# Twin Paradox: Whose time is slow? [closed]

What I understand about the twin paradox is that if a person stays at rest with something lets say the earth and a traveller moves with a great velocity with respect to the firsy person, then the time of traveller becomes very much smaller than the time of person who stays back, which led to the conclusion that one would age very much and one would not.

But if you see from the frame of the traveller, the person on rest on earth seems to be moving very fast, and according to this the person on earth should be younger than the traveller.

So, who is actually going to be younger?

One of my friends had asked me this question, and I replied that from the frame of the traveller if you measure the velocity of earth bound person you will have to take the same velocity in negative and you will get the same result. Even though he accepted my answer; I am myself not satisfied with it.

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## closed as off-topic by John Rennie, jinawee, DavePhD, Emilio Pisanty, Kyle KanosMay 14 '14 at 13:02

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This paradox has a well-known explanation/solution. Have you tried researching online or in your textbook? – BMS May 14 '14 at 1:38
Not a paradox. At some point they must compare clocks while in the same inertial frame. One of them experiences accelerations and one doesn't. So they have two quite different experiences and it is easy to tell which one accelerated and that is the one which "went faster" than the other. Plus, your SR time calculations don't account for acceleration. If they never meet, then they can't compare clocks. So it is a non-starter as far as a reasonable question to ask. – C. Towne Springer May 14 '14 at 2:23
This question shows insufficient effort. Searching this site for twin paradox finds many questions that deal with this issue. Googling finds many, many more. – John Rennie May 14 '14 at 8:44