演說(shuō)者：Tabetha Boyajian
演說(shuō)題目：宇宙中最詭異的恒星！
一個(gè)巨大、地球1000倍大小的物體遮蔽了遙遠(yuǎn)的一顆名為KIC 8462852的星星，但沒(méi)人可以確知那是什么樣的物體。在天文學(xué)家塔貝莎．菠耶金調(diào)查這顆巨大、奇特的物體可能是什么的時(shí)候，她的一位同事有個(gè)奇特的猜想：會(huì)不會(huì)是外星文明蓋的巨型建筑結(jié)構(gòu)呢？這樣超凡的想法，需要超凡的證據(jù)。這場(chǎng)演講，菠耶金將帶我們一起來(lái)看看面對(duì)未知事物時(shí)，科學(xué)家如何研究和驗(yàn)證假說(shuō)。
Extraordinary claims require extraordinary evidence, and it is my job, my responsibility, as an astronomer to remind people that alien hypotheses should always be a last resort.
00:29
Now, I want to tell you a story about that. It involves data from a NASA mission, ordinary people and one of the most extraordinary stars in our galaxy.
00:41
It began in 2009 with the launch of NASA's Kepler mission. Kepler's main scientific objective was to find planets outside of our solar system. It did this by staring at a single field in the sky, this one, with all the tiny boxes. And in this one field, it monitored the brightness of over 150,000 stars continuously for four years, taking a data point every 30 minutes. It was looking for what astronomers call a transit. This is when the planet's orbit is aligned in our line of sight, just so that the planet crosses in front of a star. And when this happens, it blocks out a tiny bit of starlight, which you can see as a dip in this curve.
01:31
And so the team at NASA had developed very sophisticated computers to search for transits in all the Kepler data.
01:39
At the same time of the first data release, astronomers at Yale were wondering an interesting thing: What if computers missed something?
01:52
And so we launched the citizen science project called Planet Hunters to have people look at the same data. The human brain has an amazing ability for pattern recognition, sometimes even better than a computer. However, there was a lot of skepticism around this. My colleague, Debra Fischer, founder of the Planet Hunters project, said that people at the time were saying, 'You're crazy. There's no way that a computer will miss a signal.' And so it was on, the classic human versus machine gamble. And if we found one planet, we would be thrilled. When I joined the team four years ago, we had already found a couple. And today, with the help of over 300,000 science enthusiasts, we have found dozens, and we've also found one of the most mysterious stars in our galaxy.
02:44
So to understand this, let me show you what a normal transit in Kepler data looks like. On this graph on the left-hand side you have the amount of light, and on the bottom is time. The white line is light just from the star, what astronomers call a light curve. Now, when a planet transits a star, it blocks out a little bit of this light, and the depth of this transit reflects the size of the object itself. And so, for example, let's take Jupiter. Planets don't get much bigger than Jupiter. Jupiter will make a one percent drop in a star's brightness. Earth, on the other hand, is 11 times smaller than Jupiter, and the signal is barely visible in the data.
03:26
So back to our mystery. A few years ago, Planet Hunters were sifting through data looking for transits, and they spotted a mysterious signal coming from the star KIC 8462852. The observations in May of 2009 were the first they spotted, and they started talking about this in the discussion forums.
03:47
They said and object like Jupiter would make a drop like this in the star's light, but they were also saying it was giant. You see, transits normally only last for a few hours, and this one lasted for almost a week.
04:01
They were also saying that it looks asymmetric, meaning that instead of the clean, U-shaped dip that we saw with Jupiter, it had this strange slope that you can see on the left side. This seemed to indicate that whatever was getting in the way and blocking the starlight was not circular like a planet. There are few more dips that happened, but for a couple of years, it was pretty quiet.
04:26
And then in March of 2011, we see this. The star's light drops by a whole 15 percent, and this is huge compared to a planet, which would only make a one percent drop. We described this feature as both smooth and clean. It also is asymmetric, having a gradual dimming that lasts almost a week, and then it snaps right back up to normal in just a matter of days.
04:52
And again, after this, not much happens until February of 2013. Things start to get really crazy. There is a huge complex of dips in the light curve that appear, and they last for like a hundred days, all the way up into the Kepler mission's end. These dips have variable shapes. Some are very sharp, and some are broad, and they also have variable durations. Some last just for a day or two, and some for more than a week. And there's also up and down trends within some of these dips, almost like several independent events were superimposed on top of each other. And at this time, this star drops in its brightness over 20 percent. This means that whatever is blocking its light has an area of over 1,000 times the area of our planet Earth.
