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**1. Homework Statement**

Suppose that we send a spaceship on a trip to Alpha Centauri, 4 light years away. The space ship travels at a constant speed of .5c, it stops at Alpha C. for 1 year and then it returns to the Earth at constant speed .5c.

a. Draw a spacetime Diagram with axes x,ct and plot the worldine of the spaceship.

b. suppose that 1 year after the departure of the spaceship we send a radio message from earth to the spaceship. Plot the worldline of the radio signal.

c. At what time does it reach the spaceship?

**2. Homework Equations**

**3. The Attempt at a Solution**

a.

ct

|\

| .\

| .. \

| ... |

| .. /

| ./

|/________________x

where the angle between the ct and x axis is given by

theta = arctan(.5)

b.)I drew a cone with an angle of 45 between the ct and x axis.

c.) this is what i'm confused about. I'm not sure if I have to take relativity into account since c is the same in all reference frames. So, my answer is 1 year after the message is sent.

Can anyone please tell me if any of this is right? Any help will be greatly appreciated.