不管你的人缘有多好，朋友圈子有多广，身边的朋友总是有亲疏之分的。有的可能只是泛泛之交，有的可以无话不谈。这就决定了你们在见面的时候会如何交流，是客套寒暄一下就完呢，还是说起来就没完。这里面起决定性作用的东西就叫做chat gravity。
Chat gravity refers to the degree of familiarity with another person, which, if you chance to encounter them on the street, will determine if you merely greet them in passing or stop to talk。
聊天重力指你跟另一个人的熟悉程度决定了你们在街头偶遇的时候是只打个招呼就过去，还是停下来聊一会儿。
For example:
We saw each other on the sidewalk and said 'hello' to each other. But she was just a friend of a friend I'd only met once or twice before, and there wasn't enough chat gravity to merit stopping and chatting。
我们在路边相遇，互相打了个招呼。不过，她只是我一个朋友的朋友，我们也只见过一两次面，所以也就没有足够的聊天重力让我停下来跟她攀谈了。