networks of reactions, now, again, requires some more supercomputers. In other parts of astronomy, if you're modeling galaxy formation, or simulations of how the universe evolves, let's look at the problem with the globular cluster that I already mentioned, where you have a million stars, and each star has a gravitational attraction on every other star. And so if you're going to calculate how each star moves, you need to calculate the gravitational force from all the other stars and then integrate that over time.

And if we go back 20 years, our computers were capable of doing that for a thousand stars. To go back ten years, they were able to do 500000 stars. But now we're getting to the point where they can do it for the million the and that now we're getting to the point where you can realistically model these clusters of stars. Then if you go to the whole galaxy, then we've got a billion stars. So though that is, they are pushing, we are always pushing toward the limit of what we can do with the computers that we have at the moment.

So that the programming skill is a very important show the research of astronomy. So what kind of language will we usually use?

You can use different languages. You can use whatever language you like.And I personally still use fortune, because fortune was the language that we originally wrote the Stellar Revolution codes in. So it originated in the 1960s. It was developed until a quarter in 1995, in about 2000. But as a scientific programming language, it's very easy to convert your equations to your computer commands. And it's similar to see, you want a language where you can compile it so that you can optimize the running of the program.

And a lot of people will use Python for everyday tasks. But when it comes to when it comes to doing the hardcore computing, you need something that you can optimize as best you can. but it doesn't really matter what language you use. I think ultimately, it depends on the quality of the compiler that converts that into the machine code that the computer actually runs on. So we rely on computer scientists to write good compilers.

I don't know if you have any experience of adjusting cameras, like using special equipment to shoot stars. Do you have some of those descriptions or details about that?

I don't actually often go to the telescopes for observing professionally, but I have visited some of them, and a couple of times, I did observe professionally. I think my best experience was that the mounts from the observatory in Australia where I was using one of their old telescopes. There was a big, but old to look at and sodium lines and stars. So we were trying to measure the abundance of sodium in stars. And that was to test the theory of the formation of sodium in stars. And the most exciting experience was that was just coming out of the dam, and now the huge kangaroo, bigger than me, standing outside. As you say, these telescopes are in the middle of nowhere. I've also worked a bit on telescopes here in Cambridge, because in Cambridge, it's cloudy every overnight, so well, there's not a lot of things you can do. But what we do have here is a machine that measures the radio velocity of stars.

And so in Cambridge, there was an astronomer who developed a machine for measuring this, and it was essentially a mechanical machine, so and worked with photographic plates. CCD, nowadays, in modern times, we would use the CCD cameras again, that we use is similar to what's in a mobile phone, but more expensive ones.

But in those days, it was all done photographically. So what he did was to take a photograph of the spectrum of a star and make a negative of that photograph, and then shine the light from another staff through that negative. And so when you can then move the negative, and when it's perfectly aligned with the star spectrum of the star, it blocks out all the light. And so that was a way of measuring very accurately the velocity of the stars, and so he could measure the state, the velocity of the stars, two less than 10 km/s. And he passed away. Now, Roger Griffin was his name, but he did that for 40，50 years. And so it has one of the longest base lines for observing binary stars. I am rather much more on the theories side than the observation of life.

I want to ask why would you choose to study astronomy, in this study field? What makes you so keen about your study area?

I'm very interested in all sorts of physics and mathematics. My particular area of astronomy, the evolution of stars, requires every single bit of physics, because stars have nuclear reactions going on in their centers. They have radiation processes. There is chemistry at the surface. You have to understand all sorts of physics, even crystallization, because when a star dies and becomes a white dwarf, it can crystallize. So, every bit of physics is involved. That's what I like about it.

I actually teach mathematics at the university, but I also teach some astronomy courses, but there are fewer of them. So, we do back teaching and research. I quite enjoy teaching too. What got me originally interested in it, was when I was born in 1964, I was just about able to understand the moon landings and inside that. I got really interested in the solar system at that point and then I was good at mathematics and physics at school, and so I just carried on with it.

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