星星是如何诞生的?

为什么有些明星是第二代?为什么打哈欠会传染?为什么月球在离我们远去?直播延迟的原因是什么?为什么不能把金属放进微波炉?恒星是如何形成的?另外，器官移植发现。克里斯·史密斯与优西比乌斯·麦克凯萨一起寻找答案……

优西比乌斯:我们的科学故事很吸引人。生物工程师——他们离实验室培养的肺有多近?

克里斯-是啊，很神奇，不是吗?我们知道全世界有数百万人需要器官移植。我们知道成千上万，如果不是成千上万，如果不是成千上万的人死在器官移植的等待名单上，这包括心脏移植，肺，肝脏，肾脏等等。最大的挑战是没有足够的捐助者。通常，那些死时拥有可用器官的人并不愿意，或者没有表明他们愿意捐献器官。而且，我们从人身上恢复的许多器官，在他们死亡的时候，已经不适合移植了这就是为什么我们有这么严重的问题。科学家们真正希望能够做的是为我们培育新的人体器官，以取代那些已经老化的器官。本周我们离成功又近了一步，因为乔·尼科尔斯，她是德克萨斯大学医学分部的研究员，她发表了一项技术，可以培养出人类大小的肺，并证明它们可以成功地移植到猪身上。现在是很早的时候，所以人们必须谨慎地解读它。动物数量很少，他们只在四头猪身上做过实验。 But what they do is they take a lung, and at the moment they're just using another pig lung, but you could imagine how you could take a lung from anywhere. They decellularise it; now what that means is you put it in a special solution that can remove all of the cells that are there and it leaves behind a scaffolding of connective tissue that sort of lung shape. And also, critically, has the right guidance signals that would direct cells, if they're applied to it, where to go, what to turn into, and how to grow and organize themselves. They then take all of the cells from another lung, put the scaffold into what they call a bio reactor, which is basically a big vat of a culture or growth medium with growth factors and oxygen added. They then added the cells and they do it in a certain set of stages, so you put the right cells in at the right time. The cells go onto the scaffolding, which has been pre-coated with the special hydrogell, a sticky material which has got growth factors in it. The cells take up residence on the scaffolding and then over a 30 day period they turn into an immature lung. And this, the researchers were then able to implant into one of their four pigs and they were able to demonstrate that these animals will survive up to two months. They've only taken experiment to two months at the moment but the lung seems to be okay. The tissue seems to perform, the blood vessels all work, it can be plumbed in. So the next stage will be to go a step further and see if it actually works properly as a lung, not just being wired into the blood supply but also can do gas exchange. But this is really phenomenal because it gives us an opportunity now to begin to push the boundaries of actually taking say a human lung that wouldn't be suitable for transplantation right now, getting the cells off of it and getting rid of those, and using that scaffolding to then repopulate it with new healthy cells and then put that into a person. So we're very close to this now. I think this is a wonderful piece of research. It's in Science Translational Medicine this week.

优西比乌斯——非常令人兴奋。安德鲁，早上好。

安德鲁-你好，尤西比乌斯。克里斯博士，我想知道为什么太阳被称为第二代黄星，我想知道哪些是第一代恒星或黄星?如果它是一颗白星，它会比现在产生更多的热量吗?

克里斯-你好，安德鲁。当我们谈论天上的星星。宇宙中大概有1000亿个星系每个星系中大概有1000亿颗恒星，简单点说。所以如果你凝视宇宙，我们会认为有22个0后面跟着1，但它们并不都是一样的。恒星的形状和大小各不相同我们的恒星，太阳，和你们发现的许多恒星相比是相当小的，但是恒星的大小影响它的大小，它燃烧的温度，燃烧的速度，因此，它的最终命运是什么。小恒星会燃烧很长时间，非常缓慢，但它们很冷——因为它们不会产生大量的热量，当它们结束生命时，它们只是缩小成一点煤渣。还有一些非常非常大的恒星。可能是太阳的100倍或更多它们燃烧得非常热，非常快，它们以巨大的超新星爆炸灾难性地结束了自己的生命。当我们谈论恒星的世代时，我们也在考虑宇宙的年龄因为宇宙大约有138亿年的历史。我们的恒星可能会燃烧100亿年，它现在大约有50亿年的历史，所以它的生命已经过去了一半。 So in the universe we've got generations of stars that were some of the first stars to form when the universe was really young, and then we've got newer stars being born today. So we talk about different generations of stars that have come along from the time that the Big Bang began. And it's all to do, the life and death of those stars, with how big they are, therefore how much fuel they've got, how much gravity they've got compressing that fuel and, therefore, how fast they burn off their fuel.

