From asteroids capable of destroying entire species, to gamma-ray bursts and supernovae that could exterminate life on Earth, outer space has no shortage of forces that could wreak havoc on our tiny planet. But there’s something in space that seems more terrifying than any of these – something that wipes out everything it comes near. Could the Earth be swallowed by a black hole?
從可以摧毀整個物種的小行星, 到可以讓地球上所有生命滅絕的 伽瑪射線暴和超級新星, 外太空一點也不缺 可以在我們的小小星球上 造成大浩劫的力量。 但在太空中,有樣東西 似乎比上述的還要更駭人—— 任何東西只要靠近它 就會被徹底消滅。 地球有沒有可能會被黑洞給吞噬?
A black hole is an object so dense that space and time around it are inescapably modified, warped into an infinite sink. Nothing, not even light, can move fast enough to escape a black hole’s gravitational pull once it passes a certain boundary, known as the event horizon. Thus, a black hole is like a cosmic vacuum cleaner with infinite capacity, gobbling up everything in its path, and letting nothing out.
黑洞是密度超高的物體, 高到它周圍的空間和時間 都無法避免地被改變, 扭曲成了無限大的槽。 即使是光也不夠快, 無法逃離黑洞的引力牽引, 一旦它超過了某條界線, 也就是所謂的事件視界, 就無法脫離了。 因此,黑洞是個容量 無限大的宇宙吸塵器, 狼吞虎咽它經過的一切, 什麼都不放過。
To determine whether a black hole could swallow the Earth, we first have to figure out where they are. But since they don’t emit light, how’s that possible? Fortunately, we’re able to observe their effect on the space around them. When matter approaches a black hole, the immense gravitational field accelerates it to high speed. This emits an enormous amount of light. And for objects too far away to be sucked in, the massive gravitational force still affects their orbits. If we observe several stars orbiting around an apparently empty point, a black hole could be leading the dance. Similarly, light that passes close enough to an event horizon will be deflected in a phenomenon known as gravitational lensing.
若要判斷一個黑洞 是否會把地球吞噬, 我們先要找到黑洞在哪裡。 但它們不會散發光線, 怎麼可能找到它們? 幸運的是,我們可以觀察 它們對於周圍空間的影響。 當物質靠近一個黑洞時, 非常大的重力場會讓它加速 到極高的速度。 這樣就會放射出大量的光。 至於太遠而不會被吸進去的物體, 極大的引力仍然會影響它們的軌道。 如果我們觀察到有許多星星明顯 在一個空的點周圍繞軌運行時, 很可能就是黑洞在帶領它們跳舞。 同樣的,路過的光 如果太靠近事件視界, 會因為所謂的重力透鏡效應而轉向。
Most of the black holes that we’ve found can be thought of as two main types. The smaller ones, called stellar mass black holes, have a mass up to 100 times larger than that of our sun. They’re formed when a massive star consumes all its nuclear fuel and its core collapses. We’ve observed several of these objects as close as 3000 light-years away, and there could be up to 100 million small black holes just in the Milky Way galaxy. So should we be worried? Probably not. Despite their large mass, stellar black holes only have a radius of around 300 kilometers or less, making the chances of a direct hit with us miniscule. Although because their gravitational fields can affect a planet from a large distance, they could be dangerous even without a direct collision. If a typical stellar-mass black hole were to pass in the region of Neptune, the orbit of the Earth would be considerably modified, with dire results.
我們所發現的黑洞 大部分可分為兩種主要類型。 比較小的叫做恆星質量黑洞, 質量比我們的太陽還要大一百倍。 當一個大質量的星星 消耗光了它所有的核燃料, 它的核心會垮掉。 我們觀察到這些物體中 有幾個距離我們近三千光年, 光是在銀河當中,可能就有 高達一億個小黑洞。 我們應該要擔心嗎?可能不用。 儘管恆星質量黑洞的質量很大, 它們的半徑只有 約三百公里,甚至更小, 因此,直接衝向我們的機會非常小。 不過,因為它們的重力場 可以在很遠的距離就影響到星球, 即使沒有直接衝撞, 它們也具有危險性。 如果一個典型的恆星質量黑洞 通過海王星一帶, 地球的軌道可能會被大大地改變, 後果會很可怕。
Still, the combination of how small they are and how vast the galaxy is means that stellar black holes don’t give us much to worry about. But we still have to meet the second type: supermassive black holes. These have masses millions or billions times greater than that of our sun and have event horizons that could span billions of kilometers. These giants have grown to immense proportions by swallowing matter and merging with other black holes. Unlike their stellar cousins, supermassive black holes aren’t wandering through space. Instead, they lie at the center of galaxies, including our own. Our solar system is in a stable orbit around a supermassive black hole that resides at the center of the Milky Way, at a safe distance of 25,000 light-years. But that could change. If our galaxy collides with another, the Earth could be thrown towards the galactic center, close enough to the supermassive black hole to be eventually swallowed up. In fact, a collision with the Andromeda Galaxy is predicted to happen 4 billion years from now, which may not be great news for our home planet.
不過,黑洞非常小, 再加上銀河非常大, 也就是說,我們不需要 太擔心恆星質量黑洞。 但我們仍然得要談談 第二種黑洞:超大質量黑洞。 它們的質量比我們的太陽 大數百萬或數十億倍, 事件視界可達數十億公里長。 這些巨物靠著吞噬物質 以及跟其他黑洞合併 而變得如此巨大。 和它們的恆星表親不同, 超大質量黑洞不會在宇宙中閒逛。 反之,它們會停留在銀河的中心, 包括我們的銀河。 我們的太陽系的運行軌道是繞著 超大質量黑洞的穩定軌道, 該黑洞就位在銀河的中心, 保持兩萬五千光年的安全距離。 但那是有可能改變的。 若我們的銀河系 和另一個銀河系相撞, 地球可能會被拋向銀河中心, 更靠近那個超大質量黑洞, 近到可能最後會被吞噬。 事實上,預測在四十億年之後 就會和仙女座星系相撞, 對於我們的家鄉地球來說, 這並不是好消息。
But before we judge them too harshly, black holes aren’t simply agents of destruction. They played a crucial role in the formation of galaxies, the building blocks of our universe. Far from being shadowy characters in the cosmic play, black holes have fundamentally contributed in making the universe a bright and astonishing place.
但在我們也不要 太嚴厲地評斷黑洞, 它們不只會帶來毀滅。 對於銀河系的形成, 它們也扮演了重要的角色, 是我們宇宙的基礎建材。 在這齣宇宙劇中, 黑洞演的並不是帶來陰影的角色, 基本上,它們做出了很多貢獻, 讓宇宙成為一個明亮、 令人驚奇的地方。