《那些古怪又讓人憂心的問題》第77期:致命中微子(2)

Similarly, it's hard to produce enoughneutrinos to get even a single one of them to interact with matter; it'sstrange to imagine a scenario in which there'd be enough of them to hurt you.

同樣，你甚至都難以製造出足夠多的中微子讓它們中哪怕只有一個和物質發生反應，要想象在什麼樣的場景下會有足以對你造成傷害的中微子就更難了。

Supernovae provide that scenario. tor, the Hobart and William Smith Colleges physicist who asked me thisquestion, told me his rule of thumb for estimating supernova-related numbers:However big you think supernovae are, they're bigger than that.

但超新星能夠提供這樣的場景。問我這個問題的霍巴特和威廉姆史密斯學院的物理學家斯佩克特博士告訴我，他推測和超新星相關的數字時的經驗法則是：不管你認爲超新星有多大，它們其實比你以爲的更大。

Here's a question to give you a sense ofscale. Which of the following would be brighter, in terms of the amount ofenergy delivered to your retina:

讓我給大家直觀地比較一下。按照你的視網膜所接收到的能量來算，以下兩者哪個更亮：

A supernova, seen from as far away as theSun is from the Earth, or the detonation of a hydrogen bomb pressed againstyour eyeball?

在一個日地距離以外觀看一顆超新星，還是在你眼珠前爆炸的氫彈？

Can you hurry up and set it off? This isheavy.

求你快點引爆這個炸彈吧，它太重了。

Applying Dr. Spector's rule of thumbsuggests that the supernova is brighter. And indeed, it is . . . by nine ordersof magnitude.

運用那位物理學家的經驗法則可知，超新星更亮一些。其實它們差了……整整9個數量級。

That's why this is a neatquestion-supernovae are unimaginably huge and neutrinos are unimaginablyinsubstantial. At what point do these two unimaginable things cancel out toproduce an effect on a human scale?

這也正是這個問題的優雅之處所在：超新星巨大到難以想象，而中微子又飄渺到難以想象。在哪個距離上這兩個難以想象的事情會相互抵消，並對人體產生影響？

A paper by radiation expert Andrew Karamprovides an answer. It explains that during certain supernovae, the collapse ofa stellar core into a neutron star, 1057 neutrinos can be released (one forevery proton in the star that collapses to become a neutron).

輻射專家安德魯•卡拉姆的一篇論文給出了答案。這篇論文指出，在某些超新星核心坍縮成中子星的過程中會放出多達1057箇中微子。（每個發生坍縮的質子都會放出一箇中微子。）

Karam calculates that the neutrinoradiation dose at a distance of 1 parsec would be around half a nanosievert, or1/500th the dose from eating a banana.

卡拉姆計算出在1秒差距距離上的中微子輻射劑量約爲0.5納西弗，也就是吃一根香蕉所受輻射的1/500。

A fatal radiation dose is about 4 g the inverse-square law, we can calculate the radiation dose:

致命劑量的輻射量約爲4西弗。利用平方反比律，我們可以計算出輻射劑量：

That's a little more than the distancebetween the Sun and Mars.

2.3個天文單位比太陽和火星之間的距離要遠那麼一點。

Core-collapse supernovae happen to giantstars, so if you observed a supernova from that distance, you'd probably beinside the outer layers of the star that created it.

發生核心坍縮的超新星此前都是巨大的恆星，因此如果你在那個距離觀看超新星，那麼你將位於恆星的外層內部。