《那些古怪又讓人憂心的問題》第4期:相對論棒球
RELATIVISTIC BASEBALL
Q. What would happen if you tried to hit a baseball pitched at 90 percent the speed of light?
如果棒球被以0.9倍光速擲出會產生什麼後果？——艾倫?麥克馬尼斯Let's set aside the question of how we got the baseball moving that fast. We'll suppose it's a normal pitch, except in the instant the pitcher releases the ball, it magically accelerates to 0.9c. From that point onward, everything proceeds according to normal physics.
讓我們先不要去糾結棒球是如何加速到這麼快的，假設這只是一次普通的投球，但在投手擲出球的那一刻，棒球被魔法加速到了0.9倍光速。從那一刻起，正常的物理規律再度開始發揮作用。
THE ANSWER TURNS OUT to be “a lot of things,” and they all happen very quickly, and it doesn't end well for the batter (or the pitcher). I sat down with some physics books, a Nolan Ryan action figure, and a bunch of videotapes of nuclear tests and tried to sort it all out. What follows is my best guess at a nanosecond-by-nanosecond portrait.
是“會發生很多事情”，而且這些事情發生在相當短的一段時間內，對於擊球手（或投球手）來說他們的結局有些悲慘。爲了弄清楚到底會發生什麼，我找來了一些物理書、一個諾蘭?萊恩1人偶，以及一堆核爆試驗的錄像帶。接下來我將向你展示盡我所能推理出來的納秒級事件記錄。The ball would be going so fast that everything else would be practically stationary. Even the molecules in the air would stand still. Air molecules would vibrate back and forth at a few hundred miles per hour, but the ball would be moving through them at 600 million miles per hour. This means that as far as the ball is concerned, they would just be hanging there, frozen. The ideas of aerodynamics wouldn't apply here. Normally, air would flow around anything moving through it. But the air molecules in front of this ball wouldn't have time to be jostled out of the way. The ball would smack into them so hard that the atoms in the air molecules would actually fuse with the atoms in the ball's surface. Each collision would release a burst of gamma rays and scattered particles.
棒球的速度實在是太快，以至於其他任何東西看上去都像靜止了一樣。即使是來回振動速度可達每小時上千千米的空氣分子，相比起移動速度高達每小時9億千米的棒球，看上去也會像凍結在空中一樣。空氣動力學在此時已經不起作用了。正常情況下，空氣會流過運動物體的表面，但此時棒球前方的空氣分子根本沒有時間躲開棒球，棒球會直直地撞上這些空氣分子，其力度之大甚至能使棒球表面空氣分子的原子核發生聚變反應。每一次碰撞都會釋放出一股伽馬射線暴和四處飛散的粒子。These gamma rays and debris would expand outward in a bubble centered on the pitcher's mound. They would start to tear apart the molecules in the air, ripping the electrons from the nuclei and turning the air in the stadium into an expanding bubble of incandescent plasma. The wall of this bubble would approach the batter at about the speed of light-only slightly ahead of the ball itself.
這些伽馬射線和碎屑會形成一個以投手丘爲中心不斷擴大的氣泡，它們會扯碎空氣中的分子，把電子從原子核裏剝離出來，整個球場內的空氣都會變成不斷膨脹的熾熱等離子泡。這個等離子泡的邊緣會以接近光速的速度（比棒球本身的速度略快一些）向擊球手飛去。The constant fusion at the front of the ball would push back on it, slowing it down, as if the ball were a rocket flying tail-first while firing its engines. Unfortunately, the ball would be going so fast that even the tremendous force from this ongoing thermonuclear explosion would barely slow it down at all. It would, however, start to eat away at the surface, blasting tiny fragments of the ball in all directions. These fragments would be going so fast that when they hit air molecules, they would trigger two or three more rounds of fusion.
