md65536 Posted October 22, 2010 Share Posted October 22, 2010 (edited) Short version: Can a space traveler ever observe Earth time appearing to go backward? I claim "no" but under that claim I keep coming around to an inconsistency where more distant things will age more than nearer things. Where am I going wrong? Long version: I'm trying to figure out what is observed by the traveling twin during an extremely fast deceleration + return acceleration phase in the twin paradox. This is also described as the rocket undergoing a frame switch. According to my understanding of what I've read, the traveling twin will see the Earth twin age a large amount in that very short period of rocket time. What happens if the rocket "frame-switches" several times while far from Earth, by coming to a stop and accelerating toward Earth, then stopping and accelerating away from Earth again (involves multiple switches between 2 frames: outbound, and return)? What happens if it repeats this, "shaking" back and forth, reaching high velocity each time, over a very little duration of rocket time? Solution 1 (no good): My calculations show that the Earth twin will continue to age rapidly during these frame switches (specifically, she will age much as length contraction takes effect when accelerating in each direction, and age not at all as length contraction is released when decelerating). However, it also is apparent that the distance that the rocket is from Earth will determine how much the Earth twin ages when the rocket does this little trick. This leads to inconsistency... Suppose the rocket has traveled to Planet X which is stationary relative to Earth, and then "shakes" for awhile. The Earth twin will age a lot relative to the rocket twin, but a Planet X twin will age only slightly faster than the rocket twin. This makes no sense because the Earth twin and Planet X twin should not age differently relative to each other. Solution 2: When the rocket switches from outbound to return frame, the Earth twin will age relatively fast, but when switching from return to outbound frame, the aging difference will be undone. One way for this to happen is for one twin to age fast and then the other twin to age fast. But if the rocket can shake many times in a short period of time, it should age only that short period of time. So if the Earth twin ages a great amount during one frame switch, it must un-age on the other frame switch. This means the rocket can observe earth time going backwards. I hope that this is NOT the case, because it punches a huge hole in my theory of how time works, and my understanding of observable reality. Solution 3: The time periods in which the Earth twin seems to age greatly actually overlap, so that if the rocket shakes for awhile, the rocket twin observes only one aging period on Earth (possibly fluctuating between fast and slow aging as the rocket shakes?). Solution 4: Not all frame switches have the same observed relative aging? Solution 5: Something I've missed? Some way in which time dilation compensates? Or a maximum possible acceleration rate? Edited October 22, 2010 by md65536 Link to comment Share on other sites More sharing options...
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