3 ms·

To reduce this article to one sentence: The answer to the question "Which happened first, Event A or Event B?" depends on where you are.

• shurcooL 13y ago
  And how fast you're moving? Or is that a non-factor?
• gus_massa 13y ago
  It doesn't depend on where you are. The "explanation" at the end of the article is misleading. If you are sited next to a door you will "see" that your door closes before the other. But as you know the distance between the doors you can make the correction and calculate the exact time when the other door closed. After the correction you will realize that both doors closed at the same time in spite you don't "see" them closing at the same time. You will have the same effect sitting at the other door. If you are sitting in between you must apply the corrections to both doors, and then you will realize that they really closed at the same time. The only point were you "see" at the same time that both doors close is in the middle, and obviously after the corrections you will realize that they really closed at the same time. The important thing is your velocity. Let's suppose that you are traveling (very) fast with the ladder, holding it at the middle point. You will first "see" that the back door closes (and reopen) before the top of the ladder get to that point. Then you will see that the front door closes (and reopen) after the bottom of the ladder passed that point. But you still have to make the corrections because both doors are far away. Even after the corrections the back door close and reopens before the front door close and reopens. If you hold the ladder form one extreme you will "see" essentially the same things, and after the corrections you will be sure that never were both doors closed at the simultaneously. An important detail is that the difference of time between the reopening of the back door and the closing of the front door doesn't depend on where are you holding the ladder. After the corrections you will get the same time interval.