05:46
This is truly remarkable. And so the citizen scientists, when they saw this, they notified the science team that they found something weird enough that it might be worth following up. And so when the science team looked at it, we're like, 'Yeah, there's probably just something wrong with the data.' But we looked really, really, really hard, and the data were good. And so what was happening had to be astrophysical, meaning that something in space was getting in the way and blocking starlight. And so at this point, we set out to learn everything we could about the star to see if we could find any clues to what was going on. And the citizen scientists who helped us in this discovery, they joined along for the ride watching science in action firsthand.
06:36
First, somebody said, you know, what if this star was very young and it still had the cloud of material it was born from surrounding it. And then somebody else said, well, what if the star had already formed planets, and two of these planets had collided, similar to the Earth-Moon forming event. Well, both of these theories could explain part of the data, but the difficulties were that the star showed no signs of being young, and there was no glow from any of the material that was heated up by the star's light, and you would expect this if the star was young or if there was a collision and a lot of dust was produced. And so somebody else said, well, how about a huge swarm of comets that are passing by this star in a very elliptical orbit? Well, it ends up that this is actually consistent with our observations. But I agree, it does feel a little contrived. You see, it would take hundreds of comets to reproduce what we're observing. And these are only the comets that happen to pass between us and the star. And so in reality, we're talking thousands to tens of thousands of comets. But of all the bad ideas we had, this one was the best. And so we went ahead and published our findings.
08:00
Now, let me tell you, this was one of the hardest papers I ever wrote. Scientists are meant to publish results, and this situation was far from that. And so we decided to give it a catchy title, and we called it: 'Where's The Flux?' I will let you work out the acronym.
08:22
So this isn't the end of the story. Around the same time I was writing this paper, I met with a colleague of mine, Jason Wright, and he was also writing a paper on Kepler data. And he was saying that with Kepler's extreme precision, it could actually detect alien megastructures around stars, but it didn't. And then I showed him this weird data that our citizen scientists had found, and he said to me, 'Aw crap, Tabby. Now I have to rewrite my paper.'
08:54
So yes, the natural explanations were weak, and we were curious now. So we had to find a way to rule out aliens. So together, we convinced a colleague of ours who works on SETI, the Search for Extraterrestrial Intelligence, that this would be an extraordinary target to pursue. We wrote a proposal to observe the star with the world's largest radio telescope at the Green Bank Observatory.
09:20
A couple months later, news of this proposal got leaked to the press and now there are thousands of articles, over 10,000 articles, on this star alone. And if you search Google Images, this is what you'll find.
09:39
Now, you may be wondering, OK, Tabby, well, how do aliens actually explain this light curve? OK, well, imagine a civilization that's much more advanced than our own. In this hypothetical circumstance, this civilization would have exhausted the energy supply of their home planet, so where could they get more energy? Well, they have a host star just like we have a sun, and so if they were able to capture more energy from this star, then that would solve their energy needs. So they would go and build huge structures. These giant megastructures, like ginormous solar panels, are called Dyson spheres.
10:22
This image above are lots of artists' impressions of Dyson spheres. It's really hard to provide perspective on the vastness of these things, but you can think of it this way. The Earth-Moon distance is a quarter of a million miles. The simplest element on one of these structures is 100 times that size. They're enormous. And now imagine one of these structures in motion around a star. You can see how it would produce anomalies in the data such as uneven, unnatural looking dips.
10:58
But it remains that even alien megastructures cannot defy the laws of physics. You see, anything that uses a lot of energy is going to produce heat, and we don't observe this. But it could be something as simple as they're just reradiating it away in another direction, just not at Earth.
11:22
Another idea that's one of my personal favorites is that we had just witnessed an interplanetary space battle and the catastrophic destruction of a planet. Now, I admit that this would produce a lot of dust that we don't observe. But if we're already invoking aliens in this explanation, then who is to say they didn't efficiently clean up all this mess for recycling purposes?
11:50
You can see how this quickly captures your imagination.
11:55
Well, there you have it. We're in a situation that could unfold to be a natural phenomenon we don't understand or an alien technology we don't understand. Personally, as a scientist, my money is on the natural explanation. But don't get me wrong, I do think it would be awesome to find aliens. Either way, there is something new and really interesting to discover.
