《那些古怪又讓人憂心的問題》第76期:致命中微子(1)
LETHAL NEUTRINOS
致命中微子
Q. How close would you have to be to asupernova to get a lethal dose of neutrino radiation?
Q．一個人要離超新星多近才能受到致命劑量的中微子輻射？
A. THE PHRASE “LETHAL DOSE of neutrino radiation”is a weird one. I had to turn it over in my head a few times afterI heard it.
A．“致命劑量的中微子輻射”這一說法很奇怪，我腦子轉了好幾圈才反應過來。
If you're not a physics person, it mightnot sound odd to you, so here's a little context for why it's such a surprisingidea:
如果你不是物理專業人士，你可能不覺得有什麼奇怪，所以我要給你科普一下爲什麼這個說法讓人很摸不着頭腦：
Neutrinos are ghostly particles that barelyinteract with the world at all. Look at your hand-there are about a trillionneutrinos from the Sun passing through it every second.
中微子就像幽靈一般，它幾乎不與任何物質發生反應。看看你的手——每秒鐘有約1萬億個來自太陽的中微子穿過你的手掌。
Okay, you can stop looking at your handnow.
好了，別一直看着你的手了。
The reason you don't notice the neutrinoflood is that neutrinos mostly ignore ordinary matter. On average, out of thatmassive flood, only one neutrino will “hit”an atom in your bodyevery few years.1
那麼你爲什麼沒有感受到洶涌的中微子洪流呢？這是因爲，這些中微子幾乎不與常見物質發生作用。平均來說，在這股中微子洪流中，每幾年纔會有1箇中微子直直“撞上”你身體中的某個原子。
In fact, neutrinos are so shadowy that theentire Earth is transparent to them; nearly all of the Sun's neutrino steamgoes straight through it unaffected. To detect neutrinos, people build gianttanks filled with hundreds of tons of target material in the hopes that they'llregister the impact of a single solar neutrino.
實際上，在中微子面前地球也幾乎是透明的，來自太陽的幾乎所有中微子都能絲毫不受影響地穿過地球。爲了探測到中微子，科學家們建造了裝有數百噸物質的大箱子，希望能記錄到哪怕是一個來自太陽的中微子與這些物質發生碰撞的記錄。
This means that when a particle accelerator(which produces neutrinos) wants to send a neutrino beam to a detectorsomewhere else in the world, all it has to do is point the beam at thedetector-even if it's on the other side of the Earth!
所以說，如果一個粒子加速器（會產生中微子）想給世界其他地方的探測器發送中微子的話，它只需要直直地瞄準探測器就行了，即使探測器在地球的另一端也無所謂！
That's why the phrase “lethal dose ofneutrino radiation” sounds weird-it mixes scales in an incongruous way. It'slike the idiom “knock me over with a feather” or the phrase “football stadiumfilled to the brim with ants.” If you have a math background, it's sort of likeseeing the expression “ln(x)e”-it's not that, taken literally, it doesn't make sense-it's that youcan't imagine a situation where it would apply.
這就是爲什麼“致命劑量的中微子輻射”聽起來很怪異——它把風馬牛不相及的數量級混在了一起。這就像說“用羽毛把你打倒在地”或者“裝滿了螞蟻的體育館”一樣，如果你有數學背景，這有點類似於看到ln(x)e這樣的表達式——我不是說它字面上沒有意義，只是你很難想象哪裏會真的出現這種情況。
