Editing Talk:1366: Train
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A train rotating the Earth is NOT physically equivalent to a train traversing the Earth. It would be true for a flat Earth, but rotation is absolute, see Newton's bucket argument. [http://en.wikipedia.org/wiki/Bucket_argument] --[[User:Gleyshon|Gleyshon]] | A train rotating the Earth is NOT physically equivalent to a train traversing the Earth. It would be true for a flat Earth, but rotation is absolute, see Newton's bucket argument. [http://en.wikipedia.org/wiki/Bucket_argument] --[[User:Gleyshon|Gleyshon]] | ||
− | I am only a layperson, but as i read it the explanation confuses coordinate systems for the description of motion with physical explanation. The reasons why the train cannot be seen as accelerating the earth/universe are so numerous (even ignoring the other objects moving in different ways) it's just for subjective fun that i'll point out a few: The rest mass of the earth is not relative, so neither is the force needed to accelerate it -- force which the train cannot create by a factor of kajillions (roughly ;^). And if it did, the area would turn into plasma. Sticking to the comic, there isn't enough friction/rigidity/etc for the wheels/rails to "grab the earth". (Notice these are local observations unaffected by any relativity.) If somehow the earth could be accelerated in this manner, the rest of the universe wouldn't go along with it. And if it did, astronomical objects wouldn't change apparent position until their light reached us. Finally, rotation of massive bodies creates {{w|Frame-dragging}} (the twisting of spacetime) which is locally observable. So: the point of the comic isn't that the view presented is counter-intuitively valid (with awkward math); rather the comic is funny because of how badly this view fails. But i don't think i'm the person to rewrite the explanation... [[User:Noobgeek|Noobgeek]] ([[User talk:Noobgeek|talk]]) 16:59, 15 May 2014 | + | I am only a layperson, but as i read it the explanation confuses coordinate systems for the description of motion with physical explanation. The reasons why the train cannot be seen as accelerating the earth/universe are so numerous (even ignoring the other objects moving in different ways) it's just for subjective fun that i'll point out a few: |
− | + | The rest mass of the earth is not relative, so neither is the force needed to accelerate it -- force which the train cannot create by a factor of kajillions (roughly ;^). And if it did, the area would turn into plasma. Sticking to the comic, there isn't enough friction/rigidity/etc for the wheels/rails to "grab the earth". (Notice these are local observations unaffected by any relativity.) If somehow the earth could be accelerated in this manner, the rest of the universe wouldn't go along with it. And if it did, astronomical objects wouldn't change apparent position until their light reached us. Finally, rotation of massive bodies creates {{w|Frame-dragging}} (the twisting of spacetime) which is locally observable. | |
− | + | So: the point of the comic isn't that the view presented is counter-intuitively valid (with awkward math); rather the comic is funny because of how badly this view fails. But i don't think i'm the person to rewrite the explanation... [[User:Noobgeek|Noobgeek]] ([[User talk:Noobgeek|talk]]) 16:59, 15 May 2014 (UTC) | |
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