Re “Learning to Travel Through Time With My Astrophysical Professor” (On the Campus, May 11): Is Professor Richard Gott ’73’s time-travel example two-way? After going back to the past, can he return to the future? What about the paradox proposed by Larry Niven? If a method of traveling to the past were discovered, would somebody go back and do something to prevent the discovery? (One-way time travel to the future is clearly possible. All of us do it continuously.)