有啥能比光速更快？

译者 lbb

FYI: Can Anything Move Faster Than Light? By Sarah Fecht

有啥能比光速更快吗？

Exceeding the Speed of Light Everett Collection

超越光速

Yes, the universe itself will eventually outpace the speed of light. Just how this will happen is a bit complicated, so let’s begin at the very beginning: the big bang. Around 14 billion years ago, all matter in the universe was thrown in every direction. That first explosion is still pushing galaxies outward. Scientists know this because of the Doppler effect, among other reasons. The wavelengths of light from other galaxies shift as they move away from us, just as the pitch of an ambulance siren changes as it moves past.

    有啥能比光速更快吗？Yes，我们所处宇宙自身的速度最终就将超过光速。只不过这事儿说起来有点复杂，那就从大爆炸开始说起吧。大约140亿年前，这个宇宙的所有物质全都被抛向四面八方，直到现在，那次原始爆炸仍在推动着宇宙中的各个星系远离爆炸中心，这是科学家根据多普勒效应从纷纭繁杂的现象中了解到的。当星系远离我们而去的时候，它发出光线的波长就会产生变化，这就象一辆救护车飞驰而过时，它的警笛声调会发生变化一样的道理。

Take Hydra, a cluster of galaxies about three billion light years away. Astronomers have measured the distance from the Earth to Hydra by looking at the light coming from the cluster. Through a prism, Hydra’s hydrogen looks like four strips of red, blue-green, blue-violet and violet. But during the time it takes Hydra’s light to reach us, the bands of color have shifted down toward the red end—the low-energy end—of the spectrum. On their journey across the universe, the wavelengths of light have stretched. The farther the light travels, the more stretched it gets. The farther the bands shift toward the red end, the farther the light has traveled. The size of the shift is called the redshift, and it helps scientists figure out the movement of stars in space. Hydra isn’t the only distant cluster of galaxies that displays a redshift, though. Everything is shifting, because the universe is expanding. It’s just easier to see Hydra’s redshift because the farther a galaxy is from our own, the faster it is moving away.

    长蛇座星团距我们约三十亿光年，这个距离是天文学家通过观察来自该星团的光线测算出来的。长蛇座的氢元素所发出的光线通过棱镜后本该呈现出红、兰绿、兰紫和紫色四条色带，但当其到达地球时，那四条色带却移动到了光谱带的红端，即光谱带的低能量谱线端。这表明，在光线穿越宇宙向地球进发的旅程中，其波长变长了。光线行进的路程越远，波长的变化越大，也就是说，谱线越靠近红端，光线行进的路程越远，其变化的幅度叫做“红移”。“红移”有助于科学家勾勒出星球在空间的运动状态。在无数遥远的星系中，并非只有长蛇座才显示出红移现象，由于宇宙一直在膨胀，所有的东西都在移动，之所以能较容易地观察到长蛇座的红移，是因为星系距我们越远，其远离我们而去的速度就越快。

There is no limit to how fast the universe can expand, says physicist Charles Bennett of Johns Hopkins University. Einstein’s theory that nothing can travel faster than the speed of light in a vacuum still holds true, because space itself is stretching, and space is nothing. Galaxies aren’t moving through space and away from each other but with space—like raisins in a rising loaf of bread. Some galaxies are already so far away from us, and moving away so quickly, that their light will never reach Earth. “It’s like running a 5K race, but the track expands while you’re running,” Bennett says. “If it expands faster than you can run, you’ll never get where you’re going."

  　　“宇宙到底能膨胀到多快并无底线”，琼斯·霍普金斯大学的物理学家查尔斯·本尼特说，“爱因斯坦‘任何物体的速度都不可能超过真空中的光速’的理论依然正确。因为空间一直在延伸，而空间就是空间，而不是物体，各星系就象在一个（因发酵而）不断隆起的面包里的葡萄干一样，只能在空间里，而不能穿越出空间彼此远离。”

    　　一些星系离我们已如此遥远，其远去的速度又是如此之快，以至于它们发出的光线永远也无法到达地球。“这就象以5公里/小时的速度跑步，在你向前跑的过程中，终点线却延伸了”本尼特说，“如果其延伸的速度快于你所能跑出的速度，那你永远也到不了终点。”

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