优西比乌斯:10点14分，如果你刚刚打开电视。当然，你听到的是克里斯熟悉的声音，裸体科学家。奥利弗，早上好。

奥利弗:早上好，优西比乌斯。一个简单的问题。为什么打哈欠会传染?

克里斯-嗨，奥利弗。你说这很简单。我想我们应该请你来回答这个问题。

优西比乌斯-我就是这么想的。

Oliver:你刚才说的是把天上的星星比作打哈欠的人。

克里斯:有道理。当我们刚刚讨论宇宙的起源和那里的恒星时，它确实看起来更平凡，不是吗?答案是，我们不知道它为什么会传染，但我们知道它似乎很常见，不仅在人类中，在其他物种中也很常见。前几天有人写信给我，问我你能从你的猫身上传染到打哈欠吗?他说他看到他的狗或猫打哈欠，这让他想打哈欠。答案是肯定的，其他动物也会打哈欠，它们也会传染给我们，所以这是一种视觉上的东西。当我们看到别人打哈欠时，我们也想打哈欠。有一些理论。有一种理论认为，这有一种唤醒或警觉性的效果。其中一个原因可能是，当你打哈欠时，它有一种冷却大脑的效果，因为它会将冷空气吸入靠近大脑的血管连接处，这可以带走血管中多余的热量，帮助你的大脑降温。 The brain temperature rises with fatigue, so if you are tired and your brain temperature goes up you can offset some of the fatigue inducing effects of that thermal increase by breathing in some cool air. One suggestion is that if your sort of winding the clock back to our evolutionary origins, if you are a group of people, humans are all sitting together as a social species. We know that we were better off in numbers than operating in isolation. If one person's feeling fatigued it's likely that the others are too. So if one person yawns and makes themselves more alert then other people catch that yawn and other people yawn sympathetically, they also become more alert. The likelihood of everyone dropping off to sleep and then becoming lunch for a wild animal is reduced and that might be one reason why yawning has evolved to be contagious. But it doesn't appear to be just humans. You can catch yawns off your pets and your pets can catch yawns off you, as far as we know.

优西比乌斯-默文，早上好。欢迎来到我们的节目。你想问克里斯什么?

Mervin -非常感谢你的宝贵时间。我听说月球正在远离地球——距离在增加。重力不是应该向我们拉回来吗?如果它离我们那么远，地球上的生命会受到什么影响?

克里斯-谢谢你的问题。你提出了一个非常有趣的观点。我们知道月球正以每年大约2厘米的速度远离地球。我们之所以知道这一点，是因为阿波罗计划的其中一个任务在地球表面放置了一面镜子，科学家们正在从地球表面向月球表面发射激光，激光在镜子上反射，并计算出光完成这一旅程所需的时间。因为我们知道光的传播速度，所以如果我们计算光到达和返回的时间，我们就能非常精确地知道月球离我们有多远，这就是我们知道它在远离我们的原因。问题是为什么月球在远离我们?月球大约有45.7亿年的历史;它形成于地球非常年轻的时候。最初形成是因为两颗行星在大致相同的轨道上，它们相撞，另一个叫做西娅的天体撞向地球并从地球表面喷射出大量物质然后在地球周围形成了一个大包裹层或裹尸布。这些覆盖物慢慢地结合形成了我们的月球，这就是为什么月球与地球的比例如此之大。 But the Moon, as it's quite close to the Earth is obviously sitting in orbit around the Earth. It takes a month for the Moon to go right round the Earth once, but the Earth turns inside the Moon every day. So the Earth turns once every 24 hours and that's why we have tides because the moon is pulling water on the surface of the Earth towards itself. But because the Earth is turning, the bulge of water on the side of the Earth close to the Moon is actually slightly ahead of the position of the Moon in the sky because the Earth is turning and it's pulling that bulge with it. So what that means is that there's a very slight torque or pull on the Moon from the bulge of water on the Earth's surface which is slightly ahead of the Moon's position and that means that the moon is feeling an acceleratory force from the Earth's surface. It's a bit like you whirling a ball on a string and you whirled the ball a bit harder, it tries to pull the string through your fingers. So the moon is actually getting a bit of energy all the time from the Earth, from the Earth's spin and this has the effect actually of making the Moon move slightly further away from the Earth. So that's why the the Moon is moving that two centimeters or so away from the Earth every year. It's going to take a really long time though before the Moon goes any appreciable distance. It has made a difference though because when the moon was much younger it was much closer to the Earth's surface, and we know that because we can see the patterns of the tides that it made written into the fossil record. You can see the heights of those tides, which would have been huge in comparison to today, because gravity obeys an inverse square law, so the effect would have been magnified historically. And as the Moon moves away our tides will become slightly smaller, but because it's creeping away ever so slowly it's not actually going to make a big consequence for us or anything in any time soon. So don't worry, we're not going to lose the Moon but it is moving away from us.

