Some scientists have taken to underground searches in hopes of catching just a few out of the multitude of dark matter particles in a rare instance of actually bouncing off of a regular particle.

一些科学家寄希望于地下的搜索，当大量的暗物质粒子通过时，在极少数的情况下，会有一些微粒被正常的粒子弹开，通过捕捉正常粒子的波动就可以抓住微量暗物质的踪迹。

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And that's the following. Let's take a particle that is moving in the x-y plane, so that at one instance-- sorry, let me change this graph-- is here--oh, this is bad.

接下来,我们来看一个物体,在 x-y 平面内运动,在这个例子中,对不起,我要重画一下这个图,在这里,这画得不好

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