On their 21st birthday, one twin gets on a moving sidewalk, which carries her out to star X at speed 0.8c; her twin brot

[answerhappygod]

On Their 21st Birthday One Twin Gets On A Moving Sidewalk Which Carries Her Out To Star X At Speed 0 8c Her Twin Brot 1 (79.86 KiB) Viewed 42 times

On their 21st birthday, one twin gets on a moving sidewalk, which carries her out to star X at speed 0.8c; her twin brother stays home. When the traveling twin gets to star X, she immediately jumps onto the returning moving sidewalk and comes back to earth, again at speed 0.8c. She arrives on her 41 th birthday (as determined by her watch). A. How old is her twin brother? B. How far away is star X? (Give your answer in light years.) Let call the outbound sidewalk system S”, the inbound one S', and the earth system S. All three systems choose their coordinates and set their master clocks such that x= x= x" = 0, t= t = t = 0 at the moment of departure. C. What are the coordinates (x, t) of the jump (from outbound to inbound sidewalk) in S? D. What are the coordinates (x, t') of the jump in S'? E. What are the coordinates (x", ť) of the jump in S"?? F. If the traveling twin wants her watch to agree with the clock in S’, how must she reset it immediately after the jump? What does her watch then read when she gets home? (This wouldn't change her age, of course - she's still 41 - it would just make her watch agree with the standard synchronization in Sl.) G. If the traveling twin is asked the question, “How old is your brother right now?”, what is the correct reply a. just before she makes the jump, b. just after she makes the jump? (Nothing dramatic happens to her brother during the split second between (a) and (b), of course; what does change abruptly is his sister's notion of what "right now, back home" means.) H. How many earth years does the return trip take? Add this to (b) from question (G) to determine how old she expects him to be at their reunion. Compare your answer to question (A).