棒球前方不斷髮生的聚變反應所產生的反作用力會把棒球向後推，慢慢地降低它的速度，就像一枚引擎點燃、尾部還在朝前飛的火箭。不幸的是，棒球的速度實在是太快，以至於這持續不斷的熱核反應所產生的巨大反作用力，仍然不足以使棒球的速度降低多少。然而它還是會不停地侵蝕棒球的表面，把棒球產生的細小碎屑向四面八方噴射出去。這些飛散的碎屑一旦撞上別的空氣分子，其本身的巨大速度又將引發兩到三輪新的核聚變。After about 70 nanoseconds the ball would arrive at home plate. The batter wouldn't even have seen the pitcher let go of the ball, since the light carrying that information would arrive at about the same time the ball would. Collisions with the air would have eaten the ball away almost completely, and it would now be a bullet-shaped cloud of expanding plasma (mainly carbon, oxygen, hydrogen, and nitrogen) ramming into the air and triggering more fusion as it went. The shell of x-rays would hit the batter first, and a handful of nanoseconds later the debris cloud would hit.
在棒球被擲出70納秒後，它已經飛到了本壘板前。此時擊球手甚至都還沒看到棒球從投球手手中擲出，因爲傳遞這一信息的光幾乎是和棒球本身同一時刻到達擊球手面前的。與空氣之間的持續碰撞幾乎已經把整個棒球侵蝕殆盡了，這時出現在擊球手面前的是一團子彈形狀的、不斷膨脹的等離子云（主要成分是碳、氧、氫和氮），撞擊着空氣，引發更多的聚變反應。最先擊中擊球手的是外層的X射線，幾納秒後碎屑雲也將接踵而至。When it would reach home plate, the center of the cloud would still be moving at an appreciable fraction of the speed of light. It would hit the bat first, but then the batter, plate, and catcher would all be scooped up and carried backward through the backstop as they disintegrated. The shell of x-rays and superheated plasma would expand outward and upward, swallowing the backstop, both teams, the stands, and the surrounding neighborhood-all in the first microsecond.
即使在飛抵本壘板後，等離子云團的核心部分仍將以接近光速的速度前進。它會先撞上球棒，但轉瞬間擊球手、本壘板和接球手都將被雲團夾帶着，撞穿後面的擋球網，同時解體。外層的X射線和熾熱的等離子氣體將繼續向上向外擴張，將擋球網、雙方隊伍、看臺以及周圍的居民區一一吞沒——而這些都將發生在球被擲出後的第一個毫秒內。Suppose you're watching from a hilltop outside the city. The first thing you would see would be a blinding light, far outshining the sun. This would gradually fade over the course of a few seconds, and a growing fireball would rise into a mushroom cloud. Then, with a great roar, the blast wave would arrive, tearing up trees and shredding houses.
如果你在城市外一個小山丘上觀看這場賽事，你先會看到一股耀眼的光線，其亮度遠遠超過太陽。幾秒鐘後這股強光慢慢消散，隨之而來的是一個不斷變大的火球升入高空，形成一個蘑菇雲。隨後衝擊波會伴隨着一聲巨響呼嘯而來，摧毀沿途的樹木和建築。Everything within roughly a mile of the park would be leveled, and a firestorm would engulf the surrounding city. The baseball diamond, now a sizable crater, would be centered a few hundred feet behind the former location of the backstop.
離球場中心大約一兩千米範圍之內的所有區域都會被夷爲平地，火焰風暴會吞噬整座城市。原先的那個棒球場所在地將會留下一個大坑，坑的中心在擋球網後面100多米的地方。Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered “hit by pitch,” and would be eligible to advance to first base.
根據職業棒球大聯盟規則的6.08（b）條款，這個球將被判定爲“觸身球”，擊球手將被保送上一壘。After I initially published this article, MIT physicist Hans Rinderknecht contacted me to say that he'd simulated this scenario on their lab's computers. He found that early in the ball's flight, most of the air molecules were actually moving too quickly to cause fusion, and would pass right through the ball, heating it more slowly and uniformly than my original article described.
在我最初發表這篇文章之後，麻省理工學院的物理學家漢斯?林德克奈徹特聯繫我說，他在他們實驗室的計算機上模擬了這一場景，他發現在棒球剛飛出去的一小段時間內，絕大多數空氣分子的移動速度甚至高到無法產生聚變，它們會直接穿透棒球飛出。較之我原先文章所描述的結果，空氣加熱的速度會更慢，同時也更均勻。