12:23
So what happens next? We need to continue to observe this star to learn more about what's happening. But professional astronomers, like me, we have limited resources for this kind of thing, and Kepler is on to a different mission.
12:39
And I'm happy to say that once again, citizen scientists have come in and saved the day. You see, this time, amateur astronomers with their backyard telescopes stepped up immediately and started observing this star nightly at their own facilities, and I am so excited to see what they find.
13:03
What's amazing to me is that this star would have never been found by computers because we just weren't looking for something like this. And what's more exciting is that there's more data to come. There are new missions that are coming up that are observing millions more stars all over the sky.
13:26
And just think: What will it mean when we find another star like this? And what will it mean if we don't find another star like this?
13:37
Thank you.
00:12
非同尋常的結(jié)論 需要非同尋常的證據(jù)。 作為天文學(xué)家， 這是我的職責(zé)和責(zé)任 去提醒人們外星人假說(shuō) 一直都該是最后一根救命稻草。
00:29
現(xiàn)在，我要給你們 講這么一個(gè)故事。 故事中有來(lái)自 NASA 項(xiàng)目中的數(shù)據(jù)， 有普通人，還有一顆 銀河系里最非同尋常的星星。
00:41
故事開(kāi)始于 2009 年， NASA 啟動(dòng)了開(kāi)普勒計(jì)劃。 開(kāi)普勒計(jì)劃的 首要科學(xué)目標(biāo) 是尋找太陽(yáng)系以外的行星。 它持續(xù)觀測(cè)一小塊天區(qū)， 就這塊，所有這些小方塊。 在這小塊區(qū)域中， 它持續(xù)觀測(cè)超過(guò) 15 萬(wàn)顆恒星的亮度， 整整四年， 每 30 分鐘就采集一次數(shù)據(jù)。 它在搜尋天文學(xué)家 叫做掩食的東西。 它發(fā)生在行星軌道和 我們的觀測(cè)視線重合情況。 這樣，行星就會(huì) 從恒星前面經(jīng)過(guò)。 這種情況下，行星 就會(huì)擋住一點(diǎn)點(diǎn)的星光。 你可以在光度曲線上 看到小小的負(fù)峰。
01:31
于是 NASA 團(tuán)隊(duì)開(kāi)發(fā)出 非常復(fù)雜的電腦程序， 來(lái)搜尋開(kāi)普勒 數(shù)據(jù)中的掩食事件。
01:39
在首次數(shù)據(jù)發(fā)布的同時(shí)， 耶魯大學(xué)的天文學(xué)家 在考慮一個(gè)有趣的問(wèn)題： 萬(wàn)一電腦錯(cuò)過(guò)了什么怎么辦？
01:52
