引力波：宇宙中看不見(jiàn)的漣漪

Harrison+Smith+兩袖清風(fēng)

You probably heard the news recently： Scientists detected something called gravitational waves， and they are over the moon1） with joy.

So， what's a gravitational wave？

Well， says Kelly Herbst， a physicist and astronomy curator2） at the Virginia Living Museum in Newport News， it's a little complicated. "You can't really feel these gravitational waves. They're not like ocean waves hitting you."

Yet the waves are strong enough that they change the very fabric3） of the universe.

Herbst explains： "The fabric of space is kind of like a big rubber sheet4）. You put a bowling ball on the sheet， and it makes this big indentation5）." Drop the ball， or roll it around， and you may see small ripples on the sheet. Other objects—think of them as being the size of tennis balls or marbles—are affected by those ripples. They may bob6） up and down or move a little to the side as the ripple passes through.

Those ripples are just like gravitational waves.

It takes a massive object—a bowling ball， not a marble—to form waves that scientists can detect. In this case， it was a pair of black holes that spun around each other faster and faster， eventually merging7） to become one.

Black holes are extremely dense. These particular ones each had the mass of about 30 suns.

Because they're so dense， they have a powerful gravitational pull. Like hungry hippos eating everything that comes near， they suck in planets， stars and anything else that crosses their path. Incredibly， even light gets sucked in. That is how black holes got their name： Practically8） invisible， they seem to be a patch of empty space in the universe.

When the two black holes combined， a huge amount of energy was released. That energy was released in the form of gravitational waves.

Just as a rock dropped into a pond goes kerplunk9） and sends ripples across the water， gravitational waves spread across the universe. In the case of those two black holes， the waves eventually reached Earth， 1.3 billion light-years from their source.

By then， the ripples were smaller than small.

How small？ You may know that living things on Earth are made up of cells， which can be seen only with powerful microscopes. In turn， those cells are made up of atoms， the building blocks of matter.

Atoms are so small that we've only recently developed devices to see them. But the nucleus10）， or center， of an atom is about 10，000 times as big as the ripple of the gravitational wave.

That tiny movement， the slightest of vibrations11）， was observed at a research center called the Laser Interferometer Gravitational-Wave Observatory （LIGO） using a sensitive system of mirrors and lasers. It confirmed a prediction made by the scientist Albert Einstein 100 years ago， but， perhaps more important， it opened the door to a new way of understanding the universe.

The scientists at LIGO， which has facilities in Louisiana and Washington state， were able to translate the vibration caused by the ripple into a sound： a brief chirp12）， the faintest echo of a powerful collision that occurred far， far away.

Instead of just watching the sky， Herbst says， we can now listen to it.

"There are things out there that we can't see very well with light. Black holes are a big one，" she said. "Now we have a whole new way of 'seeing' the universe without light."

We could soon learn more about these mysterious black holes and about the early history of the universe， according to Herbst.

"It's very exciting to see what happens next，" she said.

各位最近可能都有所耳聞：科學(xué)家們探測(cè)到了一種叫做引力波的東西，為此樂(lè)翻了天。

那么，引力波是什么呢？

這個(gè)嘛，美國(guó)紐波特紐斯市弗吉尼亞自然博物館天文分館館長(zhǎng)、物理學(xué)家凱利·赫布斯特說(shuō)，有點(diǎn)復(fù)雜?！澳銦o(wú)法真切地感受到這些引力波。它們不像海浪那樣拍打你?！?/p>

然而，引力波的力量又是如此強(qiáng)大，甚至?xí)淖冇钪娴臉?gòu)造。

赫布斯特解釋說(shuō)：“宇宙的構(gòu)造有點(diǎn)兒像一張大的橡膠板。你把一個(gè)保齡球放上去，橡膠板上就被壓出一個(gè)大坑?！睂⒈｝g球扔到或者滾到這個(gè)橡膠板上，你可能會(huì)看見(jiàn)橡膠板上出現(xiàn)許多小漣漪。橡膠板上的其他物體——將它們想象成網(wǎng)球或彈珠大小的物體——會(huì)受到這些漣漪的影響。漣漪經(jīng)過(guò)的時(shí)候，它們可能會(huì)上下起伏或往旁邊移動(dòng)一點(diǎn)點(diǎn)。

