Here are some images of clusters of galaxies.
They're exactly what they sound like.They are these huge collections of galaxies,bound together by their mutual gravity.So most of the points that you see on the screen are not individual stars,but collections of stars, or galaxies.Now, by showing you some of these images,I hope that you will quickly see that galaxy clusters are these beautiful objects,I think galaxy clusters are mysterious,Useful as the universe's most massive laboratories.And as laboratories, to describe galaxy clusters is to describe the experiments that you can do with them.就像描述实验室一样，要描述星团，就要去描述你能够通过它们做的实验。And I think there are four major types,and the first type that I want to describe is probing the very big.Well, here is an image of a particular galaxy cluster.It is so massive that the light passing through it is being bent, it's being distorted by the extreme gravity of this cluster.它的质量非常大，以至于光在经过的时候，由于其引力的作用而变弯了。And, in fact, if you look very carefully you'll be able to see rings around this cluster.事实上，如果你仔细看，能够看到这个星团周围的光环。Now, to give you a number,this particular galaxy cluster has a mass of over one million billion suns.It's just mind-boggling how massive these systems can get.But more than their mass,they have this additional feature.They are essentially isolated systems,so if we like, we can think of them as a scaled-down version of the entire universe.如果愿意的话，我们可以将它们想象为整个宇宙的缩小版本。And many of the questions that we might have about the universe at large scales,such as, how does gravity work?might be answered by studying these systems.The second things is very hot.Okay, if I take an image of a galaxy cluster,and I subtract away all of the starlight,what I'm left with is this big, blue blob.It's actually X-ray light that we're seeing.And the question is, if it's not galaxies,what is emitting this light?million-degree gas in fact, it's plasma.And the reason why it's so hot goes back to the previous slide.The extreme gravity of these systems is accelerating particles of gas to great speeds,and great speeds means great temperatures.So this is the main idea,but science is a rough draft.There are many basic properties about this plasma that still confuse us,关于等离子气体，还有很多基本性质的问题仍让我们困扰，and still push our understanding of the physics of the very hot.Third thing: probing the very small.Now, to explain this, I need to tell you a very disturbing fact.Most of the universe's matter is not made up of atoms.Most of it is made up of something very, very mysterious,which we call dark matter.Dark matter is something that doesn't like to interact very much,and of course we would like to learn more about it.If you're a particle physicist,you want to know what happens when we smash things together.And dark matter is no exception.I'm going to have to ask another one,which is, what happens when galaxy clusters collide?Since galaxy clusters are representative slices of the universe, scaled-down versions.They are mostly made up of dark matter,and that's what you see in this bluish purple.The red represents the hot gas,and, of course, you can see many galaxies.What's happened is a particle accelerator at a huge, huge scale.And this is very important,because what it means is that very, very small effects that might be difficult to detect in the lab,因为这意味着，在实验室里某些因为太小而很难检测到的效果，might be compounded and compounded into something that we could possibly observe in nature.The reason why galaxy clusters can teach us about dark matter,the reason why galaxy clusters can teach us about the physics of the very small,is precisely because they are so very big.Fourth thing: the physics of the very strange.Certainly what I've said so far is crazy.Okay, if there's anything stranger I think it has to be dark energy.If I throw a ball into the air,What I don't expect is that it go up at an ever-increasing rate.Similarly, cosmologists understand why the universe is expanding.They don't understand why it's expanding at an ever-increasing rate.They give the cause of this accelerated expansion a name,and they call it dark energy.And, again, we want to learn more about it.So, one particular question that we have is,how does dark energy affect the universe at the largest scales?Depending on how strong it is,maybe structure forms faster or slower.Well, the problem with the large-scale structure of the universe is that it's horribly complicated.Here is a computer simulation.And we need a way to simplify it.Well, I like to think about this using an analogy.If I want to understand the sinking of the Titanic,the most important thing to do is not to model the little positions of every single little piece of the boat that broke off.最重要的事情不是去模拟每一片断裂的小碎片的每一个位置。The most important thing to do is to track the two biggest parts.Similarly, I can learn a lot about the universe at the largest scales by tracking its biggest pieces and those biggest pieces are clusters of galaxies.同样，我可以通过追踪宇宙的最大的部件来学到宇宙大尺度的很多信息，而这最大的部件就是星团。So, as I come to a close,you might feel slightly cheated.I mean, I began by talking about how galaxy clusters are useful,and I've given some reasons,but what is their use really?I want to give you a quote by Henry Ford when he was asked about cars.He had this to say:If I had asked people what they wanted,they would have said faster horses.他说，如果我之前问人们他们想要什么，他们只会说更快的马。Today, we as a society are faced with many, many difficult problems.And the solutions to these problems are not obvious.They are not faster horses.They will require an enormous amount of scientific ingenuity.So, yes, we need to focus,yes, we need to concentrate,but we also need to remember that innovation, ingenuity, inspiration,these things come when we broaden our field of vision when we step back when we zoom out.但我们也要记得创造力、新颖的主意、灵感，这些是在我们开阔眼界时产生的，当我们退后一步，当我们把画面拉远And I can't think of a better way to do this than by studying the universe around us. Thanks.我想不出更好的办法做这件事，除了研究我们头顶的宇宙。谢谢。
TED演讲80篇