于是，我們又發(fā)起了一項(xiàng) 名為“行星獵人”的公民科學(xué)項(xiàng)目。 這個(gè)項(xiàng)目依靠大眾 來(lái)分析同樣的數(shù)據(jù)。 人腦有著驚人的模式識(shí)別能力， 有時(shí)候甚至比電腦都厲害。 然而，這個(gè)項(xiàng)目 遭到了很多質(zhì)疑。 我的同行，黛布拉·費(fèi)舍爾， 行星獵人項(xiàng)目的發(fā)起人， 說(shuō)那時(shí)候人們議論道： “你們瘋了。 電腦絕不可能錯(cuò)過(guò)信號(hào)?！?所以這又是人和機(jī)器 賭哪個(gè)的老段子。 如果我們發(fā)現(xiàn)了一顆行星， 那我們就會(huì)特別高興。 四年前， 在我加入這個(gè)團(tuán)隊(duì)的時(shí)候， 我們已經(jīng)有了發(fā)現(xiàn)。 而今天，通過(guò)超過(guò) 30 萬(wàn) 科學(xué)愛(ài)好者的努力， 我們已經(jīng)發(fā)現(xiàn)了數(shù)十顆行星， 而且我們發(fā)現(xiàn)了 這一顆銀河系中 最最奇異的恒星。
02:44
為了說(shuō)清楚， 請(qǐng)看一下開(kāi)普勒數(shù)據(jù)中 一次正常的掩食是什么樣子。 這幅圖中，左邊軸是光強(qiáng)度， 底下的橫軸是時(shí)間。 這條白線是單純來(lái)自恒星的光， 天文學(xué)家稱為光度曲線。 現(xiàn)在，當(dāng)一顆行星掩過(guò)恒星， 它阻擋了一點(diǎn)點(diǎn)星光， 而這個(gè)掩食的深度 反映了行星體自身的大小。 所以，例如木星。 行星通常不太會(huì) 比木星還要大。 木星會(huì)減弱百分之一的星光。 換做地球， 地球只有木星的 1/11 大， 它的信號(hào)在數(shù)據(jù)中幾乎看不見(jiàn)。
03:26
回到我們的謎題。 幾年前，行星獵人 正在篩選數(shù)據(jù)尋找掩食， 他們發(fā)現(xiàn)了一個(gè)詭異的信號(hào) 來(lái)自恒星 KIC 8462852。 2009 年五月是他們 首次發(fā)現(xiàn)這個(gè)信號(hào)， 他們開(kāi)始在論壇中 討論這個(gè)發(fā)現(xiàn)。
03:47
他們說(shuō)一個(gè)類似木星的星體 可以造成這樣的星光削弱， 但他們也說(shuō)這家伙太大了。 你看，掩食通常只持續(xù)幾個(gè)小時(shí)， 而這一個(gè)持續(xù)了將近一周。
04:01
他們也在說(shuō)譜線看起來(lái)不對(duì)稱， 這是說(shuō)，不像木星那樣 有一個(gè)干凈、U 型的負(fù)峰， 大家看，這條數(shù)據(jù)左側(cè) 的傾斜度很奇怪。 這似乎意味著， 無(wú)論闖進(jìn)來(lái) 擋住星光的是什么東西， 它不會(huì)像行星那樣是個(gè)球形。 后來(lái)陸續(xù)還有少量的負(fù)峰， 但這顆星在之后的一兩年 一直都沒(méi)什么動(dòng)靜。
04:26
然后在 2011 年三月， 我們觀察到了這個(gè)。 這顆恒星的光度 掉了整整 15%， 這比一顆行星能造成的大太多了， 行星只能造成 1% 的光度下降。 我們把這條譜線特征 描述為光滑和干凈。 它也是不對(duì)稱的， 在持續(xù)近一周的時(shí)間內(nèi) 逐步減弱， 然后在一兩天內(nèi) 立馬反彈回正常的光度。
04:52
在此之后，又是什么都沒(méi)發(fā)生， 直到 2013 年二月。 事情的發(fā)展完全出乎意料。 光度曲線上出現(xiàn)了 一大群復(fù)雜的負(fù)峰， 而且它們持續(xù)了 差不多一百天， 一直延續(xù)到 開(kāi)普勒計(jì)劃結(jié)束。 這些負(fù)峰有著各種形狀。 有一些很尖銳， 有一些很寬， 以及有不同的持續(xù)時(shí)間。 有一些只持續(xù)一兩天， 有的則超過(guò)一周。 而且在一些光度負(fù)峰中， 還出現(xiàn)上上下下的起伏， 感覺(jué)好像是幾個(gè)獨(dú)立事件 重疊在一起。 而且這次，這顆恒星的亮度 下降了超過(guò) 20%。 這說(shuō)明不管是什么東西 擋住了光， 這家伙有著超過(guò)地球 1000 倍的面積。
05:46