优西比乌斯-克里斯，在我们开始讲科学教育之前我能问你一个问题吗?只是我突然想到的一个想法。可悲的是，这个国家的脱口秀节目都是由男性主导的。但即使按照男性主导的正常标准，我发现这个节目中90%以上的科学问题都是男性听众提出的。现在女性也可以告诉我原因，我想知道你在科学方面的公共教育经验，以及英国是否做了什么?在男生和学生中有哪些人对你试图推广的关于性别的科学研究感兴趣?只是我的一个想法。

Chris:非常有趣的问题;有些人显然在许多国家对此进行了调查因为他们也观察到存在相当大的分裂。问题不在于让男女都对科学感兴趣。事实上，我们在英国和澳大利亚招聘人员没有问题，我非常仔细地研究了这两个地方的数据，因为我在这两个地方都工作。事实上，我们发现在澳大利亚上大学，接受高等教育65%的大学生是女性。所以我们在吸引女孩接受高等教育方面没有问题，当然我们在吸引女性接受高等科学教育方面也没有问题。如果你看看英国和澳大利亚的博士生人数——你知道，这是两个可比较的经济体——实际上女性的人数是相等的，如果不是略多于男性的话。在英国的医学院，大约55%到56%进入医学院的人是女性。然后你会问，“那么，那些更上层的人怎么办?”他们会坚持下去，成为这个领域的专业人士吗?” And the answer is that after they get their higher qualifications there is an exodus. So the question we should be asking is not actually how to push people into these things, but how to make the system change in a way that means that it is more supportive for everybody, because what does happen is that people go off and have babies. And when when they have babies the system is completely unsupportive for family life, whether you're male or female. And, actually, if you think about it you've got a grant, and that grant is funding your research, and the clock is ticking and you go off and have your maternity or paternity leave. It doesn't matter who goes off and has their leave, the grant doesn't stop. The world of research doesn't stop and it's very hard to then then juggle having a young baby, having families, getting grants and keeping your career on track. So lots of people think, "you know what, I don't think this is the life for me, or I don't think being Professor of Surgery is the life for me because I can't walk off the operating table and go and pick my kids up from nursery at five o'clock!" And so the system selects for a very specific group of people. And until we fix the system you can have all of these ambassadors and you can have all of these people in as role models and everything but the system is broken, and until we fix the system it's actually just always going to relapse to type. So I'm very pro helping to improve the system, because if we improve the system everything gets better for everybody.

优西比乌斯——有道理。[**]，早上好。欢迎收看今天的节目。(随机噪声……)

Chris -我很喜欢，这很有趣!

优西比乌斯:啊。我笑的部分原因是因为我能看到她想问你的问题，而这里模糊的噪音实际上，以一种迂回的方式，与她的问题有关。她想知道为什么这些收音机从来没有像你在房间或车里从手机切换到旧的无线设备时那样同步?从一台设备到另一台可能会有一到两分钟的延迟。

克里斯:好吧，希望不是一两分钟，但肯定有几秒钟你会注意到不同。老式的无线电设备就不一样了，它们是模拟的，模拟信号进来后，很快就会通过电子设备处理。它们处理事物的方式差别很小所以你得到的声音在所有设备上几乎是同步的。但是在数字时代，有很多原因可以解释为什么会有延迟和不同的延迟。换句话说，信号从发射器发出，然后从设备的扬声器发出之间存在滞后。现在音频处理非常快。这些设备有微秒级的延迟。但是如果你调到互联网，因为互联网是一个完整的连接或相互连接的站点网络，那么信息到达你的电脑的速度就会有不同的延迟或延迟。然后在你的电脑上，它被重新组合起来，有点像你从马赛克中构建一幅画，许多小碎片被重新组合成一幅大图画。这一切都需要时间，信息从源到你的电脑的路径可能不同于它到别人的数字收音机的路径，或者从一个收音机到另一个收音机的路径。 So there's processing delays in actually getting the information to your device. There's transmission delays, and then there's recompiling delays. And these all differ between different devices and so that's why you get variable lag in this digital era between different devices.

优西比乌斯:好的。西奥，早上好。谢谢你的坚持。你想问什么?

西奥-早上好，克里斯博士。你不允许把金属物品放在微波炉里，因为它会产生火花，但微波炉里面是内衬金属的。为什么呢?

