宇宙中心在何方？

還記得馬克博士嗎？2006年10月號(hào)的“探索區(qū)”中，我們就“時(shí)間旅行”這個(gè)問題請(qǐng)來馬克博士，他簡(jiǎn)潔明了的講解受到很多讀者的喜愛。時(shí)隔兩年，我們?cè)俅握?qǐng)來馬克博士。這次的問題可不簡(jiǎn)單哦——宇宙的中心在哪里？一起聽聽馬克博士的解釋吧。

Diane Fisher: Marc， today our question – a BIG one –

comes from the CATO Rocketry[火箭學(xué)] Club in Gales Ferry， Connecticut. Here goes: Is it possible to point to a direction in the sky and say “that way is the center of the universe， where the Big Bang started”?

Dr. Marc Rayman: Wow. Well…no. The “center of the universe” has always been a very intriguing[引起興趣的]

idea for humans. Until the 16th century， even learned people thought Earth – and people – were at the center of the cosmos[宇宙]. Then the Polish astronomer[天文學(xué)家]

Nicolaus Copernicus had a better idea – although still wrong – for explaining the motion of the planets

through the night sky. He thought the Sun was

actually the center of the universe， with Earth and the other planets circling the Sun. And his theory was widely condemned[譴責(zé)] and ridiculed[嘲笑，奚落] at first. Now we know that not only are we humans not at the center of the universe， but there is no center of the universe!

Fisher: Now THAT is really hard to imagine!

Rayman: It is. But a center just doesn’t fit with what scientists have learned through decades of modern astronomy. The Big Bang is the name scientists give to the events that started the universe. Although the Big Bang is often described as a huge explosion， an

explosion has a central point， such as a bomb or a spark. The Big Bang wasn’t like that.

Fisher: Why not?

Rayman: The Big Bang happened everywhere at once. It’s an expansion of space itself， not the expansion of things in space. That means everywhere in space is

moving apart from everywhere else. This has been going on in the entire universe for almost 14 billion years.

Fisher: But aren’t we located somewhere with respect to[關(guān)于，至于] the rest of the universe?

Rayman: We certainly are. We’re right here， and we know where “here” is relative to other objects in the

universe! But here is not special， like a center would be， and， for that matter， nowhere is special. That’s like asking – if we had a powerful telescope that could see all the way to the end of the universe， would we find more of the universe on one side of Earth than on the other? No. We would find that it looks the same in all directions.

Fisher: So， doesn’t that mean we are still at the center of the universe?

Rayman: Well， no， it doesn’t. Observers everywhere in the universe would find the same result. Imagine that you are on one of many dots on a spherical[球形的]

balloon. No matter which way you look along the

surface of the balloon， the end of your world seems to be the same distance from you. But that doesn’t mean you are at the center of this little world! The fact is your two-dimensional world has no center.

Fisher: But what about the continuing expansion of the universe? Doesn’t it have to expand from a center point somewhere?

Rayman: Well， suppose your balloon world is being

inflated[充氣，膨脹]

with air. All the other dots will be getting farther and farther away from you as the balloon gets

bigger. In fact， all dots get

farther from each other， so no matter where you are， it looks as if you are at the center of the expansion. The expansion of three-dimensional space is similar. Like the surface of the balloon， there is no center in the universe.

Fisher: How do we even know the universe started with a Big Bang?

Rayman: One of the ways is that scientists have been able to see the faint radiation[輻射，放射物] left over from shortly

after this cosmic birth. Some scientists predicted what this radiation would look like， and others found it using a

radio telescope[無線電天文望遠(yuǎn)鏡]. As more measurements have been made from Earth and from space， the Big Bang has

continued to provide an excellent description of how the universe has evolved.

Fisher: Is there any other way to learn about the Big Bang besides observing its leftover radiation?

Rayman: Well， yes， there are several. And scientists would like to be able to study gravitational waves[引力波] left by the Big Bang. Gravitational waves will be very hard to detect， but should tell us a lot about the universe that

electromagnetic[電磁的] radiation and matter cannot.

Detecting gravitational waves will require some very

advanced technologies， but could lead to thrilling[令人興奮的] new insights into the workings[運(yùn)動(dòng)方式，運(yùn)行] of the universe.

Fisher: Our time’s up for now. Marc， thank you for another fascinating discussion.

黛安·費(fèi)希爾：馬克，我們今天的問題，一個(gè)很廣的問題，來自（美國(guó)）康涅狄格州蓋爾斯費(fèi)里村的“CATO”火箭俱樂部。問題是這樣的：我們能否指著天空的某一個(gè)方向，然后說“那里是宇宙的中心，宇宙大爆炸就是從那里開始的”？

馬克·雷曼博士：哇，呃……不能?！坝钪嬷行摹边@個(gè)問題一直吸引著人們的注意力。直到16世紀(jì)以前，即使是有學(xué)問的人也認(rèn)為地球——和人類——是宇宙的中心。后來，波蘭天文學(xué)家尼古拉·哥白尼對(duì)行星在夜空中的運(yùn)動(dòng)有了更好的想法，雖然他的想法仍然是錯(cuò)誤的。他認(rèn)為太陽才是宇宙的中心，地球以及其它行星圍繞著太陽運(yùn)轉(zhuǎn)。起初，他的理論備受詬罵，遭人奚落。現(xiàn)在我們知道不單我們?nèi)祟惒皇怯钪娴闹行?，?shí)際上宇宙根本沒有

中心！

費(fèi)希爾：這確實(shí)讓人難以想象！

雷曼：的確如此。但“中心”這個(gè)概念實(shí)在不符合科學(xué)家多年來通過現(xiàn)代天文學(xué)得出的結(jié)論?！坝钪娲蟊ā笔强茖W(xué)家們?yōu)橛钪嫘纬傻囊幌盗惺录鸬拿?。雖然宇宙大爆炸往往被描述為一次強(qiáng)烈的爆炸，而爆炸往往有一個(gè)中心點(diǎn)，例如一個(gè)炸彈或火花，但宇宙大爆炸并非那樣。