in the distance 在远方，直接用作状语
at a distance （of）在多远的地方，一般后面接距离的名词或数词

the distance that light travels in one second is 300 thousand kilometers.. in one second 是什么意思

in one second是一秒内
distance 在句中做light travels的定语，the distance that light travels in one second 整一个在句中作主语

一颗心的距离用英文怎么说？

the distance of a heart