来自《耶鲁大学开放课程：基础物理 第3集 第3集》

• 
  
  That's just fine.
  这是肯定的
• 
  
  But suppose you are in a train
  但假如你在火车上
• 
  
  and you're moving past me and you look at this piece of chalk.
  从我面前驶过 你看着这支粉笔
• 
  
  Of course, everything in my room is going backwards for you.
  显然你看教室里的东西都在倒退
• 
  
  But things which were at rest will move at a constant velocity,
  这些静止的东西都在匀速运动
• 
  
  opposite of the velocity that you have relative to me.
  方向正好跟你相对我运动的速度方向相反
• 
  
  You will find that objects that are at constant initial velocity
  你也会发现原本匀速的物体
• 
  
  maintain the velocity.
  依然保持原来的速度
• 
  
  If I am an inertial observer,
  如果我是惯性观察者
• 
  
  another person moving relative to me at constant velocity
  那另一个相对于我做匀速运动的人
• 
  
  will also be an inertial observer.
  也是一个惯性观察者
• 
  
  Why?
  为什么