This relatively short cosmic time frame makes this event a very rare phenomenon.

这个相对来说比较短的宇宙时间范围内发生了罕见的现象。

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In principle, one can trace that history back in cosmic time by observing a so-called standard candle, a class of astronomical object whose intrinsic luminosity is uniform.

原理上，我们可以通过观测所谓的标准烛光(一种天体，它的绝对光度是相同的)来追溯宇宙内的历史。

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Another possibility is that the accelerated expansion arises not from a substance but from a modified form of gravity, one that behaves differently on cosmic scales of time and space.

另一种可能性是加速膨胀不是来自物质而是修改的重力形式，其作用在时空的宇宙尺度上是不同的。

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Its deep vision has also enabled scientists to trace the story of how galaxies have changed through cosmic time.

BBC: Herschel space telescope to go blind

But Crawford and his colleagues believe the answer is to search for clues in relatively recent lava flows, because once cooled and covered over, they could preserve the mark of cosmic rays from the time they were exposed.

FORBES: Ancient Supernova Explosions Left Their Scars on Earth

Naturally occurring neutrinos from cosmic rays, supernovae and the sun stream through the detector at the same time.

ENGADGET: NOvA neutrino detector captures cosmic rays in 3D, aims to unlock the mysteries of the universe