Dan picks up a 15-m-long pole and begins running very fast, holding the pole horizontally and pointing in the direction he's running. He heads toward a barn that is12 m long and has open doors at each end. Dan runs so fast that, to Farmer Brown standing by his barn, the ladder is only 5 m long. As soon as the pole is completely inside the barn, Farmer Brown closes both doors so that Dan and the pole are inside with both doors shut. Then, just before Dan reaches the far door, Farmer Brown opens both doors and Dan emerges, still moving at high speed. According to Dan, however, the barn is contracted to only 4 m and the pole has its full 15 m length. Farmer Brown sees the pole completely inside the barn with both doors closed.

In the farmer's reference frame, eight events occur in the following order:
1. The front of the pole reaches the back of the barn (FB).
2. The back of the pole reaches the back of the barn (BB).
3, 4. (simultaneous events) The farmer shuts the front door (SF); the farmer shuts the back door (SB).
5. The front of the pole reaches the front of the barn (FF).
6, 7. (simultaneous events) The farmer opens the front door (OF). The farmer opens the back door (OB).
8. The back of the pole reaches the front of the barn (BF).
What does Dan see happening (in the chronological order)?

In the farmer's reference frame, eight events occur in the following order:
1. The front of the pole reaches the back of the barn (FB).
2. The back of the pole reaches the back of the barn (BB).
3, 4. (simultaneous events) The farmer shuts the front door (SF); the farmer shuts the back door (SB).
5. The front of the pole reaches the front of the barn (FF).
6, 7. (simultaneous events) The farmer opens the front door (OF). The farmer opens the back door (OB).
8. The back of the pole reaches the front of the barn (BF).
What does Dan see happening (in the chronological order)?

1. FB; 2, 3. FF and OF are simultaneous; 4. SF; 5, 6. BB and OB are simultaneous; 7. SB; 8 BF.
1. FB; 2. FF; 3, 4. SF and OF are simultaneous; 5, 6. OB and SB are simultaneous; 7. BB; 8 BF.
1. FB; 2, 3. SF and OF are simultaneous; 4. FF; 5, 6. OB and SB are simultaneous; 7. BB; 8 BF.
1. FB; 2. SF; 3, 4. FF and OF are simultaneous; 5, 6. BB and SB are simultaneous; 7. OB; 8 BF.