Perhaps eternal forever is the unpredictable - space boundary which the exploration does not arrive!

永恒的或许永远是探索不到的捉摸不定的——宇宙空间的边际！

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The boundary between the two areas acts as a wall, capable of reflecting a guided EM wave on the graphene much like one would in a three dimensional space.

两个区域的边界就像是一堵墙，能反射被引导的电磁波； 这和三维空间中的墙是类似的。

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The heliopause was expected to be a rather sharp boundary between the sun's domain and interstellar space.

太阳风顶层曾被认为是处在太阳系区域和星际宇宙之间一层电磁波动极其强烈的区域。

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Such a space has no boundary, even though it has a finite volume.

ECONOMIST: The shape of the universe

Four, it follows an established set of parameters and rules, and requires some artificial boundary of time and space.

NEWYORKER: Master of Play

But we are the only species to have defined a geological period by our activity something usually performed by major glaciations, mass extinction and the colossal impact of objects from outer space, like the one that defines the upper boundary of the Cretaceous.

FORBES: On The Anthropocene Age