He said hippos cross the boundaries of ecosystems.

他说河马参与了不同的生态系统。

And another, where it crosses the boundary and plunges into the event horizon.

另一个场景是宇航员越过边界，坠入事件视界（时空曲隔界线，黑洞周围）。

It's public land, said the sheriff. They're allowed to go to the gate, as long as they don't cross the boundary.

" 这里是公共区域，" 警长说。" 只要他们不越界，就可以靠近大门。"

Time seemed to have stood still for them, and nothing " modern" ever crossed the boundaries of their " oasis" .

时间对他们来说似乎是静止的，没有任何“现代”东西能越过他们“绿洲”的界限。

The scientists reported Parker was about 13 million kilometers from the center of the sun when it crossed the boundary between the solar atmosphere and the solar wind.

科学家们报告说，当帕克太阳探测器穿过太阳大气层和太阳风之间的边界时，它距离太阳中心大约1300万公里。