引力波就好比是這些漣漪。

只有龐大物體——像保齡球而不是彈珠那樣的物體——引發(fā)的波才能被科學(xué)家探測(cè)到。就這次事件而言，引起此次引力波的龐然大物是一對(duì)相互繞轉(zhuǎn)的黑洞，二者越轉(zhuǎn)越快，最終合為一體。

黑洞的密度極大。制造引力波的這對(duì)黑洞分別擁有大約30個(gè)太陽(yáng)的質(zhì)量。

由于密度很大，這兩個(gè)黑洞具有強(qiáng)大的引力。它們就像餓起來(lái)就會(huì)吃掉靠近自己的所有東西的河馬一樣，吞掉行星、恒星以及其他所有經(jīng)過(guò)它們軌道的物體。不可思議的是，它們連光也能吞沒(méi)。黑洞之名就是由此而來(lái)的：它們幾乎是不可見(jiàn)的，好似宇宙中的一塊空缺。

這兩個(gè)黑洞合并時(shí)釋放出一股巨大的能量，這種能量便是以引力波的形式釋放出來(lái)的。

就像一塊石頭“咕咚”一聲掉進(jìn)池塘?xí)て饾M池漣漪一樣，引力波也會(huì)在宇宙中擴(kuò)散。此次事件中，這兩個(gè)黑洞制造的引力波最終到達(dá)了地球——距離其源頭13億光年的地方。

此時(shí)，這些漣漪已經(jīng)小得不能再小。

到底有多??？你可能知道，地球上的生物是由細(xì)胞構(gòu)成，這些細(xì)胞只有借助高倍顯微鏡才能看到。細(xì)胞反過(guò)來(lái)又由原子構(gòu)成——原子是構(gòu)成物質(zhì)的基本微粒。

原子實(shí)在太小了，直到近些年我們才研制出觀察它們的設(shè)備。但就是原子的核，或者說(shuō)中心，也要比這些引力波漣漪大上約10000倍。

這么微小的運(yùn)動(dòng)、如此微弱至極的振動(dòng)當(dāng)時(shí)是由一個(gè)名為激光干涉引力波天文臺(tái)（LIGO）的研究中心利用一套靈敏的反射鏡和激光系統(tǒng)探測(cè)到的。這一發(fā)現(xiàn)證實(shí)了科學(xué)家阿爾伯特·愛(ài)因斯坦100年前做出的一個(gè)預(yù)測(cè)，不過(guò)，也許更為重要的是，它開(kāi)辟了認(rèn)識(shí)宇宙的新途徑。

LIGO在美國(guó)路易斯安那州和華盛頓州都有設(shè)備，LIGO的科學(xué)家們能夠?qū)⒁Σi漪帶來(lái)的振動(dòng)轉(zhuǎn)化為聲音：一聲短促的啾聲。這一微弱無(wú)比的回響來(lái)自于距離我們極為遙遠(yuǎn)的地方所發(fā)生的一場(chǎng)威力強(qiáng)大的碰撞。

我們以前只能觀測(cè)宇宙，赫布斯特說(shuō)，而現(xiàn)在我們可以去聽(tīng)宇宙的聲音了。

“宇宙中有些東西我們靠光是看不清的，黑洞就是一大例子，”她說(shuō)，“現(xiàn)在，我們有了一種不靠光就能‘觀測(cè)宇宙的全新方式?！?img alt="" src="https://cimg.fx361.com/images/2017/01/20/xdfy201607xdfy20160734-3-l.jpg" style="">

赫布斯特表示，我們可能很快就會(huì)了解到有關(guān)這些神秘黑洞和宇宙早期歷史的更多信息。

“接下來(lái)的發(fā)現(xiàn)將會(huì)非常激動(dòng)人心?！彼f(shuō)。