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jtaravens
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As I was reading Fabric of the Cosmos, I got stumped at the relativity of simultaneity section. This led me to Google for some additional explanation. I stumbled upon http://www.phys.unsw.edu.au/einsteinlight/jw/module4_pole_paradox.htm" which made me think of this question regarding the pole and barn paradox.
I searched around the forum and I didn’t find an answer to my specific question – here goes:
If the person running with the pole appears to the spectator (at a distance) to be inside the barn completely with the doors shut, how can the person running with the pole think that the pole is hanging out of the barn?
I understand how only if the doors are simultaneously shut (according to the spectator) and immediately opened b/c the person running with the pole would not agree with the simultaneous shutting and opening. So to the runner, the first door shuts while the back door is still open allowing the pole to hang out, and then the front door opens while the front of the pole moves out of the barn and then back door shuts. But if both doors are shut, and shut for good, doesn’t it come down to whether the pole is in the barn, or whether the back door came crashing down on the end of the pole? One of my problems is right here: if the doors are closed forever, is the pole in the barn or not? Shouldn’t this be the same for both observers? The pole would either be crushed by the door or not.
If the simultaneity of the doors closing for good is still relative, couldn’t you time the closing so it appears simultaneous to the runner (i.e. have the back door close a bit earlier than the front door)? In this case it wouldn’t be simultaneous to the spectator. But we can still ask if the pole is in the barn or did it get crushed by a door?
I feel like to the runner, the pole is at a static length so it can’t ever be in the barn because it’s too big. This leads me to ask is this just an illusion based on perspectives of when doors are opening and closing and how the pole appears to the spectator (based on length contraction) to pass through the barn. I must be missing something here.
John
I searched around the forum and I didn’t find an answer to my specific question – here goes:
If the person running with the pole appears to the spectator (at a distance) to be inside the barn completely with the doors shut, how can the person running with the pole think that the pole is hanging out of the barn?
I understand how only if the doors are simultaneously shut (according to the spectator) and immediately opened b/c the person running with the pole would not agree with the simultaneous shutting and opening. So to the runner, the first door shuts while the back door is still open allowing the pole to hang out, and then the front door opens while the front of the pole moves out of the barn and then back door shuts. But if both doors are shut, and shut for good, doesn’t it come down to whether the pole is in the barn, or whether the back door came crashing down on the end of the pole? One of my problems is right here: if the doors are closed forever, is the pole in the barn or not? Shouldn’t this be the same for both observers? The pole would either be crushed by the door or not.
If the simultaneity of the doors closing for good is still relative, couldn’t you time the closing so it appears simultaneous to the runner (i.e. have the back door close a bit earlier than the front door)? In this case it wouldn’t be simultaneous to the spectator. But we can still ask if the pole is in the barn or did it get crushed by a door?
I feel like to the runner, the pole is at a static length so it can’t ever be in the barn because it’s too big. This leads me to ask is this just an illusion based on perspectives of when doors are opening and closing and how the pole appears to the spectator (based on length contraction) to pass through the barn. I must be missing something here.
John
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