克里斯-你好西奥。事实上，严格来说，你不能把金属物体放进微波炉里。你得小心哪种金属物品。如果你在你的麦片碗里放一个勺子——比如说你在煮粥或者其他什么东西，你用勺子搅拌它，实际上一个又大又厚的重型钢勺子不会造成问题。这是因为当你把勺子放进微波炉时，金属就会像天线一样接收微波并将其转换成电流在金属内部流动。一个大的钢勺子，刀叉或其他东西的内阻非常小，所以电流会向前和向后流动。没问题，它只会让金属变热。不安全，不明智，因为你可能会烧伤自己，但这可能不会造成大问题。当你把像脆皮袋这样的东西放在我们的网站nakedscientist.com/experiments上，你可以找到我们这样做。或者如果你放一个金边的陶器，虽然我没有，但是你可能有，如果你把它放进微波炉很薄的金属实际上是一个相对较差的导体，因为它通常在金属上有很小的间隙或断裂，或者金属很快就会加热，扭曲变形，打开一个间隙。 And what happens is that this charge which is surging around trying to make a circuit hits this gap and it has to jump over the gap, and that's what makes the spark. And that's why things go zap and snap in the microwave when you when you put little bits of metal in there. The inside cavity of the microwave oven is metallic because what it's effectively doing is acting as a mirror and it's producing microwaves on one side of the oven. Those go across as a wave with a wavelength of about 12 centimeters across the inside of the oven, and then they hit the opposite side, bounce or reflect off ,and come back mapping onto themselves. And that makes what we call a standing wave, which is how it does the heating effect. The grill on the front is almost like a sheet of metal except it's got little holes in it, which enable you to see what's going on because the size of the microwaves are much bigger than the size of the visible light waves. So the visible light can get out but the microwaves can't come out and cook you. So it doesn't matter that the microwave is made of metal, it's actually there to shield the room and stop the microbes escaping and also to reflect them back onto themselves so you get good cooking.

优西比乌斯:好的，我们可以挤出最后一个问题。有两个来电者。选一个数字，克里斯2号还是8号。

克里斯:这次我选8个。

优西比乌斯:好的。出于兴趣，第二个问题应该是关于地热能深入地球的问题。为什么不是这样呢?但是数字8中了彩票。理查德，你有什么问题要问克里斯?

理查德:你谈到了恒星，恒星的生命，以及它们是如何结束的。但恒星最初是如何形成的呢?

优西比乌斯:好的。

克里斯-早上好，理查德。实际上，宇宙中充满了气体和尘埃粒子。大爆炸的产物主要是氢——大量的氢——一些氦，然后是少量的锂——这三种元素。所以宇宙中有很多这样的气体和尘埃袋到处飘荡。在重力的影响下，这些气体开始结合并结合。有些东西可能会给它一个轻推，鼓励它向自己坍塌一点。例如，我们认为太阳的形成是因为我们附近的另一颗恒星爆炸了，产生了冲击波，把一些气体聚集在一起，促使重力的作用占主导地位。一旦你有了一个大的物质体，它开始向自己集中，它就会吸引更多的东西和更多的气体，从而压缩已经存在的气体。你可以看到这是怎么回事。当你到达像恒星一样大的物体时，实际上它很重，质量很大，有很大的引力推动并加速了中心的粒子它可以克服粒子之间的自然排斥它们开始融合，你开始融合氢和氢。 Four hydrogen atoms fuse to make an atom of helium and as they do so they release a lot of energy. And once you've got some energy you start making particles ram into each other even harder, so the whole thing goes into a sort of positive feedback loop making a fusion reactor. And so that's how star gets ignited in the first place. And it will burn for as long as it's got fuel to burn. Initially it will burn the hydrogen because that's the easiest, and then as it starts to make more complex elements like helium, lithium, brillion, boron, carbon, nitrogen, it begins to do what we call nucleosynthesis. And you add more elements to bigger elements and you get even bigger elements up to a point of about iron. And then when the star gets to the end of its life and goes bang, if it's a really big star and has a supernova, you get such a powerful shockwave when that happens that you then make even more big heavy elements like uranium in the outer shell of that star as it blasts itself to pieces. And the gold and all the other heavy stuff that's in your body right now was made because another star was born, died and blew itself to pieces, and blew all that stuff out into space which eventually coalesced in our neck of the woods and made us billions of years later, which is an extraordinary thought isn't it?

尤西比乌斯-克里斯，非常感谢你与我们分享你的科学知识。

克里斯-很高兴见到你。谢谢每一个人。再见。再见再见!