与周边空气相比，轮船轨迹含有更多微粒。水蒸气围绕着这些作为核子的微粒凝结。

Compared to surrounding air, ship exhaust has more particles, and each particle can act as a nucleus around which water vapor condenses.

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你们可以看到,有件事非常值得注意,可以注意到,方向的速度，is，that，the，velocity，in，the，x，direction,在整个轨迹当中-,如果没有空气阻力，也没有摩擦力-,是不会改变的。

Now, when you look at this there is something quite remarkable and the remarkable thing x - throughout this whole trajectory-- if there is no air draft, - if there is no friction-- is not changing.

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在某种程度上更为可靠的雷达观测无法区别大气中的人造飞船、流星轨迹、电离的空气、雨滴和热断层。

Radar sightings, while in certain respects more reliable, fail to discriminate between artificial objects and meteor trails, ionized gas, rain, or thermal discontinuities in the atmosphere.

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