這真心是非同尋常。 當(dāng)公民科學(xué)家發(fā)現(xiàn)這個(gè)時(shí)， 他們通知了科學(xué)家團(tuán)隊(duì)， 稱他們發(fā)現(xiàn)了足夠奇怪的東西 可能值得后續(xù)跟進(jìn)研究。 于是當(dāng)科學(xué)家團(tuán)隊(duì)看過(guò)數(shù)據(jù)之后， 我們覺(jué)得：“好吧，會(huì)不會(huì) 只是數(shù)據(jù)有點(diǎn)問(wèn)題?！?不過(guò)經(jīng)過(guò)我們非常、 非常、非常仔細(xì)的調(diào)查， 數(shù)據(jù)沒(méi)有問(wèn)題。 因此，出現(xiàn)這些負(fù)峰一定有 天體物理學(xué)的原因， 說(shuō)明太空中有什么東西 經(jīng)過(guò)了我們和恒星之間， 擋住了它的光。 這個(gè)時(shí)候， 我們竭力研究 關(guān)于這顆恒星的一切， 希望能找到任何 可以解釋這些現(xiàn)象的線索。 幫助我們發(fā)現(xiàn)這顆星的 公民科學(xué)家， 也加入了討論， 見(jiàn)證科學(xué)第一線的行動(dòng)。
06:36
首先，有人提出， 是不是這顆星非常年輕， 它仍舊保有它誕生之時(shí) 周?chē)男请H云物質(zhì)。 另外有人說(shuō)， 好吧，是不是這顆星 已經(jīng)形成了行星系統(tǒng)， 而兩顆行星相撞了， 就像地球——月球的形成過(guò)程。 好吧，這兩種假說(shuō) 都可以解釋部分?jǐn)?shù)據(jù)， 但是困難在于，這顆恒星 沒(méi)有顯示任何年輕的特征， 而且也沒(méi)有來(lái)自任何物質(zhì) 被星光加熱發(fā)出的光暈。 如果恒星年輕， 或者碰撞產(chǎn)生大量塵埃， 通常會(huì)出現(xiàn)這種現(xiàn)象。 又有人說(shuō)， 好吧，會(huì)不會(huì)是一大群彗星呢 在一個(gè)非常橢圓的軌道上 一連串地穿過(guò)這顆恒星？ 好吧，這個(gè)假說(shuō)倒是 和我們的觀測(cè)相吻合。 但是我同意， 這感覺(jué)有點(diǎn)牽強(qiáng)。 你看，需要數(shù)百顆彗星， 才能重現(xiàn)我們的觀測(cè)。 而這些只是 恰好從我們和恒星 中間穿過(guò)的彗星。 所以實(shí)際情況下， 將會(huì)有成千上萬(wàn)顆彗星。 但是在我們所有的爛解釋中， 這個(gè)算是最好的了。 于是我們發(fā)表了我們的發(fā)現(xiàn)。
08:00
要我說(shuō)，這是我寫(xiě)過(guò)的 最困難的論文之一。 科學(xué)家理應(yīng)發(fā)表明確的結(jié)果， 而這次我們離結(jié)果 還有十萬(wàn)八千里呢。 所以我們決定 起一個(gè)抓眼球的標(biāo)題， 我們的題目是： 《光去了哪里》 麻煩大家自行意會(huì)這個(gè)梗
08:17
（笑聲。標(biāo)題的英文縮寫(xiě)為 WTF，即“什么鬼”）
08:22
不過(guò)這故事還沒(méi)完呢。 在我寫(xiě)這篇論文的同時(shí)， 我見(jiàn)了一位同行， 賈森·萊特 他也在寫(xiě)一篇 有關(guān)開(kāi)普勒數(shù)據(jù)的論文。 他說(shuō)道，從開(kāi)普勒 無(wú)與倫比的精度來(lái)看， 它其實(shí)可以探測(cè)到 恒星周?chē)耐庑侨私ㄖ?但是并沒(méi)有發(fā)現(xiàn)。 然后我給他看了這個(gè)由我們 公民科學(xué)家發(fā)現(xiàn)的奇怪?jǐn)?shù)據(jù)， 然后他對(duì)我說(shuō)， “見(jiàn)鬼，塔碧。 這下我論文得重寫(xiě)了?！?/span>
08:54
所以，沒(méi)錯(cuò)， 自然解釋很牽強(qiáng)， 我們很好奇。 我們必須找到一個(gè) 排除外星人的方法。 于是我倆一起說(shuō)服了 我們?cè)?SETI（尋找地外 文明計(jì)劃）工作的一位同行， 說(shuō)這是一個(gè)非常 出色的追逐目標(biāo)。 我們起草了一份 觀測(cè)這顆恒星的項(xiàng)目書(shū) 請(qǐng)求使用綠岸天文臺(tái)的 世界上最大的射電天文望遠(yuǎn)鏡。
09:20
