7.Question 7In the twin paradox example done in lecture, it seems that Alice's and Bob's situations should be parallel or symmetric to each other. That is, Bob observes Alice travel to the star and back, but from Alice's frame of reference, it is Bob that travels away (in the opposite direction) and returns. Why aren't their situations symmetrical?1 pointActually, there is no difference between their two situations--it's why it is called a paradox. Bob undergoes acceleration, but in the opposite direction to Alice, thus causing the asymmetry which leads to the time difference.Only Alice undergoes acceleration (and deceleration), leading to a change in her frame of reference.

Question 3Consider the twin paradox example done in lecture: On Alice's outbound trip to the star, Bob observes Alice's clocks running slower than his clocks. What does Alice observe regarding Bob's clocks?

10.Question 10In the twin paradox example done in lecture, how does Alice explain the fact that when she returns, Bob has aged more than she has, even though on both legs of her trip when she was traveling at 0.6c she observed his clocks to run more slowly than hers?1 pointDue to the finite speed of light, there is a delay in when Alice sees the reading on one of Bob's clocks, which means that Alice's observation of Bob's clocks running slow is incorrect.When she turned around at the star, she changed her frame of reference, which led to his clocks jumping ahead of hers (from her perspective).Though it seemed to Alice as if Bob's clocks were running slower than hers, they were actually running faster throughout the whole trip.

9.Question 9In the twin paradox example done in lecture, just after Alice leaves the star on her return trip (and she's back up to her cruising speed of 0.6c), she observes Bob's clock back where he is located. (In other words, she has a photo taken of his clock and her corresponding clock at that location, her clock being part of her lattice of clocks.) Compared to her clock, does she observe Bob's clock to be behind, ahead, or the same time as hers?1 pointBob's clock is behind her clock.Bob's clock is ahead of her clock.Bob's clock has the same time as her clock.

Bob is moving to the right (positive x direction) in his spaceship at a velocity v, and Alice is observing him. Each has their own lattice of clocks and measuring systems, which can be represented in two spacetime diagrams, one for Bob’s frame of reference and one for Alice’s. True or false: Bob’s world line is the line of same location given by xB = 0, whether it’s drawn on Alice’s spacetime diagram or Bob’s spacetime diagram.

7.Question 7Consider two identical light clocks, designed as explained in lecture. Bob has one, and Alice takes the other on her spaceship and flies by Bob at speed V. Bob observes Alice’s clock as Alice flies by. Which of the following statements is true?1 pointBob observes Alice’s clock to tick faster than his clock.Bob observes Alice’s clock to tick at the same rate as his clock.Bob observes Alice’s clock to tick slower than his clock.