宇宙的超级大嘴
Space Supervoid Sucks Energy from Light
宇宙的超级大嘴
A vast region of space colder than expected is also largely devoid of galaxies, and the two observations are no coincidence. Clara Moskowitz reports
宇宙中那些超低温度的广阔区域中往往缺少星系，不过近来的观测表明，这两者也许并不直接相关。
撰文/播音 克拉拉·莫斯科维茨（Clara Moskowitz）
翻译 李轩
The universe is a dark, cold place. But it has a strange region that’s even colder than usual. Seen from Earth, it’s an area where the ambient cosmic microwave background light—the leftover thermal energy of the big bang—is much chillier than expected. Now astronomers say they’ve found in the same part of space a so-called supervoid—a large area mostly empty of galaxies. And they think the overlap is no coincidence.
宇宙是一个黑暗而又异常冰冷的世界。在这其中还有些更加奇特的区域，这些区域的温度比一般区域还要低很多。从地球上观测，这些区域的宇宙微波背景辐射——宇宙大爆炸的剩余能量的强度要远低于预期。近日，天文学家称，他们在被称为“超级空洞”的区域中也发现了这种能量不均的现象，而这些区域往往没有星系。
The supervoid extends 1.8 billion light-years across, making it perhaps the largest structure known in the cosmos, according to a report in the Monthly Notices of the Royal Astronomical Society. [István Szapudi et al, Detection of a supervoid aligned with the cold spot of the cosmic microwave background]
根据《皇家天文学会月报》(Monthly Notices of the Royal Astronomical Society)的一篇报道，这个超级空洞跨度18亿光年，可能是现今发现的最大的宇宙结构。
The supervoid’s relative lack of stuff could have drained energy from light that passed through it, explaining why the microwave background is colder there. Here’s how it works:
这个超级空洞虽然相对缺乏物质，但它可能可以从穿过它的光线中吸收能量，这就是为什么那里的宇宙微波背景强度要比预期低。
以下就是这其中的奥秘：
General relativity tells us that gravity bends spacetime, causing light to travel a curved path near massive objects, as if falling into a bowl. The supervoid, then, with its lack of mass, is akin to a hill. When light travels up that hill, it loses energy.
广义相对论告诉我们引力可以弯曲时空，从而光的传播路径在大质量物体附近会发生弯曲，这时光就好像落入了一个大碗。反过来，这个超级巨洞相对于周围区域缺乏物质，因此它更像一个小山，当光沿着这个小山向上“爬”时，它就会损失能量。
Normally it would regain the energy upon exiting the void—that is, when it comes down the other side of the hill. But because the expansion of space is accelerating, the hill the light tumbles down is less steep than it was when the light climbed up. And the flatter ride down means less energy recovered than was expended going up. Which translates to a low-energy region—a big chill in the remnant of the Big Bang.
不过一般而言，当光穿过这个空洞后，它又会重新获得能量——因为“下山”会补充能量。但是由于空间在加速膨胀，当光从另一边下山时，山已经变得不那么陡峭了。而山变得平坦意味着下山重新获得的能量将小于登山消耗的。这会形成一个低能量区域——大爆炸余晖中低温区。
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京ICP备11000850号-1
京公网安备11010502039775号 信息网络传播视听节目许可证0111611号
国家科技基础条件平台