兩三個(gè)月后， 這份項(xiàng)目書(shū)的消息 被媒體刺探到了 好吧，現(xiàn)在有幾千篇報(bào)道 可能超過(guò)一萬(wàn)篇， 單單關(guān)于這顆恒星。 如果你用谷歌圖片搜索， 你會(huì)找到這些。
09:39
現(xiàn)在，觀眾可能會(huì)問(wèn)， 好吧塔碧， 究竟怎么用外星人 去解釋這光度曲線？ 好吧，想象一個(gè) 遠(yuǎn)比我們發(fā)達(dá)的文明， 在這個(gè)假設(shè)條件下， 這個(gè)文明肯定耗盡了 他們母星的能源。 所以他們從哪里 獲取更多的能量？ 你看，他們有一顆宿主恒星， 就像我們有太陽(yáng)一樣， 那如果他們能夠 從恒星中抓取更多能量， 那就可以解決 他們的能源需求。 所以他們可能會(huì)去 建造這些巨型建筑。 這些巨大的超級(jí)建筑， 比如巨大的太陽(yáng)能電池板， 叫做“戴森球”。
10:22
上面這些圖片 是許多藝術(shù)家想象中的戴森球。 很難去想象這些東西 究竟有多龐大， 但你可以這么想。 地球——月球間的距離 是四十萬(wàn)公里。 這些巨型結(jié)構(gòu)中的 最簡(jiǎn)單的單元， 是 100 倍地月距離。 它們是龐然大物。 再想象，這樣一個(gè)建筑 圍繞著一顆恒星運(yùn)動(dòng)。 你可以看到這為什么 可以造成數(shù)據(jù)中異常 如此不對(duì)稱，不自然的負(fù)峰。
10:58
但是即使是 外星人的超級(jí)建筑， 也不能違反物理定律。 任何使用大量能量的東西 將會(huì)產(chǎn)生熱量， 但是我們沒(méi)有觀測(cè)到。 但這有可能只是非常簡(jiǎn)單的， 他們把熱量釋放到了另一個(gè)方向， 沒(méi)有對(duì)著地球。
11:22
我個(gè)人最喜歡的 另一種可能性是 我們恰好目睹了 一場(chǎng)星球大戰(zhàn)， 一顆行星被災(zāi)難性地 徹底摧毀了。 我承認(rèn)， 這會(huì)產(chǎn)生很多塵埃， 然而我們沒(méi)有觀測(cè)到。 但是如果我們已經(jīng) 在用外星人來(lái)解釋， 那誰(shuí)說(shuō)他們不會(huì)秋風(fēng)掃落葉 一般清理干凈塵埃， 回收利用？
11:50
你看，這很快 就激發(fā)想象力啦。
11:55
好啦，故事就是這樣。 我們的處境是， 既可以解釋成 我們沒(méi)搞清楚的自然現(xiàn)象， 又可以解釋成 我們沒(méi)搞清楚的外星人科技。 作為科學(xué)家，我個(gè)人 還是會(huì)賭這是個(gè)自然現(xiàn)象。 但是別誤解了，我絕對(duì)認(rèn)同 能找到外星人非常棒。 不管怎樣，有新東西， 非常有趣的東西等待發(fā)現(xiàn)。
12:23
那么，接下來(lái)呢？ 我們需要繼續(xù)觀測(cè)這顆恒星 去更詳細(xì)地了解發(fā)生了什么。 然而，像我這樣的職業(yè)天文學(xué)家， 我們?cè)谶@方面的資源有限。 而開(kāi)普勒望遠(yuǎn)鏡已經(jīng)在 執(zhí)行另一項(xiàng)計(jì)劃了。 所以我很高興地說(shuō)，又一次，
12:43
公民科學(xué)家加入進(jìn)來(lái)救場(chǎng)。 你看，這次， 業(yè)余天文愛(ài)好者 拿著他們的業(yè)余望遠(yuǎn)鏡 立刻加入進(jìn)來(lái)， 開(kāi)始在自己的觀測(cè)點(diǎn) 夜觀此星。 我非常期待他們的發(fā)現(xiàn)。 對(duì)我來(lái)說(shuō)，激動(dòng)人心的是 這顆恒星可能根本不會(huì)被電腦發(fā)現(xiàn)，
13:07
因?yàn)槲覀儐渭儧](méi)有把 這樣的恒星當(dāng)成目標(biāo)。 更激動(dòng)人心的是， 將來(lái)還有更多的數(shù)據(jù)。 有新的觀測(cè)項(xiàng)目要上馬， 準(zhǔn)備觀測(cè)百萬(wàn)顆恒星， 布滿全天。 思考一下：如果我們又找到 一顆這樣的恒星，意味著什么？
13:32
而如果我們一顆都沒(méi)找到， 那又意味著什么？ 謝謝。
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