科学家需要够强的冲击，让蟑螂失去平衡，但冲击的时间又要够短，短到在蟑螂走一步的时间内发生；可能短至50毫秒。

• The scientists needed jolts powerful enough to knock the roaches off balance but brief enough to test within a single roach stride, which can last as little as 50 milliseconds.