也許外星人就在我們身邊，只是我們看不到而已

What if alien spacecraft are already in our midst – and we don't know about them because they're tiny nano-structures? That's the new idea put forward by one scientist seeking to explain the Fermi paradox.

如果外星人的太空船已經來到我們人類中間，而我們卻不知道它們，因為它們是微小的納米結構呢?這是一位試圖解釋費米悖論的科學家提出的新觀點。

This paradox – named after Italian-American physicist Enrico Fermi – posits that because the Milky Way is so vast and so old, the chances of alien civilisations being out there is actually pretty high... so where are they?

這一悖論——以意大利裔美國物理學家恩里科·費米的名字命名——提出了這樣一個假設:由于銀河系如此浩瀚而古老，外星文明存在的幾率實際上相當高……那么他們在哪里呢?

Maybe they're buzzing around the Universe in micro-machines just a nanometre long, suggests astrophysicist Zaza Osmanov from the Free University of Tbilisi in Georgia. What's more, he's provided some pretty detailed calculations to go along with this slightly whacky-sounding idea.

來自格魯吉亞第比利斯自由大學的天體物理學家扎扎·奧斯馬諾夫認為，也許它們是在一納米長的微型機器里繞著宇宙飛行。更重要的是，他提供了一些非常詳細的計算，以配合這個聽起來有點古怪的想法。

Now it's worth mentioning that Osmanov's paper has yet to be peer-reviewed, so we can't place too much importance on it just yet – but it does open up an intriguing possibility about how other civilisations might one day reach us.

現(xiàn)在值得一提的是，奧斯馬諾夫的論文還沒有經過同行評議，所以我們目前還不能把它放在太重要的位置——但它確實為我們提供了一個有趣的可能性，即有一天其他文明可能會如何影響我們。

The new study is based on the established idea of von Neumann probes: the thinking goes that aliens could send out self-replicating spacecraft to explore the galaxies, without having to risk leaving their home planet themselves.

這項新研究基于馮·諾依曼探測器的既定理念:外星人可以發(fā)射自我復制的宇宙飛船去探索星系，而不必冒險離開自己的星球。

Previous attempts to figure out how von Neumann probes could function have hit a common problem – self-replication needs a steady supply of new materials, and it's not clear if deep space has enough suitable planets or rocky bodies to go around.

先前試圖找出馮·諾依曼探測器如何工作的嘗試遇到了一個共同的問題——自我復制需要穩(wěn)定的新材料供應，目前還不清楚深空是否有足夠合適的行星或巖石體環(huán)繞。

To get around the issue, Osmanov has shrunk the scale right down. Microscopic probes would need much less in the way of materials, and could rely on hydrogen atoms floating through the interstellar dust for power.

為了解決這個問題，奧斯曼諾夫將規(guī)模定位微型。微型探測器在材料方面的需求要少得多，而且可以依靠漂浮在星際塵埃中的氫原子來獲取能量。

These nanoscale probes would, in theory, be much more efficient than any previously imagined, and could replicate in just a few years – getting around the Universe relatively quickly. They'd also become very numerous (up to the level of trillions of billions) in a few short light-years of steady reproduction.

從理論上講，這些納米級的探測器比之前想象的要高效得多，而且可以在短短幾年內進行復制——以相對較快的速度環(huán)繞宇宙。它們也會在幾光年的穩(wěn)定繁殖中變得非常多(達到幾萬億級)。